Android AMS--Activity相关数据类

AMS主要是负责四大组件的启动，进程调度以及在AMS中还会启动部分系统服务，主要是其他服务:startOtherServices

1:AMS的数据结构

AMS数据结构.png

2:ActivityStackSuperVisor

ActivityStackSuperVisor是在ActivityManagerService初始化的时候创建的，ActivityStackSuperVisor主要是用来管理ActivityStack的，其内部管理了三个ActivityStack:mHomeStack,mFocusedStack,mLastFocusedStack,其中mHomeStack主要是用来管理LauncherActivity相关的Stack,mFocusedStack是指当前的焦点栈，mLastFocusedStack是上一次处于前台的栈，并且还有一个很重要的成员mActivityDisplays，在android中一块显示屏幕对应一个ActivityDisplay,可以通过ActivityDisplay来管理某一显示屏上的Activity

3:ActivityDiplay

ActivityDisplay可以理解成一块屏幕，不同的屏幕通过displayId来区分，其管理者一组ActivityStack,当然也管理着特殊的栈

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

4:ActivityStack

ActivityStack才是我们通常说的Activity栈，其维护着一组TaskRecord和当前处理running状态的ActivityRecord,当然其也维护这几个比较特殊的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对应WindowManagerService的数据结构是TaskStack

5:TaskRecord

TaskRecord是用来管理一组相同taskId的ActivityRecord,其内部有一个很重要的数组: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，代表一个真正的Activity,与应用进程中的Activity是一一对应的，应用程序，AMS,WMS可以通过appToken关联起来，appToken是在ActivityRecord的构造方法中初始化的

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中成员变量

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

通过task可以找到其对应的task,appToken是其的标识，mWindowContainerController是和WMS的AppWindowToken关联的，info存储的是Activity的所有信息