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提到ActivityManagerService许蓖，大家都知道是Android 用于管理四大組件的系統(tǒng)服務(wù)调衰，AMS具體是怎么管理四大組件的呢？
ActivityManagerService要管理四大組件米酬，那四大組件就必須在AMS中有存在的形式趋箩，這里先從AMS 如何管理Activity 談起；
Activity在AMS 中存在的形式為ActivityRecord爬早；
AMS以Task的方式管理Activity启妹，Task在AMS存在的形式為T(mén)askRecord；TaskRecord中的mActivities用棧的方式管理ActivityRecord饶米；
TaskRecord在AMS中依靠ActivityStack去管理车胡，從命名來(lái)看匈棘，ActivityStack更像Activity棧析命，但是ActivityStack并不是Activity 棧，而是負(fù)責(zé)管理TaskRecord的類(lèi)鹃愤，android系統(tǒng)中有三種ActivityStack（mHomeStack，mFocusedStack瘩将，mLastFocusedStack）凹耙；
ActivityStack同樣有管理者，ActivityStackSupervisor負(fù)責(zé)管理ActivityStack建钥；
每一個(gè)Activity和TaskRecord 都是屬于某個(gè)進(jìn)程虐沥，所以進(jìn)程還需要在AMS有存在形式，進(jìn)程在AMS中存在的形式就是ProcessRecord镐依；
TaskRecord官網(wǎng)

image.png

這里逐一介紹一下上面幾個(gè)數(shù)據(jù)結(jié)構(gòu)：

ActivityRecord

ActivityRecord是Activity在AMS中的存在形式天试，ActivityRecord保存了Activity的信息；

------> frameworks/base/services/core/java/com/android/server/am/ActivityRecord.java  
    //ams
    final ActivityManagerService service; // owner  
    //token用來(lái)和wms交互  
    final IApplicationToken.Stub appToken; // window manager token  
    final ActivityInfo info; // all about ActivityInfo  
    final ApplicationInfo appInfo; // information about activity's app
    int mActivityType; //Activity Type
    ......  
    //Activity資源信息务唐，我們?cè)贏ndroidManifest.xml中配置的內(nèi)容 
    CharSequence nonLocalizedLabel;  // the label information from the package mgr.  
    int labelRes;           // the label information from the package mgr.  
    int icon;               // resource identifier of activity's icon.  
    int logo;               // resource identifier of activity's logo.  
    int theme;              // resource identifier of activity's theme.  
    int realTheme;          // actual theme resource we will use, never 0.  
    int windowFlags;        // custom window flags for preview window.  
      
    //ActivityRecord所在的TaskRecord  
    TaskRecord task;        // the task this is in.  
    ......  
    //ActivityRecord所在進(jìn)程  
    ProcessRecord app;      // if non-null, hosting application  
    ActivityState state;    // current state we are in  
    ......

TaskRecord task變量表示該ActivityRecord所在的TaskRecord带兜；
ActivityRecord 還規(guī)定了Activity的類(lèi)型如下：

    static final int APPLICATION_ACTIVITY_TYPE = 0;
    static final int HOME_ACTIVITY_TYPE = 1;
    static final int RECENTS_ACTIVITY_TYPE = 2;

TaskRecord

我們都知道AMS以Task的方式在管理Activity刚照，TaskRecord中的mActivities是一個(gè)棧，它的作用是以棧的方式組織管理Activity。Android把用戶一次操作相關(guān)的Activity按照先后順序保存在一個(gè)Task中吠冤，這個(gè)Task在AMS中的存在形式就是TaskRecord恭理；

------> /frameworks/base/services/core/java/com/android/server/am/TaskRecord.java  
 
  final class TaskRecord {
  ...........
  final int taskId;       // Unique identifier for this task.
  int mAffiliatedTaskId; // taskId of parent affiliation or self if no parent.
  // 是指root activity的affinity，即該Task中第一個(gè)Activity; 可以理解為當(dāng)前task的name涯保；
  String affinity;        // The affinity name for this task, or null; may change identity.
  // 啟動(dòng)這個(gè)task的intent
  Intent intent;          // The original intent that started the task.
  long firstActiveTime;   // First time this task was active.
  long lastActiveTime;    // Last time this task was active, including sleep.
  boolean inRecents;      // Actually in the recents list?
  boolean isAvailable;    // Is the activity available to be launched?
  // task模式
  int mLockTaskMode;      // Which tasklock mode to launch this task in. One of
                           // ActivityManager.LOCK_TASK_LAUNCH_MODE_*

  /** List of all activities in the task arranged in history order */
  // 該Task中所有的Activity
  final ArrayList<ActivityRecord> mActivities;

  /** Current stack */
  // 管理該Task的ActivityStack
  ActivityStack stack;

  // 最近列表中,可以看到當(dāng)前Task的縮略圖
  private Bitmap mLastThumbnail; // Last thumbnail captured for this item.
  private final File mLastThumbnailFile; // File containing last thumbnail.

  final ActivityManagerService mService;
  ..........
}

TaskRecord 的affinity只有在其被創(chuàng)建的時(shí)候才有用拍嵌，以后加入這個(gè)Task的Activity循诉，即使他們通過(guò)taskAffinity指定了一個(gè)不同的字符串，也不會(huì)更改Task的名稱(chēng)狈蚤；Activity所在的Task通過(guò)AndroidManifest.xml中<Activity>標(biāo)簽中的android:taskAffinity="xxx"來(lái)指定划纽，通常不去主動(dòng)設(shè)置一個(gè)Activity的taskAffinity屬性，那么taskAffinity的值缺省使用包名靖避。正因?yàn)槿绱吮饶瑧?yīng)用中所有的Activity的taskAffinity屬性值默認(rèn)都是相同的，都是包名篡九，所以在應(yīng)用中使用FLAG_ACTIVITY_NEW_TASK標(biāo)志去啟動(dòng)一個(gè)本應(yīng)用中的一個(gè)Activity醋奠，也不會(huì)創(chuàng)建一個(gè)新的task，除非這個(gè)Activity 額外指定了不同的taskAffinity屬性值窜司；
TaskAffinity屬性使用小結(jié)

ActivityStack

ActivityStack充當(dāng)TaskRecord的Manager角色；

------> /frameworks/base/services/core/java/com/android/server/am/ActivityStack.java  
    /** 
     * The back history of all previous (and possibly still 
     * running) activities.  It contains #TaskRecord objects. 
     */  
    private final ArrayList<TaskRecord> mTaskHistory = new ArrayList<>(); //ActivityStack中所有的TaskRecord
    private final ArrayList<ActivityRecord> mLRUActivities = new ArrayList<>();//最近活動(dòng)過(guò)的ActivityRecord
    ......  
    final int mStackId;  //ActivityStack的唯一標(biāo)識(shí)
    final ActivityContainer mActivityContainer;
    /** The other stacks, in order, on the attached display. Updated at attach/detach time. */
    ArrayList<ActivityStack> mStacks; //綁定的ActivityDisplay中的所有ActivityStack
    /** The attached Display's unique identifier, or -1 if detached */
    int mDisplayId;//綁定的ActivityDisplay的id路呜，默認(rèn)為Display.DEFAULT_DISPLAY = 0；
    ......  
    /** Run all ActivityStacks through this */  
    final ActivityStackSupervisor mStackSupervisor;  //ActivityStack的管理者ActivityStackSupervisor

mTaskHistory：是一個(gè)列表漠秋，存儲(chǔ)的是ActivityStack中的所有TaskRecord對(duì)象抵屿，TaskRecord 通過(guò)mActivities變量存儲(chǔ)Task中所有的Activity，所以mTaskHistory間接管理了ActivityStack中的所有activity搂抒；
mLRUActivities：一個(gè)列表尿扯，存儲(chǔ)的是ActivityStack中按照最近活動(dòng)情況運(yùn)行的所有Activity；

ActivityStackSupervisor

ActivityStackSupervisor 用于管理ActivityStack衷笋；ActivityStackSupervisor為AMS提供管理方法辟宗；管理著系統(tǒng)中的三個(gè)ActivityStack；

------>/frameworks/base/services/core/java/com/android/server/am/ActivityStackSupervisor.java
    final ActivityManagerService mService; //
    final ActivityStackSupervisorHandler mHandler;
    ......
    /** The stack containing the launcher app. Assumed to always be attached to
     * Display.DEFAULT_DISPLAY. */
    private ActivityStack mHomeStack;

    /** The stack currently receiving input or launching the next activity. */
    private ActivityStack mFocusedStack;

    /** If this is the same as mFocusedStack then the activity on the top of the focused stack has
     * been resumed. If stacks are changing position this will hold the old stack until the new
     * stack becomes resumed after which it will be set to mFocusedStack. */
    private ActivityStack mLastFocusedStack;
        /** List of activities that are waiting for a new activity to become visible before completing
     * whatever operation they are supposed to do. */
    final ArrayList<ActivityRecord> mWaitingVisibleActivities = new ArrayList<ActivityRecord>();

    /** List of processes waiting to find out about the next visible activity. */
    final ArrayList<IActivityManager.WaitResult> mWaitingActivityVisible =
            new ArrayList<IActivityManager.WaitResult>();

    /** List of processes waiting to find out about the next launched activity. */
    final ArrayList<IActivityManager.WaitResult> mWaitingActivityLaunched =
            new ArrayList<IActivityManager.WaitResult>();

    /** List of activities that are ready to be stopped, but waiting for the next activity to
     * settle down before doing so. */
    final ArrayList<ActivityRecord> mStoppingActivities = new ArrayList<ActivityRecord>();

    /** List of activities that are ready to be finished, but waiting for the previous activity to
     * settle down before doing so.  It contains ActivityRecord objects. */
    final ArrayList<ActivityRecord> mFinishingActivities = new ArrayList<ActivityRecord>();

    /** List of activities that are in the process of going to sleep. */
    final ArrayList<ActivityRecord> mGoingToSleepActivities = new ArrayList<ActivityRecord>();
    ......    
    /** Mapping from (ActivityStack/TaskStack).mStackId to their current state */
    private SparseArray<ActivityContainer> mActivityContainers = new SparseArray<ActivityContainer>();//以mStackId為key

    /** Mapping from displayId to display current state */
    private final SparseArray<ActivityDisplay> mActivityDisplays =
            new SparseArray<ActivityDisplay>();//以displayId為key

AMS使用mHomeStack，mFocusedStack來(lái)完成系統(tǒng)全部的Activity的管理和調(diào)度容客。其中mHomeStack管理的是Launcher相關(guān)的任務(wù)，包括Launcher如捅、RecentTask调煎，Keyguad,除了上述以外的任務(wù)都?xì)wmFocusedStack管理。

AMS 通過(guò)操作ActivityStackSupervisor來(lái)管理Activity士袄；具體是如何操作的呢？ActivityStackSupervisor通過(guò)ActivityContainer來(lái)管理ActivityStack(ActivityStack的構(gòu)造方法只有在ActivityContainer的構(gòu)造方法中被調(diào)用)寓辱，ActivityContainer關(guān)聯(lián)ActivityDisplay赤拒，ActivityDisplay將自己的mStacks賦值給ActivityContainer的mStack诱鞠；mStack.mStacks = activityDisplay.mStacks这敬；

------>/frameworks/base/services/core/java/com/android/server/am/ActivityStackSupervisor.java

class ActivityContainer extends android.app.IActivityContainer.Stub {
        final static int FORCE_NEW_TASK_FLAGS = Intent.FLAG_ACTIVITY_NEW_TASK |
                Intent.FLAG_ACTIVITY_MULTIPLE_TASK | Intent.FLAG_ACTIVITY_NO_ANIMATION;
        final int mStackId;
        IActivityContainerCallback mCallback = null;
        final ActivityStack mStack; //ActivityContainer用于維護(hù)ActivityStack的
        ActivityRecord mParentActivity = null;
        String mIdString;

        boolean mVisible = true;

        /** Display this ActivityStack is currently on. Null if not attached to a Display. */
        ActivityDisplay mActivityDisplay;

        final static int CONTAINER_STATE_HAS_SURFACE = 0;
        final static int CONTAINER_STATE_NO_SURFACE = 1;
        final static int CONTAINER_STATE_FINISHING = 2;
        int mContainerState = CONTAINER_STATE_HAS_SURFACE;

        ActivityContainer(int stackId) {
            synchronized (mService) {
                mStackId = stackId;
                mStack = new ActivityStack(this);
                mIdString = "ActivtyContainer{" + mStackId + "}";
                if (DEBUG_STACK) Slog.d(TAG, "Creating " + this);
            }
        }

        void attachToDisplayLocked(ActivityDisplay activityDisplay) { 
        //ActivityContainer關(guān)聯(lián)ActivityDisplay崔涂，用
            if (DEBUG_STACK) Slog.d(TAG, "attachToDisplayLocked: " + this
                    + " to display=" + activityDisplay);
            mActivityDisplay = activityDisplay;
            mStack.mDisplayId = activityDisplay.mDisplayId;
            mStack.mStacks = activityDisplay.mStacks;

            activityDisplay.attachActivities(mStack);
            mWindowManager.attachStack(mStackId, activityDisplay.mDisplayId);
        }
......
------>/frameworks/base/services/core/java/com/android/server/am/ActivityStackSupervisor.java

    /** Exactly one of these classes per Display in the system. Capable of holding zero or more
     * attached {@link ActivityStack}s */
    class ActivityDisplay {
        /** Actual Display this object tracks. */
        int mDisplayId;
        Display mDisplay;
        DisplayInfo mDisplayInfo = new DisplayInfo();

        /** 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 */
        final ArrayList<ActivityStack> mStacks = new ArrayList<ActivityStack>();

        ActivityRecord mVisibleBehindActivity;

        ActivityDisplay() {
        }
        // After instantiation, check that mDisplay is not null before using this. The alternative
        // is for this to throw an exception if mDisplayManager.getDisplay() returns null.
        ActivityDisplay(int displayId) {
            final Display display = mDisplayManager.getDisplay(displayId);
            if (display == null) {
                return;
            }
            init(display);
        }
.......
        void attachActivities(ActivityStack stack) {
            if (DEBUG_STACK) Slog.v(TAG, "attachActivities: attaching " + stack + " to displayId="
                    + mDisplayId);
            mStacks.add(stack);
        }
......

追蹤代碼冷蚂，發(fā)現(xiàn)ActivityContainer在ActivitySupervisor的createStackOnDisplay中被初始化，createStackOnDisplay在setWindowManager或adjustStackFocus或restoreRecentTaskLocked中被調(diào)用蝙茶；這里說(shuō)說(shuō)從setWindowManager開(kāi)始的調(diào)用流程，setWindowManager在SystemServer啟動(dòng)AMS時(shí)調(diào)用钳恕，然后調(diào)用ActivityContainer.attachToDisplayLocked方法吮廉；流程的大概就是根據(jù)mDisplayId獲取ActivityDisplay畸肆，將ActivityDisplay的mStacks(代表該Display上的所有activitystack) 賦值給ActivityContainer的mStack的mStacks；同時(shí)將調(diào)用activityDisplay.attachActivities(mStack)將ActivityContainer的mStack(ActivityContainer維護(hù)的ActivityStack)添加到ActivityDisplay的mStacks 中轴脐；

ActivityStackSupervisor對(duì)ActivityRecord的管理過(guò)程如下：

ActivityStackSupervisor.mActivityDisplays
-> ActivityDisplay.mStacks
-> ActivityStack.mTaskHistory
-> TaskRecord.mActivities
-> ActivityRecord

參考資料：
Android Framework之AMS篇
Taskaffinity屬性使用小結(jié)