本文主要从3个方面来介绍这ActivityDisplay/ActivityStack/TaskRecord/ActivityRecord的关系几个类之间的关系，先从整体关系图，对4个类的关系有个大概的了解，然后通过dumpsys命令，来验证这种关系；然后从类定义的角度来看，4个类是如何互相包含的；最后从Activity启动的流程过程来看4个类是如何关联上来的。

通过阅读本文，能对ActivityDisplay/ActivityStack/TaskRecord/ActivityRecord的关系有个整体的认识和理解

1.整体关系图如下

image.png

说明：
1.在#0的ActivityDisplay上，总共有2个Stack，代表2个应用
2.在Stack #4里面，有一个TaskRecord，Task id #87
3.在TaskRecord里面，Activities列表里面只有一个ActivityRecord

ACTIVITY MANAGER ACTIVITIES (dumpsys activity activities)
Display #0 (activities from top to bottom):

  Stack #4: type=standard mode=fullscreen
  isSleeping=false
  mBounds=Rect(0, 0 - 0, 0)
    Task id #87
    * TaskRecord{3a93f6f #87 A=com.android.deskclock U=0 StackId=4 sz=1}
      userId=0 effectiveUid=u0a93 mCallingUid=u0a81 mUserSetupComplete=true mCallingPackage=com.android.launcher3
      intent={act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10200000 cmp=com.android.deskclock/.DeskClock}
      Activities=[ActivityRecord{ed5f802 u0 com.android.deskclock/.DeskClock t87}]
      mRootProcess=ProcessRecord{64a3d2f 4887:com.android.deskclock/u0a93}
      stackId=4
      hasBeenVisible=true mResizeMode=RESIZE_MODE_RESIZEABLE_VIA_SDK_VERSION mSupportsPictureInPicture=false isResizeable=true lastActiveTime=223590378 (inactive for 50s)
      * Hist #0: ActivityRecord{ed5f802 u0 com.android.deskclock/.DeskClock t87}
          app=ProcessRecord{64a3d2f 4887:com.android.deskclock/u0a93}
          Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10200000 cmp=com.android.deskclock/.DeskClock bnds=[35,503][237,780] }    
          state=RESUMED stopped=false delayedResume=false finishing=false
    Running activities (most recent first):
      TaskRecord{3a93f6f #87 A=com.android.deskclock U=0 StackId=4 sz=1}
        Run #0: ActivityRecord{ed5f802 u0 com.android.deskclock/.DeskClock t87}
    mResumedActivity: ActivityRecord{ed5f802 u0 com.android.deskclock/.DeskClock t87}
    mLastPausedActivity: ActivityRecord{ed5f802 u0 com.android.deskclock/.DeskClock t87}

  Stack #0: type=home mode=fullscreen
  isSleeping=false
  mBounds=Rect(0, 0 - 0, 0)
    Task id #83
    mBounds=Rect(0, 0 - 0, 0)
    mMinWidth=-1
    mMinHeight=-1
    mLastNonFullscreenBounds=null
    * TaskRecord{6dee666 #83 ?? U=0 StackId=0 sz=1}
      userId=0 effectiveUid=u0a81 mCallingUid=u0a81 mUserSetupComplete=true mCallingPackage=com.android.launcher3
      intent={act=android.intent.action.MAIN cat=[android.intent.category.HOME] flg=0x10000100 cmp=com.android.launcher3/.Launcher}
      Activities=[ActivityRecord{3e98fcb u0 com.android.launcher3/.Launcher t83}]
      mRootProcess=ProcessRecord{d9a8f3c 2055:com.android.launcher3/u0a81}
      stackId=0
      hasBeenVisible=true mResizeMode=RESIZE_MODE_RESIZEABLE mSupportsPictureInPicture=false isResizeable=true lastActiveTime=223589976 (inactive for 50s)
      * Hist #0: ActivityRecord{3e98fcb u0 com.android.launcher3/.Launcher t83}        
          app=ProcessRecord{d9a8f3c 2055:com.android.launcher3/u0a81}
          Intent { act=android.intent.action.MAIN cat=[android.intent.category.HOME] flg=0x10000100 cmp=com.android.launcher3/.Launcher }
          state=STOPPED stopped=true delayedResume=false finishing=false
    Running activities (most recent first):
      TaskRecord{6dee666 #83 ?? U=0 StackId=0 sz=1}
        Run #0: ActivityRecord{3e98fcb u0 com.android.launcher3/.Launcher t83}
    mLastPausedActivity: ActivityRecord{3e98fcb u0 com.android.launcher3/.Launcher t83}
 ResumedActivity:ActivityRecord{ed5f802 u0 com.android.deskclock/.DeskClock t87}
  ResumedActivity: ActivityRecord{ed5f802 u0 com.android.deskclock/.DeskClock t87}

2.类定义相关介绍

整体类图如下：

image.png

2.1 ActivityDisplay

ActivityDisplay 类有如下关键变量

    DisplayContent mDisplayContent;  // 对应WindowManagerService的显示
    /** Actual Display this object tracks. */
    int mDisplayId;  // id

    /**
     * All of the stacks on this display. Order matters, topmost stack is in front of all other
     * stacks, bottommost behind. Accessed directly by ActivityManager package classes. Any calls
     * changing the list should also call {@link #onStackOrderChanged()}.
     */
     // 当前显示屏上的所有ActivityStack
    private final ArrayList<ActivityStack> mStacks = new ArrayList<>();

2.2 ActivityStack

ActivityStack类有如下关键变量

    final int mStackId;  // 唯一ID
    /** The attached Display's unique identifier, or -1 if detached */
    int mDisplayId;  // 所处的显示屏id,如果detach则为-1
    /**
     * The back history of all previous (and possibly still
     * running) activities.  It contains #TaskRecord objects.
     */
    // ActivityStack里面所包含的所有TaskRecord对象
    private final ArrayList<TaskRecord> mTaskHistory = new ArrayList<>();

    TaskStack mTaskStack;  // 对应WindowManagerService里面的

      /**
     * Current activity that is resumed, or null if there is none.
     */
    ActivityRecord mResumedActivity = null; // 当前resume状态的Activity

2.3 TaskRecord

TaskRecord 类有如下关键变量

    final int taskId;       // Unique identifier for this task.

     /** List of all activities in the task arranged in history order */
    final ArrayList<ActivityRecord> mActivities; // 当前Task里面所包含的所有Activity对象

    /** Current stack. Setter must always be used to update the value. */
    private ActivityStack mStack;  // 所属的ActivityStack

    Task mTask; // 对应WindowManagerService里面的

2.4 ActivityRecord

ActivityRecord 类有如下关键变量

   
    final IApplicationToken.Stub appToken; // window manager token
    // TODO: Remove after unification
    AppWindowToken mAppWindowToken; // 继承自WindowToken,代表一种window类型，为应用窗口
    // activity相关的信息
    final ActivityInfo info; // all about me
    
    private TaskRecord task;        // the task this is in.
    // ActivityRecord在初始化的时候会创建Token对象，作为服务端
   static class Token extends IApplicationToken.Stub

3.ActivityDisplay/ActivityStack/TaskRecord/ActivityRecord如何关联

详细流程可以阅读Activity 启动流程log分析

3.1 ActivityRecord创建

在startActivity的过程中，会先new ActivityRecord

08-23 17:30:21.261  1314  4528 V ActivityTaskManager: java.lang.Throwable
08-23 17:30:21.261  1314  4528 V ActivityTaskManager:   at com.android.server.wm.ActivityRecord.setState(ActivityRecord.java:1857)
08-23 17:30:21.261  1314  4528 V ActivityTaskManager:   at com.android.server.wm.ActivityRecord.<init>(ActivityRecord.java:964)
08-23 17:30:21.261  1314  4528 V ActivityTaskManager:   at com.android.server.wm.ActivityStarter.startActivity(ActivityStarter.java:902)

3.2 ActivityStack创建以及和ActivityDisplay的关联

ActivityStack也在是startActivity的过程中创建的

08-23 17:30:21.285  1314  4528 D ActivityTaskManager:   at com.android.server.wm.ActivityStack.<init>(ActivityStack.java:511)
08-23 17:30:21.285  1314  4528 D ActivityTaskManager:   at com.android.server.wm.ActivityDisplay.createStackUnchecked(ActivityDisplay.java:465)
08-23 17:30:21.285  1314  4528 D ActivityTaskManager:   at com.android.server.wm.ActivityDisplay.createStack(ActivityDisplay.java:455)
08-23 17:30:21.285  1314  4528 D ActivityTaskManager:   at com.android.server.wm.ActivityDisplay.getOrCreateStack(ActivityDisplay.java:383)
08-23 17:30:21.285  1314  4528 D ActivityTaskManager:   at com.android.server.wm.ActivityDisplay.getOrCreateStack(ActivityDisplay.java:401)
08-23 17:30:21.285  1314  4528 D ActivityTaskManager:   at com.android.server.wm.RootActivityContainer.getLaunchStack(RootActivityContainer.java:1737)
08-23 17:30:21.285  1314  4528 D ActivityTaskManager:   at com.android.server.wm.ActivityStarter.getLaunchStack(ActivityStarter.java:2704)
08-23 17:30:21.285  1314  4528 D ActivityTaskManager:   at com.android.server.wm.ActivityStarter.computeStackFocus(ActivityStarter.java:2612)
08-23 17:30:21.285  1314  4528 D ActivityTaskManager:   at com.android.server.wm.ActivityStarter.setTaskFromReuseOrCreateNewTask(ActivityStarter.java:2323)
08-23 17:30:21.285  1314  4528 D ActivityTaskManager:   at com.android.server.wm.ActivityStarter.startActivityUnchecked(ActivityStarter.java:1688)
08-23 17:30:21.285  1314  4528 D ActivityTaskManager:   at com.android.server.wm.ActivityStarter.startActivity(ActivityStarter.java:1404)

在ActivityStack的构造方法中，会调用ActivityDisplay的addChild方法，

display.addChild(this, onTop ? POSITION_TOP : POSITION_BOTTOM);

将自己加入到ActivityDisplay的mStack里面，mStack定义如下

ArrayList<ActivityStack> mStacks

此时，ActivityDisplay和ActivityStack关联起来

3.3 TaskRecord创建以及和ActivityStack的关联

TaskRecord也在是startActivity的过程中创建的

08-23 17:30:21.292  1314  4528 D ActivityTaskManager:   at com.android.server.wm.TaskRecord.create(TaskRecord.java:2704)
08-23 17:30:21.292  1314  4528 D ActivityTaskManager:   at com.android.server.wm.ActivityStack.createTaskRecord(ActivityStack.java:5515)
08-23 17:30:21.292  1314  4528 D ActivityTaskManager:   at com.android.server.wm.ActivityStarter.setTaskFromReuseOrCreateNewTask(ActivityStarter.java:2330)
08-23 17:30:21.292  1314  4528 D ActivityTaskManager:   at com.android.server.wm.ActivityStarter.startActivityUnchecked(ActivityStarter.java:1688)

在ActivityStack.createTaskRecord方法里面，调用addTask将TaskRecord和ActivityStack关联起来

addTask(task, toTop, "createTaskRecord");

将task加入 mTaskHistory，其定义如下

private final ArrayList<TaskRecord> mTaskHistory = new ArrayList<>();

3.4 TaskRecord和ActivityRecord的关联
在3.1 和3.3节分别创建了ActivityRecord和TaskRecord对象，

08-23 17:30:21.296  1314  4528 D ActivityTaskManager:   at com.android.server.wm.ActivityStarter.addOrReparentStartingActivity(ActivityStarter.java:2574)
08-23 17:30:21.296  1314  4528 D ActivityTaskManager:   at com.android.server.wm.ActivityStarter.setTaskFromReuseOrCreateNewTask(ActivityStarter.java:2335)
08-23 17:30:21.296  1314  4528 D ActivityTaskManager:   at com.android.server.wm.ActivityStarter.startActivityUnchecked(ActivityStarter.java:1688)
08-23 17:30:21.296  1314  4528 D ActivityTaskManager:   at com.android.server.wm.ActivityStarter.startActivity(ActivityStarter.java:1404)

在setTaskFromReuseOrCreateNewTask方法里面，先调用createTaskRecord来创建TaskRecord，然后调用addOrReparentStartingActivity来设置Activity与TaskRecord的关系

setTaskFromReuseOrCreateNewTask () {
     .....
     final TaskRecord task = mTargetStack.createTaskRecord(
                    mSupervisor.getNextTaskIdForUserLocked(mStartActivity.mUserId),
                    mNewTaskInfo != null ? mNewTaskInfo : mStartActivity.info,
                    mNewTaskIntent != null ? mNewTaskIntent : mIntent, mVoiceSession,
                    mVoiceInteractor, toTop, mStartActivity, mSourceRecord, mOptions);
     addOrReparentStartingActivity(task, "setTaskFromReuseOrCreateNewTask - mReuseTask");
     .....
}

private void addOrReparentStartingActivity(TaskRecord parent, String reason) {
        Slog.d(TAG,"addOrReparentStartingActivity",new Throwable());
        // 如果当前ActivityRecord没有设置TaskRecord或者已经设置过就是给定的parent,则添加到mActivities列表里面
        if (mStartActivity.getTaskRecord() == null || mStartActivity.getTaskRecord() == parent) {
            parent.addActivityToTop(mStartActivity); // 会调用r.setTask(this)设置关联关系
        } else {
            // 将当前要启动的Activity重新关联到给定的parent 上
            mStartActivity.reparent(parent, parent.mActivities.size() /* top */, reason);
        }
 }

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版权声明：本文为CSDN博主「chadm」的原创文章，遵循CC 4.0 BY-SA版权协议，转载请附上原文出处链接及本声明。
原文链接：https://blog.csdn.net/weixin_42695485/article/details/108680240