Activity启动模式（一）之 launchMode

launchMode简介

Activity启动模式，即Activity启动的方式。 lauchMode可以配置在清单文件AndroidManifest.xml文件中。也可通过java代码动态配置。

知识储备

任务栈（Task）

在讲解Activity启动模式前，先讲解下Activity的管理方式：任务栈（Task），这有利于我们理解Activity启动模式。

采用任务栈任务栈（Task）的形式管理Activity
任务栈采用“先进后出”的栈结构
每按一次Back键或finish一个Activity，就有一个栈顶的Activity出栈

任务栈-先进后出

终端使用adb shell指令

Android还为开发者提供了adb(Android Debug Bridge)，这是非常强大的调试工具。最常用的自然是logcat来显示日志记录。另外一个很强大的指令就是这里要提到的dumpsys。dumpsys还可以添加不同的参数来指示需要输出哪一类Service的信息。对于本文提到的内容，需要查看的就是activity。

adb shell dumpsys activity

 ACTIVITY MANAGER PENDING INTENTS (dumpsys activity intents)    //注意一下
  * PendingIntentRecord{c8486ed com.xiaomi.xmsf startService}
  * PendingIntentRecord{dd7d922 com.xiaomi.xmsf startService}
  * PendingIntentRecord{b5bffb3 android broadcastIntent}
 // 省略 N 行 ...

ACTIVITY MANAGER BROADCAST STATE (dumpsys activity broadcasts)  //注意一下
  Historical broadcasts [foreground]:
  #0: BroadcastRecord{88e1b3a u-1 android.intent.action.TIME_TICK}
    act=android.intent.action.TIME_TICK flg=0x50000014 (has extras)
    extras: Bundle[{android.intent.extra.ALARM_COUNT=1}]
  #1: BroadcastRecord{9a973eb u-1 android.intent.action.TIME_TICK}
    act=android.intent.action.TIME_TICK flg=0x50000014 (has extras)
    extras: Bundle[{android.intent.extra.ALARM_COUNT=1}]
 // 省略 N 行 ...

ACTIVITY MANAGER CONTENT PROVIDERS (dumpsys activity providers) //注意一下
  Published single-user content providers (by class):
  * ContentProviderRecord{2af5291 u0 com.android.providers.telephony/.TelephonyProvider}
    proc=ProcessRecord{108d60f 4086:com.android.phone/1001}
    singleton=true
    authority=telephony
  // 省略 N 行 ...

ACTIVITY MANAGER URI PERMISSIONS (dumpsys activity permissions) //注意一下
  Granted Uri Permissions:
  * UID 1000 holds:
    UriPermission{e61888e 0 @ content://downloads/all_downloads/125}
    UriPermission{2f698af 0 @ content://downloads/all_downloads/126}
 // 省略 N 行 ...

ACTIVITY MANAGER SERVICES (dumpsys activity services)   //注意一下
  User 0 active services:
  * ServiceRecord{2e1e671 u0 com.android.bluetooth/.hid.HidService}
    app=ProcessRecord{b328630 4915:com.android.bluetooth/1002}
    created=-3d15h37m1s744ms started=true connections=1
    Connections:
      act=android.bluetooth.IBluetoothInputDevice -> 2989:com.android.systemui/1000
 // 省略 N 行 ...

ACTIVITY MANAGER RECENT TASKS (dumpsys activity recents)    //注意一下
  Recent tasks:
  * Recent #0: TaskRecord{f3e16fb #1558 A=com.nhtzj.appb U=0 sz=1}
  * Recent #1: TaskRecord{663d296 #1405 A=com.miui.home U=0 sz=1}
  * Recent #2: TaskRecord{1a325b8 #1557 A=com.nhtzj.learnapplication U=0 sz=1}
  * Recent #3: TaskRecord{141234a #1427 A=.delinstalledapk U=0 sz=0}
  * Recent #4: TaskRecord{6b8c2bb #1425 A=com.miui.packageinstaller U=0 sz=0}
  * Recent #5: TaskRecord{fa213d8 #1406 A=android.task.stk.StkLauncherActivity U=0 sz=0}
 // 省略 N 行 ...

ACTIVITY MANAGER ACTIVITIES (dumpsys activity activities)   //注意一下
Display #0 (activities from top to bottom):
  Stack #23:
    Task id #1558
      TaskRecord{f3e16fb #1558 A=com.nhtzj.appb U=0 sz=1}
      Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10200000 cmp=com.nhtzj.appb/.sample.MainActivity (has extras) }
        Hist #0: ActivityRecord{e4adca6 u0 com.nhtzj.appb/.sample.MainActivity t1558}
          Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10200000 cmp=com.nhtzj.appb/.sample.MainActivity bnds=[76,625][258,807] (has extras) }
          ProcessRecord{36e1c21 9302:com.nhtzj.appb/u0a267}
 // 省略 N 行 ...

ACTIVITY MANAGER RUNNING PROCESSES (dumpsys activity processes) //注意一下
  Isolated process list (sorted by uid):
    Isolated # 0: ProcessRecord{284e1aa 2979:WebViewLoader-armeabi-v7a/1037}

  UID states:
    UID 1000: UidRecord{2d2119b 1000 P  procs:13}
    UID 1001: UidRecord{db0e938 1001 P  procs:2}
 // 省略 N 行 ...

该命令返回一大串内容，但也能清晰看出它们比较详细的分类

每一个类别都有一个括号内容，给出了更加详细的指令来查看该类别下更多具体内容。

比如本次用到的类别：ACTIVITY MANAGER ACTIVITIES (dumpsys activity activities)

括号内的dumpsys activity activities为activity的详细指令。

因此再来尝试指令：

db shell dumpsys activity activities

ACTIVITY MANAGER ACTIVITIES (dumpsys activity activities)
Display #0 (activities from top to bottom):
  Stack #12:
    Task id #1302
    * TaskRecord{5fb98dc #1302 A=com.nhtzj.learnapplication U=0 sz=3}
      userId=0 effectiveUid=u0a238 mCallingUid=2000 mCallingPackage=null
      affinity=com.nhtzj.learnapplication
      intent={act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.nhtzj.learnapplication/.activity.main.MainActivity}
      realActivity=com.nhtzj.learnapplication/.activity.main.MainActivity
      autoRemoveRecents=false isPersistable=true numFullscreen=3 taskType=0 mTaskToReturnTo=1
      rootWasReset=false mNeverRelinquishIdentity=true mReuseTask=false mLockTaskAuth=LOCK_TASK_AUTH_PINNABLE
      Activities=[ActivityRecord{772a6cc u0 com.nhtzj.learnapplication/.activity.main.MainActivity t1302}, ActivityRecord{182f696 u0 com.nhtzj.learnapplication/.activity.sample.lanchmode.standard.StandardActivity t1302}, ActivityRecord{d4a426e u0 com.nhtzj.learnapplication/.activity.sample.lanchmode.standard.StandardActivity t1302}]
      askedCompatMode=false inRecents=true isAvailable=true
      lastThumbnail=null lastThumbnailFile=/data/system/recent_images/1302_task_thumbnail.png
      stackId=12
      hasBeenVisible=true mResizeable=false firstActiveTime=1524119334682 lastActiveTime=1524119334682 (inactive for 147s)
      * Hist #2: ActivityRecord{d4a426e u0 com.nhtzj.learnapplication/.activity.sample.lanchmode.standard.StandardActivity t1302}
          packageName=com.nhtzj.learnapplication processName=com.nhtzj.learnapplication
          launchedFromUid=10238 launchedFromPackage=com.nhtzj.learnapplication userId=0
          app=ProcessRecord{32912fe 28815:com.nhtzj.learnapplication/u0a238}
          Intent { cmp=com.nhtzj.learnapplication/.activity.sample.lanchmode.standard.StandardActivity }
          frontOfTask=false task=TaskRecord{5fb98dc #1302 A=com.nhtzj.learnapplication U=0 sz=3}
          taskAffinity=com.nhtzj.learnapplication
          realActivity=com.nhtzj.learnapplication/.activity.sample.lanchmode.standard.StandardActivity
          baseDir=/data/app/com.nhtzj.learnapplication-2/base.apk
          dataDir=/data/user/0/com.nhtzj.learnapplication
          stateNotNeeded=false componentSpecified=true mActivityType=0
          compat={480dpi} labelRes=0x0 icon=0x7f0b0000 theme=0x7f0d0005
          config={1.0 460mcc7mnc zh_CN ldltr sw360dp w360dp h576dp 480dpi nrml port finger -keyb/v/h -nav/h s.41 themeChanged=0 themeChangedFlags=0}
          stackConfigOverride={1.0 ?mcc?mnc ?locale ?layoutDir ?swdp ?wdp ?hdp ?density ?lsize ?long ?orien ?uimode ?night ?touch ?keyb/?/? ?nav/? themeChanged=0 themeChangedFlags=0}
          taskDescription: iconFilename=null label="null" color=ff3f51b5
          launchFailed=false launchCount=1 lastLaunchTime=-2m27s763ms
          haveState=false icicle=null
          state=RESUMED stopped=false delayedResume=false finishing=false
          keysPaused=false inHistory=true visible=true sleeping=false idle=true
          fullscreen=true noDisplay=false immersive=false launchMode=0
          frozenBeforeDestroy=false forceNewConfig=false
          mActivityType=APPLICATION_ACTIVITY_TYPE
          waitingVisible=false nowVisible=true lastVisibleTime=-2m27s389ms
          realComponentName=com.nhtzj.learnapplication/.activity.sample.lanchmode.standard.StandardActivity

整个log显示了当前所有在运行的任务栈，它们的id分别是什么。对于每个Task，也有Activity数量等信息，同时也列出了其中的Activity列表，并且对于每个Activity也有比较详细的描述，比如启动它的Intent的内容。

如果觉得内容过多，只想看看栈的内容，也可以直接跳到”Running activities (most recent first)”那部分，比较简洁而又明了的列出了栈中得Activity列表，就能知道当按下返回键的时候会应该会回到哪个Activity以后是要退出程序。

对于”Running activities”的内容在dumpsys activity中就有，并不需要dumpsys activity activities，也可以用下边的指令来限制仅输出”Running activities”列表：

adb shell dumpsys activity activities | sed -En -e ‘/Running activities/,/Run #0/p’

➜  ~ adb shell dumpsys activity activities | sed -En -e '/Running activities/,/Run #0/p'
    Running activities (most recent first):
      TaskRecord{5fb98dc #1302 A=com.nhtzj.learnapplication U=0 sz=3}
        Run #2: ActivityRecord{d4a426e u0 com.nhtzj.learnapplication/.activity.sample.lanchmode.standard.StandardActivity t1302}
        Run #1: ActivityRecord{182f696 u0 com.nhtzj.learnapplication/.activity.sample.lanchmode.standard.StandardActivity t1302}
        Run #0: ActivityRecord{772a6cc u0 com.nhtzj.learnapplication/.activity.main.MainActivity t1302}
    Running activities (most recent first):
      TaskRecord{77ff1c8 #4 A=com.miui.home U=0 sz=1}
        Run #0: ActivityRecord{98a1459 u0 com.miui.home/.launcher.Launcher t4}

其中，TaskRecord中的“A=”的值，即为taskAffinity设定的值。 taskAffinity的说明，请参考下文Activity启动模式之 taskAffinity

四大启动模式

code	简介
standard	标准模式
singleTop	栈顶复用模式
singleTask	栈内复用模式
singleInstance	单例模式

具体介绍

点击查看：lanchMode测试源码

标准模式（standard）

标准模式,每次启动Activity都会创建一个新的Activity实例,并且将其压入任务栈栈顶,而不管这个Activity是否已经存在。并且存在于启动它的Activity实例所在的task之中。

标准模式为activity的默认启动方式，在清单文件中可以不写明。即默认为“standard”。

清单文件配置

   <activity
android:name=".activity.sample.lanchmode.standard.StandardActivity"
        android:label="启动模式-standard"
        android:launchMode="standard" />

或不写明

1
2
3

<activity
      android:name=".activity.sample.lanchmode.standard.StandardActivity"
     android:label="启动模式-standard"/>

task中的形式如下： standard-task

栈顶复用模式（singleTop）

如果需要新建的Activity位于任务栈栈顶，那么此Activity的实例就不会重建，而是重用栈顶的实例( 调用实例的 onNewIntent() 、不调用onCreate()和onStart())。
否则就会创建该Activity新的实例，并放入栈顶

流程图如下： singleTop流程图

栈内复用模式（singleTask）

官方说明：

The system creates the activity at the root of a new task and routes the intent to it. However, if an instance of the activity already exists, the system routes the intent to existing instance through a call to its onNewIntent() method, rather than creating a new one.

翻译过来就是：

在singleTask模式下，如果是第一次创建该Activity实例时，则会新建task并将该Activity添加到该task中。否则(该Activity的实例已存在)，则会将栈内该Activity实例之后加入的Activity关闭，并打开已有的Activity实例，并调用Activity的onNewIntent()方法，而不会新建Activity实例。

流程图如下： singleTask流程图