versions/nougat/android-7.0-changes.jd

page.title=Cc thay i Hnh vi
page.keywords=preview,sdk,compatibility
meta.tags="preview", "compatibility"
page.tags="preview", "developer preview"
page.image=images/cards/card-n-changes_2x.png
@jd:body


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

<h2>Trong ti liu ny</h2>

<ol>
  <li><a href="#perf">Ci thin Hiu nng</a>
    <ol>
      <li><a href="#doze">Ch  Ng su</a></li>
      <li><a href="#bg-opt">Ti u ha Chy ngm</a></li>
    </ol>
  </li>
  <li><a href="#perm">Thay i Quyn</a></li>
  <li><a href="#accessibility">Ci thin Tr nng</a>
    <ol>
      <li><a href="#screen-zoom">Thu phng Mn hnh</a></li>
      <li><a href="#vision-settings">Ci t Kh nng nhn trong Trnh Thit lp</a></li>
    </ol>
  </li>
  <li><a href="#ndk">Lin kt ng dng NDK vi Th vin Nn tng</a></li>
  <li><a href="#afw">Android cho Cng vic</a></li>
</ol>

<h2>Xem thm</h2>
<ol>
  <li><a href="{@docRoot}preview/api-overview.html">
    Tng quan v API Android N</a></li>
</ol>

</div>
</div>


<p>
  Vi cc tnh nng v kh nng mi, Android N
  cng c mt s cc thay i hnh vi ca h thng v API. Ti liu
  ny nu bt mt s cc thay i quan trng m bn cn bit v cn nhc cho
   ng dng ca mnh.
</p>

<p>
  Nu bn  tng pht hnh ng dng cho Android, hy lu  rng cc thay i
  trong nn tng ny c th tc ng n ng dng ca bn.
</p>


<h2 id="perf">Ci thin Hiu nng</h2>

<p>
  Android N c cha cc thay i hnh vi ca h thng nhm ci thin thi lng
  pin ca thit b, s dng RAM v hiu nng ng dng. Cc thay i ny c th tc ng n
   tnh kh dng ca ti nguyn v cc thng bo h thng i ti ng dng. Bn
  nn tm hiu cc thay i ny v nh gi xem ng dng cn phi iu chnh nh th no i vi
  cc thay i.
</p>

<h3 id="doze">Ch  Ng su</h3>

<p>
  c a vo Android 6.0 (Mc API 23), Ch  Ng su ci thin thi lng pin bng cch
  tr hon cc hot ng ca CPU v mng khi ngi dng khng cm sc,
   khng di chuyn v tt mn hnh thit b. Android N
  thm cc ci tin cho Ch  Ng su bng cch s dng mt tp con cc hn ch ca CPU v mng
  khi thit b khng c cm sc vi mn hnh b tt, nhng khng nht thit
  phi  mt ch, v d nh mt thit b cm tay di chuyn trong ti ca ngi dng.
</p>


<img src="{@docRoot}images/android-7.0/doze-diagram-1.png" alt="" height="251px" id="figure1" />
<p class="img-caption">
  <strong>Hnh 1.</strong> Minh ha cch thc Ch  Ng su p dng  cp u tin ca
  cc hn ch hot ng h thng nhm ci thin thi lng pin.
</p>

<p>
  Khi mt thit b dng ngun in t pin v mn hnh b tt trong mt khong thi gian
  nht nh, thit b s chuyn vo Ch  Ng su v p dng tp con u tin ca cc hn ch: N
  s ngt truy cp mng ca ng dng v tr hon cc tc v v cc ng b. Nu thit b
  c t mt ch trong mt khong thi gian nht nh sau khi vo Ch  Ng su th h thng s p dng
   cc hn ch cn li ca Ch  Ng su thnh {@link android.os.PowerManager.WakeLock}, bo thc
{@link android.app.AlarmManager}, GPS, qut Wi-Fi. Cho d
  mt s hoc tt c cc hn ch ca Ch  Ng su c c p dng hay khng th h thng s nh thc
  thit b trong cc khong thi gian bo tr ngn, trong  cc ng dng c php
  truy cp mng v c th thc thi mi tc v/ng b b tr hon.
</p>


<img src="{@docRoot}images/android-7.0/doze-diagram-2.png" alt="" id="figure2" />
<p class="img-caption">
  <strong>Hnh 2.</strong> Minh ha cch Ch  Ng su p dng cp th hai ca
   cc hn ch hot ng h thng sau khi thit b c t mt ch trong mt khong thi gian nht nh.
</p>

<p>
  Lu  rng vic bt mn hnh hoc cm sc s a thit b thot Ch  Ng su v
  loi b cc hn ch x l ny. Hnh vi b sung ny khng
  nh hng n cc khuyn ngh v cc thc hnh tt nht khi thch ng cho ng dng ca bn vi phin bn
  Ch  Ng su c a vo Android 6.0 (API mc 23) trc , nh m t trong
  <a href="{@docRoot}training/monitoring-device-state/doze-standby.html">
  Ti u ha Ch  Ng su v Ch  Ch ca ng dng</a>.  Bn nn tip tc
  lm theo cc khuyn ngh , v d nh s dng Google Cloud Messaging (GCM)
  gi v nhn tin nhn, v hy tin hnh p dng cc bn cp nht  nhn
  hnh vi Ch  Ng su b sung.
</p>


<h3 id="bg-opt">D n Svelte: Ti u ha Chy ngm</h3>

<p>
  Android N g b ba truyn pht khng biu th  gip ti u ha c
  vic s dng b nh ln tiu th in nng. Thay i ny l iu cn thit bi cc truyn pht
  khng biu th thng xuyn khi ng cc ng dng  c ng k  lng nghe chng di
  nn. G b cc truyn pht ny c th em li li ch ln i vi hiu nng
  ca thit b v tri nghim ngi dng.
</p>

<p>
  Cc thit b di ng thng xuyn gp phi nhng thay i v kt ni, chng hn nh khi di chuyn
  gia Wi-Fi v d liu di ng. Hin ti, cc ng dng c th theo di nhng thay i v
  kt ni bng cch ng k mt b thu truyn pht cho {@link
  android.net.ConnectivityManager#CONNECTIVITY_ACTION} khng biu th trong bn k khai
  ca chng. V nhiu ng dng ng k  nhn truyn pht ny do  mt hot ng chuyn mng
  duy nht cng c th khin tt c cc ng dng thc dy v x l truyn pht  ngay
  lp tc.
</p>

<p>
  Tng t, cc ng dng c th ng k nhn truyn pht {@link
  android.hardware.Camera#ACTION_NEW_PICTURE} v {@link
  android.hardware.Camera#ACTION_NEW_VIDEO} khng biu th t cc ng dng khc, v d nh
ng dng Camera. Khi mt ngi dng chp nh vi ng dng Camera th nhng ng dng ny s thc dy
   x l truyn pht .
</p>

<p>
   loi b cc vn  ny, Android N p dng cc cch ti u ha
  sau:
</p>

<ul>
  <li>ng dng nhm mc tiu Android N s khng nhn cc truyn pht {@link
  android.net.ConnectivityManager#CONNECTIVITY_ACTION}, ngay c khi chng
  c cc mc nhp ca trong bn k khai yu cu thng bo v cc s kin ny. Nhng ng dng ang chy
   tin cnh vn c th lng nghe {@code CONNECTIVITY_CHANGE} qua
 lung chnh ca chng nu yu cu thng bo bng {@link
  android.content.BroadcastReceiver}.
  </li>

  <li>ng dng khng th gi hoc nhn cc truyn pht {@link
  android.hardware.Camera#ACTION_NEW_PICTURE} hoc {@link
  android.hardware.Camera#ACTION_NEW_VIDEO}. Cch ti u ny
  tc ng n mi ng dng, khng ch cc ng dng nhm mc tiu Android N.
  </li>
</ul>

<p>
  Cc ln pht hnh Android sau ny c th loi b thm cc truyn pht khng biu th, cng
   nh cc dch v chy ngm khng cn lin kt. V l do ny, bn nn trnh dng hoc
  g b cc ph thuc trn cc b thu c khai bo trong bn k khai i vi cc truyn pht khng biu th,
  cng nh cc dch v chy ngm.
</p>

<p>
  Khun kh Android cung cp mt s gii php  gim thiu s cn thit i vi
  cc truyn pht khng biu th hoc cc dch v chy ngm ny. V d, API {@link
  android.app.job.JobScheduler} cung cp mt c ch ln lch hiu qu
 cho cc hot ng mng khi p ng cc iu kin c ch nh, v d nh kt ni ti mt
  mng khng o lu lng. Bn cn c th s dng {@link
  android.app.job.JobScheduler}  phn ng li cc thay i i vi trnh cung cp ni dung.
</p>

<p>
   bit thm thng tin v thay i hnh vi ny v cch thch ng ng dng ca bn,
  hy xem <a href="{@docRoot}preview/features/background-optimization.html">Ti u ha
 Chy ngm</a>.
</p>


<h2 id="perm">Thay i Quyn</h2>

<p>
  Android N c cc thay i i vi quyn c th tc ng n ng dng ca bn,
  bao gm cc quyn ti khon ngi dng v mt quyn mi cho php ghi vo
  b nh ngoi.  Sau y l phn tm tt cc quyn  thay i trong
 bn xem trc:
</p>

<ul>
  <li>{@code GET_ACCOUNTS} (B loi b)
    <p>
      Quyn GET_ACCOUNTS nay  b loi b. H thng s b qua quyn
  ny i vi cc ng dng nhm mc tiu Android N.
    </p>
  </li>

</ul>


<h2 id="accessibility">Ci thin Tr nng</h2>

<p>
  Android N c cc thay i nhm nng cao kh nng s dng
  ca nn tng cho nhng ngi dng c th lc km hoc khim th. Nhn chung, cc thay i ny s khng
  yu cu thay i m ngun trong ng dng ca bn. Tuy nhin, bn cn xem li
  cc tnh nng ny v kim th chng vi ng dng ca mnh  nh gi cc tc ng tim tng i vi tri nghim
 ngi dng.
</p>


<h3 id="screen-zoom">Thu phng Mn hnh</h3>

<p>
  Android N cho php ngi dng t <strong>Display size</strong>  phng to
  hoc thu nh tt c cc phn t trn mn hnh, nh  ci thin tr nng ca thit b
  cho nhng ngi dng c th lc km. Ngi dng khng th thu phng mn hnh vt qu chiu rng mn hnh
  ti thiu <a href="http://developer.android.com/guide/topics/resources/providing-resources.html">
  sw320dp</a>. y l chiu rng ca Nexus 4, mt my in thoi ph bin c kch c trung bnh.
</p>

<div class="cols">

<div class="col-6">
  <img src="{@docRoot}images/android-7.0/screen-zoom-1.png" alt="" height="XXX" id="figure1" />
</div>
<div class="col-6">
  <img src="{@docRoot}images/android-7.0/screen-zoom-2.png" alt="" height="XXX" id="figure1" />
</div>

</div> <!-- end cols -->
<p class="img-caption">
  <strong>Hnh 3.</strong> Mn hnh bn phi hin th tc ng ca
  vic tng kch c Hin th ca mt thit b ang chy nh h thng Android N.
</p>


<p>
  Khi mt  ca thit b thay i, h thng s thng bo cho cc ng dng ang chy theo
  nhng cch sau:
</p>

<ul>
  <li>Nu mt ng dng nhm mc tiu mc API 23 hoc thp hn th h thng s t ng tt
  tt c cc tin trnh chy ngm ca ng dng . iu ny c ngha l nu mt ngi dng ri khi
  ng dng   m mn hnh <em>Settings</em> v thay i
  <strong>Display size</strong> th h thng s tt ng dng ging
 nh trong trng hp thit b thiu b nh. Nu ng dng  c bt k tin trnh no
  chy  tin cnh th h thng s thng bo cho cc tin trnh  v thay i cu hnh nh
  m t trong <a href="{@docRoot}guide/topics/resources/runtime-changes.html">X l
 Thay i Thi gian chy</a>, ging nh hng ca thit b va thay i.
  </li>

  <li>Nu ng dng nhm mc tiu Android N th mi tin trnh ca n
   (chy  tin cnh v chy ngm) u c thng bo v thay i cu hnh nh
  m t trong <a href="{@docRoot}guide/topics/resources/runtime-changes.html">X l
 Thay i Thi gian chy</a>.
  </li>
</ul>

<p>
  Hu ht cc ng dng khng cn thc hin bt k thay i no  h tr tnh nng ny, min l
   cc ng dng  tun theo cc thc hnh tt nht ca Android. Nhng iu c th cn kim tra:
</p>

<ul>
  <li>Kim th ng dng ca bn trn mt thit b c chiu rng mn hnh <code><a href=
  "{@docRoot}guide/topics/resources/providing-resources.html">sw320dp</a></code>
  v m bo n hot ng ng.
  </li>

  <li>Khi cu hnh ca thit b thay i, hy cp nht mi thng tin c lu tr trong b m
   ph thuc vo mt , v d nh cc nh bitmap c lu m hoc cc ti nguyn c ti t
  mng. Hy kim tra cc thay i cu hnh khi ng dng khi phc t trng thi
  tm dng.
    <p class="note">
      <strong>Lu :</strong> Nu bn lu tr trong b m cc d liu ph thuc vo cu hnh th nn
   thm siu d liu lin quan nh kch c
     mn hnh ph hp hoc mt  im nh cho d liu . Vic lu siu d liu ny cho php bn
     quyt nh liu bn c cn phi lm mi d liu c lu tr m sau khi mt cu hnh
     thay i.
    </p>
  </li>

  <li>Trnh ch nh cc kch thc theo n v px v chng khng thay i t l theo
   mt  mn hnh. Thay vo , hy ch nh cc kch thc bng cc n v <a href="{@docRoot}guide/practices/screens_support.html">im nh
   c lp vi mt </a> (<code>dp</code>).
  </li>
</ul>

<h3 id="vision-settings">Ci t Kh nng nhn trong Trnh Thit lp</h3>

<p>
  Android N c Ci t Kh nng nhn trn mn hnh Cho mng, ni ngi dng c th
   thit lp cc ci t tr nng sau y trn mt thit b mi:
 <strong>Magnification gesture</strong>, <strong>Font size</strong>,
  <strong>Display size</strong> v <strong>TalkBack</strong>. Thay i ny
   s tng kh nng thy c cc khim khuyt lin quan n nhng ci t mn hnh khc nhau.
  nh gi tc ng ca tnh nng ny, bn c th kim th ng dng ca mnh vi cc
  ci t sau c bt. Bn c th tm cc ci t ny trong <strong>Settings &gt;
  Accessibility</strong>.
</p>

<h2 id="ndk">Lin kt ng dng NDK vi Th vin Nn tng</h2>

<p>
  Android N c cc thay i i vi khng gian tn  ngn vic ti cc API khng cng khai.
 Nu bn s dng NDK, bn ch nn s dng cc API cng khai t nn tng
  Android. S dng cc API khng cng khai trong bn pht hnh chnh thc tip theo ca Android
   c th khin ng dng b treo.
</p>

<p>
   cnh bo cho bn vic s dng cc API khng cng khai, cc ng dng chy trn thit b
   Android N s to ra mt li trong phn xut ra ca logcat khi mt ng dng gi mt API khng cng khai.
  Li ny cng c hin th trn mn hnh thit b di dng thng bo  h tr
  nng cao nhn bit i vi tnh hung ny. Bn nn xem li m ca ng dng
  g b phn s dng cc API nn tng khng cng khai v kim th k lng ng dng bng
   mt thit b hoc b gi lp ca bn xem trc.
</p>

<p>
  Nu ng dng ca bn ph thuc vo cc th vin ca nn tng, hy xem ti liu NDK  bit
  cc cch khc phc c bn nhm thay th cc API khng cng khai bng cc API cng khai tng ng.
   Bn cng c th lin kt vi cc th vin ca nn tng m khng nhn bit ng dng,
   c bit nu ng dng ca bn s dng th vin thuc mt phn ca nn tng (nh
  <code>libpng</code>), nhng khng thuc NDK. Trong trng hp , hy m bo rng
    tp APK ca bn c cha tt c cc tp .so bn d nh lin kt vi.
</p>

<p class="caution">
  <strong>Cn trng:</strong> Mt s th vin ca bn th ba c th lin kt vi cc API
  khng cng khai. Nu ng dng ca bn s dng cc th vin ny th ng dng ca bn c th gp li sp  khi ang chy
  trong ln pht hnh Android chnh thc k tip.
</p>

<p>
  Cc ng dng khng nn ph thuc vo hoc s dng cc th vin gc khng km theo trong
  NDK bi v chng c th thay i hoc b g b khi khi pht hnh bn Android khc
  thay cho bn c. Vic chuyn t OpenSSL sang BoringSSL l mt v d v s thay i .
  Ngoi ra, cc thit b khc nhau c th cung cp cc mc  tng thch khc nhau bi
  khng c yu cu no v kh nng tng thch cho cc th vin nn tng khng i km vi
  NDK. Nu bn buc phi s dng cc th vin khng thuc NDK trn cc thit b c, hy thc hin
  qu trnh ti ph thuc vo mc Android API.
</p>

<p>
  Nhm gip bn chn on cc loi vn  ny, sau y l mt s li Java v NDK
 v d bn c th gp phi khi c dng ng dng vi Android N:
</p>

<p>V d li Java:</p>
<pre class="no-pretty-print">
java.lang.UnsatisfiedLinkError: dlopen failed: library "/system/lib/libcutils.so"
    is not accessible for the namespace "classloader-namespace"
</pre>

<p>V d li NDK:</p>
<pre class="no-pretty-print">
dlopen failed: cannot locate symbol "__system_property_get" referenced by ...
</pre>


<p>
  Sau y l mt s cch khc phc i vi ng dng gp phi cc kiu li ny:
</p>

<ul>
  <li>Vic s dng getJavaVM v getJNIEnv trong libandroid_runtime.so c th c thay
  bng cc hm JNI chun:
<pre class="no-pretty-print">
AndroidRuntime::getJavaVM -&gt; GetJavaVM from &lt;jni.h&gt;
AndroidRuntime::getJNIEnv -&gt; JavaVM::GetEnv or
JavaVM::AttachCurrentThread from &lt;jni.h&gt;.
</pre>
  </li>

  <li>Vic s dng k hiu {@code property_get} trong {@code libcutils.so} c th c
    thay bng phng thc {@code __system_property_get} cng khai thay th.
    lm iu ny, hy dng {@code __system_property_get} vi cu lnh include sau:
<pre>
#include &lt;sys/system_properties.h&gt;
</pre>
  </li>

  <li>Vic s dng k hiu {@code SSL_ctrl} trong {@code libcrypto.so} nn c
  thay bng mt k hiu cc b ca ng dng. V d, bn nn lin kt tnh
  {@code libcyrpto.a} trong tp {@code .so} hoc thm tham chiu
  {@code libcrypto.so} ng ca ring mnh t BoringSSL hoc OpenSSL trong ng dng ca bn.
  </li>
</ul>

<h2 id="afw">Android cho Cng vic</h2>
<p>
  Android N c cc thay i cho ng dng nhm mc tiu Android cho Cng vic, bao gm
  cc thay i i vi ci t chng ch, t li mt khu, qun l ngi dng
  th hai v truy cp cc m nh danh ca thit b. Nu bn ang dng cc ng dng dnh cho
  cc mi trng Android cho Cng vic th bn nn xem li cc thay i ny v chnh sa
  ng dng ca mnh cho ph hp.
</p>

<ul>
  <li>Bn phi ci t mt trnh ci t chng ch y thc trc khi DPC c th t
  n. i vi c ng dng ngi s hu cu hnh v ng dng ngi s hu thit b nhm mc tiu SDK N, bn cn
  ci t trnh ci t chng ch y thc trc khi trnh kim sot
  chnh sch ca thit b (DPC) gi
  <code>DevicePolicyManager.setCertInstallerPackage()</code>. Nu trnh ci t
  cha c ci th h thng s a ra mt
  <code>IllegalArgumentException</code>.
  </li>

  <li>Gi y cc hn ch t li mt khu cho ngi qun l thit b s p dng vi ngi s hu
   cu hnh. Ngi qun l thit b khng th s dng
  <code>DevicePolicyManager.resetPassword()</code> c na  xa mt khu hoc thay i
  cc mt khu  t. Ngi qun l thit b vn c th t mt mt khu nhng ch
  khi thit b khng c mt khu, m PIN hoc mu hnh.
  </li>

  <li>Ngi s hu thit b hoc cu hnh c th qun l cc ti khon ngay c khi cc hn ch c
  t. Ngi s hu thit b v ngi s hu cu hnh c th gi cc API Qun l ti khon
  ngay c khi cc hn ch ngi dng <code>DISALLOW_MODIFY_ACCOUNTS</code>  c sn.
  </li>

  <li>Ngi s hu thit b c th qun l nhng ngi dng th cp d dng hn. Khi mt thit b
  ang chy trong ch  ngi s hu thit b, hn ch <code>DISALLOW_ADD_USER</code>
  s c t t ng. iu ny ngn ngi dng to cc ngi dng
  th cp khng c qun l. Ngoi ra, cc phng thc <code>CreateUser()</code> v
  <code>createAndInitial()</code>  b loi b; phng thc
<code>DevicePolicyManager.createAndManageUser()</code> mi s thay th chng.
  </li>

  <li>Ngi s hu thit b c th truy cp cc m nh danh ca thit b. Mt ngi s hu thit b c th truy cp
 a ch MAC ca Wi-Fi ca mt thit b, bng phng thc
  <code>DevicePolicyManagewr.getWifiMacAddress()</code>. Nu Wi-Fi cha tng
  c bt trn thit b  th phng thc ny s tr v mt gi tr {@code null}.
  </li>
</ul>

<p>
   bit thm thng tin v cc thay i i vi Android cho Cng vic trong Android N, hy xem
   <a href="{@docRoot}preview/features/afw.html">Cp nht ca Android cho Cng vic</a>.
</p>

<h2 id="other">Cc im quan trng khc</h2>

<ul>
<li>Khi mt ng dng ang chy trn Android N nhng nhm mc tiu mc API thp hn,
v ngi dng thay i kch c hin th th tin trnh ca ng dng s b tt. ng dng
phi c kh nng x l tnh hung ny mt cch tinh t. Nu khng, ng dng s b li sp
khi ngi dng khi phc n t mc Gn y.

<p>
Bn cn kim th ng dng  m bo
rng hnh vi ny khng xy ra.
Bn c th thc hin iu  bng cch gy ra mt li sp  ging vy
khi tt ng dng mt cch th cng qua DDMS.
</p>

<p>
Cc ng dng nhm mc tiu N v cao hn s khng b tt t ng khi c cc thay i v mt ;
tuy nhin, chng c th phn hi kh khn i vi cc thay i cu hnh.
</p>
</li>

<li>
Cc ng dng trn Android N cn c kh nng x l cc thay i cu hnh mt cch tinh t,
v khng b li sp  trong cc ln khi ng tip theo. Bn c th kim tra hnh vi ng dng
bng cch thay i kch c phng ch (<strong>Setting</strong> &gt;
<strong>Display</strong> &gt; <strong>Font size</strong>), v sau  khi phc
ng dng t mc Gn y.
</li>
</ul>