Android13 WMS窗口层级树

1，认识层级树
可以通过dumpsys activity containers 看到 WMS 层级树的结构

ACTIVITY MANAGER CONTAINERS (dumpsys activity containers)
ROOT type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 Display 0 name="Built-in Screen" type=undefined mode=fullscreen override-mode=fullscreen requested-bounds=[0,0][1440,2960] bounds=[0,0][1440,2960]#2 Leaf:36:36 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#1 WindowToken{6cc524e type=2024 android.os.BinderProxy@8ffb949} type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 888c47c ScreenDecorOverlayBottom type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 WindowToken{4346895 type=2024 android.os.BinderProxy@ad2b04c} type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 da08538 ScreenDecorOverlay type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#1 HideDisplayCutout:32:35 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#2 OneHanded:34:35 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 FullscreenMagnification:34:35 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 Leaf:34:35 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#1 FullscreenMagnification:33:33 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 Leaf:33:33 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 OneHanded:32:32 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 Leaf:32:32 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 WindowedMagnification:0:31 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#6 HideDisplayCutout:26:31 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 OneHanded:26:31 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#2 FullscreenMagnification:29:31 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 Leaf:29:31 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#1 Leaf:28:28 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 FullscreenMagnification:26:27 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 Leaf:26:27 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#5 Leaf:24:25 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#1 WindowToken{914ccc0 type=2024 android.os.BinderProxy@60ae43} type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 20f913e pip-dismiss-overlay type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 WindowToken{4af2b8f type=2019 android.os.BinderProxy@d5bc069} type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 e66fa25 NavigationBar0 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#4 HideDisplayCutout:18:23 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 OneHanded:18:23 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 FullscreenMagnification:18:23 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 Leaf:18:23 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#3 OneHanded:17:17 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 FullscreenMagnification:17:17 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 Leaf:17:17 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 WindowToken{2cb42e4 type=2040 android.os.BinderProxy@9c0076} type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 bbfae02 NotificationShade type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#2 HideDisplayCutout:16:16 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 OneHanded:16:16 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 FullscreenMagnification:16:16 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 Leaf:16:16 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#1 OneHanded:15:15 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 FullscreenMagnification:15:15 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 Leaf:15:15 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 WindowToken{36a0a7c type=2000 android.os.BinderProxy@57ea84e} type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 f20fb5a StatusBar type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 HideDisplayCutout:0:14 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 OneHanded:0:14 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#1 ImePlaceholder:13:14 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 ImeContainer type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 WindowToken{18b2fcb type=2011 android.os.Binder@f3da9a} type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 3a9ce61 InputMethod type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 FullscreenMagnification:0:12 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#2 Leaf:3:12 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 WindowToken{fc9ff07 type=2038 android.os.BinderProxy@d280149} type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 d5c8415 ShellDropTarget type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#1 DefaultTaskDisplayArea type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#2 Task=1 type=home mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 Task=24 type=home mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 ActivityRecord{7246b16 u0 com.android.launcher3/.uioverrides.QuickstepLauncher} t24} type=home mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 bd08f5d com.android.launcher3/com.android.launcher3.uioverrides.QuickstepLauncher type=home mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#1 Task=3 type=undefined mode=fullscreen override-mode=fullscreen requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 Task=4 type=undefined mode=fullscreen override-mode=fullscreen requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#1 Task=6 type=undefined mode=multi-window override-mode=multi-window requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 Task=5 type=undefined mode=multi-window override-mode=multi-window requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 Leaf:0:1 type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 WallpaperWindowToken{a0c14b1 token=android.os.Binder@c234b58} type=undefined mode=fullscreen override-mode=fullscreen requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]#0 b9a90a8 com.android.systemui.ImageWallpaper type=undefined mode=fullscreen override-mode=undefined requested-bounds=[0,0][0,0] bounds=[0,0][1440,2960]

可以看出，层级机构树一共有37层，层级越高，越接近我们的"眼睛"，以上父子关系，做成图表格式，可以看的更直观，如下：

2，层级结构树的构建过程
SystemServer启动时，调用startOtherServices方法

private void startOtherServices(@NonNull TimingsTraceAndSlog t) {//省略t.traceBegin("SetWindowManagerService");mActivityManagerService.setWindowManager(wm);t.traceEnd();//省略
}

AMS.setWindowManager

 public void setWindowManager(WindowManagerService wm) {synchronized (this) {mWindowManager = wm;mWmInternal = LocalServices.getService(WindowManagerInternal.class);mActivityTaskManager.setWindowManager(wm);}}

ATMS.setWindowManager

public void setWindowManager(WindowManagerService wm) {synchronized (mGlobalLock) {//省略mRootWindowContainer.setWindowManager(wm);//省略}}

RootWindowContainer.setWindowManager

void setWindowManager(WindowManagerService wm) {//省略final Display[] displays = mDisplayManager.getDisplays();//得到系统有几个显示设备for (int displayNdx = 0; displayNdx < displays.length; ++displayNdx) {//遍历displayfinal Display display = displays[displayNdx];final DisplayContent displayContent = new DisplayContent(display, this);//创建DisplayContentaddChild(displayContent, POSITION_BOTTOM);//将DisplayContent挂在root下if (displayContent.mDisplayId == DEFAULT_DISPLAY) {mDefaultDisplay = displayContent;}}//省略}

对于每个显示设备，系统都会创建一个DisplayContent对象，并将DisplayContent对象挂在root下。接着来看一下DisplayContent的创建

DisplayContent(Display display, RootWindowContainer root) {//省略configureSurfaces(pendingTransaction);//省略
}

configureSurfaces

 private void configureSurfaces(Transaction transaction) {final SurfaceControl.Builder b = mWmService.makeSurfaceBuilder(mSession).setOpaque(true).setContainerLayer().setCallsite("DisplayContent");mSurfaceControl = b.setName(getName()).setContainerLayer().build();if (mDisplayAreaPolicy == null) {// Setup the policy and build the display area hierarchy.// Build the hierarchy only after creating the surface so it is reparented correctlymDisplayAreaPolicy = mWmService.getDisplayAreaPolicyProvider().instantiate(mWmService, this /* content */, this /* root */,mImeWindowsContainer);}//省略

getDisplayAreaPolicyProvider得到的是DefaultProvider对象，然后调用其instantiate方法。源码路径：frameworks/base/services/core/java/com/android/server/wm/DisplayAreaPolicy.java

static final class DefaultProvider implements DisplayAreaPolicy.Provider {@Overridepublic DisplayAreaPolicy instantiate(WindowManagerService wmService,DisplayContent content, RootDisplayArea root,DisplayArea.Tokens imeContainer) {final TaskDisplayArea defaultTaskDisplayArea = new TaskDisplayArea(content, wmService,"DefaultTaskDisplayArea", FEATURE_DEFAULT_TASK_CONTAINER);//创建DefaultTaskDisplayAreafinal List<TaskDisplayArea> tdaList = new ArrayList<>();tdaList.add(defaultTaskDisplayArea);// Define the features that will be supported under the root of the whole logical// display. The policy will build the DisplayArea hierarchy based on this.final HierarchyBuilder rootHierarchy = new HierarchyBuilder(root);// Set the essential containers (even if the display doesn't support IME).rootHierarchy.setImeContainer(imeContainer).setTaskDisplayAreas(tdaList);//1if (content.isTrusted()) {// Only trusted display can have system decorations.configureTrustedHierarchyBuilder(rootHierarchy, wmService, content);//2}// Instantiate the policy with the hierarchy defined above. This will create and attach// all the necessary DisplayAreas to the root.return new DisplayAreaPolicyBuilder().setRootHierarchy(rootHierarchy).build(wmService);//3}

首先创建HierarchyBuilder对象，注释1处将imeContainer和tdaList（tdaList此时只有一个元素就是DefaultTaskDisplayArea）分别保存在HierarchyBuilder对象中的mImeContainer和mTaskDisplayAreas中。注释2处创建Feature并设置Feature的层级。注释3处开始构建层级树

2.1，创建Feature
configureTrustedHierarchyBuilder

//frameworks/base/services/core/java/com/android/server/wm/DisplayAreaPolicy.java
private void configureTrustedHierarchyBuilder(HierarchyBuilder rootHierarchy,WindowManagerService wmService, DisplayContent content) {// WindowedMagnification should be on the top so that there is only one surface// to be magnified.rootHierarchy.addFeature(new Feature.Builder(wmService.mPolicy, "WindowedMagnification",FEATURE_WINDOWED_MAGNIFICATION).upTo(TYPE_ACCESSIBILITY_MAGNIFICATION_OVERLAY).except(TYPE_ACCESSIBILITY_MAGNIFICATION_OVERLAY)// Make the DA dimmable so that the magnify window also mirrors the dim layer..setNewDisplayAreaSupplier(DisplayArea.Dimmable::new).build());if (content.isDefaultDisplay) {// Only default display can have cutout.// See LocalDisplayAdapter.LocalDisplayDevice#getDisplayDeviceInfoLocked.rootHierarchy.addFeature(new Feature.Builder(wmService.mPolicy, "HideDisplayCutout",FEATURE_HIDE_DISPLAY_CUTOUT).all().except(TYPE_NAVIGATION_BAR, TYPE_NAVIGATION_BAR_PANEL, TYPE_STATUS_BAR,TYPE_NOTIFICATION_SHADE).build()).addFeature(new Feature.Builder(wmService.mPolicy, "OneHanded",FEATURE_ONE_HANDED).all().except(TYPE_NAVIGATION_BAR, TYPE_NAVIGATION_BAR_PANEL,TYPE_SECURE_SYSTEM_OVERLAY).build());}rootHierarchy.addFeature(new Feature.Builder(wmService.mPolicy, "FullscreenMagnification",FEATURE_FULLSCREEN_MAGNIFICATION).all().except(TYPE_ACCESSIBILITY_MAGNIFICATION_OVERLAY, TYPE_INPUT_METHOD,TYPE_INPUT_METHOD_DIALOG, TYPE_MAGNIFICATION_OVERLAY,TYPE_NAVIGATION_BAR, TYPE_NAVIGATION_BAR_PANEL).build()).addFeature(new Feature.Builder(wmService.mPolicy, "ImePlaceholder",FEATURE_IME_PLACEHOLDER).and(TYPE_INPUT_METHOD, TYPE_INPUT_METHOD_DIALOG).build());}}

可以看出，这里创建了几个Feature，以及它们对应的层级是：

1. WindowedMagnification：0~31
2. HideDisplayCutout： 0~ 14 16 18~ 23 26~35
3. OneHanded：0~ 23 26~ 32 34~35
4. FullscreenMagnification：0~ 12 15~ 23 26~ 27 29~ 31 33~35
5. ImePlaceholder：13 14
   至于层级是怎么得出来的，具体查看Feature.Builder的 all，except等等方法。Feature以及对应的层级设置好之后，接下来就是要开始构建层级树了。

2.2, 层级树的构建
源码路径:frameworks/base/services/core/java/com/android/server/wm/DisplayAreaPolicyBuilder.java

Result build(WindowManagerService wmService) {validate();// Attach DA group roots to screen hierarchy before adding windows to group hierarchies.mRootHierarchyBuilder.build(mDisplayAreaGroupHierarchyBuilders);//省略}

mRootHierarchyBuilder就是之前创建的HierarchyBuilder对象，调用其build方法。构建层级树的核心就是该方法，来分步分析它

2.2.1 挂载 Feature

private void build(@Nullable List<HierarchyBuilder> displayAreaGroupHierarchyBuilders) {final WindowManagerPolicy policy = mRoot.mWmService.mPolicy;final int maxWindowLayerCount = policy.getMaxWindowLayer() + 1;// 37final DisplayArea.Tokens[] displayAreaForLayer =new DisplayArea.Tokens[maxWindowLayerCount];final Map<Feature, List<DisplayArea<WindowContainer>>> featureAreas =new ArrayMap<>(mFeatures.size());//前面创建了5个Feature，所以size为5for (int i = 0; i < mFeatures.size(); i++) {featureAreas.put(mFeatures.get(i), new ArrayList<>());}PendingArea[] areaForLayer = new PendingArea[maxWindowLayerCount];final PendingArea root = new PendingArea(null, 0, null);Arrays.fill(areaForLayer, root)；//此时里面的每个元素都是root 0,0// Create DisplayAreas to cover all defined features.final int size = mFeatures.size();for (int i = 0; i < size; i++) {final Feature feature = mFeatures.get(i);PendingArea featureArea = null;for (int layer = 0; layer < maxWindowLayerCount; layer++) {if (feature.mWindowLayers[layer]) {if (featureArea == null || featureArea.mParent != areaForLayer[layer]) {// No suitable DisplayArea:// Create a new one under the previous area (as parent) for this layer.featureArea = new PendingArea(feature, layer, areaForLayer[layer]);areaForLayer[layer].mChildren.add(featureArea);}areaForLayer[layer] = featureArea;} else {featureArea = null;}}}

创建一个临时的层级结构树PendingArea（后面还需要转换成真正的层级树的）,对于Feature,其构造结果如下

2.2.2,挂载leaf叶子结点

private void build(@Nullable List<HierarchyBuilder> displayAreaGroupHierarchyBuilders) {//省略// Create Tokens as leaf for every layer.PendingArea leafArea = null;int leafType = LEAF_TYPE_TOKENS;for (int layer = 0; layer < maxWindowLayerCount; layer++) {int type = typeOfLayer(policy, layer);// Check whether we can reuse the same Tokens with the previous layer. This happens// if the previous layer is the same type as the current layer AND there is no// feature that applies to only one of them.if (leafArea == null || leafArea.mParent != areaForLayer[layer]|| type != leafType) {// Create a new Tokens for this layer.leafArea = new PendingArea(null /* feature */, layer, areaForLayer[layer]);areaForLayer[layer].mChildren.add(leafArea);leafType = type;if (leafType == LEAF_TYPE_TASK_CONTAINERS) {// We use the passed in TaskDisplayAreas for task container type of layer.// Skip creating Tokens even if there is no TDA.addTaskDisplayAreasToApplicationLayer(areaForLayer[layer]);addDisplayAreaGroupsToApplicationLayer(areaForLayer[layer],displayAreaGroupHierarchyBuilders);leafArea.mSkipTokens = true;} else if (leafType == LEAF_TYPE_IME_CONTAINERS) {// We use the passed in ImeContainer for ime container type of layer.// Skip creating Tokens even if there is no ime container.leafArea.mExisting = mImeContainer;leafArea.mSkipTokens = true;}}leafArea.mMaxLayer = layer;}
}

首先也是创建临时的叶子PendingArea，leafType默认为LEAF_TYPE_TOKENS，在typeOfLayer方法中，对于IME和Application 有处理，将其leafType设为LEAF_TYPE_TASK_CONTAINERS和LEAF_TYPE_IME_CONTAINERS。注意对于这两种类型，有特殊的处理，mSkipTokens设置为了true，后续将临时的结构树转成真正的层级树的时候有用。
经过这一步，此时结构树的构造结果如下

2.2.3 将临时的结构树转成真正的结构树

在build方法的最后，调用instantiateChildren方法，进行结构树的转换

void instantiateChildren(DisplayArea<DisplayArea> parent, DisplayArea.Tokens[] areaForLayer,int level, Map<Feature, List<DisplayArea<WindowContainer>>> areas) {mChildren.sort(Comparator.comparingInt(pendingArea -> pendingArea.mMinLayer));for (int i = 0; i < mChildren.size(); i++) {final PendingArea child = mChildren.get(i);final DisplayArea area = child.createArea(parent, areaForLayer);//转换if (area == null) {// TaskDisplayArea and ImeContainer can be set at different hierarchy, so it can// be null.continue;}parent.addChild(area, WindowContainer.POSITION_TOP);if (child.mFeature != null) {areas.get(child.mFeature).add(area);}child.instantiateChildren(area, areaForLayer, level + 1, areas);//迭代的过程}}

在createArea中，对于IME和Application Layer是有特殊处理的，删掉上面对应结点下的leaf叶子，最终转换好的结构树如下