一文了解 Window 层级顺序

type 取值范围 [1,99]

/*** Start of window types that represent normal application windows.*/
public static final int FIRST_APPLICATION_WINDOW = 1;
// activity 会使用 此 type
public static final int TYPE_BASE_APPLICATION   = 1;
// dialog 会使用 此 type
public static final int TYPE_APPLICATION        = 2;
// 冷启动会显示的 Window,真正启动页面显示之前的画面
public static final int TYPE_APPLICATION_STARTING = 3;
// 没玩过
public static final int TYPE_DRAWN_APPLICATION = 4;
/*** End of types of application windows.*/
public static final int LAST_APPLICATION_WINDOW = 99;

Sub Window： 子窗口

子窗口：顾名思义，对应有主窗口。子窗口需要附在主窗口上，如PopWindow

type 取值范围 [1000,1999]

/*** Start of types of sub-windows.  The {@link #token} of these windows* must be set to the window they are attached to.  These types of* windows are kept next to their attached window in Z-order, and their* coordinate space is relative to their attached window.*/
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;
/*** End of types of sub-windows.*/
public static final int LAST_SUB_WINDOW = 1999;

System Window ：系统窗口

type 取值范围 [2000,2999]

如Toast，ANR 窗口，输入法，StatusBar，NavigationBar 等。

/*** Start of system-specific window types.  These are not normally* created by applications.*/
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;
/*** End of types of system windows.*/
public static final int LAST_SYSTEM_WINDOW      = 2999;

之前好像看过文章说 type 值越大，层级越高,这个观点是错的。

具体层级是下面逻辑代码，返回值越大，层级越高，最终在屏幕上显示时就越靠近用户。

frameworks/base/services/core/java/com/android/server/policy/WindowManagerPolicy.java
/*** Returns the layer assignment for the window type. Allows you to control how different* kinds of windows are ordered on-screen.** @param type The type of window being assigned.* @param canAddInternalSystemWindow If the owner window associated with the type we are*        evaluating can add internal system windows. I.e they have*        {@link Manifest.permission#INTERNAL_SYSTEM_WINDOW}. If true, alert window*        types {@link android.view.WindowManager.LayoutParams#isSystemAlertWindowType(int)}*        can be assigned layers greater than the layer for*        {@link android.view.WindowManager.LayoutParams#TYPE_APPLICATION_OVERLAY} Else, their*        layers would be lesser.* @param roundedCornerOverlay {#code true} to indicate that the owner window is rounded corner*                             overlay.* @return int An arbitrary integer used to order windows, with lower numbers below higher ones.*/
default int getWindowLayerFromTypeLw(int type, boolean canAddInternalSystemWindow,boolean roundedCornerOverlay) {// Always put the rounded corner layer to the top most.if (roundedCornerOverlay && canAddInternalSystemWindow) {return getMaxWindowLayer();}if (type >= FIRST_APPLICATION_WINDOW && type <= LAST_APPLICATION_WINDOW) {return APPLICATION_LAYER;// APPLICATION_LAYER = 2}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:case TYPE_DOCK_DIVIDER:case TYPE_QS_DIALOG: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 thingreturn  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// Type is deprecated for non-system apps. For system apps, this type should be// in a higher layer than TYPE_APPLICATION_OVERLAY.return  canAddInternalSystemWindow ? 13 : 10;case TYPE_APPLICATION_OVERLAY:return  12;case TYPE_INPUT_METHOD:// on-screen keyboards and other such input method user interfaces go here.return  15;case TYPE_INPUT_METHOD_DIALOG:// on-screen keyboards and other such input method user interfaces go here.return  16;case TYPE_STATUS_BAR:return  17;case TYPE_STATUS_BAR_ADDITIONAL:return  18;case TYPE_NOTIFICATION_SHADE:return  19;case TYPE_STATUS_BAR_SUB_PANEL:return  20;case TYPE_KEYGUARD_DIALOG:return  21;case TYPE_VOLUME_OVERLAY:// the on-screen volume indicator and controller shown when the user// changes the device volumereturn  22;case TYPE_SYSTEM_OVERLAY:// the on-screen volume indicator and controller shown when the user// changes the device volumereturn  canAddInternalSystemWindow ? 23 : 11;case TYPE_NAVIGATION_BAR:// the navigation bar, if available, shows atop most thingsreturn  24;case TYPE_NAVIGATION_BAR_PANEL:// some panels (e.g. search) need to show on top of the navigation barreturn  25;case TYPE_SCREENSHOT:// screenshot selection layer shouldn't go above system error, but it should cover// navigation bars at the very least.return  26;case TYPE_SYSTEM_ERROR:// system-level error dialogsreturn  canAddInternalSystemWindow ? 27 : 10;case TYPE_MAGNIFICATION_OVERLAY:// used to highlight the magnified portion of a displayreturn  28;case TYPE_DISPLAY_OVERLAY:// used to simulate secondary display devicesreturn  29;case TYPE_DRAG:// the drag layer: input for drag-and-drop is associated with this window,// which sits above all other focusable windowsreturn  30;case TYPE_ACCESSIBILITY_OVERLAY:// overlay put by accessibility services to intercept user interactionreturn  31;case TYPE_ACCESSIBILITY_MAGNIFICATION_OVERLAY:return 32;case TYPE_SECURE_SYSTEM_OVERLAY:return  33;case TYPE_BOOT_PROGRESS:return  34;case TYPE_POINTER:// the (mouse) pointer layerreturn  35;default:Slog.e("WindowManager", "Unknown window type: " + type);return 3;}
}

以上方法，返回layer，type -> layer，以上代码可以得到如下信息。

layer 取值范围 【1，36】

App 对应 APPLICATION_LAYER，值为2，仅比 TYPE_WALLPAPER 大

Window 层级具体是怎么计算的呢？

从 System Window 中 基本已经找到答案。本章节具体说下实现细节：

mBaseLayer & mSubLayer
用来计算层级的两个参数

mSubLayer：用来计算子窗口的层级，默认值为0

mBaseLayer：用来计算主窗口的层级。

frameworks/base/services/core/java/com/android/server/wm/WindowState.javaif (mAttrs.type >= FIRST_SUB_WINDOW && mAttrs.type <= LAST_SUB_WINDOW) {mBaseLayer = mPolicy.getWindowLayerLw(parentWindow)* TYPE_LAYER_MULTIPLIER + TYPE_LAYER_OFFSET;// layer * 10000 + 1000mSubLayer = mPolicy.getSubWindowLayerFromTypeLw(a.type);
} else {mBaseLayer = mPolicy.getWindowLayerLw(this)* TYPE_LAYER_MULTIPLIER + TYPE_LAYER_OFFSET;// layer * 10000 + 1000mSubLayer = 0;
}

WindowState 中 mBaseLayer，mSubLayer

mBaseLayer：主窗口的 type 对应 value ，计算如下

如 Activity，type 是 TYPE_BASE_APPLICATION ，getWindowLayerLw 计算返回 APPLICATION_LAYER（2），mBaseLayer = 2 * 10000 + 1000

TYPE_LAYER_MULTIPLIER：为什么要 * 10000，将阈值扩大10000倍，系统中可能存在相同类型的窗口有很多。

TYPE_LAYER_OFFSET：为了移动同一层级的一组窗口

以上两个常量具体怎么使用，没有研究，该值不影响本文的分析。

mSubLayer：计算规则如下，取值范围 [-2,3]，TYPE_APPLICATION_ATTACHED_DIALOG 值为 1，APPLICATION_MEDIA_SUBLAYER 值为 -2，看到这里就可以想到子窗口是可以在主窗口下方，主窗口如果可以看到子窗口，必须透明。
 

frameworks/base/services/core/java/com/android/server/policy/WindowManagerPolicy.javadefault int getSubWindowLayerFromTypeLw(int type) {switch (type) {case TYPE_APPLICATION_PANEL:case TYPE_APPLICATION_ATTACHED_DIALOG:return APPLICATION_PANEL_SUBLAYER;// 1case TYPE_APPLICATION_MEDIA:return APPLICATION_MEDIA_SUBLAYER;// -2case TYPE_APPLICATION_MEDIA_OVERLAY:return APPLICATION_MEDIA_OVERLAY_SUBLAYER;// -1case TYPE_APPLICATION_SUB_PANEL:return APPLICATION_SUB_PANEL_SUBLAYER; // 2case TYPE_APPLICATION_ABOVE_SUB_PANEL:return APPLICATION_ABOVE_SUB_PANEL_SUBLAYER;// 3}Slog.e("WindowManager", "Unknown sub-window type: " + type);return 0;
}

Sub Window 排序

frameworks/base/services/core/java/com/android/server/wm/WindowState.java/*** Compares two window sub-layers and returns -1 if the first is lesser than the second in terms* of z-order and 1 otherwise.*/
private static final Comparator sWindowSubLayerComparator =new Comparator() {@Overridepublic int compare(WindowState w1, WindowState w2) {final int layer1 = w1.mSubLayer;final int layer2 = w2.mSubLayer;if (layer1 < layer2 || (layer1 == layer2 && layer2 < 0 )) {// We insert the child window into the list ordered by// the sub-layer.  For same sub-layers, the negative one// should go below others; the positive one should go// above others.return -1;}return 1;};};

根据上文 mSubLayer 的值排序，如果是新插入的 window ，如果 sublayer 相等且为负值，放在下方，如果 sublayer 相等且为正值，放在上方。

frameworks/base/services/core/java/com/android/server/wm/WindowToken.java/*** Compares two child window of this token and returns -1 if the first is lesser than the* second in terms of z-order and 1 otherwise.*/
private final Comparator mWindowComparator =(WindowState newWindow, WindowState existingWindow) -> {final WindowToken token = WindowToken.this;if (newWindow.mToken != token) {throw new IllegalArgumentException("newWindow=" + newWindow+ " is not a child of token=" + token);}if (existingWindow.mToken != token) {throw new IllegalArgumentException("existingWindow=" + existingWindow+ " is not a child of token=" + token);}return isFirstChildWindowGreaterThanSecond(newWindow, existingWindow) ? 1 : -1;
};protected boolean isFirstChildWindowGreaterThanSecond(WindowState newWindow,WindowState existingWindow) {// New window is considered greater if it has a higher or equal base layer.return newWindow.mBaseLayer >= existingWindow.mBaseLayer;
}

与 Sub Window 排序类似，按照 mBaseLayer 大小排序，如果是新插入的，且相等，放在上方。

主 window 排序图示

子 window 排序图示

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版权声明：本文为CSDN博主「Jingle.zhang」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/m0_58994853/article/details/125493914