AMS主要是負責四大組件的啟動，進程調度以及在AMS中還會啟動部分系統服務，主要是其他服務:startOtherServices

1:AMS的數據結構

AMS數據結構.png

2:ActivityStackSuperVisor

ActivityStackSuperVisor是在ActivityManagerService初始化的時候創建的，ActivityStackSuperVisor主要是用來管理ActivityStack的，其內部管理了三個ActivityStack:mHomeStack,mFocusedStack,mLastFocusedStack,其中mHomeStack主要是用來管理LauncherActivity相關的Stack,mFocusedStack是指當前的焦點棧，mLastFocusedStack是上一次處于前臺的棧，并且還有一個很重要的成員mActivityDisplays，在android中一塊顯示屏幕對應一個ActivityDisplay,可以通過ActivityDisplay來管理某一顯示屏上的Activity

3:ActivityDiplay

ActivityDisplay可以理解成一塊屏幕，不同的屏幕通過displayId來區分，其管理者一組ActivityStack,當然也管理著特殊的棧

 private ActivityStack mHomeStack = null;
 private ActivityStack mRecentsStack = null;
 private ActivityStack mPinnedStack = null;
 private ActivityStack mSplitScreenPrimaryStack = null;

4:ActivityStack

ActivityStack才是我們通常說的Activity棧，其維護著一組TaskRecord和當前處理running狀態的ActivityRecord,當然其也維護這幾個比較特殊的Activity

   /**
     * The back history of all previous (and possibly still
     * running) activities.  It contains #TaskRecord objects.
     */
    private final ArrayList<TaskRecord> mTaskHistory = new ArrayList<>();
    /**
     * List of running activities, sorted by recent usage.
     * The first entry in the list is the least recently used.
     * It contains HistoryRecord objects.
     */
    final ArrayList<ActivityRecord> mLRUActivities = new ArrayList<>
   /**
     * When we are in the process of pausing an activity, before starting the
     * next one, this variable holds the activity that is currently being paused.
     */
    ActivityRecord mPausingActivity = null;
    /**
     * This is the last activity that we put into the paused state.  This is
     * used to determine if we need to do an activity transition while sleeping,
     * when we normally hold the top activity paused.
     */
    ActivityRecord mLastPausedActivity = null;
    /**
     * Activities that specify No History must be removed once the user navigates away from them.
     * If the device goes to sleep with such an activity in the paused state then we save it here
     * and finish it later if another activity replaces it on wakeup.
     */
    ActivityRecord mLastNoHistoryActivity = null;
    /**
     * Current activity that is resumed, or null if there is none.
     */
    ActivityRecord mResumedActivity = null;

ActivityStack對應WindowManagerService的數據結構是TaskStack

5:TaskRecord

TaskRecord是用來管理一組相同taskId的ActivityRecord,其內部有一個很重要的數組:ArrayList<ActivityRecord> mActivities

 final int taskId;       // Unique identifier for this task.
 String affinity;
 /** List of all activities in the task arranged in history order */
 final ArrayList<ActivityRecord> mActivities;
 /** Current stack. Setter must always be used to update the value. */
 private ActivityStack mStack;

6:ActivityRecord

ActivityRecord是Activity在AMS中的描述，代表一個真正的Activity,與應用進程中的Activity是一一對應的，應用程序，AMS,WMS可以通過appToken關聯起來，appToken是在ActivityRecord的構造方法中初始化的

ActivityRecord(ActivityManagerService _service, ProcessRecord _caller, int _launchedFromPid,
            int _launchedFromUid, String _launchedFromPackage, Intent _intent, String _resolvedType,
            ActivityInfo aInfo, Configuration _configuration,
            ActivityRecord _resultTo, String _resultWho, int _reqCode,
            boolean _componentSpecified, boolean _rootVoiceInteraction,
            ActivityStackSupervisor supervisor, ActivityOptions options,
            ActivityRecord sourceRecord) {
        service = _service;
        appToken = new Token(this, _intent);

ActivityRecord中成員變量

private TaskRecord task;        // the task this is in.
final IApplicationToken.Stub appToken; // window manager token
AppWindowContainerController mWindowContainerController;
final ActivityInfo info; // all about me

通過task可以找到其對應的task,appToken是其的標識，mWindowContainerController是和WMS的AppWindowToken關聯的，info存儲的是Activity的所有信息