xref: /frameworks/base/docs/html-intl/intl/vi/guide/topics/ui/settings.jd

page.title=Thit t
page.tags=preference,preferenceactivity,preferencefragment

@jd:body


<div id="qv-wrapper">
<div id="qv">

<h2>Trong ti liu ny</h2>
<ol>
  <li><a href="#Overview">Tng quan</a>
    <ol>
      <li><a href="#SettingTypes">Ty chn</a></li>
    </ol>
  </li>
  <li><a href="#DefiningPrefs">nh ngha Ty chn trong XML</a>
    <ol>
      <li><a href="#Groups">To nhm thit t</a></li>
      <li><a href="#Intents">S dng  nh</a></li>
    </ol>
  </li>
  <li><a href="#Activity">To mt Hot ng Ty chn</a></li>
  <li><a href="#Fragment">S dng Phn on Ty chn</a></li>
  <li><a href="#Defaults">Thit t Gi tr Mc nh</a></li>
  <li><a href="#PreferenceHeaders">S dng Tiu  Ty chn</a>
    <ol>
      <li><a href="#CreateHeaders">To tp tiu </a></li>
      <li><a href="#DisplayHeaders">Hin th tiu </a></li>
      <li><a href="#BackCompatHeaders">H tr cc phin bn c hn vi tiu  ty chn</a></li>
    </ol>
  </li>
  <li><a href="#ReadingPrefs">c Ty chn</a>
    <ol>
      <li><a href="#Listening">Theo di thay i ty chn</a></li>
    </ol>
  </li>
  <li><a href="#NetworkUsage">Qun l S dng Mng</a></li>
  <li><a href="#Custom">Xy dng mt Thit t Ty chnh</a>
    <ol>
      <li><a href="#CustomSelected">Quy nh mt giao din ngi dng</a></li>
      <li><a href="#CustomSave">Lu gi tr ca thit t</a></li>
      <li><a href="#CustomInitialize">Khi to gi tr hin ti</a></li>
      <li><a href="#CustomDefault">Cung cp mt gi tr mc nh</a></li>
      <li><a href="#CustomSaveState">Lu v khi phc trng thi ca Ty chn</a></li>
    </ol>
  </li>
</ol>

<h2>Lp kha</h2>
<ol>
  <li>{@link android.preference.Preference}</li>
  <li>{@link android.preference.PreferenceActivity}</li>
  <li>{@link android.preference.PreferenceFragment}</li>
</ol>


<h2>Xem thm</h2>
<ol>
  <li><a href="{@docRoot}design/patterns/settings.html">Hng dn thit k Thit t</a></li>
</ol>
</div>
</div>




<p>ng dng thng bao gm nhng thit t cho php ngi dng sa i cc tnh nng v hnh vi ca ng dng. V
d, mt s ng dng cho php ngi dng quy nh xem thng bo c c kch hot hay khng hoc quy nh tn sut
ng dng s ng b d liu vi m my.</p>

<p>Nu mun cung cp thit t cho ng dng ca mnh, bn nn s dng
cc API {@link android.preference.Preference} ca Android  xy dng mt giao din ph hp vi
tri nghim ngi dng trong cc ng dng Android khc (bao gm thit t h thng). Ti liu ny m t
cch xy dng thit t ng dng ca bn bng cch s dng cc API {@link android.preference.Preference}.</p>

<div class="note design">
<p><strong>Thit k Thit t</strong></p>
  <p> bit thng tin v cch thit k thit t ca bn, hy c hng dn thit k <a href="{@docRoot}design/patterns/settings.html">Thit t</a>.</p>
</div>


<img src="{@docRoot}images/ui/settings/settings.png" alt="" width="435" />
<p class="img-caption"><strong>Hnh 1.</strong> nh chp mn hnh t thit t ca ng dng
Messaging trn Android. Chn mt mc c nh ngha bi mt {@link android.preference.Preference} 
s m ra mt giao din  thay i thit t.</p>




<h2 id="Overview">Tng quan</h2>

<p>Thay v s dng cc i tng {@link android.view.View}  xy dng giao din ngi dng, thit t c
xy dng bng cch s dng cc lp con khc nhau ca lp {@link android.preference.Preference} m bn
khai bo trong mt tp XML.</p>

<p>i tng {@link android.preference.Preference} l mt khi dng cho mt thit t
n l. Mi {@link android.preference.Preference} xut hin nh mt mc trong mt danh sch v cung cp
UI ph hp  ngi dng sa i thit t. V d, mt {@link
android.preference.CheckBoxPreference} to mt mc danh sch hin th mt hp kim, v mt {@link
android.preference.ListPreference} to mt mc m ra mt hp thoi vi danh sch la chn.</p>

<p>Mi {@link android.preference.Preference} m bn thm c mt cp kha-gi tr tng ng m
h thng s dng  lu thit t trong mt tp {@link android.content.SharedPreferences}
mc nh cho thit t ca ng dng ca bn. Khi ngi dng thay i mt thit t, h thng s cp nht gi tr
tng ng trong tp {@link android.content.SharedPreferences} cho bn. Ln duy nht m bn nn
trc tip tng tc vi tp {@link android.content.SharedPreferences} c lin kt  l khi bn
cn c gi tr  xc nh xem hnh vi ng dng ca mnh c c da trn thit t ca ngi dng khng.</p>

<p>Gi tr c lu trong {@link android.content.SharedPreferences} cho tng thit t c th l mt trong cc kiu d liu
sau:</p>

<ul>
  <li>Boolean</li>
  <li>Float</li>
  <li>Int</li>
  <li>Long</li>
  <li>String</li>
  <li>String {@link java.util.Set}</li>
</ul>

<p>V thit t ca ng dng ca bn c xy dng bng cch s dng cc i tng {@link android.preference.Preference}
thay v i tng
{@link android.view.View}, bn nn s dng mt lp con {@link android.app.Activity} hoc 
{@link android.app.Fragment} chuyn dng  hin th thit t danh sch:</p>

<ul>
  <li>Nu ng dng ca bn h tr cc phin bn Android c hn 3.0 (API mc 10 v thp hn), bn phi
xy dng hot ng nh mt phn m rng ca lp {@link android.preference.PreferenceActivity}.</li>
  <li>Trn phin bn Android 3.0 tr ln, thay vo , bn nn s dng mt {@link android.app.Activity}
truyn thng ni lu gi {@link android.preference.PreferenceFragment}  hin th thit t ng dng ca bn.
Tuy nhin, bn cng c th s dng {@link android.preference.PreferenceActivity}  to mt b tr hai bng
cho mn hnh ln khi bn c nhiu nhm thit t.</li>
</ul>

<p>Cch thit t {@link android.preference.PreferenceActivity} ca bn v cc thc th ca {@link
android.preference.PreferenceFragment} c trnh by trong cc phn v <a href="#Activity">To mt Hot ng Ty chn</a> v <a href="#Fragment">S dng
Phn on Ty chn</a>.</p>


<h3 id="SettingTypes">Ty chn</h3>

<p>Mi thit t cho ng dng ca bn u c biu din bi mt lp con c th ca lp {@link
android.preference.Preference}. Mi lp con li bao gm mt tp hp cc tnh cht ct li cho php bn
quy nh nhng th nh tiu  cho thit t v gi tr mc nh. Mi lp con cng cung cp
cc tnh cht v giao din ngi dng chuyn dng ca chnh n. V d, hnh 1 mnh ha mt nh chp mn hnh t thit t ca ng dng
Messaging. Mi mc danh sch trong mn hnh thit t c h tr bi mt i tng {@link
android.preference.Preference} khc nhau.</p>

<p>Sau y l mt s ty chn ph bin nht:</p>

<dl>
  <dt>{@link android.preference.CheckBoxPreference}</dt>
  <dd>Hin th mt mc km mt hp kim cho thit t hoc c kch hot hoc b v hiu ha. Gi tr
c lu l mt boolean (<code>true</code> nu n c chn).</dd>

  <dt>{@link android.preference.ListPreference}</dt>
  <dd>M mt hp thoi km danh sch nt chn mt. Gi tr c lu
c th l bt k loi gi tr c h tr no (lit k bn trn).</dd>

  <dt>{@link android.preference.EditTextPreference}</dt>
  <dd>M mt hp thoi km mt widget {@link android.widget.EditText}. Gi tr c lu l mt {@link
java.lang.String}.</dd>
</dl>

<p>Xem lp {@link android.preference.Preference}  bit danh sch tt c cc lp con khc v tnh cht
tng ng ca chng.</p>

<p>D nhin, cc lp tch hp khng p ng mi nhu cu v ng dng ca bn c th yu cu
lp con chuyn dng hn. V d, nn tng ny hin cha cung cp mt lp {@link
android.preference.Preference} cho vic chn mt s hay ngy. V th, bn c th cn phi nh ngha
lp con {@link android.preference.Preference} ca chnh mnh.  c tr gip khi lm vy, hy xem phn v <a href="#Custom">Xy dng Thit t Ty chnh</a>.</p>



<h2 id="DefiningPrefs">nh ngha Ty chn trong XML</h2>

<p>Mc d bn c th khi to cc i tng {@link android.preference.Preference} mi vo thi gian chy, bn
nn nh ngha danh sch cc thit t ca mnh trong XML km mt phn cp ca cc i tng {@link android.preference.Preference}
. Vic s dng mt tp XML  nh ngha b su tp thit t ca bn s c u tin v tp
cung cp mt cu trc d c, cp nht n gin. Bn cnh , cc thit t ng dng ca bn thng c
xc nh trc, mc d bn vn c th sa i b su tp vo thi gian chy.</p>

<p>Mi lp con {@link android.preference.Preference} c th c khai bo bng mt phn t XML m
khp vi tn lp , chng hn nh {@code &lt;CheckBoxPreference&gt;}.</p>

<p>Bn phi lu tp XML trong th mc {@code res/xml/}. Mc d bn c th t tn tp l
bt c th g mnh mun, n thng c t tn l{@code preferences.xml}. Bn thng ch cn mt tp,
bi cc nhnh trong phn cp (m m danh sch thit t ca ring chng) s c khai bo bng cch s dng cc thc th
lng nhau ca {@link android.preference.PreferenceScreen}.</p>

<p class="note"><strong>Lu :</strong> Nu bn mun to mt b tr a bng cho thit t
ca mnh, vy bn nn tch ring cc tp XML cho tng phn on.</p>

<p>Node gc cho tp XML phi l mt phn t {@link android.preference.PreferenceScreen
&lt;PreferenceScreen&gt;}. Trong phn t ny l ni bn thm tng {@link
android.preference.Preference}. Tng phn t con m bn thm vo trong phn t
{@link android.preference.PreferenceScreen &lt;PreferenceScreen&gt;} s xut hin nh mt mc
n l trong danh sch thit t.</p>

<p>V d:</p>

<pre>
&lt;?xml version="1.0" encoding="utf-8"?>
&lt;PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
    &lt;CheckBoxPreference
        android:key="pref_sync"
        android:title="@string/pref_sync"
        android:summary="@string/pref_sync_summ"
        android:defaultValue="true" />
    &lt;ListPreference
        android:dependency="pref_sync"
        android:key="pref_syncConnectionType"
        android:title="@string/pref_syncConnectionType"
        android:dialogTitle="@string/pref_syncConnectionType"
        android:entries="@array/pref_syncConnectionTypes_entries"
        android:entryValues="@array/pref_syncConnectionTypes_values"
        android:defaultValue="@string/pref_syncConnectionTypes_default" />
&lt;/PreferenceScreen>
</pre>

<p>Trong v d ny, c mt {@link android.preference.CheckBoxPreference} v mt {@link
android.preference.ListPreference}. C hai mc u bao gm ba thuc tnh sau:</p>

<dl>
  <dt>{@code android:key}</dt>
  <dd>Thuc tnh ny c yu cu cho cc ty chn duy tr mt gi tr d liu. N quy nh kha
(xu) duy nht m h thng s dng khi lu gi tr ca thit t ny trong {@link
android.content.SharedPreferences}. 
  <p>Cc thc th duy nht m thuc tnh ny khng <em>c yu cu</em> l khi ty chn l mt
{@link android.preference.PreferenceCategory} hoc {@link android.preference.PreferenceScreen}, hoc
ty chn quy nh mt {@link android.content.Intent}  gi ra (bng phn t <a href="#Intents">{@code &lt;intent&gt;}</a>) hoc {@link android.app.Fragment}  hin th (bng thuc tnh <a href="{@docRoot}reference/android/preference/Preference.html#attr_android:fragment">{@code
android:fragment}</a>).</p>
  </dd>
  <dt>{@code android:title}</dt>
  <dd>Thuc tnh ny cung cp mt tn hin th vi ngi dng cho thit t.</dd>
  <dt>{@code android:defaultValue}</dt>
  <dd>N quy nh gi tr ban u m h thng nn t trong tp {@link
android.content.SharedPreferences}. Bn nn cung cp mt gi tr mc nh cho tt c
thit t.</dd>
</dl>

<p> bit thng tin v tt c thuc tnh c h tr khc, hy xem ti liu {@link
android.preference.Preference} (v lp con tng ng).</p>


<div class="figure" style="width:300px">
  <img src="{@docRoot}images/ui/settings/settings-titles.png" alt="" />
  <p class="img-caption"><strong>Hnh 2.</strong> Thit t th loi
    c tiu . <br/><b>1.</b> Th loi c quy nh bi phn t {@link
android.preference.PreferenceCategory &lt;PreferenceCategory&gt;}. <br/><b>2.</b> Tiu 
c quy nh bng thuc tnh {@code android:title}.</p>
</div>


<p>Khi danh sch thit t ca bn vt qu khong 10 mc, bn c th mun thm tiu  
nh ngha cc nhm thit t hoc hin th cc nhm  trong mt
mn hnh ring. Nhng ty chn ny c m t trong cc phn sau.</p>


<h3 id="Groups">To nhm thit t</h3>

<p>Nu bn trnh by mt danh sch t 10 thit t tr ln, ngi dng
c th gp kh khn trong vic d tm, hiu v x l chng. Bn c th khc phc iu ny bng cch
chia mt s hoc tt c thit t thnh cc nhm, qua  bin mt danh sch di thnh nhiu
danh sch ngn hn. Mt nhm cc thit t c lin quan c th c trnh by bng mt trong hai cch:</p>

<ul>
  <li><a href="#Titles">S dng tiu </a></li>
  <li><a href="#Subscreens">S dng mn hnh con</a></li>
</ul>

<p>Bn c th s dng mt hoc c hai k thut to nhm ny  sp xp cc thit t cho ng dng ca mnh. Khi
quyt nh s dng ci no v lm th no  chia cc thit t ca mnh, bn nn tun theo cc hng dn trong ti liu hng dn
<a href="{@docRoot}design/patterns/settings.html">Thit t</a> ca Thit k Android.</p>


<h4 id="Titles">S dng tiu </h4>

<p>Nu bn mun cung cp cc thanh chia c tiu  gia cc nhm thit t (nh minh ha trong hnh 2),
hy t tng nhm i tng {@link android.preference.Preference} vo bn trong mt {@link
android.preference.PreferenceCategory}.</p>

<p>V d:</p>

<pre>
&lt;PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
    &lt;PreferenceCategory 
        android:title="&#64;string/pref_sms_storage_title"
        android:key="pref_key_storage_settings">
        &lt;CheckBoxPreference
            android:key="pref_key_auto_delete"
            android:summary="&#64;string/pref_summary_auto_delete"
            android:title="&#64;string/pref_title_auto_delete"
            android:defaultValue="false"... />
        &lt;Preference 
            android:key="pref_key_sms_delete_limit"
            android:dependency="pref_key_auto_delete"
            android:summary="&#64;string/pref_summary_delete_limit"
            android:title="&#64;string/pref_title_sms_delete"... />
        &lt;Preference 
            android:key="pref_key_mms_delete_limit"
            android:dependency="pref_key_auto_delete"
            android:summary="&#64;string/pref_summary_delete_limit"
            android:title="&#64;string/pref_title_mms_delete" ... />
    &lt;/PreferenceCategory>
    ...
&lt;/PreferenceScreen>
</pre>


<h4 id="Subscreens">S dng mn hnh con</h4>

<p>Nu bn mun t cc nhm thit t vo mt mn hnh con (nh minh ha trong hnh 3), hy t nhm
cc i tng {@link android.preference.Preference} vo bn trong mt {@link
android.preference.PreferenceScreen}.</p>

<img src="{@docRoot}images/ui/settings/settings-subscreen.png" alt="" />
<p class="img-caption"><strong>Hnh 3.</strong> Mn hnh con thit t. Phn t {@code
&lt;PreferenceScreen&gt;} s to
mt mc m, khi c chn, n s m ra mt danh sch ring  hin th cc thit t lng nhau.</p>

<p>V d:</p>

<pre>
&lt;PreferenceScreen  xmlns:android="http://schemas.android.com/apk/res/android">
    &lt;!-- opens a subscreen of settings -->
    &lt;PreferenceScreen
        android:key="button_voicemail_category_key"
        android:title="&#64;string/voicemail"
        android:persistent="false">
        &lt;ListPreference
            android:key="button_voicemail_provider_key"
            android:title="&#64;string/voicemail_provider" ... />
        &lt;!-- opens another nested subscreen -->
        &lt;PreferenceScreen
            android:key="button_voicemail_setting_key"
            android:title="&#64;string/voicemail_settings"
            android:persistent="false">
            ...
        &lt;/PreferenceScreen>
        &lt;RingtonePreference
            android:key="button_voicemail_ringtone_key"
            android:title="&#64;string/voicemail_ringtone_title"
            android:ringtoneType="notification" ... />
        ...
    &lt;/PreferenceScreen>
    ...
&lt;/PreferenceScreen>
</pre>


<h3 id="Intents">S dng  nh</h3>

<p>Trong mt s trng hp, bn c th mun mt mc ty chn m mt hot ng khc thay v mt
mn hnh thit t, chng hn nh mt trnh duyt web  xem mt trang web.  gi ra mt {@link
android.content.Intent} khi ngi dng chn mt mc ty chn, hy thm mt phn t {@code &lt;intent&gt;}
lm con ca phn t {@code &lt;Preference&gt;} tng ng.</p>

<p>V d, sau y l cch bn c th s dng mt mc ty chn  m mt trang web:</p>

<pre>
&lt;Preference android:title="@string/prefs_web_page" >
    &lt;intent android:action="android.intent.action.VIEW"
            android:data="http://www.example.com" />
&lt;/Preference>
</pre>

<p>Bn c th to c  nh biu th v khng biu th bng cch s dng cc thuc tnh sau:</p>

<dl>
  <dt>{@code android:action}</dt>
    <dd>Hnh ng cn gn, theo mi phng php {@link android.content.Intent#setAction setAction()}
.</dd>
  <dt>{@code android:data}</dt>
    <dd>D liu cn gn, theo mi phng php {@link android.content.Intent#setData setData()}.</dd>
  <dt>{@code android:mimeType}</dt>
    <dd>Kiu MIME cn gn, theo mi phng php {@link android.content.Intent#setType setType()}
.</dd>
  <dt>{@code android:targetClass}</dt>
    <dd>Phn lp ca tn thnh phn, theo mi phng php {@link android.content.Intent#setComponent
setComponent()}.</dd>
  <dt>{@code android:targetPackage}</dt>
    <dd>Phn gi ca tn thnh phn, theo mi phng php {@link
android.content.Intent#setComponent setComponent()}.</dd>
</dl>



<h2 id="Activity">To mt Hot ng Ty chn</h2>

<p> hin th thit t ca bn trong mt hot ng, hy m rng lp {@link
android.preference.PreferenceActivity}. y l phn m rng ca lp {@link
android.app.Activity} truyn thng m hin th mt danh sch cc thit t da trn mt phn cp ca cc i tng {@link
android.preference.Preference}. {@link android.preference.PreferenceActivity}
s t ng duy tr cc thit t lin kt vi tng {@link
android.preference.Preference} khi ngi dng thc hin mt thay i.</p>

<p class="note"><strong>Lu :</strong> Nu bn ang pht trin ng dng ca mnh cho phin bn Android 3.0 v
cao hn, thay vo  bn nn s dng {@link android.preference.PreferenceFragment}. i n phn
tip theo v <a href="#Fragment">S dng Phn on Ty chn</a>.</p>

<p>iu quan trng nht cn nh  l bn khng c ti mt b tr dng xem trong khi gi li {@link
android.preference.PreferenceActivity#onCreate onCreate()}. Thay vo , bn hy gi {@link
android.preference.PreferenceActivity#addPreferencesFromResource addPreferencesFromResource()} 
thm ty chn m bn  khai bo trong mt tp XML vo hot ng. V d, sau y l on m ti thiu
cn thit cho mt {@link android.preference.PreferenceActivity} chc nng:</p>

<pre>
public class SettingsActivity extends PreferenceActivity {
    &#64;Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.preferences);
    }
}
</pre>

<p>y l on m va  cho mt s ng dng bi ngay khi ngi dng sa i mt ty chn,
h thng s lu thay i i vi tp {@link android.content.SharedPreferences} mc nh m cc
thnh phn ng dng khc ca bn c th c khi bn cn kim tra thit t ca ngi dng. Tuy nhin,
nhiu ng dng li yu cu thm m  theo di nhng thay i xy ra vi cc ty chn .
 bit thng tin v vic theo di thay i trong tp {@link android.content.SharedPreferences},
hy xem phn v <a href="#ReadingPrefs">c Ty chn</a>.</p>




<h2 id="Fragment">S dng Phn on Ty chn</h2>

<p>Nu bn ang pht trin cho phin bn Android 3.0 (API mc 11) tr ln, bn nn s dng mt {@link
android.preference.PreferenceFragment}  hin th danh sch cc i tng {@link android.preference.Preference}
ca bn. Bn c th thm mt {@link android.preference.PreferenceFragment} vo bt k hot ng no&mdash;bn khng cn
s dng {@link android.preference.PreferenceActivity}.</p>

<p><a href="{@docRoot}guide/components/fragments.html">Phn on</a> cung cp mt kin trc
linh hot hn cho ng dng ca bn, so vi vic s dng ch cc hot ng, d loi hot ng
m bn ang xy dng l g. Nh vy, chng ti gi  bn s dng {@link
android.preference.PreferenceFragment}  kim sot hin th cc thit t ca mnh thay cho {@link
android.preference.PreferenceActivity} khi c th.</p>

<p>Vic trin khai {@link android.preference.PreferenceFragment} c th ch n gin nh
nh ngha phng php {@link android.preference.PreferenceFragment#onCreate onCreate()}  ti mt
tp ty chn bng {@link android.preference.PreferenceFragment#addPreferencesFromResource
addPreferencesFromResource()}. V d:</p>

<pre>
public static class SettingsFragment extends PreferenceFragment {
    &#64;Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Load the preferences from an XML resource
        addPreferencesFromResource(R.xml.preferences);
    }
    ...
}
</pre>

<p>Khi , bn c th thm phn on ny vo mt {@link android.app.Activity} ging nh cch m bn s lm vi bt k
{@link android.app.Fragment} no khc. V d:</p>

<pre>
public class SettingsActivity extends Activity {
    &#64;Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Display the fragment as the main content.
        getFragmentManager().beginTransaction()
                .replace(android.R.id.content, new SettingsFragment())
                .commit();
    }
}
</pre>

<p class="note"><strong>Lu :</strong> {@link android.preference.PreferenceFragment} khng c mt
i tng {@link android.content.Context} ca chnh n. Nu bn cn mt i tng {@link android.content.Context}
, bn c th gi {@link android.app.Fragment#getActivity()}. Tuy nhin, hy chc chn l ch gi
{@link android.app.Fragment#getActivity()} khi phn on  c gn km vi mt hot ng. Khi
phn on cha c gn km, hoc b b gn km trong khi kt thc vng i ca n, {@link
android.app.Fragment#getActivity()} s tr v rng.</p>


<h2 id="Defaults">Thit t Gi tr Mc nh</h2>

<p>Ty chn m bn to c th nh ngha mt s hnh vi quan trng cho ng dng ca bn, v th
bn cn phi khi to tp {@link android.content.SharedPreferences} km theo vi cc
gi tr mc nh cho tng {@link android.preference.Preference} khi ngi dng ln u m
ng dng ca bn.</p>

<p>iu u tin bn phi lm  l quy nh mt gi tr mc nh cho tng i tng {@link
android.preference.Preference}
trong tp XML ca bn bng cch s dng thuc tnh {@code android:defaultValue}. Gi tr  c th l bt k kiu
d liu no m ph hp vi i tng {@link android.preference.Preference} tng ng. V
d:</p>

<pre>
&lt;!-- default value is a boolean -->
&lt;CheckBoxPreference
    android:defaultValue="true"
    ... />

&lt;!-- default value is a string -->
&lt;ListPreference
    android:defaultValue="@string/pref_syncConnectionTypes_default"
    ... />
</pre>

<p>Khi , t phng php {@link android.app.Activity#onCreate onCreate()} trong hot ng chnh
&mdash;ca ng dng ca bn v trong bt k hot ng no khc m thng qua  ngi dng c th vo ng dng ca bn ln
u tin&mdash;hy gi {@link android.preference.PreferenceManager#setDefaultValues
setDefaultValues()}:</p>

<pre>
PreferenceManager.setDefaultValues(this, R.xml.advanced_preferences, false);
</pre>

<p>Vic gi ny trong khi {@link android.app.Activity#onCreate onCreate()} s m bo rng
ng dng ca bn c khi to ph hp vi cc thit t mc nh m ng dng ca bn c th cn
c  xc nh mt s hnh vi (chng hn nh c ti xung d liu trong khi ang trn
mng di ng hay khng).</p>

<p>Phng php ny dng ba tham i:</p>
<ul>
  <li>{@link android.content.Context} ng dng ca bn.</li>
  <li>ID ti nguyn cho tp XML ty chn m bn mun t cc gi tr mc nh cho.</li>
  <li>Mt boolean cho bit cc gi tr mc nh c nn c t nhiu hn mt ln hay khng.
<p>Khi tham i ny l <code>false</code>, h thng s t cc gi tr mc nh ch khi phng php ny cha tng c
gi trc y (hoc {@link android.preference.PreferenceManager#KEY_HAS_SET_DEFAULT_VALUES}
trong tp ty chn c chia s gi tr mc nh l sai).</p></li>
</ul>

<p>Min l bn t tham i th ba ny thnh <code>false</code>, bn c th gi phng php ny mt cch an ton
mi khi hot ng ca bn bt u m khng khng ch cc ty chn  lu ca ngi dng bng cch t li chng thnh
mc nh. Tuy nhin, nu bn t n thnh <code>true</code>, bn s khng ch mi gi tr
trc  bng cc gi tr mc nh.</p>



<h2 id="PreferenceHeaders">S dng Tiu  Ty chn</h2>

<p>Trong vi trng hp him gp, bn c th mun thit k cc thit t ca mnh sao cho mn hnh th nht
ch hin th mt danh sch <a href="#Subscreens">cc mn hnh con</a> (chng hn nh trong ng dng Thit t ca h thng,
nh minh ha trong cc hnh 4 v 5). Khi pht trin thit k nh vy cho phin bn Android 3.0 tr ln, bn
nn s dng tnh nng "tiu " mi trong Android 3.0, thay v xy dng mn hnh con vi cc phn t
{@link android.preference.PreferenceScreen} lng nhau.</p>

<p> xy dng thit t c tiu  ca mnh, bn cn:</p>
<ol>
  <li>Tch ring tng nhm thit t thnh cc thc th ring ca {@link
android.preference.PreferenceFragment}. C th, mi nhm thit t cn mt tp XML
ring.</li>
  <li>To mt tp tiu  XML lit k tng nhm thit t v khai bo phn on no
cha danh sch thit t tng ng.</li>
  <li>M rng lp {@link android.preference.PreferenceActivity}  lu tr cc thit t ca bn.</li>
  <li>Trin khai lnh gi li {@link
android.preference.PreferenceActivity#onBuildHeaders onBuildHeaders()}  quy nh
tp tiu .</li>
</ol>

<p>Mt li ch tuyt vi i vi vic s dng thit k ny  l {@link android.preference.PreferenceActivity}
t ng trnh by b tr hai bng nh minh ha trong hnh 4 khi chy trn mn hnh ln.</p>

<p>Ngay c khi ng dng ca bn h tr cc phin bn Android c hn 3.0, bn c th xy dng ng dng
ca mnh  s dng {@link android.preference.PreferenceFragment} cho mt trnh chiu hai bng trn
cc thit b mi hn, trong khi vn h tr phn cp a mn hnh truyn thng trn cc thit b
c hn (xem phn ni v <a href="#BackCompatHeaders">H tr cc phin bn c hn
vi tiu  ty chn</a>).</p>

<img src="{@docRoot}images/ui/settings/settings-headers-tablet.png" alt="" />
<p class="img-caption"><strong>Hnh 4.</strong> B tr c hai bng vi tiu . <br/><b>1.</b> 
Tiu  c nh ngha trong mt tp tiu  XML. <br/><b>2.</b> Mi nhm thit t c nh ngha bi mt
{@link android.preference.PreferenceFragment}, c quy nh bi mt phn t {@code &lt;header&gt;} trong tp tiu 
.</p>

<img src="{@docRoot}images/ui/settings/settings-headers-handset.png" alt="" />
<p class="img-caption"><strong>Hnh 5.</strong> Thit b cm tay vi cc tiu  thit t. Khi mt
mc c chn, {@link android.preference.PreferenceFragment} c lin kt s thay th
tiu .</p>


<h3 id="CreateHeaders" style="clear:left">To tp tiu </h3>

<p>Mi nhm thit t trong danh sch tiu  ca bn c quy nh bi mt phn t {@code &lt;header&gt;}
n l bn trong mt phn t {@code &lt;preference-headers&gt;} gc. V d:</p>

<pre>
&lt;?xml version="1.0" encoding="utf-8"?>
&lt;preference-headers xmlns:android="http://schemas.android.com/apk/res/android">
    &lt;header 
        android:fragment="com.example.prefs.SettingsActivity$SettingsFragmentOne"
        android:title="@string/prefs_category_one"
        android:summary="@string/prefs_summ_category_one" />
    &lt;header 
        android:fragment="com.example.prefs.SettingsActivity$SettingsFragmentTwo"
        android:title="@string/prefs_category_two"
        android:summary="@string/prefs_summ_category_two" >
        &lt;!-- key/value pairs can be included as arguments for the fragment. -->
        &lt;extra android:name="someKey" android:value="someHeaderValue" />
    &lt;/header>
&lt;/preference-headers>
</pre>

<p>Vi thuc tnh {@code android:fragment}, mi tiu  s khai bo mt thc th ca {@link
android.preference.PreferenceFragment} m s m khi ngi dng chn tiu  .</p>

<p>Phn t {@code &lt;extras&gt;} cho php bn chuyn cc cp kha-gi tr sang phn on trong mt {@link
android.os.Bundle}. Phn on c th truy xut cc tham i bng cch gi {@link
android.app.Fragment#getArguments()}. Bn c th chuyn cc tham i ti phn on v nhiu
l do khc nhau, nhng mt l do chnh ng  l  s dng li cng lp con ca {@link
android.preference.PreferenceFragment} cho mi nhm v s dng tham i  quy nh
tp XML ty chn no m phn on cn ti.</p>

<p>V d, sau y l mt phn on m c th c ti s dng cho nhiu nhm thit t, khi tng
tiu  nh ngha mt tham i {@code &lt;extra&gt;} vi kha {@code "settings"}:</p>

<pre>
public static class SettingsFragment extends PreferenceFragment {
    &#64;Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        String settings = getArguments().getString("settings");
        if ("notifications".equals(settings)) {
            addPreferencesFromResource(R.xml.settings_wifi);
        } else if ("sync".equals(settings)) {
            addPreferencesFromResource(R.xml.settings_sync);
        }
    }
}
</pre>



<h3 id="DisplayHeaders">Hin th tiu </h3>

<p> hin th tiu  ty chn, bn phi trin khai phng php gi li {@link
android.preference.PreferenceActivity#onBuildHeaders onBuildHeaders()} v gi
{@link android.preference.PreferenceActivity#loadHeadersFromResource
loadHeadersFromResource()}. V d:</p>

<pre>
public class SettingsActivity extends PreferenceActivity {
    &#64;Override
    public void onBuildHeaders(List&lt;Header> target) {
        loadHeadersFromResource(R.xml.preference_headers, target);
    }
}
</pre>

<p>Khi ngi dng chn mt mc t danh sch tiu , h thng s m {@link
android.preference.PreferenceFragment} km theo.</p>

<p class="note"><strong>Lu :</strong> Khi s dng tiu  ty chn, lp con {@link
android.preference.PreferenceActivity} ca bn khng cn trin khai phng php {@link
android.preference.PreferenceActivity#onCreate onCreate()}, v tc v cn thit duy nht
cho hot ng  l ti tiu .</p>


<h3 id="BackCompatHeaders">H tr cc phin bn c hn vi tiu  ty chn</h3>

<p>Nu ng dng ca bn h tr cc phin bn Android c hn 3.0, bn vn c th s dng tiu  
cung cp mt b tr hai bng khi chy trn Android 3.0 tr ln. Tt c nhng vic bn cn lm  l to mt
tp XML ty chn b sung c s dng phn t c bn {@link android.preference.Preference
&lt;Preference&gt;} ng vai tr nh mc tiu  ( dng cho cc phin bn Android
c hn).</p>

<p>Tuy nhin, thay v m mt {@link android.preference.PreferenceScreen} mi, tng phn t {@link
android.preference.Preference &lt;Preference&gt;} s gi mt {@link android.content.Intent} ti
{@link android.preference.PreferenceActivity} m quy nh tp XML ty chn cn
ti.</p>

<p>V d, sau y l mt tp XML cho cc tiu  ty chn c s dng trn Android 3.0
tr ln ({@code res/xml/preference_headers.xml}):</p> 

<pre>
&lt;preference-headers xmlns:android="http://schemas.android.com/apk/res/android">
    &lt;header 
        android:fragment="com.example.prefs.SettingsFragmentOne"
        android:title="@string/prefs_category_one"
        android:summary="@string/prefs_summ_category_one" />
    &lt;header 
        android:fragment="com.example.prefs.SettingsFragmentTwo"
        android:title="@string/prefs_category_two"
        android:summary="@string/prefs_summ_category_two" />
&lt;/preference-headers>
</pre>

<p>V sau y l mt tp ty chn cung cp cng cc tiu  cho cc phin bn c hn
Android 3.0 ({@code res/xml/preference_headers_legacy.xml}):</p>

<pre>
&lt;PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
    &lt;Preference 
        android:title="@string/prefs_category_one"
        android:summary="@string/prefs_summ_category_one"  >
        &lt;intent 
            android:targetPackage="com.example.prefs"
            android:targetClass="com.example.prefs.SettingsActivity"
            android:action="com.example.prefs.PREFS_ONE" />
    &lt;/Preference>
    &lt;Preference 
        android:title="@string/prefs_category_two"
        android:summary="@string/prefs_summ_category_two" >
        &lt;intent 
            android:targetPackage="com.example.prefs"
            android:targetClass="com.example.prefs.SettingsActivity"
            android:action="com.example.prefs.PREFS_TWO" />
    &lt;/Preference>
&lt;/PreferenceScreen>
</pre>

<p>V h tr dnh cho {@code &lt;preference-headers&gt;}  c thm trong Android 3.0, h thng s gi
{@link android.preference.PreferenceActivity#onBuildHeaders onBuildHeaders()} trong {@link
android.preference.PreferenceActivity} ca bn ch khi ang chy trn phin bn Androd 3.0 hoc cao hn.  ti
tp tiu  "k tha" ({@code preference_headers_legacy.xml}), bn phi kim tra phin bn Android
v, nu phin bn c hn Android 3.0 ({@link
android.os.Build.VERSION_CODES#HONEYCOMB}), hy gi {@link
android.preference.PreferenceActivity#addPreferencesFromResource addPreferencesFromResource()} 
ti tp tiu  k tha. V d:</p>

<pre>
&#64;Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    ...

    if (Build.VERSION.SDK_INT &lt; Build.VERSION_CODES.HONEYCOMB) {
        // Load the legacy preferences headers
        addPreferencesFromResource(R.xml.preference_headers_legacy);
    }
}

// Called only on Honeycomb and later
&#64;Override
public void onBuildHeaders(List&lt;Header> target) {
   loadHeadersFromResource(R.xml.preference_headers, target);
}
</pre>

<p>Vic duy nht cn li cn lm  l x l {@link android.content.Intent} m c chuyn vo
hot ng  nhn bit tp ty chn no cn ti. V vy, hy truy xut hnh ng ca  nh v so snh n vi
cc xu hnh ng  bit m bn  s dng trong tag {@code &lt;intent&gt;} ca XML ty chn:</p>

<pre>
final static String ACTION_PREFS_ONE = "com.example.prefs.PREFS_ONE";
...

&#64;Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    String action = getIntent().getAction();
    if (action != null &amp;&amp; action.equals(ACTION_PREFS_ONE)) {
        addPreferencesFromResource(R.xml.preferences);
    }
    ...

    else if (Build.VERSION.SDK_INT &lt; Build.VERSION_CODES.HONEYCOMB) {
        // Load the legacy preferences headers
        addPreferencesFromResource(R.xml.preference_headers_legacy);
    }
}
</pre>

<p>Lu  rng cc lnh gi lin tip n {@link
android.preference.PreferenceActivity#addPreferencesFromResource addPreferencesFromResource()} s
xp chng tt c ty chn trong mt danh sch duy nht, v th hy chc chn rng n ch c gi mt ln bng cch lin kt cc
iu kin vi mnh  else-if.</p>





<h2 id="ReadingPrefs">c Ty chn</h2>

<p>Theo mc nh, tt c ty chn ca ng dng ca bn u c lu vo mt tp c th truy cp t bt k ni no
trong ng dng ca bn bng cch gi phng php tnh {@link
android.preference.PreferenceManager#getDefaultSharedPreferences
PreferenceManager.getDefaultSharedPreferences()}. iu ny s tr v i tng {@link
android.content.SharedPreferences} cha tt c cp kha-gi tr lin kt
vi cc i tng {@link android.preference.Preference} c s dng trong {@link
android.preference.PreferenceActivity}.</p>

<p>V d, sau y l cch bn c th c mt trong cc gi tr ty chn t bt k hot ng no khc trong ng dng
ca mnh:</p>

<pre>
SharedPreferences sharedPref = PreferenceManager.getDefaultSharedPreferences(this);
String syncConnPref = sharedPref.getString(SettingsActivity.KEY_PREF_SYNC_CONN, "");
</pre>



<h3 id="Listening">Theo di thay i ty chn</h3>

<p>C mt vi l do khin bn c th mun c thng bo cng sm cng tt nu ngi dng thay i mt trong cc
ty chn.  nhn mt phng php gi li khi thay i xy ra vi bt k ty chn no,
hy trin khai giao din {@link android.content.SharedPreferences.OnSharedPreferenceChangeListener
SharedPreference.OnSharedPreferenceChangeListener} v ng k i tng theo di cho i tng
{@link android.content.SharedPreferences} bng cch gi {@link
android.content.SharedPreferences#registerOnSharedPreferenceChangeListener
registerOnSharedPreferenceChangeListener()}.</p>

<p>Giao din ny ch c mt phng php gi li, {@link
android.content.SharedPreferences.OnSharedPreferenceChangeListener#onSharedPreferenceChanged
onSharedPreferenceChanged()}, v bn c th thy y l cch d nht  trin khai giao din nh mt phn
hot ng ca mnh. V d:</p>

<pre>
public class SettingsActivity extends PreferenceActivity
                              implements OnSharedPreferenceChangeListener {
    public static final String KEY_PREF_SYNC_CONN = "pref_syncConnectionType";
    ...

    public void onSharedPreferenceChanged(SharedPreferences sharedPreferences,
        String key) {
        if (key.equals(KEY_PREF_SYNC_CONN)) {
            Preference connectionPref = findPreference(key);
            // Set summary to be the user-description for the selected value
            connectionPref.setSummary(sharedPreferences.getString(key, ""));
        }
    }
}
</pre>

<p>Trong v d ny, phng php s kim tra xem thit t b thay i c p dng cho mt kha ty chn  bit khng. N
s gi {@link android.preference.PreferenceActivity#findPreference findPreference()}  nhn i tng
{@link android.preference.Preference}  b thay i  n c th sa i tm tt
ca mc  thnh m t la chn ca ngi dng. C th, khi thit t l mt {@link
android.preference.ListPreference} hoc thit t nhiu la chn khc, bn nn gi {@link
android.preference.Preference#setSummary setSummary()} khi thit t thay i  hin th
trng thi hin ti (chng hn nh thit t Ng nh minh ha trong hnh 5).</p>

<p class="note"><strong>Lu :</strong> Nh  m t trong ti liu Thit k Android v <a href="{@docRoot}design/patterns/settings.html">Thit t</a>, chng ti khuyn bn nn cp nht
tm tt cho {@link android.preference.ListPreference} mi khi ngi dng thay i ty chn  
m t thit t hin ti.</p>

<p> qun l vng i trong hot ng cho ph hp, chng ti khuyn rng bn nn ng k v b ng k
{@link android.content.SharedPreferences.OnSharedPreferenceChangeListener} ca mnh tng ng trong {@link
android.app.Activity#onResume} v cc lnh gi li {@link android.app.Activity#onPause}:</p>

<pre>
&#64;Override
protected void onResume() {
    super.onResume();
    getPreferenceScreen().getSharedPreferences()
            .registerOnSharedPreferenceChangeListener(this);
}

&#64;Override
protected void onPause() {
    super.onPause();
    getPreferenceScreen().getSharedPreferences()
            .unregisterOnSharedPreferenceChangeListener(this);
}
</pre>

<p class="caution"><strong>Ch :</strong> Khi bn gi {@link
android.content.SharedPreferences#registerOnSharedPreferenceChangeListener
registerOnSharedPreferenceChangeListener()}, trnh qun l ty chn hin
khng lu tr mt tham chiu mnh ti i tng theo di. Bn phi lu tr mt tham chiu
mnh ti i tng theo di, nu khng n s d b thu thp thng tin rc. Chng ti
khuyn bn nn gi mt tham chiu ti i tng theo di trong d liu thc th ca mt i tng
m s tn ti min l bn cn cn i tng theo di .</p>

<p>V d, trong on m sau, hm gi khng gi tham chiu ti
i tng theo di. Kt qu l i tng theo di s b thu thp thng tin rc,
v n s b li ti mt thi im khng xc nh trong tng lai:</p>

<pre>
prefs.registerOnSharedPreferenceChangeListener(
  // Bad! The listener is subject to garbage collection!
  new SharedPreferences.OnSharedPreferenceChangeListener() {
  public void onSharedPreferenceChanged(SharedPreferences prefs, String key) {
    // listener implementation
  }
});
</pre>

<p>Thay vo , hy lu mt tham chiu ti i tng theo di trong mt trng d liu thc th ca mt
i tng m s tn ti min l cn cn i tng theo di :</p>

<pre>
SharedPreferences.OnSharedPreferenceChangeListener listener =
    new SharedPreferences.OnSharedPreferenceChangeListener() {
  public void onSharedPreferenceChanged(SharedPreferences prefs, String key) {
    // listener implementation
  }
};
prefs.registerOnSharedPreferenceChangeListener(listener);
</pre>

<h2 id="NetworkUsage">Qun l S dng Mng</h2>


<p>Bt u vi Android 4.0, ng dng Thit t ca h thng s cho php ngi dng xem
ng dng ca h ang s dng bao nhiu d liu mng khi ang  tin cnh v di nn. Khi , ngi dng c th
v hiu ha vic s dng d liu chy ngm cho tng ng dng.  trnh vic ngi dng v hiu ha truy cp d liu
ca ng dng ca bn t di nn, bn nn s dng kt ni d liu mt cch hiu qu v cho php
ngi dng tinh chnh mc s dng d liu cho ng dng ca bn thng qua thit t ng dng.<p>

<p>V d, bn c th cho php ngi dng kim sot tn sut ng dng ca bn ng b d liu, ng dng ca bn
ch c thc hin ti ln/ti xung khi trn Wi-Fi, ng dng ca bn s dng d liu trong khi ang chuyn vng d liu, v.v... hay khng. Vi 
nhng kim sot ny, ngi dng s t c kh nng v hiu ha truy cp d liu ca ng dng ca bn
hn nhiu khi h t gn mc gii hn t ra trong Thit t h thng, v thay vo , h c th kim sot chnh xc
lng d liu m ng dng ca bn s dng.</p>

<p>Sau khi bn  thm cc ty chn cn thit trong {@link android.preference.PreferenceActivity}
ca mnh  kim sot cc thi quen d liu ca ng dng ca bn, bn nn thm mt b lc  nh cho {@link
android.content.Intent#ACTION_MANAGE_NETWORK_USAGE} trong tp bn k khai ca mnh. V d:</p>

<pre>
&lt;activity android:name="SettingsActivity" ... >
    &lt;intent-filter>
       &lt;action android:name="android.intent.action.MANAGE_NETWORK_USAGE" />
       &lt;category android:name="android.intent.category.DEFAULT" />
    &lt;/intent-filter>
&lt;/activity>
</pre>

<p>B lc  nh ny cho h thng bit rng y l hot ng kim sot mc s dng d liu
ca ng dng ca bn. V th, khi ngi dng kim tra lng d liu m ng dng ca bn ang dng t ng dng
Thit t ca h thng, s c mt nt <em>Xem thit t ng dng</em> khi chy
{@link android.preference.PreferenceActivity} ca bn, v th ngi dng c th tinh chnh lng d liu m ng dng ca bn
dng.</p>







<h2 id="Custom">Xy dng mt Thit t Ty chnh</h2>

<p>Khun kh Android bao gm nhiu lp con {@link android.preference.Preference} m
cho php bn xy dng mt UI cho mt vi loi thit t khc nhau.
Tuy nhin, bn c th khm ph thit t mnh cn m cha c gii php tch hp sn, chng hn nh mt
b chn s hay b chn ngy. Trong trng hp nh vy, bn s cn to mt ty chn ty chnh bng cch m rng
lp {@link android.preference.Preference} hoc mt trong cc lp con khc.</p>

<p>Khi bn m rng lp {@link android.preference.Preference}, c mt vi iu quan trng
m bn cn lm:</p>

<ul>
  <li>Quy nh giao din ngi dng s xut hin khi ngi dng chn thit t.</li>
  <li>Lu gi tr ca thit t khi ph hp.</li>
  <li>Khi to {@link android.preference.Preference} bng gi tr hin ti (hoc mc nh) 
khi xt ti dng xem.</li>
  <li>Cung cp gi tr mc nh khi h thng yu cu.</li>
  <li>Nu {@link android.preference.Preference} cung cp UI ca chnh mnh (chng hn nh mt hp thoi), hy lu
v khi phc trng thi  x l cc thay i trong vng i (chng hn nh khi ngi dng xoay mn hnh).</li>
</ul>

<p>Cc phn sau m t cch hon thnh tng tc v ny.</p>



<h3 id="CustomSelected">Quy nh mt giao din ngi dng</h3>

  <p>Nu bn trc tip m rng lp {@link android.preference.Preference}, bn cn trin khai
{@link android.preference.Preference#onClick()}  nh ngha hnh ng xy ra khi ngi dng
chn mc. Tuy nhin, hu ht cc thit t ty chnh s m rng {@link android.preference.DialogPreference} 
hin th mt hp thoi, iu ny lm n gin ha quy trnh. Khi bn m rng {@link
android.preference.DialogPreference}, bn phi gi {@link
android.preference.DialogPreference#setDialogLayoutResource setDialogLayoutResourcs()} trong khi ang  trong
hm dng lp  quy nh b tr cho hp thoi.</p>

  <p>V d, sau y l hm dng cho mt {@link
android.preference.DialogPreference} ty chnh m khai bo b tr v quy nh vn bn cho
cc nt hp thoi tch cc v tiu cc mc nh:</p>

<pre>
public class NumberPickerPreference extends DialogPreference {
    public NumberPickerPreference(Context context, AttributeSet attrs) {
        super(context, attrs);
        
        setDialogLayoutResource(R.layout.numberpicker_dialog);
        setPositiveButtonText(android.R.string.ok);
        setNegativeButtonText(android.R.string.cancel);
        
        setDialogIcon(null);
    }
    ...
}
</pre>



<h3 id="CustomSave">Lu gi tr ca thit t</h3>

<p>Bn c th lu mt gi tr cho thit t vo bt c lc no bng cch gi mt trong cc phng php ca lp {@link
android.preference.Preference}, {@code persist*()}, chng hn nh {@link
android.preference.Preference#persistInt persistInt()} nu gi tr ca thit t l mt s nguyn hoc
{@link android.preference.Preference#persistBoolean persistBoolean()}  lu mt boolean.</p>

<p class="note"><strong>Lu :</strong> Mi {@link android.preference.Preference} ch c th lu mt
kiu d liu, v th bn phi s dng phng php {@code persist*()} ph hp cho kiu d liu c s dng bi
{@link android.preference.Preference} ty chnh ca mnh.</p>

<p>Thi im bn chn duy tr thit t c th ph thuc vo lp {@link
android.preference.Preference} no m bn m rng. Nu m rng {@link
android.preference.DialogPreference}, khi  bn nn duy tr gi tr  ch khi hp thoi
ng li do kt qu tch cc (ngi dng chn nt "OK").</p>

<p>Khi {@link android.preference.DialogPreference} ng li, h thng s gi phng php {@link
android.preference.DialogPreference#onDialogClosed onDialogClosed()}. Phng php bao gm mt
tham i boolean quy nh xem ngi dng c tr v kt qu "tch cc" hay khng&mdash;nu kt qu l
<code>true</code>, khi , ngi dng  chn nt tch cc v bn nn lu gi tr mi ny. V
d:</p>

<pre>
&#64;Override
protected void onDialogClosed(boolean positiveResult) {
    // When the user selects "OK", persist the new value
    if (positiveResult) {
        persistInt(mNewValue);
    }
}
</pre>

<p>Trong v d ny, <code>mNewValue</code> l mt thnh vin lp lu gi gi tr
hin ti ca thit t. Vic gi {@link android.preference.Preference#persistInt persistInt()} s lu gi tr vo
tp {@link android.content.SharedPreferences} (t ng s dng kha m
c quy nh trong tp XML cho {@link android.preference.Preference} ny).</p>


<h3 id="CustomInitialize">Khi to gi tr hin ti</h3>

<p>Khi h thng thm {@link android.preference.Preference} ca bn vo mn hnh, n
gi {@link android.preference.Preference#onSetInitialValue onSetInitialValue()}  thng bo
vi bn xem thit t c gi tr c duy tr hay khng. Nu khng c gi tr c duy tr, lnh gi ny s cung cp
cho bn gi tr mc nh.</p>

<p>Phng php {@link android.preference.Preference#onSetInitialValue onSetInitialValue()} chuyn mt
boolean, <code>restorePersistedValue</code>,  cho bit liu gi tr  c duy tr 
cho thit t hay khng. Nu n l <code>true</code>, khi  bn nn truy xut gi tr c duy tr bng cch gi
mt trong cc phng php ca lp {@link
android.preference.Preference}, {@code getPersisted*()}, chng hn nh {@link
android.preference.Preference#getPersistedInt getPersistedInt()} i vi mt gi tr s nguyn. Bn s
thng mun truy xut gi tr c duy tr sao cho bn c th cp nht UI cho ph hp  phn nh
gi tr  lu trc .</p>

<p>Nu <code>restorePersistedValue</code> l <code>false</code>, vy bn
nn s dng gi tr mc nh c chuyn trong tham i th hai.</p>

<pre>
&#64;Override
protected void onSetInitialValue(boolean restorePersistedValue, Object defaultValue) {
    if (restorePersistedValue) {
        // Restore existing state
        mCurrentValue = this.getPersistedInt(DEFAULT_VALUE);
    } else {
        // Set default state from the XML attribute
        mCurrentValue = (Integer) defaultValue;
        persistInt(mCurrentValue);
    }
}
</pre>

<p>Mi phng php {@code getPersisted*()} s ly mt tham i quy nh
gi tr mc nh s s dng trong trng hp thc s khng c gi tr c duy tr hoc kha khng tn ti. Trong 
v d trn, mt hng s cc b c s dng  quy nh gi tr mc nh trong trng hp {@link
android.preference.Preference#getPersistedInt getPersistedInt()} khng th tr v mt gi tr c duy tr.</p>

<p class="caution"><strong>Ch :</strong> Bn <strong>khng th</strong> s dng
<code>defaultValue</code> lm gi tr mc nh trong phng php {@code getPersisted*()}, bi
gi tr ca n lun rng khi <code>restorePersistedValue</code> l <code>true</code>.</p>


<h3 id="CustomDefault">Cung cp mt gi tr mc nh</h3>

<p>Nu trng hp lp {@link android.preference.Preference} ca bn quy nh mt gi tr mc nh
(vi thuc tnh {@code android:defaultValue}), khi  h thng
s gi {@link android.preference.Preference#onGetDefaultValue
onGetDefaultValue()} khi n khi to i tng  truy xut gi tr. Bn phi
trin khai phng php ny  h thng lu gi tr mc nh trong {@link
android.content.SharedPreferences}. V d:</p>

<pre>
&#64;Override
protected Object onGetDefaultValue(TypedArray a, int index) {
    return a.getInteger(index, DEFAULT_VALUE);
}
</pre>

<p>Cc tham i ca phng php cung cp mi th bn cn: mng thuc tnh v v tr ch mc
ca {@code android:defaultValue} m bn phi truy xut. L do bn phi trin khai
phng php ny nhm trch xut gi tr mc nh t thuc tnh  l bi bn phi quy nh
mt gi tr mc nh cc b cho thuc tnh trong trng hp gi tr khng c nh ngha.</p>



<h3 id="CustomSaveState">Lu v khi phc trng thi ca Ty chn</h3>

<p>Ging nh {@link android.view.View} trong mt b tr, lp con {@link android.preference.Preference}
ca bn chu trch nhim lu v khi phc trng thi ca n trong trng hp hot ng hoc phn on
c khi ng li (chng hn nh khi ngi dng xoay mn hnh).  lu v khi phc
trng thi ca lp {@link android.preference.Preference} ca bn cho ng, bn phi trin khai cc
phng php gi li vng i {@link android.preference.Preference#onSaveInstanceState
onSaveInstanceState()} v {@link
android.preference.Preference#onRestoreInstanceState onRestoreInstanceState()}.</p>

<p>Trng thi ca {@link android.preference.Preference} ca bn c nh ngha bi mt i tng m trin khai
giao din {@link android.os.Parcelable}. Khun kh Android s cung cp mt i tng nh vy cho bn
nh mt im bt u  nh ngha i tng trng thi ca bn: lp {@link
android.preference.Preference.BaseSavedState}.</p>

<p> nh ngha cch thc lp {@link android.preference.Preference} ca bn lu trng thi ca n
hy m rng lp {@link android.preference.Preference.BaseSavedState}. Bn cn khng ch ch
 mt vi phng php v nh ngha i tng {@link android.preference.Preference.BaseSavedState#CREATOR}
.</p>

<p>i vi hu ht ng dng, bn c th sao chp trin khai sau v ch cn thay i cc dng
x l {@code value} nu lp con {@link android.preference.Preference} ca bn lu mt kiu
d liu khc s nguyn.</p>

<pre>
private static class SavedState extends BaseSavedState {
    // Member that holds the setting's value
    // Change this data type to match the type saved by your Preference
    int value;

    public SavedState(Parcelable superState) {
        super(superState);
    }

    public SavedState(Parcel source) {
        super(source);
        // Get the current preference's value
        value = source.readInt();  // Change this to read the appropriate data type
    }

    &#64;Override
    public void writeToParcel(Parcel dest, int flags) {
        super.writeToParcel(dest, flags);
        // Write the preference's value
        dest.writeInt(value);  // Change this to write the appropriate data type
    }

    // Standard creator object using an instance of this class
    public static final Parcelable.Creator&lt;SavedState> CREATOR =
            new Parcelable.Creator&lt;SavedState>() {

        public SavedState createFromParcel(Parcel in) {
            return new SavedState(in);
        }

        public SavedState[] newArray(int size) {
            return new SavedState[size];
        }
    };
}
</pre>

<p>Vi trin khai {@link android.preference.Preference.BaseSavedState} bn trn c thm
vo ng dng ca bn (thng di dng mt lp con ca lp con {@link android.preference.Preference} ca bn), khi 
bn cn trin khai cc phng php {@link android.preference.Preference#onSaveInstanceState
onSaveInstanceState()} v {@link
android.preference.Preference#onRestoreInstanceState onRestoreInstanceState()} cho lp con
{@link android.preference.Preference} ca mnh.</p>

<p>V d:</p>

<pre>
&#64;Override
protected Parcelable onSaveInstanceState() {
    final Parcelable superState = super.onSaveInstanceState();
    // Check whether this Preference is persistent (continually saved)
    if (isPersistent()) {
        // No need to save instance state since it's persistent,
        // use superclass state
        return superState;
    }

    // Create instance of custom BaseSavedState
    final SavedState myState = new SavedState(superState);
    // Set the state's value with the class member that holds current
    // setting value
    myState.value = mNewValue;
    return myState;
}

&#64;Override
protected void onRestoreInstanceState(Parcelable state) {
    // Check whether we saved the state in onSaveInstanceState
    if (state == null || !state.getClass().equals(SavedState.class)) {
        // Didn't save the state, so call superclass
        super.onRestoreInstanceState(state);
        return;
    }

    // Cast state to custom BaseSavedState and pass to superclass
    SavedState myState = (SavedState) state;
    super.onRestoreInstanceState(myState.getSuperState());
    
    // Set this Preference's widget to reflect the restored state
    mNumberPicker.setValue(myState.value);
}
</pre>