topics/resources/runtime-changes.jd

page.title=X l Thay i Thi gian chy
page.tags=hot ng,vng i
@jd:body

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

  <h2>Trong ti liu ny</h2>
  <ol>
    <li><a href="#RetainingAnObject">Gi li mt i tng trong khi Thay i Cu hnh</a></li>
    <li><a href="#HandlingTheChange">T mnh X l Thay i Cu hnh</a>
  </ol>

  <h2>Xem thm</h2>
  <ol>
    <li><a href="providing-resources.html">Cung cp Ti nguyn</a></li>
    <li><a href="accessing-resources.html">Truy cp Ti nguyn</a></li>
    <li><a href="http://android-developers.blogspot.com/2009/02/faster-screen-orientation-change.html">Thay i
        Hng Mn hnh Nhanh hn</a></li>
  </ol>
</div>
</div>

<p>Mt s cu hnh thit b c th thay i trong thi gian chy
(chng hn nh hng mn hnh, s sn c ca bn phm, v ngn ng). Khi s thay i nh vy din ra,
Android s khi ng li vic chy
{@link android.app.Activity} ({@link android.app.Activity#onDestroy()} s c gi, sau  l {@link
android.app.Activity#onCreate(Bundle) onCreate()}). Hnh vi khi ng li c thit k  gip
ng dng iu chnh ph hp vi cu hnh mi bng cch t ng ti li ng dng ca bn bng
cc ti nguyn thay th khp vi cu hnh thit b mi.</p>

<p> x l khi ng li cho ng, iu quan trng l hot ng ca bn khi phc li trng thi trc
ca n thng qua vng i <a href="{@docRoot}guide/components/activities.html#Lifecycle">Hot ng
thng thng</a>, trong  Android s gi
{@link android.app.Activity#onSaveInstanceState(Bundle) onSaveInstanceState()} trc khi n hy
hot ng ca bn sao cho bn c th lu d liu v trng thi ca ng dng. Khi , bn c th khi phc trng thi
trong khi {@link android.app.Activity#onCreate(Bundle) onCreate()} hoc {@link
android.app.Activity#onRestoreInstanceState(Bundle) onRestoreInstanceState()}.</p>

<p> kim tra xem ng dng ca bn c t khi ng li m gi nguyn trng thi ng dng hay khng,
bn cn gi ra cc thay i cu hnh (chng hn nh thay i hng mn hnh) trong khi thc hin cc
tc v khc nhau trong ng dng ca bn. ng dng ca bn s c th khi ng li vo bt c lc no m khng b mt
d liu ca ngi dng hay trng thi  x l cc s kin nh thay i cu hnh hoc khi ngi dng nhn c
mt cuc gi n ri quay li ng dng ca bn mun hn nhiu sau khi tin trnh
ng dng ca bn c th  b hy.  tm hiu v cch bn c th khi phc trng thi hot ng ca mnh, hy c v <a href="{@docRoot}guide/components/activities.html#Lifecycle">Vng i ca hot ng</a>.</p>

<p>Tuy nhin, bn c th gp phi mt tnh hung trong  vic khi ng li ng dng ca bn v
khi phc phn ln d liu c th tn km v to nn tri nghim ngi dng km. Trong
tnh hung nh vy, bn c hai ty chn:</p>

<ol type="a">
  <li><a href="#RetainingAnObject">Gi li mt i tng trong khi thay i cu hnh</a>
  <p>Cho php hot ng ca bn khi ng li khi cu hnh thay i, nhng mang theo mt
i tng c trng thi ti thc th mi ca hot ng ca bn.</p>

  </li>
  <li><a href="#HandlingTheChange">T mnh x l thay i cu hnh</a>
  <p>Ngn khng cho h thng khi ng li hot ng ca bn trong nhng thay i
cu hnh nht nh, nhng nhn mt lnh gi li khi cu hnh thay i, sao cho bn c th cp nht th cng
hot ng ca mnh nu cn.</p>
  </li>
</ol>


<h2 id="RetainingAnObject">Gi li mt i tng trong khi Thay i Cu hnh</h2>

<p>Nu vic khi ng li hot ng ca bn yu cu bn phi khi phc nhiu tp hp d liu ln, hy thit lp li kt ni
mng, hoc thc hin cc thao tc tng cng khc, khi  khi ng li hon ton do thay i cu hnh
c th gy ra tri nghim ngi dng chm chp. ng thi, c th bn s khng th hon ton khi phc c
trng thi hot ng ca mnh vi {@link android.os.Bundle} m h thng lu cho bn bng phng php gi li {@link
android.app.Activity#onSaveInstanceState(Bundle) onSaveInstanceState()}&mdash;n khng
c thit k  mang cc i tng ln (chng hn nh bitmap) v d liu trong n phi c ni tip ha ri
b ni tip ha, iu ny c th tiu tn nhiu b nh v khin vic thay i cu hnh din ra chm. Trong mt
tnh hung nh vy, bn c th g b gnh nng khi to li hot ng ca mnh bng cch gi li {@link
android.app.Fragment} khi hot ng ca bn c khi ng li do thay i cu hnh. Phn on ny
c th cha cc tham chiu ti i tng c trng thi m bn mun gi li.</p>

<p>Khi h thng Android tt hot ng ca bn do mt thay i cu hnh, cc phn on
ca hot ng m bn  nh du  gi li s khng b hy. Bn c th thm cc phn on ny vo
hot ng ca mnh  gi li cc i tng c trng thi.</p>

<p> gi li cc i tng c trng thi trong mt phn on trong khi thay i cu hnh thi gian chy:</p>

<ol>
  <li>M rng lp {@link android.app.Fragment} v khai bo cc tham chiu ti i tng
      c trng thi ca bn.</li>
  <li>Gi {@link android.app.Fragment#setRetainInstance(boolean)} khi phn on c to.
      </li>
  <li>Thm phn on vo hot ng ca bn.</li>
  <li>S dng {@link android.app.FragmentManager}  truy xut phn on khi hot ng
      c khi ng li.</li>
</ol>

<p>V d, nh ngha phn on ca bn nh sau:</p>

<pre>
public class RetainedFragment extends Fragment {

    // data object we want to retain
    private MyDataObject data;

    // this method is only called once for this fragment
    &#64;Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // retain this fragment
        setRetainInstance(true);
    }

    public void setData(MyDataObject data) {
        this.data = data;
    }

    public MyDataObject getData() {
        return data;
    }
}
</pre>

<p class="caution"><strong>Ch :</strong> Trong khi bn c th lu tr bt k i tng no, bn
khng nn chuyn mt i tng c gn vi {@link android.app.Activity}, chng hn nh {@link
android.graphics.drawable.Drawable}, {@link android.widget.Adapter}, {@link android.view.View}
hay bt k i tng no khc i km vi mt {@link android.content.Context}. Nu bn lm vy, n s
r r tt c dng xem v ti nguyn ca thc th hot ng gc. (R r ti nguyn
c ngha l ng dng ca bn duy tr vic lu gi ti nguyn v chng khng th c thu dn b nh rc, v th
rt nhiu b nh c th b mt.)</p>

<p>Khi , hy s dng {@link android.app.FragmentManager}  thm phn on vo hot ng.
Bn c th thu c i tng d liu t phn on khi hot ng bt u li trong khi
thay i cu hnh thi gian chy. V d, nh ngha hot ng ca bn nh sau:</p>

<pre>
public class MyActivity extends Activity {

    private RetainedFragment dataFragment;

    &#64;Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        // find the retained fragment on activity restarts
        FragmentManager fm = getFragmentManager();
        dataFragment = (DataFragment) fm.findFragmentByTag(data);

        // create the fragment and data the first time
        if (dataFragment == null) {
            // add the fragment
            dataFragment = new DataFragment();
            fm.beginTransaction().add(dataFragment, data).commit();
            // load the data from the web
            dataFragment.setData(loadMyData());
        }

        // the data is available in dataFragment.getData()
        ...
    }

    &#64;Override
    public void onDestroy() {
        super.onDestroy();
        // store the data in the fragment
        dataFragment.setData(collectMyLoadedData());
    }
}
</pre>

<p>Trong v d ny, {@link android.app.Activity#onCreate(Bundle) onCreate()} thm mt phn on
hoc khi phc mt tham chiu n n. {@link android.app.Activity#onCreate(Bundle) onCreate()} cng
lu tr i tng c trng thi bn trong thc th phn on .
{@link android.app.Activity#onDestroy() onDestroy()} cp nht i tng c trng thi bn trong
thc th phn on c gi li.</p>


<h2 id="HandlingTheChange">T mnh X l Thay i Cu hnh</h2>

<p>Nu ng dng ca bn khng cn cp nht cc ti nguyn trong mt thay i
cu hnh c th <em>v</em> bn c gii hn v hiu nng yu cu bn phi
trnh khi ng li hot ng, khi  bn c th khai bo rng hot ng ca bn t mnh x l thay i cu hnh
, lm vy s trnh cho h thng khi ng li hot ng ca bn.</p>

<p class="note"><strong>Lu :</strong> Vic t mnh x l thay i cu hnh c th khin vic
s dng cc ti nguyn thay th kh khn hn nhiu, v h thng khng t ng p dng chng
cho bn. K thut ny nn c coi l gii php cui cng khi bn phi trnh khi ng li do mt
thay i cu hnh v khng c khuyn co i vi hu ht ng dng.</p>

<p> khai bo rng hot ng ca bn x l mt thay i cu hnh, hy chnh sa phn t <a href="{@docRoot}guide/topics/manifest/activity-element.html">{@code &lt;activity&gt;}</a> ph hp trong
tp bn k khai ca bn  bao gm thuc tnh <a href="{@docRoot}guide/topics/manifest/activity-element.html#config">{@code
android:configChanges}</a> vi mt gi tr c chc nng biu din cu hnh m bn mun
x l. Cc gi tr c th c lit k trong ti liu dnh cho thuc tnh <a href="{@docRoot}guide/topics/manifest/activity-element.html#config">{@code
android:configChanges}</a> (cc gi tr thng c s dng nht l {@code "orientation"}
ngn khi ng li khi hng mn hnh thay i v {@code "keyboardHidden"}  ngn
khi ng li khi tnh sn c ca bn phm thay i).  Bn c th khai bo nhiu gi tr cu hnh trong
thuc tnh bng cch tch chng bng mt k t {@code |} ng dn ni.</p>

<p>V d, on m bn k khai sau khai bo mt hot ng c chc nng x l c
thay i v hng mn hnh v thay i v tnh sn c ca bn phm:</p>

<pre>
&lt;activity android:name=".MyActivity"
          android:configChanges="orientation|keyboardHidden"
          android:label="@string/app_name">
</pre>

<p>Lc ny, khi mt trong nhng cu hnh ny thay i, {@code MyActivity} khng khi ng li.
Thay vo , {@code MyActivity} nhn c mt lnh gi ti {@link
android.app.Activity#onConfigurationChanged(Configuration) onConfigurationChanged()}. Phng php ny
c chuyn bi mt i tng {@link android.content.res.Configuration} m quy nh
cu hnh thit b mi. Bng cch c cc trng trong {@link android.content.res.Configuration},
bn c th xc nh cu hnh mi v thc hin nhng thay i ph hp bng cch cp nht
ti nguyn c s dng trong giao din ca bn. Ti
thi im phng php ny c gi, i tng {@link android.content.res.Resources} ca hot ng ca bn c cp nht
 tr v cc ti nguyn da trn cu hnh mi, sao cho bn c th d dng
t li cc phn t trong UI ca mnh m khng  h thng khi ng li hot ng ca bn.</p>

<p class="caution"><strong>Ch :</strong> Bt u vi Android 3.2 (API mc 13), <strong>
"kch c mn hnh" cng thay i</strong> khi thit b chuyn gia hng dc v kh ngang
. V th, nu bn mun ngn cn vic khi ng li vo thi gian chy do thay i hng khi pht trin
cho API mc 13 hoc cao hn (nh c khai bo bi cc thuc tnh <a href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#min">{@code minSdkVersion}</a> v <a href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#target">{@code targetSdkVersion}</a>
), bn phi bao gm gi tr {@code "screenSize"} bn cnh gi tr {@code
"orientation"}. C th, bn phi khai bo {@code
android:configChanges="orientation|screenSize"}. Tuy nhin, nu ng dng ca bn nhm ti API mc
12 hoc thp hn, khi  hot ng ca bn lun t mnh x l thay i cu hnh ny (thay i
cu hnh ny khng khi ng li hot ng ca bn, ngay c khi ang chy trn mt thit b phin bn Android 3.2 hoc cao hn).</p>

<p>V d, vic trin khai {@link
android.app.Activity#onConfigurationChanged(Configuration) onConfigurationChanged()} sau
s kim tra hng thit b hin ti:</p>

<pre>
&#64;Override
public void onConfigurationChanged(Configuration newConfig) {
    super.onConfigurationChanged(newConfig);

    // Checks the orientation of the screen
    if (newConfig.orientation == Configuration.ORIENTATION_LANDSCAPE) {
        Toast.makeText(this, "landscape", Toast.LENGTH_SHORT).show();
    } else if (newConfig.orientation == Configuration.ORIENTATION_PORTRAIT){
        Toast.makeText(this, "portrait", Toast.LENGTH_SHORT).show();
    }
}
</pre>

<p>i tng {@link android.content.res.Configuration} biu din tt c cu hnh
hin ti, khng ch nhng cu hnh  thay i. Trong phn ln thi gian, bn s khng quan tm chnh xc xem
cu hnh  thay i nh th no v c th n gin gn li tt c ti nguyn ca mnh vi chc nng cung cp ni dung thay th
cho cu hnh m bn ang x l. V d, do i tng {@link
android.content.res.Resources} nay  c cp nht, bn c th t li
bt k{@link android.widget.ImageView} no vi {@link android.widget.ImageView#setImageResource(int)
setImageResource()}
v ti nguyn ph hp cho cu hnh mi c s dng (nh c m t trong phn <a href="providing-resources.html#AlternateResources">Cung cp Ti nguyn</a>).</p>

<p>Lu  rng gi tr t cc trng {@link
android.content.res.Configuration} l nhng s nguyn khp vi hng s c th
t lp {@link android.content.res.Configuration}. i vi ti liu v nhng hng s
cn s dng vi mi trng, hy tham kho trng ph hp trong tham chiu {@link
android.content.res.Configuration}.</p>

<p class="note"><strong>Hy ghi nh:</strong> Khi bn khai bo hot ng ca mnh  x l mt
thay i cu hnh, bn c trch nhim t li bt k phn t no m bn cung cp ni dung thay th cho. Nu bn
khai bo hot ng ca mnh  x l thay i hng v c nhng hnh nh nn thay i
gia kh ngang v hng dc, bn phi gn li tng ti nguyn cho tng phn t trong khi {@link
android.app.Activity#onConfigurationChanged(Configuration) onConfigurationChanged()}.</p>

<p>Nu bn khng cn cp nht ng dng ca mnh da trn nhng thay i
cu hnh ny, thay vo  bn c th <em>khng</em> trin khai {@link
android.app.Activity#onConfigurationChanged(Configuration) onConfigurationChanged()}. Trong
trng hp , tt c ti nguyn c s dng trc khi thay i cu hnh s vn c s dng
v bn ch mi trnh c vic khi ng li hot ng ca mnh. Tuy nhin, ng dng ca bn cn lun c kh nng
tt v khi ng li vi trng thi trc  ca n c gi nguyn, v th bn khng nn coi
k thut ny nh mt cch  thot khi vic gi li trng thi ca mnh trong vng i ca hot ng bnh thng. Khng ch bi
c nhng thay i cu hnh khc m bn khng th ngn khng cho khi ng li ng dng ca mnh, m
c bi v bn nn x l nhng s kin nh l khi ngi dng ri khi ng dng ca bn v n b
hy trc khi ngi dng quay li.</p>

<p> bit thm v nhng thay i cu hnh no m bn c th x l trong hot ng ca mnh, hy xem ti liu <a href="{@docRoot}guide/topics/manifest/activity-element.html#config">{@code
android:configChanges}</a> v lp {@link android.content.res.Configuration}
.</p>