【Android】图文解密Android WindowManagerService

柔光的暖阳◎ 2022-04-23 02:44 269阅读 0赞

### 文章目录 ###

*   *  1、简介
     *  2、启动
     *  3、addView
     *  4、Layer
     *  5、WindowState
     *  6、WindowToken
     *  7、Session
     *  8、Surface

## 1、简介 ##

WindowManagerService（WMS）是Android中很重要的一个服务，主要的职责是与ActivityManagerService（AMS）交互以管理Window，与InputManagerService（IMS）交互以派发事件。分析WMS，先从下面的类图开始吧，看看相关的类都有哪些，主要的类包括WindowManagerService、WindowManagerImpl、PhoneWindowManager、WindowManagerGlobal、ViewRootImpl等。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2lFZWFydGg_size_16_color_FFFFFF_t_70]

## 2、启动 ##

WMS是在SystemServer中启动的，下面的时序图展示了WMS及AMS、IMS的启动过程，以及它们是如何建立联系的。

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2lFZWFydGg_size_16_color_FFFFFF_t_70 1]

## 3、addView ##

addView是一个常用的方法，流程图如下。从WindowManagerImpl开始，经WindowManagerGlobal、ViewRootImpl、Session，最后到WindowManagerService结束。在WMS的addWindow中，首先要检查权限，然后通过WindowToken、WindowState完成。

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2lFZWFydGg_size_16_color_FFFFFF_t_70 2]

## 4、Layer ##

Window有三种类型，Application Window、Sub Window和System Window，这些Window有不同的Type，用int表示， Application Window从1到99，Sub Window从1000到1999，System Window从2000到2999，它们在WindowManager中定义，代码如下所示。

public static final int FIRST_APPLICATION_WINDOW = 1;
            public static final int TYPE_BASE_APPLICATION   = 1;
            public static final int TYPE_APPLICATION        = 2;
            public static final int TYPE_APPLICATION_STARTING = 3;
            public static final int TYPE_DRAWN_APPLICATION = 4;
            public static final int LAST_APPLICATION_WINDOW = 99;
    
            public static final int FIRST_SUB_WINDOW = 1000;
            public static final int TYPE_APPLICATION_PANEL = FIRST_SUB_WINDOW;
            public static final int TYPE_APPLICATION_MEDIA = FIRST_SUB_WINDOW + 1;
            public static final int TYPE_APPLICATION_SUB_PANEL = FIRST_SUB_WINDOW + 2;
            public static final int TYPE_APPLICATION_ATTACHED_DIALOG = FIRST_SUB_WINDOW + 3;
            public static final int TYPE_APPLICATION_MEDIA_OVERLAY  = FIRST_SUB_WINDOW + 4;
            public static final int TYPE_APPLICATION_ABOVE_SUB_PANEL = FIRST_SUB_WINDOW + 5;
            public static final int LAST_SUB_WINDOW = 1999;
    
            public static final int FIRST_SYSTEM_WINDOW     = 2000;
            public static final int TYPE_STATUS_BAR         = FIRST_SYSTEM_WINDOW;
            public static final int TYPE_SEARCH_BAR         = FIRST_SYSTEM_WINDOW+1;
            public static final int TYPE_PHONE              = FIRST_SYSTEM_WINDOW+2;
            public static final int TYPE_SYSTEM_ALERT       = FIRST_SYSTEM_WINDOW+3;
            public static final int TYPE_KEYGUARD           = FIRST_SYSTEM_WINDOW+4;
            public static final int TYPE_TOAST              = FIRST_SYSTEM_WINDOW+5;
            public static final int TYPE_SYSTEM_OVERLAY     = FIRST_SYSTEM_WINDOW+6;
            public static final int TYPE_PRIORITY_PHONE     = FIRST_SYSTEM_WINDOW+7;
            public static final int TYPE_SYSTEM_DIALOG      = FIRST_SYSTEM_WINDOW+8;
            public static final int TYPE_KEYGUARD_DIALOG    = FIRST_SYSTEM_WINDOW+9;
            public static final int TYPE_SYSTEM_ERROR       = FIRST_SYSTEM_WINDOW+10;
            public static final int TYPE_INPUT_METHOD       = FIRST_SYSTEM_WINDOW+11;
            public static final int TYPE_INPUT_METHOD_DIALOG= FIRST_SYSTEM_WINDOW+12;
            public static final int TYPE_WALLPAPER          = FIRST_SYSTEM_WINDOW+13;
            public static final int TYPE_STATUS_BAR_PANEL   = FIRST_SYSTEM_WINDOW+14;
            public static final int TYPE_SECURE_SYSTEM_OVERLAY = FIRST_SYSTEM_WINDOW+15;
            public static final int TYPE_DRAG               = FIRST_SYSTEM_WINDOW+16;
            public static final int TYPE_STATUS_BAR_SUB_PANEL = FIRST_SYSTEM_WINDOW+17;
            public static final int TYPE_POINTER = FIRST_SYSTEM_WINDOW+18;
            public static final int TYPE_NAVIGATION_BAR = FIRST_SYSTEM_WINDOW+19;
            public static final int TYPE_VOLUME_OVERLAY = FIRST_SYSTEM_WINDOW+20;
            public static final int TYPE_BOOT_PROGRESS = FIRST_SYSTEM_WINDOW+21;
            public static final int TYPE_INPUT_CONSUMER = FIRST_SYSTEM_WINDOW+22;
            public static final int TYPE_DREAM = FIRST_SYSTEM_WINDOW+23;
            public static final int TYPE_NAVIGATION_BAR_PANEL = FIRST_SYSTEM_WINDOW+24;
            public static final int TYPE_DISPLAY_OVERLAY = FIRST_SYSTEM_WINDOW+26;
            public static final int TYPE_MAGNIFICATION_OVERLAY = FIRST_SYSTEM_WINDOW+27;
            public static final int TYPE_PRIVATE_PRESENTATION = FIRST_SYSTEM_WINDOW+30;
            public static final int TYPE_VOICE_INTERACTION = FIRST_SYSTEM_WINDOW+31;
            public static final int TYPE_ACCESSIBILITY_OVERLAY = FIRST_SYSTEM_WINDOW+32;
            public static final int TYPE_VOICE_INTERACTION_STARTING = FIRST_SYSTEM_WINDOW+33;
            public static final int TYPE_DOCK_DIVIDER = FIRST_SYSTEM_WINDOW+34;
            public static final int TYPE_QS_DIALOG = FIRST_SYSTEM_WINDOW+35;
            public static final int TYPE_SCREENSHOT = FIRST_SYSTEM_WINDOW + 36;
            public static final int TYPE_PRESENTATION = FIRST_SYSTEM_WINDOW + 37;
            public static final int TYPE_APPLICATION_OVERLAY = FIRST_SYSTEM_WINDOW + 38;
            public static final int LAST_SYSTEM_WINDOW      = 2999;

Window都有自己的Layer，即z-order，表示在屏幕上显示的层级顺序。Application Window都属于Application Layer，值为2，其它的则不同，它们在WindowManagerPolicy可以找到，代码如下。

int APPLICATION_LAYER = 2;
        int APPLICATION_MEDIA_SUBLAYER = -2;
        int APPLICATION_MEDIA_OVERLAY_SUBLAYER = -1;
        int APPLICATION_PANEL_SUBLAYER = 1;
        int APPLICATION_SUB_PANEL_SUBLAYER = 2;
        int APPLICATION_ABOVE_SUB_PANEL_SUBLAYER = 3;
    
        default int getWindowLayerFromTypeLw(int type, boolean canAddInternalSystemWindow) {
            if (type >= FIRST_APPLICATION_WINDOW && type <= LAST_APPLICATION_WINDOW) {
                return APPLICATION_LAYER;
            }
    
            switch (type) {
                case TYPE_WALLPAPER:
                    // wallpaper is at the bottom, though the window manager may move it.
                    return  1;
                case TYPE_PRESENTATION:
                case TYPE_PRIVATE_PRESENTATION:
                    return  APPLICATION_LAYER;
                case TYPE_DOCK_DIVIDER:
                    return  APPLICATION_LAYER;
                case TYPE_QS_DIALOG:
                    return  APPLICATION_LAYER;
                case TYPE_PHONE:
                    return  3;
                case TYPE_SEARCH_BAR:
                case TYPE_VOICE_INTERACTION_STARTING:
                    return  4;
                case TYPE_VOICE_INTERACTION:
                    // voice interaction layer is almost immediately above apps.
                    return  5;
                case TYPE_INPUT_CONSUMER:
                    return  6;
                case TYPE_SYSTEM_DIALOG:
                    return  7;
                case TYPE_TOAST:
                    // toasts and the plugged-in battery thing
                    return  8;
                case TYPE_PRIORITY_PHONE:
                    // SIM errors and unlock.  Not sure if this really should be in a high layer.
                    return  9;
                case TYPE_SYSTEM_ALERT:
                    // like the ANR / app crashed dialogs
                    return  canAddInternalSystemWindow ? 11 : 10;
                case TYPE_APPLICATION_OVERLAY:
                    return  12;
                case TYPE_DREAM:
                    // used for Dreams (screensavers with TYPE_DREAM windows)
                    return  13;
                case TYPE_INPUT_METHOD:
                    // on-screen keyboards and other such input method user interfaces go here.
                    return  14;
                case TYPE_INPUT_METHOD_DIALOG:
                    // on-screen keyboards and other such input method user interfaces go here.
                    return  15;
                case TYPE_STATUS_BAR_SUB_PANEL:
                    return  17;
                case TYPE_STATUS_BAR:
                    return  18;
                case TYPE_STATUS_BAR_PANEL:
                    return  19;
                case TYPE_KEYGUARD_DIALOG:
                    return  20;
                case TYPE_VOLUME_OVERLAY:
                    // the on-screen volume indicator and controller shown when the user
                    // changes the device volume
                    return  21;
                case TYPE_SYSTEM_OVERLAY:
                    // the on-screen volume indicator and controller shown when the user
                    // changes the device volume
                    return  canAddInternalSystemWindow ? 22 : 11;
                case TYPE_NAVIGATION_BAR:
                    // the navigation bar, if available, shows atop most things
                    return  23;
                case TYPE_NAVIGATION_BAR_PANEL:
                    // some panels (e.g. search) need to show on top of the navigation bar
                    return  24;
                case TYPE_SCREENSHOT:
                    // screenshot selection layer shouldn't go above system error, but it should cover
                    // navigation bars at the very least.
                    return  25;
                case TYPE_SYSTEM_ERROR:
                    // system-level error dialogs
                    return  canAddInternalSystemWindow ? 26 : 10;
                case TYPE_MAGNIFICATION_OVERLAY:
                    // used to highlight the magnified portion of a display
                    return  27;
                case TYPE_DISPLAY_OVERLAY:
                    // used to simulate secondary display devices
                    return  28;
                case TYPE_DRAG:
                    // the drag layer: input for drag-and-drop is associated with this window,
                    // which sits above all other focusable windows
                    return  29;
                case TYPE_ACCESSIBILITY_OVERLAY:
                    // overlay put by accessibility services to intercept user interaction
                    return  30;
                case TYPE_SECURE_SYSTEM_OVERLAY:
                    return  31;
                case TYPE_BOOT_PROGRESS:
                    return  32;
                case TYPE_POINTER:
                    // the (mouse) pointer layer
                    return  33;
                default:
                    Slog.e("WindowManager", "Unknown window type: " + type);
                    return APPLICATION_LAYER;
            }
        }
    
        default int getSubWindowLayerFromTypeLw(int type) {
            switch (type) {
                case TYPE_APPLICATION_PANEL:
                case TYPE_APPLICATION_ATTACHED_DIALOG:
                    return APPLICATION_PANEL_SUBLAYER;
                case TYPE_APPLICATION_MEDIA:
                    return APPLICATION_MEDIA_SUBLAYER;
                case TYPE_APPLICATION_MEDIA_OVERLAY:
                    return APPLICATION_MEDIA_OVERLAY_SUBLAYER;
                case TYPE_APPLICATION_SUB_PANEL:
                    return APPLICATION_SUB_PANEL_SUBLAYER;
                case TYPE_APPLICATION_ABOVE_SUB_PANEL:
                    return APPLICATION_ABOVE_SUB_PANEL_SUBLAYER;
            }
            Slog.e("WindowManager", "Unknown sub-window type: " + type);
            return 0;
        }

Window的Layer，上面只是从1开始逐个递增1，在转换为z-order时，还要进行转换，首先乘10000，然后偏移1000，同类的Window逐个递增5，这些值在WindowManagerService中定义，代码如下所示。

/** How much to multiply the policy's type layer, to reserve room
         * for multiple windows of the same type and Z-ordering adjustment
         * with TYPE_LAYER_OFFSET. */
        static final int TYPE_LAYER_MULTIPLIER = 10000;
    
        /** Offset from TYPE_LAYER_MULTIPLIER for moving a group of windows above
         * or below others in the same layer. */
        static final int TYPE_LAYER_OFFSET = 1000;
    
        /** How much to increment the layer for each window, to reserve room
         * for effect surfaces between them.
         */
        static final int WINDOW_LAYER_MULTIPLIER = 5;

Java层与Native层的Layer设置是通过SurfaceControl的setLayer完成的，在Native层由SurfaceComposer进行合成。

## 5、WindowState ##

WindowState是Android中的事实Window，WindowManager真正管理的是WindowState而不是Window。WindowState在WindowManagerService中创建，从上面的addView的时序图中可以看出。创建WindowState之后，还需要设置上文提到的Window Layer，通过InputChannel与IMS取得联系，将Session中维护的Window个数加1，最后通过WindowToken将这个WindowState添加到WindowContainer中。

## 6、WindowToken ##

WindowToken是个容器，将相关的WindowState收集到一起，同样是在WindowManagerService中创建。真正的token是IBinder类型的成员变量token，用于IPC。WindowToken有个子类AppWindowToken，用于Application和Activity。

## 7、Session ##

Session是个客户端对象，每个进程只有一个，与WindowManagerService进行交互。Session对应的interface为IWindowSession，在WindowManagerGlobal中实例化。

## 8、Surface ##

View或Window真正地是在一个Surface上进行描画的，Surface即一个Buffer，由辅助类SurfaceControl进行控制，上文提到的Window Layer的设置就是由SurfaceControl与Native层进行交互的。

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