xref: /frameworks/base/docs/html-intl/intl/vi/guide/components/tasks-and-back-stack.jd

page.title=Tc v v Ngn xp
parent.title=Hot ng
parent.link=activities.html
@jd:body

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

<h2>Trong ti liu ny</h2>
<ol>
<li><a href="#ActivityState">Lu Trng thi ca Hot ng</a></li></li>
<li><a href="#ManagingTasks">Qun l Tc v</a>
  <ol>
    <li><a href="#TaskLaunchModes">nh ngha cc ch  khi chy</a></li>
    <li><a href="#Affinities">X l quan h</a></li>
    <li><a href="#Clearing">Xa ngn xp</a></li>
    <li><a href="#Starting">Bt u mt tc v</a></li>
  </ol>
</li>
</ol>

<h2>Bi vit</h2>
<ol>
  <li><a href="http://android-developers.blogspot.com/2010/04/multitasking-android-way.html">
  a nhim theo cch ca Android</a></li>
</ol>

<h2>Xem thm</h2>
<ol>
  <li><a href="{@docRoot}design/patterns/navigation.html">Thit k Android:
iu hng</a></li>
  <li><a href="{@docRoot}guide/topics/manifest/activity-element.html">Phn t bn k khai {@code &lt;activity&gt;}
</a></li>
  <li><a href="{@docRoot}guide/components/recents.html">Mn hnh Tng quan</a></li>
</ol>
</div>
</div>


<p>Mt ng dng thng cha nhiu <a href="{@docRoot}guide/components/activities.html">hot ng</a>. Mi hot ng
nn c thit k xung quanh mt kiu hnh ng c th m ngi dng c th thc hin v bt u cc hot ng
khc. V d, mt ng dng e-mail c th c mt hot ng  hin th mt danh sch cc th mi.
Khi ngi dng chn mt th, mt hot ng mi s m ra  xem th .</p>

<p>Hot ng thm ch c th bt u cc hot ng tn ti trong cc ng dng khc trn thit b. V
d, nu ng dng ca bn mun gi mt th e-mail, bn c th nh ngha mt  nh  thc hin mt hnh ng
"gi" v bao gm mt s d liu, chng hn nh a ch e-mail v ni dung. Mt hot ng t mt ng dng
khc t khai bo l c kh nng x l kiu  nh ny s m ra. Trong trng hp ny,
 nh s gi mt e-mail, sao cho hot ng "son" ca mt ng dng e-mail s bt u (nu nhiu hot ng
h tr cng  nh, khi  h thng cho php ngi dng chn hot ng s s dng). Khi e-mail c
gi, hot ng ca bn tip tc v dng nh hot ng e-mail l mt phn ng dng ca bn. Mc d
cc hot ng c th n t nhng ng dng khc nhau, Android duy tr tri nghim ngi dng
mt m ny bng cch gi c hai hot ng trong cng <em>tc v</em>.</p>

<p>Tc v l mt tp hp gm nhiu hot ng m ngi dng tng tc vi
khi thc hin mt cng vic nht nh. Cc hot ng c sp xp trong mt chng (<em>ngn xp</em>), theo
th t m mi hot ng.</p>

<!-- SAVE FOR WHEN THE FRAGMENT DOC IS ADDED
<div class="sidebox-wrapper">
<div class="sidebox">
<h3>Adding fragments to a task's back stack</h3>

<p>Your activity can also include {@link android.app.Fragment}s to the back stack. For example,
suppose you have a two-pane layout using fragments, one of which is a list view (fragment A) and the
other being a layout to display an item from the list (fragment B). When the user selects an item
from the list, fragment B is replaced by a new fragment (fragment C). In this case, it might be
desireable for the user to navigate back to reveal fragment B, using the <em>Back</em> button.</p>
<p>In order to add fragment B to the back stack so that this is possible, you must call {@link
android.app.FragmentTransaction#addToBackStack addToBackStack()} before you {@link
android.app.FragmentTransaction#commit()} the transaction that replaces fragment B with fragment
C.</p>
<p>For more information about using fragments and adding them to the back stack, see the {@link
android.app.Fragment} class documentation.</p>

</div>
</div>
-->

<p>Mn hnh Trang ch ca thit b l ni bt u i vi hu ht tc v. Khi ngi dng chm vo mt biu tng trong trnh khi chy
ng dng
 (hoc li tt trn mn hnh Trang ch), tc v ca ng dng  s tin ra tin cnh. Nu khng
c tc v no cho ng dng (ng dng cha c s dng gn y), khi  mt tc v mi
s c to v hot ng "chnh" cho ng dng  s m ra thnh hot ng gc trong chng.</p>

<p>Khi hot ng hin ti bt u mt hot ng khc, hot ng mi s b y ln trn cng ca chng v
c tiu im. Hot ng trc vn nm trong chng, nhng b dng li. Khi mt hot ng
dng, h thng gi li trng thi hin ti ca giao din ngi dng ca hot ng . Khi ngi dng nhn nt
<em>Quay li</em>
, hot ng hin ti c bt khi trn cng ca chng (hot ng b hy) v
hot ng trc tip tc (trng thi trc  ca UI ca n c khi phc). Cc hot ng trong chng
khng bao gi c sp xp li, m ch b y v bt khi chng&mdash;b y ln trn chng khi c bt u bi
hot ng hin ti v b bt khi chng khi ngi dng ri n bng cch s dng nt <em>Quay li</em>. Nh vy,
ngn xp
vn hnh nh mt cu trc i tng "vo cui, ra u". Hnh 1 minh ha
hnh vi ny cng mt dng thi gian th hin tin  gia cc hot ng dc theo ngn xp
hin ti  tng thi im.</p>

<img src="{@docRoot}images/fundamentals/diagram_backstack.png" alt="" />
<p class="img-caption"><strong>Hnh 1.</strong> Biu din cch mi hot ng mi trong mt
tc v thm mt mc vo ngn xp. Khi ngi dng nhn nt <em>Quay li</em>, hot ng
hin ti
b hy v hot ng trc  tip tc.</p>


<p>Nu ngi dng tip tc nhn <em>Quay li</em>, khi  mi hot ng trong chng b bt khi 
hin ra
hot ng trc, ti khi ngi dng quay li mn hnh Trang ch (hoc tr v hot ng ang chy khi
tc v bt u). Khi tt c hot ng b loi b khi chng, tc v s khng cn tn ti.</p>

<div class="figure" style="width:287px">
<img src="{@docRoot}images/fundamentals/diagram_multitasking.png" alt="" /> <p
class="img-caption"><strong>Hnh 2.</strong> Hai tc v: Tc v B nhn tng tc ngi dng
trong tin cnh, trong khi Tc v A nm di nn, ch c tip tc.</p>
</div>
<div class="figure" style="width:215px">
  <img src="{@docRoot}images/fundamentals/diagram_multiple_instances.png" alt="" /> <p
class="img-caption"><strong>Hnh 3.</strong> Mt hot ng n l c khi to nhiu ln.</p>
</div>

<p>Tc v l mt n v dnh kt, c th di chuyn ti "nn" khi ngi dng bt u mt tc v mi hoc i n
mn hnh Trang ch, thng qua nt <em>Home</em>. Khi  trong nn, tt c hot ng trong
tc v b
dng, nhng ngn xp cho tc v vn khng b nh hng&mdash;tc v ch n thun mt tiu im trong khi
mt tc v khc thay th, nh minh ha trong hnh 2. Khi , mt tc v c th quay li "tin cnh"  ngi dng
c th chn  ni h  ri i. V d, gi s rng tc v hin ti (Tc v A) c ba
hot ng trong chng ca mnh&mdash;hai trong s  nm di hot ng hin ti. Ngi dng nhn nt <em>Trang ch</em>
, sau 
bt u mt ng dng mi t trnh khi chy ng dng. Khi mn hnh Trang ch xut hin, Tc v A i vo
nn. Khi ng dng mi bt u, h thng s bt u mt tc v cho ng dng 
(Tc v B) bng chng cc hot ng ca chnh mnh. Sau khi tng tc vi
ng dng , ngi dng quay li Trang ch ln na v chn ng dng
 bt u Tc v A lc u. Lc ny, Tc v A i n
tin cnh&mdash;c ba hot ng trong chng ca n u gi nguyn v hot ng trn cng
ca chng c tip tc. Ti
im ny, ngi dng cng c th chuyn tr li Tc v B bng cch n Trang ch v chn biu tng ng dng
 bt u tc v  (hoc bng cch chn tc v ca ng dng t
<a href="{@docRoot}guide/components/recents.html">mn hnh tng quan</a>).
y l mt v d v a nhim trn Android.</p>

<p class="note"><strong>Lu :</strong> Nhiu tc v c th c lu gi cng lc trong nn.
Tuy nhin, nu ngi dng ang chy nhiu tc v nn ti cng thi im, h thng c th bt u
hy cc hot ng nn  khi phc b nh, khin trng thi ca hot ng b mt.
Xem phn sau y v <a href="#ActivityState">Trng thi ca hot ng</a>.</p>

<p>V cc hot ng trong ngn xp khng bao gi c sp xp li, nu ng dng ca bn cho php
ngi dng bt u mt hot ng c th t nhiu hn mt hot ng, mt thc th mi ca
hot ng  s c to v y ln chng (thay v mang bt k thc th no trc  ca
hot ng ln trn cng). Nh vy, mt hot ng trong ng dng ca bn c th c to phin bn nhiu
ln (thm ch t cc tc v khc nhau), nh minh ha trong hnh 3. Nh vy, nu ngi dng iu hng ngc li
bng cch s dng nt <em>Quay li</em>, mi thc th ca hot ng c hin th theo th t c
m (mi hot ng
c trng thi UI ca chnh chng). Tuy nhin, bn c th sa i hnh vi ny nu khng mun mt hot ng c
khi to nhiu hn mt ln. Cch lm nh vy c bn trong phn sau v <a href="#ManagingTasks">Qun l Tc v</a>.</p>


<p> tm tt hnh vi mc nh i vi cc hot ng v tc v:</p>

<ul>
  <li>Khi Hot ng A bt u Hot ng B, Hot ng A b dng, nhng h thng gi li trng thi ca n
(chng hn nh v tr cun v vn bn c nhp vo cc mu).
Nu ngi dng nhn nt <em>Quay li</em> khi ang trong Hot ng B, Hot ng A s tip tc vi trng thi
c khi phc.</li>
  <li>Khi ngi dng ri khi mt tc v bng cch nhn nt <em>Trang ch</em>, hot ng hin ti b
dng v
tc v ca n s a xung di nn. H thng s gi li trng thi ca mi hot ng trong tc v. Nu
sau  ngi dng tip tc tc v bng cch chn biu tng trnh khi chy  bt u tc v, tc v s vo
tin cnh v tip tc hot ng  trn cng ca chng.</li>
  <li>Nu ngi dng nhn nt <em>Quay li</em>, hot ng hin ti b bt khi chng
v
b hy. Hot ng trc   trong chng s c tip tc. Khi mt hot ng b hy, h thng
<em>khng</em> gi li trng thi ca hot ng .</li>
  <li>Hot ng c th c khi to nhiu ln, thm ch t cc tc v khc.</li>
</ul>


<div class="note design">
<p><strong>Thit k iu hng</strong></p>
  <p> bit thm v cch iu hng ng dng hot ng trn Android, hy c hng dn <a href="{@docRoot}design/patterns/navigation.html">iu hng</a> ca Thit k Android.</p>
</div>


<h2 id="ActivityState">Lu Trng thi ca Hot ng</h2>

<p>Nh c  cp  trn, hnh vi mc nh ca h thng gi nguyn trng thi ca mt hot ng khi n b
dng. Bng cch ny, khi ngi dng iu hng tr li mt hot ng trc , giao din ngi dng ca n s xut hin
 nh lc b ri i. Tuy nhin, bn c th&mdash;v <strong>nn</strong>&mdash;ch ng gi li
trng thi ca cc hot ng ca mnh bng cch s dng cc phng php gi li, trong trng hp hot ng b hy v phi
c to li.</p>

<p>Khi h thng dng mt trong cc hot ng ca bn (chng hn nh khi mt hot ng mi bt u hoc tc v
di chuyn v nn), h thng c th hon ton hy hot ng  nu n cn khi phc
b nh h thng. Khi iu ny xy ra, thng tin v trng thi ca hot ng s b mt. Nu iu ny xy ra, 
h thng vn
bit rng hot ng c mt v tr trong ngn xp, nhng khi hot ng c a ti v tr trn cng
ca chng, h thng phi to li n (thay v tip tc).  trnh
lm mt cng vic ca ngi dng, bn nn ch ng gi li n bng cch trin khai phng php gi li
{@link android.app.Activity#onSaveInstanceState onSaveInstanceState()} trong
hot ng ca mnh.</p>

<p> bit thm thng tin v cch lu trng thi hot ng ca mnh, hy xem ti liu <a href="{@docRoot}guide/components/activities.html#SavingActivityState">Hot ng</a>
.</p>



<h2 id="ManagingTasks">Qun l Tc v</h2>

<p>Cch Android qun l tc v v ngn xp, nh c m t bn trn&mdash;bng cch t tt c
hot ng c bt u ni tip nhau vo cng tc v v trong mt chng "vo cui, ra u"&mdash;rt
hiu qu i vi hu ht ng dng v bn khng phi lo lng v cch thc cc hot ng ca mnh c lin kt vi
cc tc v hay cch chng tn ti trong ngn xp. Tuy nhin, bn c th quyt nh rng mnh mun gin on
hnh vi thng thng. C th bn mun mt hot ng trong ng dng ca mnh bt u mt tc v mi khi n c
bt u (thay v c t trong tc v hin ti); hoc, khi bn bt u mt hot ng, bn mun
mang ln trc mt thc th hin ti ca n (thay v to mt
thc th mi trn cng ca ngn xp); hoc, bn mun ngn xp ca mnh c xa sch tt c cc
hot ng, ngoi tr hot ng gc khi ngi dng ri khi tc v.</p>

<p>Bn c th lm nhng iu ny v nhiu iu khc vi cc thuc tnh trong phn t bn k khai
<a href="{@docRoot}guide/topics/manifest/activity-element.html">{@code &lt;activity&gt;}</a>
v c trong  nh m bn chuyn cho
{@link android.app.Activity#startActivity startActivity()}.</p>

<p>V mt ny, cc thuc tnh <a href="{@docRoot}guide/topics/manifest/activity-element.html">
{@code &lt;activity&gt;}</a> chnh m bn c th s dng l:</p>

<ul class="nolist">
  <li><a href="{@docRoot}guide/topics/manifest/activity-element.html#aff">
  {@code taskAffinity}</a></li>
  <li><a href="{@docRoot}guide/topics/manifest/activity-element.html#lmode">
  {@code launchMode}</a></li>
  <li><a href="{@docRoot}guide/topics/manifest/activity-element.html#reparent">
  {@code allowTaskReparenting}</a></li>
  <li><a href="{@docRoot}guide/topics/manifest/activity-element.html#clear">
  {@code clearTaskOnLaunch}</a></li>
  <li><a href="{@docRoot}guide/topics/manifest/activity-element.html#always">
  {@code alwaysRetainTaskState}</a></li>
  <li><a href="{@docRoot}guide/topics/manifest/activity-element.html#finish">
  {@code finishOnTaskLaunch}</a></li>
</ul>

<p>V cc c  nh chnh m bn c th s dng l:</p>

<ul class="nolist">
  <li>{@link android.content.Intent#FLAG_ACTIVITY_NEW_TASK}</li>
  <li>{@link android.content.Intent#FLAG_ACTIVITY_CLEAR_TOP}</li>
  <li>{@link android.content.Intent#FLAG_ACTIVITY_SINGLE_TOP}</li>
</ul>

<p>Trong nhng phn sau, bn s thy cch bn c th s dng nhng thuc tnh ca bn k khai
v c  nh ny  nh ngha cch cc hot ng c lin kt vi tc v v hnh vi ca chng nh th no trong ngn xp.</p>

<p>Bn cnh , c phn bn ring v vic cn nhc cch cc tc v v hot ng c th
c biu din v qun l trong mn hnh tng quan. Xem phn <a href="{@docRoot}guide/components/recents.html">Mn hnh Tng quan</a>
 bit thm thng tin. Thng thng, bn nn cho php h thng nh ngha tc v v cc hot ng
ca bn c biu din nh th no trong mn hnh tng quan, v bn khng cn sa i hnh vi ny.</p>

<p class="caution"><strong>Ch :</strong> Hu ht cc ng dng khng nn gin on hnh vi
mc nh cho cc hot ng v tc v. Nu bn xc nh rng hot ng ca bn cn phi sa i
hnh vi mc nh, hy thn trng v m bo kim tra kh nng s dng c ca hot ng  trong khi
khi chy v khi iu hng tr li n t cc hot ng v tc v khc bng nt <em>Quay li</em>.
m bo kim tra hnh vi iu hng m c th xung t vi hnh vi c k vng ca ngi dng.</p>


<h3 id="TaskLaunchModes">nh ngha cc ch  khi chy</h3>

<p>Cc ch  khi chy cho php bn nh ngha mt thc th mi ca mt hot ng c lin kt vi tc v hin ti
nh th no. Bn c th nh ngha cc ch  khi chy khc nhau theo hai cch:</p>
<ul class="nolist">
  <li><a href="#ManifestForTasks">S dng tp bn k khai</a>
    <p>Khi bn khai bo mt hot ng trong tp bn k khai ca mnh, bn c th quy nh hot ng
s lin kt vi cc tc v nh th no khi n bt u.</li>
  <li><a href="#IntentFlagsForTasks">S dng c  nh</a>
    <p>Khi bn gi {@link android.app.Activity#startActivity startActivity()},
bn c th thm mt c vo {@link android.content.Intent} m khai bo cch (hoc
liu c hay khng) hot ng mi s lin kt vi tc v hin ti.</p></li>
</ul>

<p>Nh vy, nu Hot ng A bt u Hot ng B, Hot ng B c th nh ngha trong bn k khai ca mnh cch n
s lin kt vi tc v hin ti (nu c) v Hot ng A cng c th yu cu cch m Hot ng
B s lin kt vi tc v hin ti. Nu c hai hot ng u nh ngha cch Hot ng B
nn lin kt vi mt tc v th yu cu ca Hot ng A (nh nh ngha trong  nh) c u tin
so vi yu cu ca Hot ng B (nh c nh ngha trong bn k khai ca n).</p>

<p class="note"><strong>Lu :</strong> Mt s ch  khi chy sn c cho tp bn k khai
khng sn c di dng c cho mt  nh v, tng t, mt s ch  khi chy sn c di dng c
cho mt  nh khng th c nh ngha trong bn k khai.</p>


<h4 id="ManifestForTasks">S dng tp bn k khai</h4>

<p>Khi khai bo mt hot ng trong tp bn k khai ca bn, bn c th quy nh cch m hot ng
s lin kt vi mt tc v bng cch s dng thuc tnh ca phn t <a href="{@docRoot}guide/topics/manifest/activity-element.html">{@code &lt;activity&gt;}</a>
, <a href="{@docRoot}guide/topics/manifest/activity-element.html#lmode">{@code
launchMode}</a>.</p>

<p>Thuc tnh <a href="{@docRoot}guide/topics/manifest/activity-element.html#lmode">{@code
launchMode}</a> quy nh mt ch lnh v cch hot ng s c khi chy vo mt
tc v. C bn ch  khi chy khc nhau m bn c th gn cho thuc tnh
<code><a href="{@docRoot}guide/topics/manifest/activity-element.html#lmode">launchMode</a></code>
:</p>

<dl>
<dt>{@code "standard"} (ch  mc nh)</dt>
  <dd>Mc nh. H thng to mt thc th mi ca hot ng trong tc v l ni
m n c bt u v nh tuyn  nh ti . Hot ng c th c khi to nhiu ln,
mi thc th c th thuc v cc tc v khc nhau, v mt tc v c th c nhiu thc th.</dd>
<dt>{@code "singleTop"}</dt>
  <dd>Nu mt thc th ca hot ng  tn ti  trn cng ca tc v hin ti, h thng
s nh tuyn  nh ti thc th  thng qua mt lnh gi ti phng php {@link
android.app.Activity#onNewIntent onNewIntent()} ca n, thay v to mt thc th mi ca
hot ng. Hot ng c th c to phin bn nhiu ln, mi thc th c th
thuc v cc tc v khc nhau, v mt tc v c th c nhiu thc th (nhng ch nu
hot ng nm trn cng ca ngn xp <em>khng</em> phi l mt thc th ca hot ng hin c).
  <p>V d, gi s ngn xp ca mt tc v bao gm hot ng gc A vi cc hot ng B, C,
v D  trn cng (chng l A-B-C-D; D  trn cng). Mt  nh n cho loi hot ng D.
Nu D c ch  khi chy {@code "standard"} mc nh, mt thc th mi ca lp s c khi chy v
chng tr thnh A-B-C-D-D. Tuy nhin, nu ch  khi chy ca D l {@code "singleTop"}, thc th hin ti 
ca D s nhn  nh thng qua {@link
android.app.Activity#onNewIntent onNewIntent()}, bi n nm  v tr trn cng ca chng&mdash;chng
vn l A-B-C-D. Tuy nhin, nu mt  nh n cho hot ng loi B, khi  mt thc th
mi ca B s c thm vo chng ngay c khi ch  khi chy ca n l {@code "singleTop"}.</p>
  <p class="note"><strong>Lu :</strong> Khi mt thc th mi ca hot ng c to,
ngi dng c th nhn nt <em>Quay li</em>  quay v hot ng trc . Nhng khi mt thc th
hin ti ca
hot ng x l mt  nh mi, ngi dng khng th nhn nt <em>Quay li</em>  quay v trng thi
ca
hot ng trc khi  nh mi n trong {@link android.app.Activity#onNewIntent
onNewIntent()}.</p>
</dd>

<dt>{@code "singleTask"}</dt>
  <dd>H thng s to ra mt tc v mi v khi to hot ng  gc ca tc v mi.
Tuy nhin, nu mt thc th ca hot ng  tn ti trong mt tc v ring, h thng s nh tuyn
 nh ti thc th hin ti thng qua mt lnh gi ti phng php {@link
android.app.Activity#onNewIntent onNewIntent()} ca n thay v to mt thc th mi. Ch
mt thc th ca hot ng c th tn ti  mt thi im.
  <p class="note"><strong>Lu :</strong> Mc d hot ng bt u mt tc v mi, nt
<em>Quay li</em> s vn a ngi dng quay v hot ng trc .</p></dd>
<dt>{@code "singleInstance"}.</dt>
  <dd>Ging nh {@code "singleTask"}, tr khi h thng khng khi chy bt k hot ng no khc vo
tc v ang nm gi thc th. Hot ng lun l thnh vin n l v duy nht ca tc v;
bt k hot ng no c bt u bi hot ng ny s m ra trong mt tc v ring.</dd>
</dl>


<p>Ly mt v d khc, ng dng Trnh duyt ca Android khai bo rng hot ng trnh duyt web s
lun m tc v ca chnh mnh&mdash;bng cch quy nh ch  khi chy {@code singleTask} trong phn t <a href="{@docRoot}guide/topics/manifest/activity-element.html">{@code &lt;activity&gt;}</a>.
iu ny c ngha rng nu ng dng ca bn pht hnh mt
 nh  m Trnh duyt Android, hot ng ca n <em>khng</em> c t trong cng
tc v nh ng dng ca bn. Thay vo , hoc l mt tc v mi bt u cho Trnh duyt hoc, nu Trnh duyt
 c mt tc v ang chy trong nn th tc v  s c a ln trc  x l
 nh mi.</p>

<p>Khng ph thuc vo vic mt hot ng bt u trong mt tc v mi hay trong cng tc v m hot ng
 bt u, nt <em>Quay li</em> s lun a ngi dng v hot ng trc . Tuy nhin, nu bn
bt u mt hot ng m quy nh ch  khi chy {@code singleTask}, khi  nu mt thc th ca
hot ng  tn ti trong mt tc v nn, ton b tc v  s c a ra tin cnh. Ti thi im ny
, lc ny ngn xp bao gm tt c hot ng t tc v c mang ra,  v tr trn cng ca
chng. Hnh 4 minh ha loi kch bn ny.</p>

<img src="{@docRoot}images/fundamentals/diagram_backstack_singletask_multiactivity.png" alt="" />
<p class="img-caption"><strong>Hnh 4.</strong> Biu din cch thc mt hot ng vi
ch  khi chy "singleTask" c thm vo ngn xp. Nu hot ng  l mt phn ca mt
tc v nn vi ngn xp ca chnh n, khi  ton b ngn xp cng tin
v pha trc,  trn cng tc v hin ti.</p>

<p> bit thm thng tin v vic s dng cc ch  khi chy trong tp bn k khai, hy xem ti liu phn t
<code><a href="{@docRoot}guide/topics/manifest/activity-element.html">&lt;activity&gt;</a></code>
, trong  c trnh by thm v thuc tnh {@code launchMode} v cc gi tr
c chp nhn.</p>

<p class="note"><strong>Lu :</strong> Hnh vi m bn quy nh cho hot ng ca mnh bng thuc tnh <a href="{@docRoot}guide/topics/manifest/activity-element.html#lmode">{@code launchMode}</a> c th
b khng ch bi c c  nh bt u hot ng ca bn, nh c trnh by trong
phn tip theo.</p>



<h4 id="#IntentFlagsForTasks">S dng c  nh</h4>

<p>Khi bt u mt hot ng, bn c th sa i lin kt mc nh gia mt hot ng vi tc v ca n
bng cch thm c vo trong  nh m bn chuyn ti {@link
android.app.Activity#startActivity startActivity()}. Nhng c m bn c th s dng  sa i
hnh vi mc nh l:</p>

<p>
  <dt>{@link android.content.Intent#FLAG_ACTIVITY_NEW_TASK}</dt>
    <dd>Bt u mt hot ng trong mt tc v mi. Nu  c mt tc v ang chy cho hot ng m bn ang
bt u, tc v  s c a ra tin cnh vi trng thi cui cng c khi phc v hot ng
nhn  nh mi trong {@link android.app.Activity#onNewIntent onNewIntent()}.
    <p>iu ny s to ra cng hnh vi nh gi tr {@code "singleTask"} <a href="{@docRoot}guide/topics/manifest/activity-element.html#lmode">{@code launchMode}</a>,
 c trnh by  phn trc.</p></dd>
  <dt>{@link android.content.Intent#FLAG_ACTIVITY_SINGLE_TOP}</dt>
    <dd>Nu hot ng ang c bt u l hot ng hin ti ( trn cng ca ngn xp), khi 
thc th hin c s nhn mt lnh gi n {@link android.app.Activity#onNewIntent onNewIntent()},
thay v to mt thc th ca hot ng mi.
    <p>iu ny s to ra cng hnh vi nh gi tr {@code "singleTop"} <a href="{@docRoot}guide/topics/manifest/activity-element.html#lmode">{@code launchMode}</a>,
 c trnh by  phn trc.</p></dd>
  <dt>{@link android.content.Intent#FLAG_ACTIVITY_CLEAR_TOP}</dt>
    <dd>Nu hot ng ang c bt u ang chy trong tc v hin ti, khi 
thay v khi chy mt thc th mi ca hot ng , tt c cc hot ng khc bn trn n u
b hy v  nh ny c chuyn ti thc th c tip tc ca hot ng (lc ny ang  trn cng),
thng qua {@link android.app.Activity#onNewIntent onNewIntent()}).
    <p>Khng c gi tr cho thuc tnh <a href="{@docRoot}guide/topics/manifest/activity-element.html#lmode">{@code launchMode}</a>
m sinh ra hnh vi ny.</p>
    <p>{@code FLAG_ACTIVITY_CLEAR_TOP} c s dng thng xuyn nht cng vi
    {@code FLAG_ACTIVITY_NEW_TASK}.
Khi c s dng cng nhau, nhng c ny l mt cch  nh v hot ng hin ti
trong mt tc v khc v t n vo v tr ni n c th hi p  nh. </p>
    <p class="note"><strong>Lu :</strong> Nu ch  khi chy ca hot ng c ch nh l
    {@code "standard"},
n cng b loi b khi chng v mt thc th mi s c khi chy thay ch n  x l
 nh n.   l bi mt thc th mi lun c to cho  nh mi khi ch  khi chy
l {@code "standard"}. </p>
</dd>
</dl>





<h3 id="Affinities">X l quan h</h3>

<p><em>Quan h</em> s cho bit mt hot ng u tin thuc v tc v no hn. Theo mc nh, tt c
cc hot ng t cng ng dng c quan h vi nhau. V th, theo mc nh, tt c
hot ng trong cng ng dng u tin  trong cng tc v hn. Tuy nhin, bn c th sa i
quan h mc nh cho mt hot ng. Cc hot ng c nh ngha trong
cc ng dng khc nhau c th chia s mt quan h, hoc cc hot ng c nh ngha trong cng ng dng c th
c gn cc quan h tc v khc nhau.</p>

<p>Bn c th sa i quan h cho bt k hot ng  cho no bng thuc tnh <a href="{@docRoot}guide/topics/manifest/activity-element.html#aff">{@code taskAffinity}</a> ca
phn t <a href="{@docRoot}guide/topics/manifest/activity-element.html">{@code &lt;activity&gt;}</a>
.</p>

<p>Thuc tnh <a href="{@docRoot}guide/topics/manifest/activity-element.html#aff">{@code taskAffinity}</a>
ly mt gi tr xu,  phi l gi tr duy nht t tn gi mc nh
c khai bo trong phn t <a href="{@docRoot}guide/topics/manifest/manifest-element.html">
{@code &lt;manifest&gt;}
</a>, do h thng s dng tn   nhn bit quan h
tc v mc nh cho ng dng.</p>

<p>Vn  quan h c xt trong hai trng hp:</p>
<ul>
  <li>Khi  nh khi chy hot ng cha c
  {@link android.content.Intent#FLAG_ACTIVITY_NEW_TASK}
.

<p>Theo mc nh, mt hot ng mi c khi chy vo tc v ca hot ng
 gi {@link android.app.Activity#startActivity startActivity()}. N c y ln cng
ngn xp nh trnh gi.  Tuy nhin, nu  nh c chuyn ti
{@link android.app.Activity#startActivity startActivity()}
cha c {@link android.content.Intent#FLAG_ACTIVITY_NEW_TASK}
, h thng s tm mt tc v khc  cha hot ng mi. Thng th  l mt tc v mi.
Tuy nhin, khng nht thit phi nh vy.  Nu  c mt tc v hin ti vi cng quan h nh
hot ng mi, hot ng s c khi chy vo tc v .  Nu khng, n s bt u mt tc v mi.</p>

<p>Nu c ny khin mt hot ng bt u mt tc v mi v ngi dng nhn nt <em>Home</em>
 ri
n th phi c mt cch no   ngi dng iu hng quay li tc v. Mt s i tng (chng hn nh
trnh qun l thng bo) lun bt u cc hot ng trong mt tc v bn ngoi, khng bao gi bt u trong chnh tc v ca mnh, v th
chng lun t {@code FLAG_ACTIVITY_NEW_TASK} vo  nh m chng chuyn ti
{@link android.app.Activity#startActivity startActivity()}.
Nu bn c mt hot ng c th c gi ra bi
mt i tng bn ngoi m c th s dng c ny, hy lu  l ngi dng c mt cch c lp  quay li
tc v  c bt u, chng hn nh bng mt biu tng trnh khi chy (hot ng gc ca tc v
c mt b lc  nh {@link android.content.Intent#CATEGORY_LAUNCHER}; xem phn <a href="#Starting">Bt u mt tc v</a>  bn di).</p>
</li>

  <li>Khi mt hot ng c thuc tnh <a href="{@docRoot}guide/topics/manifest/activity-element.html#reparent">
{@code allowTaskReparenting}</a> ca n c t thnh {@code "true"}.
  <p>Trong trng hp ny, hot ng c th di chuyn t tc v m n bt u ti tc v m n c quan h
 khi tc v  i ra tin cnh.</p>
  <p>V d, gi s rng mt hot ng vi chc nng bo co tnh hnh thi tit  cc thnh ph c chn
c nh ngha l mt phn trong mt ng dng du lch.  N c cng quan h nh cc hot ng khc trong cng
ng dng (quan h ng dng mc nh) v n cho php to li tp m vi thuc tnh ny.
Khi mt trong cc hot ng ca bn bt u hot ng trnh bo co thi tit, ban u n thuc v cng
tc v nh hot ng ca bn. Tuy nhin, khi tc v ca ng dng du lch i ra tin cnh, hot ng
ca trnh bo co thi tit c gn li cho tc v  v c hin th bn trong n.</p>
</li>
</ul>

<p class="note"><strong>Mo:</strong> Nu mt tp {@code .apk} cha nhiu hn mt "ng dng"
t quan im ca ngi dng, bn c th mun s dng thuc tnh <a href="{@docRoot}guide/topics/manifest/activity-element.html#aff">{@code taskAffinity}</a>
 gn cc quan h khc nhau cho hot ng c lin kt vi tng "ng dng".</p>



<h3 id="Clearing">Xa ngn xp</h3>

<p>Nu ngi dng ri mt tc v trong khong thi gian di, h thng s xa tc v ca tt c hot ng ngoi tr
hot ng gc.  Khi ngi dng quay tr li tc v, ch hot ng gc c khi phc.
H thng s hot ng theo cch ny, v, sau mt khong thi gian di, ngi dng c th  t b
vic m h ang lm trc  v quay li tc v  bt u mt vic mi. </p>

<p>C mt s thuc tnh hot ng m bn c th s dng  sa i hnh vi ny: </p>

<dl>
<dt><code><a
href="{@docRoot}guide/topics/manifest/activity-element.html#always">alwaysRetainTaskState</a></code>
</dt>
<dd>Nu thuc tnh ny c t thnh {@code "true"} trong hot ng gc ca mt tc v,
hnh vi mc nh c m t s khng xy ra.
Tc v gi li tt c hot ng trong chng ca mnh k c sau mt khong thi gian di.</dd>

<dt><code><a
href="{@docRoot}guide/topics/manifest/activity-element.html#clear">clearTaskOnLaunch</a></code></dt>
<dd>Nu thuc tnh ny c t thnh {@code "true"} trong hot ng gc ca mt tc v,
chng s b xa ti hot ng gc bt c khi no ngi dng ri khi tc v
v quay li.  Ni cch khc, n ngc vi
<a href="{@docRoot}guide/topics/manifest/activity-element.html#always">
{@code alwaysRetainTaskState}</a>. Ngi dng lun quay li tc v 
trng thi ban u ca n, ngay c sau khi ri khi tc v trong ch mt lc.</dd>

<dt><code><a
href="{@docRoot}guide/topics/manifest/activity-element.html#finish">finishOnTaskLaunch</a></code>
</dt>
<dd>Thuc tnh ny ging nh <a href="{@docRoot}guide/topics/manifest/activity-element.html#clear">{@code clearTaskOnLaunch}</a>,
nhng n hot ng trn mt tc v
n l ch khng phi mt tc v ton b.  N cng c th khin bt k hot ng no
thot mt, bao gm c hot ng gc.  Khi n c t thnh {@code "true"}, hot ng
vn l mt b phn ca tc v ch cho phin lm vic hin ti.  Nu ngi dng ri i
ri quay li tc v, n khng cn xut hin na.</dd>
</dl>




<h3 id="Starting">Bt u mt tc v</h3>

<p>Bn c th thit lp mt hot ng lm im bt u cho mt tc v bng cch a cho n mt b lc  nh vi
{@code "android.intent.action.MAIN"} l hnh ng c quy nh v
{@code "android.intent.category.LAUNCHER"}
l th loi c quy nh. V d:</p>

<pre>
&lt;activity ... &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>Mt b lc  nh loi ny khin mt biu tng v nhn cho
hot ng c hin th trong trnh khi chy ng dng, cho php ngi dng khi chy hot ng v
quay li tc v m n to ra vo bt c lc no sau khi n c khi chy.
</p>

<p>Kh nng th hai ny l quan trng: Ngi dng chc chn c th ri mt tc v ri quay li
sau bng cch s dng trnh khi chy hot ng ny. V l do ny, hai <a href="#LaunchModes">ch 
khi chy</a> m nh du cc hot ng l lun khi to mt tc v, {@code "singleTask"} v
{@code "singleInstance"}, s ch c s dng khi hot ng c mt
{@link android.content.Intent#ACTION_MAIN}
v mt b lc {@link android.content.Intent#CATEGORY_LAUNCHER}. V d, hy tng tng chuyn g
s xy ra nu thiu b lc: Mt  nh khi chy mt hot ng {@code "singleTask"}, khi u mt
tc v mi v ngi dng dnh mt khong thi gian lm vic trong tc v . Khi , ngi dng nhn nt <em>Home</em>
. Lc ny, tc v c gi ti nn v khng hin th. By gi, ngi dng khng c cch no  quay li
tc v bi n khng c biu din trong trnh khi chy ng dng.</p>

<p>i vi nhng trng hp m bn khng mun ngi dng c th quay li mt hot ng, hy t gi tr ca phn t 
<code><a href="{@docRoot}guide/topics/manifest/activity-element.html">&lt;activity&gt;</a></code>
, 
<a href="{@docRoot}guide/topics/manifest/activity-element.html#finish">{@code finishOnTaskLaunch}</a>
thnh {@code "true"} (xem <a href="#Clearing">Xa chng</a>).</p>

<p>Bn c th tham kho thm thng tin v cch cc tc v v hot ng c trnh by v qun l trong
mn hnh tng quan sn c ti phn <a href="{@docRoot}guide/components/recents.html">
Mn hnh Tng quan</a>.</p>

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

<p>For more information about how to use intents to
activate other application components and publish the intents to which your components
respond, continue with the <b><a
href="{@docRoot}guide/components/intents-filters.html">Intents and Intent
Filters</a></b> document.</p>
-->