xref: /frameworks/base/docs/html-intl/intl/vi/guide/components/activities.jd

page.title=Cc hot ng
page.tags=hot ng, nh
@jd:body

<div id="qv-wrapper">
<div id="qv">
<h2>Trong ti liu ny</h2>
<ol>
  <li><a href="#Creating">To mt Hot ng</a>
    <ol>
      <li><a href="#UI">Trin khai mt giao din ngi dng</a></li>
      <li><a href="#Declaring">Khai bo hot ng trong bn k khai</a></li>
    </ol>
  </li>
  <li><a href="#StartingAnActivity">Bt u mt Hot ng</a>
    <ol>
      <li><a href="#StartingAnActivityForResult">Bt u mt hot ng cho mt kt qu</a></li>
    </ol>
  </li>
  <li><a href="#ShuttingDown">Tt mt Hot ng</a></li>
  <li><a href="#Lifecycle">Qun l Vng i ca Hot ng</a>
    <ol>
      <li><a href="#ImplementingLifecycleCallbacks">Trin khai gi li vng i</a></li>
      <li><a href="#SavingActivityState">Lu trng thi ca hot ng</a></li>
      <li><a href="#ConfigurationChanges">X l thay i v cu hnh</a></li>
      <li><a href="#CoordinatingActivities">iu phi hot ng</a></li>
    </ol>
  </li>
</ol>

<h2>Lp kha</h2>
<ol>
  <li>{@link android.app.Activity}</li>
</ol>

<h2>Xem thm</h2>
<ol>
  <li><a href="{@docRoot}guide/components/tasks-and-back-stack.html">Tc v v Ngn
Xp</a></li>
</ol>

</div>
</div>



<p>{@link android.app.Activity} l mt thnh phn ng dng cung cp mt mn hnh m vi n
ngi dng c th tng tc  thc hin mt iu g , chng hn nh quay s in thoi, chp nh, gi e-mail hoc
xem bn . Mi hot ng c cho trong mt ca s l ni  v giao din ngi dng ca n. Ca s ny
thng lp y mn hnh, nhng c th nh hn mn hnh v ni bn trn cc ca s
khc.</p>

<p> ng dng thng bao gm nhiu hot ng c lin kt lng lo
vi nhau. Thng th mt hot ng trong mt ng dng s c quy nh l hot ng "chnh", n c
trnh by trc ngi dng khi khi chy ng dng ln u. Sau , mi
hot ng c th bt u mt hot ng khc  thc hin cc hnh ng khc nhau. Mi khi mt hot ng
mi bt u, hot ng trc  s b dng li, nhng h thng vn gi nguyn hot ng
trong mt ngn xp ("back stack"). Khi mt hot ng mi bt u, n c y ln ngn xp v
chim ly tiu im ca ngi dng. Ngn xp s tun theo c ch xp chng c bn "vo cui, ra u",
v th, khi ngi dng kt thc hot ng hin ti v nhn nt <em>Quay li</em>, n
s c y ra khi ngn xp (v b hy) v hot ng trc  s tip tc. (Ngn xp c
 cp k hn trong ti liu <a href="{@docRoot}guide/components/tasks-and-back-stack.html">Tc v
v Ngn Xp</a>.)</p>

<p>Khi mt hot ng b dng v mt hot ng mi bt u, n c thng bo v s thay i trng thi ny
qua cc phng php gi li vng i ca hot ng.
C mt vi phng php gi li vng i m mt hot ng c th nhn, do mt thay i v
trng thi ca n&mdash;d h thng ang to, dng hay tip tc n, hay hy n&mdash;v
mi ln gi li cho bn c hi thc hin cng vic c th
ph hp vi s thay i trng thi . V d, khi b dng, hot ng ca bn s gii phng mi
i tng ln, chng hn nh cc kt ni mng hoc c s d liu. Khi hot ng tip tc, bn c th
thu li nhng ti nguyn cn thit v tip tc nhng hnh ng b gin on. Nhng chuyn tip trng thi ny
u l mt phn ca vng i hot ng.</p>

<p>Phn cn li ca ti liu ny bn n nhng ni dung c bn v cch xy dng v s dng mt hot ng,
bao gm mt ni dung  cp y  v cch vn hnh ca vng i hot ng,  bn c th qun l tt
s chuyn tip gia cc trng thi hot ng khc nhau.</p>



<h2 id="Creating">To mt Hot ng</h2>

<p> to mt hot ng, bn phi to mt lp con ca {@link android.app.Activity} (hoc
mt lp con hin ti ca n). Trong lp con ca mnh, bn cn trin khai cc phng php gi li m h thng
gi khi hot ng chuyn tip gia cc trng thi khc nhau trong vng i, chng hn nh khi
hot ng ang c to, dng, tip tc, hoc hy. Hai phng php gi li quan trng nht
l:</p>

<dl>
  <dt>{@link android.app.Activity#onCreate onCreate()}</dt>
  <dd>Bn phi trin khai phng php ny. H thng gi phng php ny khi to hot ng
ca bn. Trong qu trnh thc hin ca mnh, bn nn khi chy nhng thnh phn thit yu cho hot ng
ca mnh.
    Quan trng nht, y l lc bn phi gi {@link android.app.Activity#setContentView
    setContentView()}  nh ngha b tr cho giao din ngi dng ca hot ng.</dd>
  <dt>{@link android.app.Activity#onPause onPause()}</dt>
  <dd>H thng gi phng php ny l du hiu u tin v vic ngi dng ang ri khi hot ng
ca bn (mc d khng phi lc no cng c ngha rng hot ng ang b hy). Trng hp ny thng l khi bn
nh thc hin bt k thay i no vn cn c hiu lc ngoi phin ca ngi dng hin thi (v
ngi dng c th khng quay li).</dd>
</dl>

<p>C mt vi phng php gi li vng i khc m bn nn s dng  em n
mt tri nghim ngi dng mt m gia cc hot ng v x l nhng gin on bt ng khin hot ng ca bn
b dng v thm ch b hy. Tt c phng php gi li vng i c bn sau trong phn
ni v <a href="#Lifecycle">Qun l Vng i ca Hot ng</a>.</p>



<h3 id="UI">Trin khai mt giao din ngi dng</h3>

<p> Giao din ngi dng cho mt hot ng s c cung cp theo phn cp dng xem&mdash;i tng c suy ra
t lp {@link android.view.View}.  Mi ch  xem kim sot mt khng gian ch nht ring
trong ca s ca hot ng v c th phn hi trc tng tc ca ngi dng. V d, ch  xem c th l
mt nt khi xng mt hnh ng khi ngi dng chm vo n.</p>

<p>Android cung cp nhiu ch  xem sn c m bn c th s dng  thit k v t chc cho b tr
ca mnh. "Widget" l nhng ch  xem cung cp nhng phn t trc quan (v tng tc) cho mn hnh, chng hn nh
nt, trng vn bn, hp kim, hay ch l mt hnh nh. "B tr" l nhng ch  xem c suy ra t {@link
android.view.ViewGroup} cung cp mt m hnh b tr duy nht cho cc ch  xem con ca n, chng hn nh b tr
tuyn tnh, b tr li, hoc b tr tng i. Bn cng c th chia thnh lp con {@link android.view.View} v cc lp
{@link android.view.ViewGroup} (hoc cc lp con hin ti)  to widget v
b tr ca chnh mnh v p dng chng vo b tr hot ng ca bn.</p>

<p>Cch ph bin nht  nh ngha mt b tr bng cch s dng cc ch  xem l dng mt tp b tr XML c lu trong ti nguyn ng dng
ca bn. Bng cch ny, bn c th duy tr thit k giao din ngi dng ca mnh c lp vi
m ngun nh ngha hnh vi ca hot ng. Bn c th t b tr lm UI cho hot ng
ca mnh bng {@link android.app.Activity#setContentView(int) setContentView()}, chuyn
ID ti nguyn cho b tr. Tuy nhin, bn cng c th to {@link android.view.View} mi trong m hot ng
ca mnh v xy dng mt cp bc ch  xem bng cch chn cc {@link
android.view.View} mi vo mt {@link android.view.ViewGroup}, sau  s dng b tr  bng cch chuyn root
{@link android.view.ViewGroup} sang {@link android.app.Activity#setContentView(View)
setContentView()}.</p>

<p> bit thng tin v vic to mt giao din ngi dng, hy xem ti liu <a href="{@docRoot}guide/topics/ui/index.html">Giao din Ngi dng</a>.</p>



<h3 id="Declaring">Khai bo hot ng trong bn k khai</h3>

<p>Bn phi khai bo hot ng ca mnh trong tp bn k khai  hot ng
c th truy cp c vo h thng.  khai bo hot ng ca mnh, hy m tp bn k khai ca bn v thm mt phn t  <a href="{@docRoot}guide/topics/manifest/activity-element.html">{@code &lt;activity&gt;}</a>
lm con ca phn t <a href="{@docRoot}guide/topics/manifest/application-element.html">{@code &lt;application&gt;}</a>
. V d:</p>

<pre>
&lt;manifest ... &gt;
  &lt;application ... &gt;
      &lt;activity android:name=".ExampleActivity" /&gt;
      ...
  &lt;/application ... &gt;
  ...
&lt;/manifest &gt;
</pre>

<p>C vi thuc tnh khc m bn c th nu trong phn t ny,  nh ngha cc thuc tnh
nh nhn cho hot ng, biu tng cho hot ng, hoc ch  m t kiu UI ca
hot ng. Thuc tnh <a href="{@docRoot}guide/topics/manifest/activity-element.html#nm">{@code android:name}</a>
l thuc tnh bt buc duy nht&mdash;n quy nh tn lp ca hot ng. Mt khi
bn pht hnh ng dng ca mnh, bn khng nn thay i tn ny, v nu bn lm vy, bn c th lm hng
mt s tnh nng, chng hn nh cc li tt ca ng dng (hy c bi ng trn blog, <a href="http://android-developers.blogspot.com/2011/06/things-that-cannot-change.html">Nhng iu
Khng Thay i c</a>).</p>

<p>Xem ti liu tham kho phn t <a href="{@docRoot}guide/topics/manifest/activity-element.html">{@code &lt;activity&gt;}</a>
 bit thm thng tin v vic khai bo hot ng ca bn trong bn k khai.</p>


<h4>S dng cc b lc  nh</h4>

<p>Mt phn t <a href="{@docRoot}guide/topics/manifest/activity-element.html">{@code
&lt;activity&gt;}</a> cng c th quy nh cc b lc  nh khc nhau&mdash;bng cch s dng phn t <a href="{@docRoot}guide/topics/manifest/intent-filter-element.html">{@code
&lt;intent-filter&gt;}</a> &mdash; khai bo cch thc m cc thnh phn khc ca ng dng c th
kch hot n.</p>

<p>Khi bn to mt ng dng mi bng cch s dng cc cng c SDK ca Android, hot ng chng trnh nh
c to cho bn s t ng bao gm mt b lc  nh khai bo hot ng
phn hi li hnh ng "chnh" v nn c t trong th loi "trnh khi chy". B lc  nh
trng nh th ny:</p>

<pre>
&lt;activity android:name=".ExampleActivity" android:icon="@drawable/app_icon"&gt;
    &lt;intent-filter&gt;
        &lt;action android:name="android.intent.action.MAIN" /&gt;
        &lt;category android:name="android.intent.category.LAUNCHER" /&gt;
    &lt;/intent-filter&gt;
&lt;/activity&gt;
</pre>

<p>Phn t <a href="{@docRoot}guide/topics/manifest/action-element.html">{@code
&lt;action&gt;}</a> quy nh rng y l im mc nhp "chnh" i vi ng dng. Phn t <a href="{@docRoot}guide/topics/manifest/category-element.html">{@code
&lt;category&gt;}</a> quy nh rng hot ng ny nn c lit k trong trnh khi chy ng dng ca h thng
( cho php ngi dng khi chy hot ng ny).</p>

<p>Nu bn c  nh cho ng dng ca mnh c c lp v khng cho php cc ng dng khc
kch hot cc hot ng ca n, vy bn khng cn bt k b lc  nh no khc. Ch mt hot ng nn c
hnh ng "chnh" v th loi "trnh khi chy" nh trong v d trc. Nhng hot ng m
bn khng mun cung cp sn cho cc ng dng khc khng nn c b lc  nh v bn c th
t mnh bt u chng bng cch s dng cc  nh r rng (nh c  cp trong phn sau).</p>

<p>Tuy nhin, nu bn mun hot ng ca mnh phn hi li nhng  nh ngm m c chuyn giao t
cc ng dng khc (v chnh bn), th bn phi nh ngha cc b lc  nh b sung cho hot ng
ca mnh. Vi mi loi  nh m bn mun phn hi, bn phi nu mt <a href="{@docRoot}guide/topics/manifest/intent-filter-element.html">{@code
&lt;intent-filter&gt;}</a> bao gm mt phn t
<a href="{@docRoot}guide/topics/manifest/action-element.html">{@code
&lt;action&gt;}</a> v, khng bt buc, mt phn t <a href="{@docRoot}guide/topics/manifest/category-element.html">{@code
&lt;category&gt;}</a> v/hoc mt phn t <a href="{@docRoot}guide/topics/manifest/data-element.html">{@code
&lt;data&gt;}</a>. Nhng phn t ny quy nh loi  nh m hot ng ca bn c th
phn hi.</p>

<p> bit thm thng tin v cch thc cc hot ng ca bn c th phn hi li  nh, hy xem ti liu <a href="{@docRoot}guide/components/intents-filters.html"> nh v B lc  nh</a>
.</p>



<h2 id="StartingAnActivity">Bt u mt Hot ng</h2>

<p>Bn c th bt u mt hot ng khc bng cch gi {@link android.app.Activity#startActivity
  startActivity()}, chuyn cho n mt {@link android.content.Intent} m m t hot ng bn
mun bt u.  nh ny s quy nh hoc hot ng chnh xc m bn mun bt u hoc m t
 loi hnh ng m bn mun thc hin (v h thng la chn hot ng ph hp cho bn,
thm ch
c th t mt ng dng khc). Mt  nh cng c th mang theo lng nh d liu s c
 s dng bi hot ng c bt u.</p>

<p>Khi ang lm vic trong ng dng ca chnh mnh, bn thng s cn khi chy mt hot ng  bit.
 Bn c th lm vy bng cch to mt  nh trong  quy nh r hot ng bn mun bt u,
s dng tn lp . V d, sau y l cch mt hot ng bt u mt hot ng khc c tn {@code
SignInActivity}:</p>

<pre>
Intent intent = new Intent(this, SignInActivity.class);
startActivity(intent);
</pre>

<p>Tuy nhin, ng dng ca bn cng c th mun thc hin mt s hnh ng, chng hn nh gi mt e-mail, tin nhn
 vn bn, hoc cp nht trng thi, bng cch s dng d liu t hot ng ca bn. Trong trng hp ny, ng dng ca bn c th
 khng c cc hot ng ca chnh n  thc hin nhng hnh ng , v vy, thay vo , bn c th tn dng nhng hot ng
 c cung cp bi cc ng dng khc trn thit b m c th thc hin hnh ng cho bn. y l lc
 nh thc s c gi tr&mdash;bn c th to mt  nh m t mt hnh ng bn mun
thc hin v h thng
 s khi chy hot ng ph hp  t mt ng dng khc. Nu c
 nhiu hot ng m c th x l  nh, vy ngi dng c th chn hot ng no s s dng. V
 d, nu bn mun cho php ngi dng gi e-mail, bn c th to
  nh sau:</p>

<pre>
Intent intent = new Intent(Intent.ACTION_SEND);
intent.putExtra(Intent.EXTRA_EMAIL, recipientArray);
startActivity(intent);
</pre>

<p>{@link android.content.Intent#EXTRA_EMAIL} ph c thm vo  nh l mt mng xu ca
 cc a ch e-mail m e-mail s c gi ti. Khi mt ng dng e-mail phn hi
  nh ny, n c mng xu c cung cp trong phn ph v t n vo trng "n" ca mu son tho
 e-mail. Trong trng hp ny, hot ng ca ng dng e-mail bt u v khi ngi dng
 lm xong, hot ng ca bn s tip tc.</p>




<h3 id="StartingAnActivityForResult">Bt u mt hot ng cho mt kt qu</h3>

<p>i khi bn c th mun nhn c mt kt qu t hot ng m bn bt u. Trong trng hp ,
hy bt u hot ng bng cch gi {@link android.app.Activity#startActivityForResult
  startActivityForResult()} (thay v {@link android.app.Activity#startActivity
  startActivity()}). Ri  nhn c kt qu t hot ng
sau , hy trin khai phng php gi li {@link android.app.Activity#onActivityResult onActivityResult()}
. Khi hot ng sau  din ra xong, n tr v mt kt qu trong mt {@link
android.content.Intent} cho phng php {@link android.app.Activity#onActivityResult onActivityResult()}
ca bn.</p>

<p>V d, bn c th mun ngi dng chn mt trong cc lin lc ca h, v vy hot ng ca bn c th
lm g  vi thng tin trong lin lc . y l cch bn c th to mt  nh nh vy v
x l kt qu:</p>

<pre>
private void pickContact() {
    // Create an intent to "pick" a contact, as defined by the content provider URI
    Intent intent = new Intent(Intent.ACTION_PICK, Contacts.CONTENT_URI);
    startActivityForResult(intent, PICK_CONTACT_REQUEST);
}

&#64;Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    // If the request went well (OK) and the request was PICK_CONTACT_REQUEST
    if (resultCode == Activity.RESULT_OK &amp;&amp; requestCode == PICK_CONTACT_REQUEST) {
        // Perform a query to the contact's content provider for the contact's name
        Cursor cursor = getContentResolver().query(data.getData(),
        new String[] {Contacts.DISPLAY_NAME}, null, null, null);
        if (cursor.moveToFirst()) { // True if the cursor is not empty
            int columnIndex = cursor.getColumnIndex(Contacts.DISPLAY_NAME);
            String name = cursor.getString(columnIndex);
            // Do something with the selected contact's name...
        }
    }
}
</pre>

<p>V d ny th hin l-gic c bn m bn s s dng trong phng php {@link
android.app.Activity#onActivityResult onActivityResult()} ca mnh  x l mt
kt qu hot ng. iu kin u tin kim tra xem yu cu c thnh cng khng&mdash;nu c th
{@code resultCode} s l {@link android.app.Activity#RESULT_OK}&mdash;v liu yu cu
m kim tra ny ang phn hi c c bit hay khng&mdash;trong trng hp ny, {@code requestCode} ph hp vi
tham s th hai c gi bng {@link android.app.Activity#startActivityForResult
startActivityForResult()}. T , m x l kt qu hot ng bng cch truy vn
d liu c tr v trong {@link android.content.Intent} (tham s {@code data}).</p>

<p>iu xy ra  l, {@link
android.content.ContentResolver} s thc hin mt truy vn i vi nha cung cp ni dung, truy vn ny tr v mt
{@link android.database.Cursor} cho php c d liu c truy vn.  bit thm thng tin, hy xem ti liu
<a href="{@docRoot}guide/topics/providers/content-providers.html">Trnh cung cp Ni dung</a>.</p>

<p> bit thm thng tin v vic s dng  nh, hy xem ti liu <a href="{@docRoot}guide/components/intents-filters.html"> nh v B lc
 nh</a>.</p>


<h2 id="ShuttingDown">Tt mt Hot ng</h2>

<p>Bn c th tt mt hot ng bng cch gi phng php {@link android.app.Activity#finish
finish()} ca n. Bn cng c th tt mt hot ng ring m trc  bn  bt u bng cch gi
{@link android.app.Activity#finishActivity finishActivity()}.</p>

<p class="note"><strong>Lu :</strong> Trong hu ht trng hp, bn khng nn kt thc mt hot ng mt cch r rng
bng cch s dng nhng phng php ny. Nh  cp trong phn sau v vng i ca hot ng, h thng
Android qun l tui th ca mt hot ng cho bn, v vy bn khng cn kt thc cc hot ng
ca chnh mnh. Vic gi nhng phng php ny c th nh hng tiu cc ti tri nghim ngi dng
k vng v ch nn c s dng khi bn tuyt i khng mun ngi dng quay li thc th ny ca
hot ng.</p>


<h2 id="Lifecycle">Qun l Vng i ca Hot ng</h2>

<p>Vic qun l vng i cc hot ng ca bn bng cch trin khai cc phng php gi li
rt quan trng i vi vic xy dng mt ng dng mnh
v linh hot. Vng i ca mt hot ng trc tip b nh hng bi s lin kt gia n vi
cc hot ng khc, tc v ca n v ngn xp (back stack).</p>

<p>V c bn, mt hot ng c th tn ti  ba trng thi:</p>

<dl>
  <dt><i>Tip tc</i></dt>
    <dd>Hot ng  tin cnh ca mn hnh v c tiu im ca ngi dng. (Trng thi ny
i khi cng c gi l "ang chy".)</dd>

  <dt><i>Tm dng</i></dt>
    <dd>Mt hot ng khc  tin cnh v c tiu im, nhng hot ng ny vn hin th. C th,
mt hot ng khc hin th  trn hot ng ny v hot ng  trong sut mt phn hoc khng
che ton b mn hnh. Trng thi tm dng hon ton ang hot ng (i tng {@link android.app.Activity}
c gi li trong b nh, n duy tr tt c thng tin v trng thi v thnh vin, v vn gn vi
trnh qun l ca s), nhng c th b h thng tt b trong trng hp b nh cc k thp.</dd>

  <dt><i>Dng</i></dt>
    <dd>Hot ng b che khut hon ton bi mt hot ng khc (hot ng hin ang
di nn"). Hot ng dng cng vn ang hot ng ({@link android.app.Activity}
i tng c gi li trong b nh, n duy tr tt c thng tin v trng thi v thnh vin, nhng <em>khng</em>
gn vi trnh qun l ca s). Tuy nhin, hot ng khng cn hin th vi ngi dng na v h thng
c th tt b hot ng ny khi cn b nh  ni khc.</dd>
</dl>

<p>Nu mt hot ng b tm dng hoc dng, h thng c th b n khi b nh hoc bng cch yu cu n
kt thc (gi phng php {@link android.app.Activity#finish finish()} ca n), hoc n gin l tt b tin trnh
ca hot ng.  Khi hot ng c m li (sau khi b kt thc hoc tt b), n phi c to
li hon ton.</p>



<h3 id="ImplementingLifecycleCallbacks">Trin khai gi li vng i</h3>

<p>Khi mt hot ng chuyn tip vo ra cc trng thi khc nhau nu trn, n c thng bo
thng qua cc phng php gi li. Tt c phng php gi li u l nhng mc (hook) m bn
c th khng ch  lm cng vic ph hp khi trng thi hot ng ca bn thay i. Hot ng khung sau
bao gm tng phng php trong cc phng php vng i c bn:</p>


<pre>
public class ExampleActivity extends Activity {
    &#64;Override
    public void {@link android.app.Activity#onCreate onCreate}(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // The activity is being created.
    }
    &#64;Override
    protected void {@link android.app.Activity#onStart onStart()} {
        super.onStart();
        // The activity is about to become visible.
    }
    &#64;Override
    protected void {@link android.app.Activity#onResume onResume()} {
        super.onResume();
        // The activity has become visible (it is now "resumed").
    }
    &#64;Override
    protected void {@link android.app.Activity#onPause onPause()} {
        super.onPause();
        // Another activity is taking focus (this activity is about to be "paused").
    }
    &#64;Override
    protected void {@link android.app.Activity#onStop onStop()} {
        super.onStop();
        // The activity is no longer visible (it is now "stopped")
    }
    &#64;Override
    protected void {@link android.app.Activity#onDestroy onDestroy()} {
        super.onDestroy();
        // The activity is about to be destroyed.
    }
}
</pre>

<p class="note"><strong>Lu :</strong> Vic bn trin khai nhng phng php vng i ny phi lun
gi trin khai siu lp trc khi lm bt k cng vic no, nh minh ha trong cc v d bn trn.</p>

<p>Cng nhau, nhng phng php ny nh ngha ton b vng i ca mt hot ng. Bng vic trin khai nhng phng php
ny, bn c th theo di ba vng lp lng nhau trong vng i ca hot ng: </p>

<ul>
<li><b>Ton b vng i</b> ca mt hot ng s xy ra t thi im lnh gi n {@link
android.app.Activity#onCreate onCreate()} cho ti thi im lnh gi n {@link
android.app.Activity#onDestroy}. Hot ng ca bn nn thc hin thit lp
trng thi "chung" (chng hn nh nh ngha b tr) trong {@link android.app.Activity#onCreate onCreate()}, v
gii phng tt c ti nguyn cn li trong {@link android.app.Activity#onDestroy}. V d, nu hot ng ca bn
c mt lung ang chy ngm  ti xung d liu t mng, n c th to
lung  trong {@link android.app.Activity#onCreate onCreate()} ri dng lung trong {@link
android.app.Activity#onDestroy}.</li>

<li><p><b>Vng i hin th</b> ca mt hot ng xy ra t thi im lnh gi n {@link
android.app.Activity#onStart onStart()} cho ti lnh gi n {@link
android.app.Activity#onStop onStop()}. Trong thi gian ny, ngi dng c th thy hot ng
trn mn hnh v tng tc vi n. V d, {@link android.app.Activity#onStop onStop()} c gi
khi mt hot ng mi bt u v khng cn hin th na. Gia hai phng php ny, bn c th
duy tr cc ti nguyn cn  cho ngi dng thy hot ng. V d, bn c th ng k mt
{@link android.content.BroadcastReceiver} trong {@link
android.app.Activity#onStart onStart()}  theo di cc thay i tc ng ti UI ca mnh, v b ng k
n trong {@link android.app.Activity#onStop onStop()} khi ngi dng khng cn thy th bn ang
hin th na. H thng c th gi {@link android.app.Activity#onStart onStart()} v {@link
android.app.Activity#onStop onStop()} nhiu ln trong sut vng i ca hot ng, khi 
hot ng lun chuyn gia trng thi hin th v n vi ngi dng.</p></li>

<li><p><b>Vng i  tin cnh</b> ca mt hot ng xy ra t thi im lnh gi n {@link
android.app.Activity#onResume onResume()} cho ti thi im lnh gi n {@link android.app.Activity#onPause
onPause()}. Trong thi gian ny, hot ng s  pha trc tt c hot ng khc trn mn hnh v c
tiu im u vo ca ngi dng.  Hot ng c th thng xuyn chuyn tip vo v ra tin cnh&mdash;v
d, {@link android.app.Activity#onPause onPause()} c gi khi thit b vo trng thi ng hoc
khi mt hp thoi xut hin. V trng thi ny c th chuyn tip thng xuyn, m trong hai phng php ny nn
tng i nh  trnh chuyn tip chm khin ngi dng phi i.</p></li>
</ul>

<p>Hnh 1 minh ha nhng vng lp ny v cc ng dn m mt hot ng c th din ra gia cc trng thi.
Hnh ch nht i din cho cc phng php gi li bn c th trin khai  thc hin thao tc khi
hot ng chuyn tip gia nhng trng thi ny. <p>

<img src="{@docRoot}images/activity_lifecycle.png" alt="" />
<p class="img-caption"><strong>Hnh 1.</strong> Vng i ca hot ng.</p>

<p>Nhng phng php gi li vng i ny cng c lit k trong bng 1, trong  m t tng phng php
gi li mt cch chi tit hn v xc nh tng phng php
trong vng i tng th ca hot ng, bao gm vic h thng c th tt b hot ng hay khng sau khi
phng php gi li hon tt.</p>

<p class="table-caption"><strong>Bng 1.</strong> Tm tt cc phng php gi li
trong vng i ca hot ng.</p>

<table border="2" width="85%" frame="hsides" rules="rows">
<colgroup align="left" span="3"></colgroup>
<colgroup align="left"></colgroup>
<colgroup align="center"></colgroup>
<colgroup align="center"></colgroup>

<thead>
<tr><th colspan="3">Phng php</th> <th>M t</th> <th>C th tt b sau?</th> <th>Tip theo</th></tr>
</thead>

<tbody>
<tr>
  <td colspan="3" align="left"><code>{@link android.app.Activity#onCreate onCreate()}</code></td>
  <td>c gi khi hot ng mi c to.
      y l lc bn nn thc hin tt c thit lp c nh thng thng ca mnh &mdash;
      to ch  xem, kt ghp d liu vi danh sch, v.v.  Phng php ny c chuyn cho
      mt i tng Gi cha trng thi trc y ca hot ng, nu trng thi
       c thu li (xem phn <a href="#actstate">Lu Trng thi Hot ng</a>,
       on sau).
      <p>Lun c theo sau bi {@code onStart()}.</p></td>
  <td align="center">Khng</td>
      <td align="center">{@code onStart()}</td>
</tr>

<tr>
   <td rowspan="5" style="border-left: none; border-right: none;">&nbsp;&nbsp;&nbsp;&nbsp;</td>
   <td colspan="2" align="left"><code>{@link android.app.Activity#onRestart
onRestart()}</code></td>
   <td>c gi sau khi hot ng  c dng, ngay trc khi hot ng c
       bt u li.
       <p>Lun c theo sau bi {@code onStart()}</p></td>
   <td align="center">Khng</td>
   <td align="center">{@code onStart()}</td>
</tr>

<tr>
   <td colspan="2" align="left"><code>{@link android.app.Activity#onStart onStart()}</code></td>
   <td>c gi ngay trc khi hot ng hin th trc ngi dng.
       <p>c theo sau bi {@code onResume()} nu hot ng vo
       tin cnh, hoc {@code onStop()} nu hot ng b n.</p></td>
    <td align="center">Khng</td>
    <td align="center">{@code onResume()} <br/>hoc<br/> {@code onStop()}</td>
</tr>

<tr>
   <td rowspan="2" style="border-left: none;">&nbsp;&nbsp;&nbsp;&nbsp;</td>
   <td align="left"><code>{@link android.app.Activity#onResume onResume()}</code></td>
   <td>c gi ngay trc khi hot ng bt u
       tng tc vi ngi dng.  Ti im ny, hot ng nm 
       trn cng ca chng hot ng, trong  mc nhp ca ngi dng s n hot ng ny.
       <p>Lun c theo sau bi {@code onPause()}.</p></td>
   <td align="center">Khng</td>
   <td align="center">{@code onPause()}</td>
</tr>

<tr>
   <td align="left"><code>{@link android.app.Activity#onPause onPause()}</code></td>
   <td>c gi khi h thng sp bt u tip tc mt hot ng
       khc.  Phng php ny thng c s dng  thc hin cc thay i cha lu cho
       d liu lin tc, dng cc hot nh v nhng vic khc m c th tiu tn cng sut
       CPU, v.v.  N s thc hin rt nhanh, v
       hot ng tip theo s khng c tip tc ti khi n tr li.
       <p>c theo sau hoc bi {@code onResume()} nu hot ng
       tr li pha trc, hoc bi {@code onStop()} nu n
       khng hin th vi ngi dng.</td>
   <td align="center"><strong style="color:#800000">C</strong></td>
   <td align="center">{@code onResume()} <br/>hoc<br/> {@code onStop()}</td>
</tr>

<tr>
   <td colspan="2" align="left"><code>{@link android.app.Activity#onStop onStop()}</code></td>
   <td>c gi khi hot ng khng cn hin th vi ngi dng.  iu ny
       c th xy ra v n ang b hy, hoc v mt hot ng khc
       (ang tn ti hoc mi)  c tip tc v ang che khut n.
       <p>c theo sau hoc bi {@code onRestart()} nu
       hot ng ang quay li  tng tc vi ngi dng, hoc bi
       {@code onDestroy()} nu hot ng ny s i mt.</p></td>
   <td align="center"><strong style="color:#800000">C</strong></td>
   <td align="center">{@code onRestart()} <br/>hoc<br/> {@code onDestroy()}</td>
</tr>

<tr>
   <td colspan="3" align="left"><code>{@link android.app.Activity#onDestroy
onDestroy()}</code></td>
   <td>c gi trc khi hot ng b hy.  y l ln gi cui cng
       m hot ng s nhn c.  Nn gi n hoc v
       hot ng ang kt thc (ai   gi <code>{@link android.app.Activity#finish
       finish()}</code> trn n), hoc v h thng ang tm thi hy thc th ny ca
       hot ng  tit kim b nh trng.  Bn c th phn bit
       nhng nhng kch bn ny bng phng php <code>{@link
       android.app.Activity#isFinishing isFinishing()}</code>.</td>
   <td align="center"><strong style="color:#800000">C</strong></td>
   <td align="center"><em>khng c g</em></td>
</tr>
</tbody>
</table>

<p>Ct ghi "C th tt b sau?" cho bit liu h thng c th
tt b tin trnh ang lu tr hot ng vo bt c lc no <em>sau khi phng php tr v</em>, m khng
thc hin mt dng m khc ca hot ng hay khng.  Ba phng php c ghi l "c": ({@link
android.app.Activity#onPause
onPause()}, {@link android.app.Activity#onStop onStop()}, v {@link android.app.Activity#onDestroy
onDestroy()}). V {@link android.app.Activity#onPause onPause()} l phng php u tin
trong ba phng php, sau khi hot ng c to, {@link android.app.Activity#onPause onPause()} l
phng php cui cng c bo m s c gi trc khi tin trnh <em>c th</em> b tt b&mdash;nu
h thng phi khi phc b nh trong mt tnh hung khn cp, khi  {@link
android.app.Activity#onStop onStop()} v {@link android.app.Activity#onDestroy onDestroy()} c th
khng c gi. V th, bn nn s dng {@link android.app.Activity#onPause onPause()}  ghi
d liu c nh quan trng (chng hn nh nhng chnh sa ca ngi dng) vo thit b lu tr. Tuy nhin, bn nn chn lc
thng tin no phi c gi li trong {@link android.app.Activity#onPause onPause()}, v bt k
th tc chn no trong phng php ny cng chn chuyn tip sang hot ng k tip v lm chm tri nghim
ca ngi dng.</p>

<p> Nhng phng php c ghi "Khng" trong ct <b>C th tt b</b> s bo v tin trnh ang lu tr
hot ng khi b tt b t thi im chng c gi.  V th, mt hot ng c th tt b c
t thi im {@link android.app.Activity#onPause onPause()} tr v ti thi im
{@link android.app.Activity#onResume onResume()} s c gi. N s khng th li tt b c ti khi
{@link android.app.Activity#onPause onPause()} li c gi v tr v. </p>

<p class="note"><strong>Lu :</strong> Mt hot ng m khng th "tt b c" v mt k thut bi
nh ngha ny trong bng 1 vn c th b h thng tt b&mdash;nhng iu  ch xy ra trong
nhng hon cnh cc oan khi khng cn gii php no khc. Thi im mt hot ng c th b tt b c
 cp k hn trong ti liu <a href="{@docRoot}guide/components/processes-and-threads.html">Tin trnh v
Lung</a>.</p>


<h3 id="SavingActivityState">Lu trng thi ca hot ng</h3>

<p>Phn gii thiu v <a href="#Lifecycle">Qun l Vng i ca Hot ng</a> c  cp s qua
rng
khi mt hot ng b tm dng hoc dng, trng thi ca hot ng  s c gi li. iu ny ng v
i tng {@link android.app.Activity} vn c gi trong b nh khi n b tm dng hoc
dng&mdash;tt c thng tin v cc thnh vin v trng thi hin ti ca n vn hot ng. V th, bt k thay i no
m ngi dng  thc hin trong hot ng u c gi li sao cho khi hot ng tr v
tin cnh (khi n "tip tc"), th nhng thay i ny vn cn .</p>

<p>Tuy nhin, khi h thng hy mt hot ng  khi phc b nh, i tng {@link
android.app.Activity} b hy, v vy h thng khng th n thun tip tc hot ng vi trng thi
khng b nh hng. Thay vo , h thng phi to li i tng {@link android.app.Activity} nu ngi dng
iu hng tr li n. Tuy vy, ngi dng khng bit
rng h thng  hy hot ng v to li n v, v th, c th
cho rng hot ng s vn nguyn nh c. Trong tnh hung ny, bn c th m bo rng
thng tin quan trng v trng thi ca hot ng c gi nguyn bng cch trin khai mt phng php gi li
b sung cho php bn lu thng tin v trng thi ca hot ng ca mnh: {@link
android.app.Activity#onSaveInstanceState onSaveInstanceState()}.</p>

<p>H thng gi {@link android.app.Activity#onSaveInstanceState onSaveInstanceState()}
trc khi khin hot ng d b hy. H thng chuyn cho phng php ny
mt {@link android.os.Bundle} trong  bn c th lu
thng tin trng thi v hot ng nh cp tn gi tr, bng cch s dng cc phng php nh {@link
android.os.Bundle#putString putString()} v {@link
android.os.Bundle#putInt putInt()}. Sau , nu h thng tt b tin trnh ng dng ca bn
v ngi dng iu hng tr li hot ng ca bn, h thng s to li hot ng  v
chuyn {@link android.os.Bundle} cho c {@link android.app.Activity#onCreate onCreate()} v {@link
android.app.Activity#onRestoreInstanceState onRestoreInstanceState()}. S dng mt trong
hai phng php ny, bn c th trch xut trng thi  lu ca mnh t {@link android.os.Bundle} v khi phc
trng thi ca hot ng. Nu khng c thng tin trng thi  khi phc, khi  {@link
android.os.Bundle} c chuyn cho bn s rng (l trng hp khi hot ng c to
ln u).</p>

<img src="{@docRoot}images/fundamentals/restore_instance.png" alt="" />
<p class="img-caption"><strong>Hnh 2.</strong> Hai cch m theo  mt hot ng tr v tiu im
ca ngi dng vi trng thi khng thay i: hoc hot ng b hy, ri to li v hot ng phi khi phc
trng thi  lu trc , hoc hot ng b dng, ri tip tc v trng thi ca hot ng
gi nguyn khng i.</p>

<p class="note"><strong>Lu :</strong> Khng c g bo m rng {@link
android.app.Activity#onSaveInstanceState onSaveInstanceState()} s c gi trc khi hot ng
ca bn b hy, v c nhng trng hp m s khng cn lu trng thi
(chng hn nh khi ngi dng ri b hot ng ca bn bng cch s dng nt <em>Quay li</em>, v ngi dng
r rng
ang ng hot ng). Nu h thng gi {@link android.app.Activity#onSaveInstanceState
onSaveInstanceState()}, n lm vy trc {@link
android.app.Activity#onStop onStop()} v c th trc c {@link android.app.Activity#onPause
onPause()}.</p>

<p>Tuy nhin, ngay c khi bn khng lm g v khng trin khai {@link
android.app.Activity#onSaveInstanceState onSaveInstanceState()}, mt phn trng thi ca hot ng c khi phc
bi vic lp {@link android.app.Activity} trin khai mc nh {@link
android.app.Activity#onSaveInstanceState onSaveInstanceState()}. C th, trin khai
mc nh s gi phng php {@link
android.view.View#onSaveInstanceState onSaveInstanceState()} tng ng cho mi {@link
android.view.View} trong b tr, n cho php mi ch  xem cung cp thng tin v chnh n
m s c lu. Gn nh mi widget trong khun kh Android u trin khai phng php ny nu
ph hp, sao cho mi thay i hin th i vi UI u t ng c lu v khi phc khi hot ng
ca bn c to li. V d, widget {@link android.widget.EditText} lu mi vn bn
do ngi dng in vo v widget {@link android.widget.CheckBox} lu s thng tin cho d  c kim tra
hay cha. Vic duy nht bn cn lm  l cung cp mt ID duy nht (vi thuc tnh <a href="{@docRoot}guide/topics/resources/layout-resource.html#idvalue">{@code android:id}</a>
) cho mi widget bn mun lu trng thi ca n. Nu mt widget khng c ID th h thng
khng th lu trng thi ca n.</p>

<div class="sidebox-wrapper">
<div class="sidebox">
<p>Bn cng c th r rng dng mt ch  xem trong b tr ca mnh khi vic lu trng thi ca n bng cch t thuc tnh
{@link android.R.attr#saveEnabled android:saveEnabled} thnh {@code "false"} hoc bng cch gi
phng php {@link android.view.View#setSaveEnabled setSaveEnabled()}. Thng th bn khng nn
v hiu ha iu ny, nhng c th lm nu bn mun khi phc trng thi ca UI hot ng khc i.</p>
</div>
</div>

<p>Mc d vic trin khai mc nh {@link
android.app.Activity#onSaveInstanceState onSaveInstanceState()} lu thng tin hu ch v
UI hot ng ca bn, bn c th vn cn khng ch n  lu thm thng tin.
V d, bn c th cn lu cc gi tr thnh vin  thay i trong vng i ca hot ng (m
c th tng quan vi cc gi tr c khi phc trong UI, nhng cc thnh vin nm gi gi tr UI  khng c
khi phc theo mc nh).</p>

<p>V vic trin khai mc nh {@link
android.app.Activity#onSaveInstanceState onSaveInstanceState()} gip lu trng thi ca UI, nu
bn khng ch phng php  lu thm thng tin trng thi, bn nn lun lun gi
trin khai siu lp ca {@link android.app.Activity#onSaveInstanceState onSaveInstanceState()}
trc khi thc hin bt k cng vic no. Tng t, bn cng nn gi trin khai siu lp {@link
android.app.Activity#onRestoreInstanceState onRestoreInstanceState()} nu bn khng ch n, 
trin khai mc nh c th khi phc cc trng thi xem.</p>

<p class="note"><strong>Lu :</strong> V {@link android.app.Activity#onSaveInstanceState
onSaveInstanceState()} khng m bo
s c gi, bn ch nn s dng n  ghi trng thi giao thi ca hot ng (trng thi ca
UI)&mdash;bn khng nn s dng n  lu gi d liu lin tc.  Thay vo , bn nn s dng  {@link
android.app.Activity#onPause onPause()}  lu gi d liu lin tc (chng hn nh d liu m nn c lu
vo mt c s d liu) khi ngi dng ri b hot ng.</p>

<p>Mt cch hay  kim tra kh nng khi phc trng thi ca ng dng ca bn  l ch cn xoay
thit b sao cho hng mn hnh thay i. Khi hng mn hnh thay i, h thng
hy v to li hot ng  p dng cc ti nguyn thay th m c th c sn
cho cu hnh mn hnh mi. Ch vi l do ny m mt iu rt quan trng  l hot ng ca bn
hon ton khi phc trng thi ca mnh khi n c to li, v ngi dng thng xoay mn hnh trong khi
s dng ng dng.</p>


<h3 id="ConfigurationChanges">X l thay i v cu hnh</h3>

<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  din ra, Android to li hot ng ang chy
(h thng gi {@link android.app.Activity#onDestroy}, ri ngay lp tc gi {@link
android.app.Activity#onCreate onCreate()}). Hnh vi ny
c thit k  gip ng dng ca bn iu chnh theo nhng cu hnh mi bng cch t ng ti li ng dng
ca bn bng cc ti nguyn thay th m bn  cung cp (chng hn nh b tr khc cho
cc hng v kch c mn hnh khc).</p>

<p>Nu bn thit k hot ng ca mnh mt cch ph hp  x l khi ng li do thay i hng mn hnh v
khi phc trng thi hot ng nh nu trn, ng dng ca bn s linh hot hn trc
nhng s kin bt ng khc trong vng i ca hot ng.</p>

<p>Cch tt nht  x l khi ng li  l
 lu v khi phc trng thi hot ng ca bn bng cch s dng {@link
  android.app.Activity#onSaveInstanceState onSaveInstanceState()} v {@link
android.app.Activity#onRestoreInstanceState onRestoreInstanceState()} (hoc {@link
android.app.Activity#onCreate onCreate()}), nh   cp trong phn trc.</p>

<p> bit thm thng tin v nhng thay i cu hnh xy ra ti thi im chy v cch bn c th x l
chng, hy c hng dn <a href="{@docRoot}guide/topics/resources/runtime-changes.html">X l
Thay i trong Thi gian chy</a>.</p>



<h3 id="CoordinatingActivities">iu phi hot ng</h3>

 <p>Khi mt hot ng bt u mt hot ng khc, c hai u tri qua nhng chuyn tip vng i. Hot ng th nht
tm dng v dng (tuy nhin, n s khng dng nu vn hin th c di nn), trong khi hot ng kia
c to. Trong trng hp nhng hot ng ny chia s d liu c lu vo a hoc ni khc, iu quan trng l
phi hiu rng hot ng th nht khng b dng hon ton trc khi hot ng th hai c to.
Thay vo , tin trnh bt u hot ng th hai chng lp vi tin trnh dng hot ng
th nht.</p>

<p>Th t gi li vng i c nh ngha r, c th l khi hai hot ng trong cng tin trnh
v hot ng ny bt u hot ng kia. Sau y l th t thao tc din ra khi Hot ng
A bt u Hot ng B: </p>

<ol>
<li>Phng php {@link android.app.Activity#onPause onPause()} ca Hot ng A thc thi.</li>

<li>{@link android.app.Activity#onCreate onCreate()} ca Hot ng B, {@link
android.app.Activity#onStart onStart()}, v cc phng php {@link android.app.Activity#onResume onResume()}
thc thi theo trnh t. (Hot ng B lc ny c tiu im ca ngi dng.)</li>

<li>Sau , nu Hot ng A khng cn hin th trn mn hnh, phng php {@link
android.app.Activity#onStop onStop()} ca n s thc thi.</li>
</ol>

 <p>Trnh t gi li vng i c th d on ny cho php bn qun l chuyn tip
thng tin t hot ng ny sang hot ng khc. V d, nu bn phi ghi vo mt c s d liu khi
hot ng th nht dng sao cho hot ng theo sau c th c n, khi  bn nn ghi vo
c s d liu trong khi {@link android.app.Activity#onPause onPause()} thay v trong khi {@link
android.app.Activity#onStop onStop()}.</p>

<!--
<h2>Beginner's Path</h2>

<p>For more information about how Android maintains a history of activities and
enables user multitasking, continue with the <b><a
href="{@docRoot}guide/components/tasks-and-back-stack.html">Tasks and Back
Stack</a></b> document.</p>
-->