Window，表示一个窗口的抽象的概念；同时也是一个抽象类，唯一的实现是PhoneWindow。在PhoneWindow中有一个顶级View—DecorView，继承自FrameLayout，我们可以通过getDecorView()获得它，当我们调用Activity的setContentView时，其实最终会调用Window的setContentView，当我们调用Activity的findViewById时，其实最终调用的是Window的findViewById，这也间接的说明了Window是View的直接管理者。 但是Window并不是真实存在的，它更多的表示一种抽象的功能集合，View才是Android中的视图呈现形式，绘制到屏幕上的是View不是Window，但是View不能单独存在，它必需依附在Window这个抽象的概念上面，Android中需要依赖Window提供视图的有Activity，Dialog，Toast，PopupWindow，StatusBarWindow（系统状态栏），输入法窗口等，因此Activity，Dialog等视图都对应着一个Window。
创建Window，通过WindowManager即可完成。WindowManager是操作Window的入口，Window的具体实现是在WindowManagerService中。WindowManager和WindowManagerService交互是IPC（跨进程通信）过程。
Window是View的管理者，当我们说创建Window时，一方面指实例化这个管理者，一方面指 用WindowManager.addView()添加view，以view的形式来呈现Window这个概念。
一、Window和WindowManager
1.1 window
先看创建window的代码
WindowManager windowManager = getWindowManager();
Button view = new Button(this);
view.setText("添加到window中的button");
WindowManager.LayoutParams layoutParams = new WindowManager.LayoutParams();
layoutParams.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
| WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL
| WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED;
layoutParams.type = WindowManager.LayoutParams.TYPE_APPLICATION;
layoutParams.format = PixelFormat.TRANSPARENT;
layoutParams.gravity = Gravity.TOP | Gravity.LEFT;
layoutParams.x = 100;
layoutParams.y = 100;
layoutParams.width = ViewGroup.LayoutParams.WRAP_CONTENT;
layoutParams.height = ViewGroup.LayoutParams.WRAP_CONTENT;
windowManager.addView(view, layoutParams);
实际就只有一句windowManager.addView(view, layoutParams)，这样就添加了一个Window，这个window只有一个button。看下LayoutParams的两个不太认识的属性，flags、type。
flags，决定window的显示特性，有很多值，看下常用的：
FLAG_NOT_FOCUSABLE，不需要获取焦点、不需要 输入事件，同时会自定开启FLAG_NOT_TOUCH_MODAL，最终事件会传递给下层具有焦点的window。
FLAG_NOT_TOUCH_MODAL，window区域以外的单击事件会传递给下层window，window范围内的事件自己处理。一般需要开启此标记，否则其他window不能收到事件。
FLAG_SHOW_WHEN_LOCKED，开启后 可以让window显示在锁屏的界面上。
type参数表示window的类型。window有三种类型，应用window、子window、系统window。应用window对应activity；子window要依附在父window上，如dialog；系统window需要申明权限才能创建，比如toast、系统状态栏。 window是分层的，每个window都有对应的z-ordered，层级大的在层级小的上层。应用window的层级范围是1-99，子window是1000-1999，系统window是2000-2999，即type的值。
如果想window位于所有window顶层，那就用系统window。可以设置layoutParams.type = WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY，并且，要申明使用权限，且6.0以后要让用户手动打开权限。
<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW"/>
否则会报错：
Caused by: android.view.WindowManager$BadTokenException: Unable to add window android.view.ViewRootImpl$W@305c3bc -- permission denied for window type 2038
at android.view.ViewRootImpl.setView(ViewRootImpl.java:958)
at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:398)
at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:131)
at com.hfy.demo01.MainActivity.initCustomWindow(MainActivity.java:266)
at com.hfy.demo01.MainActivity.initView(MainActivity.java:170)
at com.hfy.demo01.MainActivity.onCreate(MainActivity.java:116)
at android.app.Activity.performCreate(Activity.java:7458)
at android.app.Activity.performCreate(Activity.java:7448)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1286)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3409)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3614)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:86)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2199)
at android.os.Handler.dispatchMessage(Handler.java:112)
at android.os.Looper.loop(Looper.java:216)
at android.app.ActivityThread.main(ActivityThread.java:7625)
使用系统window的完整代码：
private void initCustomWindow() {
//6.0以上需要用户手动打开权限
// (SYSTEM_ALERT_WINDOW and WRITE_SETTINGS, 这两个权限比较特殊，
// 不能通过代码申请方式获取，必须得用户打开软件设置页手动打开，才能授权。Manifest申请该权限是无效的。)
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M){
if (!Settings.canDrawOverlays(this)) {
//打开设置页，让用户打开设置
Toast.makeText(this, "can not DrawOverlays", Toast.LENGTH_SHORT).show();
Intent intent = new Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION, Uri.parse("package:" + MainActivity.this.getPackageName()));
startActivityForResult(intent, OVERLAY_PERMISSION_REQ_CODE);
}else {
//已经打开了权限
handleAddWindow();
}
}else {
//6.0以下直接 Manifest申请该权限 就行。
handleAddWindow();
}
}
private void handleAddWindow() {
Button view = new Button(this);
view.setText("添加到window中的button");
WindowManager.LayoutParams layoutParams = new WindowManager.LayoutParams(
WindowManager.LayoutParams.WRAP_CONTENT,
WindowManager.LayoutParams.WRAP_CONTENT,
0, 0,
PixelFormat.TRANSPARENT
);
// flag 设置 Window 属性
layoutParams.flags= WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE | WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL;
// type 设置 Window 类别（层级）：系统window
layoutParams.type = WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY;
layoutParams.gravity = Gravity.TOP | Gravity.LEFT;
layoutParams.x = 100;
layoutParams.y = 100;
WindowManager windowManager = getWindowManager();
windowManager.addView(view, layoutParams);
}
@Override
protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
super.onActivityResult(requestCode, resultCode, data);
switch (requestCode){
case OVERLAY_PERMISSION_REQ_CODE:
if (Settings.canDrawOverlays(this)) {
//打开了权限
handleAddWindow();
}else {
Toast.makeText(this, "can not DrawOverlays", Toast.LENGTH_SHORT).show();
}
break;
default:
break;
}
}
按home键后效果：
1.2 WindowManager
WindowManager是个接口，继承自ViewManager：
public interface ViewManager{
public void addView(View view, ViewGroup.LayoutParams params);
public void updateViewLayout(View view, ViewGroup.LayoutParams params);
public void removeView(View view);
}
所以，windowManager就是 添加、更新、删除 view，实际使用的就是这三个方法，上面创建window的例子用的就是addView方法。所以，操作window就是操作view。
二、window的内部机制
window是抽象的概念，在视图中不是实际存在，它以view的形式呈现。一个window就对应一个view，window操作view实际是通过ViewRootImpl实现。使用中是通过WindowManager对的操作，无法直接访问window。下面就看看WindowManager的三个方法。
2.1 window的添加
WindowManager的实现类是WindowManagerImpl，那么看看操作view的三个方法的实现：
@Override
public void addView(@NonNull View view, @NonNull ViewGroup.LayoutParams params) {
applyDefaultToken(params);
mGlobal.addView(view, params, mContext.getDisplay(), mParentWindow);
}
@Override
public void updateViewLayout(@NonNull View view, @NonNull ViewGroup.LayoutParams params) {
applyDefaultToken(params);
mGlobal.updateViewLayout(view, params);
}
@Override
public void removeView(View view) {
mGlobal.removeView(view, false);
}
可以看到，全都交给mGlobal处理了，那看下mGlobal，是个单例对象：
private final WindowManagerGlobal mGlobal = WindowManagerGlobal.getInstance();
public static WindowManagerGlobal getInstance() {
synchronized (WindowManagerGlobal.class) {
if (sDefaultWindowManager == null) {
sDefaultWindowManager = new WindowManagerGlobal();
}
return sDefaultWindowManager;
}
}
那么来看下mGlobal.addView，具体简要概括为3个步骤：
- 数据检查
- 更新各种参数列表
- RootViewImpl添加view（含window的添加）
public void addView(View view, ViewGroup.LayoutParams params,
Display display, Window parentWindow) {
//1、数据检查
if (view == null) {
throw new IllegalArgumentException("view must not be null");
}
if (display == null) {
throw new IllegalArgumentException("display must not be null");
}
if (!(params instanceof WindowManager.LayoutParams)) {
throw new IllegalArgumentException("Params must be WindowManager.LayoutParams");
}
final WindowManager.LayoutParams wparams = (WindowManager.LayoutParams) params;
if (parentWindow != null) {
parentWindow.adjustLayoutParamsForSubWindow(wparams);
} else {
// If there's no parent, then hardware acceleration for this view is
// set from the application's hardware acceleration setting.
final Context context = view.getContext();
if (context != null
&& (context.getApplicationInfo().flags
& ApplicationInfo.FLAG_HARDWARE_ACCELERATED) != 0) {
wparams.flags |= WindowManager.LayoutParams.FLAG_HARDWARE_ACCELERATED;
}
}
ViewRootImpl root;
View panelParentView = null;
...
//创建viewRoot（一个window对应一个viewRoot）
root = new ViewRootImpl(view.getContext(), display);
view.setLayoutParams(wparams);
//2、更新各种参数列：所有window的--view的列表、rootView的列表、view参数的列表
mViews.add(view);
mRoots.add(root);
mParams.add(wparams);
// do this last because it fires off messages to start doing things
try {
// 3、RootViewImpl添加view（含window的添加）
root.setView(view, wparams, panelParentView);
} catch (RuntimeException e) {
// BadTokenException or InvalidDisplayException, clean up.
if (index >= 0) {
removeViewLocked(index, true);
}
throw e;
}
}
}
接着看ViewRootImpl的setView：
public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView) {
...
//1.绘制view
requestLayout();
if ((mWindowAttributes.inputFeatures
& WindowManager.LayoutParams.INPUT_FEATURE_NO_INPUT_CHANNEL) == 0) {
mInputChannel = new InputChannel();
}
mForceDecorViewVisibility = (mWindowAttributes.privateFlags
& PRIVATE_FLAG_FORCE_DECOR_VIEW_VISIBILITY) != 0;
try {
mOrigWindowType = mWindowAttributes.type;
mAttachInfo.mRecomputeGlobalAttributes = true;
collectViewAttributes();
//2.通过session与WMS建立通信：完成window的添加
res = mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes,
getHostVisibility(), mDisplay.getDisplayId(), mWinFrame,
mAttachInfo.mContentInsets, mAttachInfo.mStableInsets,
mAttachInfo.mOutsets, mAttachInfo.mDisplayCutout, mInputChannel);
} catch (RemoteException e) {
mAdded = false;
mView = null;
mAttachInfo.mRootView = null;
mInputChannel = null;
mFallbackEventHandler.setView(null);
unscheduleTraversals();
setAccessibilityFocus(null, null);
throw new RuntimeException("Adding window failed", e);
}
...
}
两个步骤：1、调用requestLayout()异步刷新view，2、mWindowSession.addToDisplay()完成window的添加。
requestLayout()内部最后走到performTraversals()，我们知道这是view绘制流程入口。如下所示：
@Override
public void requestLayout() {
if (!mHandlingLayoutInLayoutRequest) {
checkThread();
mLayoutRequested = true;
scheduleTraversals();
}
}
void scheduleTraversals() {
if (!mTraversalScheduled) {
mTraversalScheduled = true;
mTraversalBarrier = mHandler.getLooper().getQueue().postSyncBarrier();
mChoreographer.postCallback(
Choreographer.CALLBACK_TRAVERSAL, mTraversalRunnable, null);
if (!mUnbufferedInputDispatch) {
scheduleConsumeBatchedInput();
}
notifyRendererOfFramePending();
pokeDrawLockIfNeeded();
}
}
final class TraversalRunnable implements Runnable {
@Override
public void run() {
doTraversal();
}
}
void doTraversal() {
if (mTraversalScheduled) {
mTraversalScheduled = false;
mHandler.getLooper().getQueue().removeSyncBarrier(mTraversalBarrier);
if (mProfile) {
Debug.startMethodTracing("ViewAncestor");
}
// 绘制流程
performTraversals();
if (mProfile) {
Debug.stopMethodTracing();
mProfile = false;
}
}
}
至于mWindowSession.addToDisplay()，先看mWindowSession，类型是IWindowSession，是个Binder对象，具体是com.android.server.wm.Session，所以window的添加是一个IPC过程。 mWindowSessionde 是在ViewRootImpl创建时获取，由WindowManagerGlobal通过获取WindowManagerService来为 每个应用创建一个单独的session。
public ViewRootImpl(Context context, Display display) {
mContext = context;
mWindowSession = WindowManagerGlobal.getWindowSession();
...
}
public static IWindowSession getWindowSession() {
synchronized (WindowManagerGlobal.class) {
if (sWindowSession == null) {
try {
InputMethodManager imm = InputMethodManager.getInstance();
IWindowManager windowManager = getWindowManagerService();
sWindowSession = windowManager.openSession(
new IWindowSessionCallback.Stub() {
@Override
public void onAnimatorScaleChanged(float scale) {
ValueAnimator.setDurationScale(scale);
}
},
imm.getClient(), imm.getInputContext());
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
}
return sWindowSession;
}
}
public static IWindowManager getWindowManagerService() {
synchronized (WindowManagerGlobal.class) {
if (sWindowManagerService == null) {
sWindowManagerService = IWindowManager.Stub.asInterface(
ServiceManager.getService("window"));
try {
if (sWindowManagerService != null) {
ValueAnimator.setDurationScale(
sWindowManagerService.getCurrentAnimatorScale());
}
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
}
return sWindowManagerService;
}
}
然后是WindowManagerService的openSession：
@Override
public IWindowSession openSession(IWindowSessionCallback callback, IInputMethodClient client,
IInputContext inputContext) {
if (client == null) throw new IllegalArgumentException("null client");
if (inputContext == null) throw new IllegalArgumentException("null inputContext");
Session session = new Session(this, callback, client, inputContext);
return session;
}
接着看Session的addToDisplay：
@Override
public int addToDisplay(IWindow window, int seq, WindowManager.LayoutParams attrs,
int viewVisibility, int displayId, Rect outFrame, Rect outContentInsets,
Rect outStableInsets, Rect outOutsets,
DisplayCutout.ParcelableWrapper outDisplayCutout, InputChannel outInputChannel) {
return mService.addWindow(this, window, seq, attrs, viewVisibility, displayId, outFrame,
outContentInsets, outStableInsets, outOutsets, outDisplayCutout, outInputChannel);
}
window的添加就交给WindowManagerService了。 WindowManagerService主要作用：
窗口管理： 是先进行窗口的权限检查，因为系统窗口需要声明权限，然后根据相关的Display信息以及窗口信息对窗口进行校对，再然后获取对应的WindowToken，再根据不同的窗口类型检查窗口的有效性，如果上面一系列步骤都通过了，就会为该窗口创建一个WindowState对象，以维护窗口的状态和根据适当的时机调整窗口状态，最后就会通过WindowState的attach方法与SurfaceFlinger通信。因此SurfaceFlinger能使用这些Window信息来合成surfaces,并渲染输出到显示设备。
输入事件的中转站：当我们的触摸屏幕时就会产生输入事件，在Android中负责管理事件的输入是InputManagerService，它里面有一个InputManager，在启动IMS的同时会创建InputManager，在创建InputManager同时创建InputReader和InputDispatcher，InputReader会不断的从设备节点中读取输入事件，InputReader将这些原始输入事件加工后就交给InputDispatcher，而InputDispatcher它会寻找一个最合适的窗口来处理输入事件，WMS是窗口的管理者，WMS会把所有窗口的信息更新到InputDispatcher中，这样InputDispatcher就可以将输入事件派发给合适的Window，Window就会把这个输入事件传给顶级View，然后就会涉及我们熟悉的事件分发机制。
2.2 window的更新
直接看mGlobal.updateViewLayout(view, params)：
public void updateViewLayout(View view, ViewGroup.LayoutParams params) {
//1、参数检查
if (view == null) {
throw new IllegalArgumentException("view must not be null");
}
if (!(params instanceof WindowManager.LayoutParams)) {
throw new IllegalArgumentException("Params must be WindowManager.LayoutParams");
}
final WindowManager.LayoutParams wparams = (WindowManager.LayoutParams)params;
//2、更新layoutParams及参数列表列表
view.setLayoutParams(wparams);
synchronized (mLock) {
int index = findViewLocked(view, true);
ViewRootImpl root = mRoots.get(index);
mParams.remove(index);
mParams.add(index, wparams);
//3、RootViewImpl更新布局
root.setLayoutParams(wparams, false);
}
}
再看ViewRootIml.setLayoutParams()中会调用scheduleTraversals() 重新绘制布局，其中也会调用mWindowSession.relayout来更新window ，也是IPC过程。
2.3 window 删除
直接看mGlobal.removeView(view, false)：
public void removeView(View view, boolean immediate) {
if (view == null) {
throw new IllegalArgumentException("view must not be null");
}
synchronized (mLock) {
//找到要移除view在列表中的index
int index = findViewLocked(view, true);
View curView = mRoots.get(index).getView();
//移除
removeViewLocked(index, immediate);
if (curView == view) {
return;
}
throw new IllegalStateException("Calling with view " + view
+ " but the ViewAncestor is attached to " + curView);
}
}
再看removeViewLocked(index, immediate)：
private void removeViewLocked(int index, boolean immediate) {
//找到对应的ViewRoot
ViewRootImpl root = mRoots.get(index);
View view = root.getView();
if (view != null) {
InputMethodManager imm = InputMethodManager.getInstance();
if (imm != null) {
imm.windowDismissed(mViews.get(index).getWindowToken());
}
}
//ViewRoot用die来删除
boolean deferred = root.die(immediate);
if (view != null) {
view.assignParent(null);
if (deferred) {
//记录要删除的view
mDyingViews.add(view);
}
}
}
继续看root.die(immediate)：
boolean die(boolean immediate) {
// 如果是立刻删除，直接调doDie()
if (immediate && !mIsInTraversal) {
doDie();
return false;
}
if (!mIsDrawing) {
destroyHardwareRenderer();
} else {
Log.e(mTag, "Attempting to destroy the window while drawing!\n" +
" window=" + this + ", title=" + mWindowAttributes.getTitle());
}
//不是立刻删，就放入队列
mHandler.sendEmptyMessage(MSG_DIE);
return true;
}
继续看doeDie()：
void doDie() {
checkThread();
if (LOCAL_LOGV) Log.v(mTag, "DIE in " + this + " of " + mSurface);
synchronized (this) {
if (mRemoved)
return;
}
mRemoved = true;
if (mAdded) {
//删除操作
dispatchDetachedFromWindow();
}
...
//移除对应列表中的root、view、param、dyingView
WindowManagerGlobal.getInstance().doRemoveView(this);
}
看下dispatchDetachedFromWindow()：
void dispatchDetachedFromWindow() {
mFirstInputStage.onDetachedFromWindow();
if (mView != null && mView.mAttachInfo != null) {
mAttachInfo.mTreeObserver.dispatchOnWindowAttachedChange(false);
//回调view的dispatchDetachedFromWindow方法，意思是view要从window中移除了。一般可在其中做一些资源回收工作，如 停止动画等。
mView.dispatchDetachedFromWindow();
}
//移除各种回调
mAccessibilityInteractionConnectionManager.ensureNoConnection();
mAccessibilityManager.removeAccessibilityStateChangeListener(
mAccessibilityInteractionConnectionManager);
mAccessibilityManager.removeHighTextContrastStateChangeListener(
mHighContrastTextManager);
removeSendWindowContentChangedCallback();
destroyHardwareRenderer();
setAccessibilityFocus(null, null);
mView.assignParent(null);
mView = null;
mAttachInfo.mRootView = null;
mSurface.release();
if (mInputQueueCallback != null && mInputQueue != null) {
mInputQueueCallback.onInputQueueDestroyed(mInputQueue);
mInputQueue.dispose();
mInputQueueCallback = null;
mInputQueue = null;
}
if (mInputEventReceiver != null) {
mInputEventReceiver.dispose();
mInputEventReceiver = null;
}
try {
//删除window
mWindowSession.remove(mWindow);
} catch (RemoteException e) {
}
// Dispose the input channel after removing the window so the Window Manager
// doesn't interpret the input channel being closed as an abnormal termination.
if (mInputChannel != null) {
mInputChannel.dispose();
mInputChannel = null;
}
mDisplayManager.unregisterDisplayListener(mDisplayListener);
unscheduleTraversals();
}
好了，window的三个view操作就这些了。
三、常见Window的创建过程
View依附于Window这个抽象概念，有Activity、Dialog、Toast、PopupWindow等。
3.1 Activity的Window创建
Activity的启动略复杂，这里先看ActivityThread里的performLaunchActivity()：
private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {
...
//创建activity实例：通过类加载器创建
java.lang.ClassLoader cl = appContext.getClassLoader();
activity = mInstrumentation.newActivity(cl, component.getClassName(), r.intent);
...
//调用Activity的attach方法--关联上下文环境变量
activity.attach(appContext, this, getInstrumentation(), r.token,
r.ident, app, r.intent, r.activityInfo, title, r.parent,
r.embeddedID, r.lastNonConfigurationInstances, config,
r.referrer, r.voiceInteractor, window, r.configCallback);
...
}
接着看activity.attach方法：
//实例化window，就是Window的唯一实现PhoneWindow
mWindow = new PhoneWindow(this, window, activityConfigCallback);
...
//把activity作为回调接口传入window，这样window从外界接受的状态变化都会交给activity
//例如：dispatchTouchEvent、onAttachedToWindow、onDetachedFromWindow
mWindow.setCallback(this);
...
//设置windowManager，实际就是WindowManagerImpl的实例，在activity中getWindowManager()获取的就是这个实例
mWindow.setWindowManager(
(WindowManager)context.getSystemService(Context.WINDOW_SERVICE),
mToken, mComponent.flattenToString(),
(info.flags & ActivityInfo.FLAG_HARDWARE_ACCELERATED) != 0);
...
mWindowManager = mWindow.getWindowManager();
OK，activity视图的管理者window已创建，那么什么时候用windowManager.addView() 来把activity的视图依附在window上呢？
先看Activity的setContentView方法，我们activity的视图由此方法设置：
public void setContentView(@LayoutRes int layoutResID) {
getWindow().setContentView(layoutResID);
initWindowDecorActionBar();
}
接着看PhonrWindow的setContentView：
public void setContentView(int layoutResID) {
// mContentParent为空，就调installDecor()，猜想installDecor()里面创建了mContentParent。且从名字看出mContentParent就是内容视图的容器
if (mContentParent == null) {
installDecor();
} else if (!hasFeature(FEATURE_CONTENT_TRANSITIONS)) {
mContentParent.removeAllViews();
}
if (hasFeature(FEATURE_CONTENT_TRANSITIONS)) {
final Scene newScene = Scene.getSceneForLayout(mContentParent, layoutResID,
getContext());
transitionTo(newScene);
} else {
//这里看到，确实把我们的视图加载到mContentParent了
mLayoutInflater.inflate(layoutResID, mContentParent);
}
...
}
那就看installDecor():
private void installDecor() {
if (mDecor == null) {
//创建mDecor
mDecor = generateDecor(-1);
mDecor.setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS);
mDecor.setIsRootNamespace(true);
if (!mInvalidatePanelMenuPosted && mInvalidatePanelMenuFeatures != 0) {
mDecor.postOnAnimation(mInvalidatePanelMenuRunnable);
}
} else {
mDecor.setWindow(this);
}
if (mContentParent == null) {
//创建mContentParent
mContentParent = generateLayout(mDecor);
...
}
看下generateDecor(-1)，就是new了个DecorView：
protected DecorView generateDecor(int featureId) {
Context context;
if (mUseDecorContext) {
Context applicationContext = getContext().getApplicationContext();
if (applicationContext == null) {
context = getContext();
} else {
context = new DecorContext(applicationContext, getContext());
if (mTheme != -1) {
context.setTheme(mTheme);
}
}
} else {
context = getContext();
}
return new DecorView(context, featureId, this, getAttributes());
}
继续看generateLayout(mDecor)：
// Apply data from current theme.
TypedArray a = getWindowStyle();
...
// 这里下面一堆代码是 根据主题，获取DecorView的布局资源
int layoutResource;
int features = getLocalFeatures();
if ((features & (1 << FEATURE_SWIPE_TO_DISMISS)) != 0) {
layoutResource = R.layout.screen_swipe_dismiss;
setCloseOnSwipeEnabled(true);
} else if ((features & ((1 << FEATURE_LEFT_ICON) | (1 << FEATURE_RIGHT_ICON))) != 0)
...
//把布局给到mDecor，这样mDecor就有视图了。
mDecor.onResourceLoaded(mLayoutInflater, layoutResource)
//findViewById就是getDecorView().findViewById(id);
//所以从DecorView中找到id为ID_ANDROID_CONTENT = com.android.internal.R.id.content 的容器，就用用来存放我们activity中设置的视图的。
ViewGroup contentParent = (ViewGroup)findViewById(ID_ANDROID_CONTENT);
...
return contentParent;
}
好了，通过以上流程，就清楚了activity中通过setContentView设置的布局实际是加载到DecorView的id为com.android.internal.R.id.content容器中。我们查看DecorView所有的主题的布局，发现都有这个id的容器，且是FrameLayout。
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:fitsSystemWindows="true">
<!-- Popout bar for action modes -->
<ViewStub android:id="@+id/action_mode_bar_stub"
android:inflatedId="@+id/action_mode_bar"
android:layout="@layout/action_mode_bar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="?attr/actionBarTheme" />
<FrameLayout android:id="@android:id/title_container"
android:layout_width="match_parent"
android:layout_height="?android:attr/windowTitleSize"
android:transitionName="android:title"
style="?android:attr/windowTitleBackgroundStyle">
</FrameLayout>
//这个容器
<FrameLayout android:id="@android:id/content"
android:layout_width="match_parent"
android:layout_height="0dip"
android:layout_weight="1"
android:foregroundGravity="fill_horizontal|top"
android:foreground="?android:attr/windowContentOverlay" />
</LinearLayout>
最后一步，就是windowManager.addView了，在哪呢？ 在ActivityThred的handleResumeActivity()中:
r.activity.makeVisible();
再看activity.makeVisible()：
void makeVisible() {
if (!mWindowAdded) {
ViewManager wm = getWindowManager();
//1、windowManager.addView
wm.addView(mDecor, getWindow().getAttributes());
mWindowAdded = true;
}
//2、Decor可见
mDecor.setVisibility(View.VISIBLE);
}
好了，activity的window加载过程就这样了。
3.2 Dialog的window创建
先看Dialog的构造方法:
Dialog(@NonNull Context context, @StyleRes int themeResId, boolean createContextThemeWrapper) {
...
//获取windowManager
mWindowManager = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
//实例化PhoneWindow
final Window w = new PhoneWindow(mContext);
mWindow = w;
//设置回调
w.setCallback(this);
w.setOnWindowDismissedCallback(this);
w.setOnWindowSwipeDismissedCallback(() -> {
if (mCancelable) {
cancel();
}
});
w.setWindowManager(mWindowManager, null, null);
...
}
接着看setContentView，和activity类似，把内容视图放入DecorView：
public void setContentView(@LayoutRes int layoutResID) {
mWindow.setContentView(layoutResID);
}
再看下show方法：
public void show() {
...
mDecor = mWindow.getDecorView();
...
WindowManager.LayoutParams l = mWindow.getAttributes();
boolean restoreSoftInputMode = false;
if ((l.softInputMode
& WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION) == 0) {
l.softInputMode |=
WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION;
restoreSoftInputMode = true;
}
//使用WindowManager.addView
mWindowManager.addView(mDecor, l);
...
}
注意，一般创建dialog时 传入的context必须是Activity。如果要传Application，那么要dialog.getWindow().setType()，设置系统window的type。
3.3 Toast的window创建
使用Toast方式：
Toast.makeText(this, "hehe", Toast.LENGTH_SHORT).show();
看makeText()，就是new一个Toast，设置mNextView为TextView、mDuration：
public static Toast makeText(Context context, CharSequence text, @Duration int duration) {
return makeText(context, null, text, duration);
}
public static Toast makeText(@NonNull Context context, @Nullable Looper looper,
@NonNull CharSequence text, @Duration int duration) {
//实例化
Toast result = new Toast(context, looper);
LayoutInflater inflate = (LayoutInflater)
context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View v = inflate.inflate(com.android.internal.R.layout.transient_notification, null);
TextView tv = (TextView)v.findViewById(com.android.internal.R.id.message);
tv.setText(text);
//设置视图、时间
result.mNextView = v;
result.mDuration = duration;
return result;
}
Toast构造方法:
public Toast(@NonNull Context context, @Nullable Looper looper) {
mContext = context;
//有个TN，是个Binder对象
mTN = new TN(context.getPackageName(), looper);
mTN.mY = context.getResources().getDimensionPixelSize(
com.android.internal.R.dimen.toast_y_offset);
mTN.mGravity = context.getResources().getInteger(
com.android.internal.R.integer.config_toastDefaultGravity);
}
实际也可以用setView（）自定义视图：
public void setView(View view) {
mNextView = view;
}
再看show():
public void show() {
//没有视图不行
if (mNextView == null) {
throw new RuntimeException("setView must have been called");
}
INotificationManager service = getService();
String pkg = mContext.getOpPackageName();
TN tn = mTN;
tn.mNextView = mNextView;
try {
//IPC过程：NotificationManagerServcice.enqueueToast(),为啥要IPC过程呢？（注意这里的tn就是Toast构造方法里的new的TN）
service.enqueueToast(pkg, tn, mDuration);
} catch (RemoteException e) {
// Empty
}
}
看下NotificationManagerServcice.enqueueToast()：
//创建ToastRecord，callback就是传进来的TN
record = new ToastRecord(callingPid, pkg, callback, duration, token);
mToastQueue.add(record);
...
if (index == 0) {
//这里看起来是show方法
showNextToastLocked();
}
看不showNextToastLocked()：
void showNextToastLocked() {
//取出第一个record，这里为啥第0个？
ToastRecord record = mToastQueue.get(0);
while (record != null) {
if (DBG) Slog.d(TAG, "Show pkg=" + record.pkg + " callback=" + record.callback);
try {
//这里跑到TN的show方法了，显然是系统服务NotificationManagerServcice向我们的APP发起IPC过程，完成最终的show。这个保留疑问后面再看~
record.callback.show(record.token);
//这个就是 定时 调TN的hide方法，时间就是我们的toast的设置的show时间？为啥这么说，往下看~
scheduleDurationReachedLocked(record);
return;
}
...
}
}
看下scheduleDurationReachedLocked(record)：
private void scheduleDurationReachedLocked(ToastRecord r)
{
mHandler.removeCallbacksAndMessages(r);
Message m = Message.obtain(mHandler, MESSAGE_DURATION_REACHED, r);
long delay = r.duration == Toast.LENGTH_LONG ? LONG_DELAY : SHORT_DELAY;
//handler发送定时任务MESSAGE_DURATION_REACHED，看名字就是隐藏toast，时间就是我们的long或者short
mHandler.sendMessageDelayed(m, delay);
}
这个mHandler就是NMS中的handler，找到上面任务的处理方法：
private void handleDurationReached(ToastRecord record)
{
synchronized (mToastQueue) {
int index = indexOfToastLocked(record.pkg, record.callback);
if (index >= 0) {
cancelToastLocked(index);
}
}
}
接着看：
void cancelToastLocked(int index) {
ToastRecord record = mToastQueue.get(index);
try {
//果然，是TN的hide方法，哈哈
record.callback.hide();
} catch (RemoteException e)
...
ToastRecord lastToast = mToastQueue.remove(index);
if (mToastQueue.size() > 0) {
// 开始下一个~~~
showNextToastLocked();
}
}
总结下NotificationManagerServcice.enqueueToast（）这个IPC的作用：使用NMS中的mHandler 处理队列中的ToastRecord，具体就是通过IPC调用Toast中的TN的show()，然后在定时调用TN的hide（）。就是说，系统来保证toast的循序排队，及展示时间。 另外还一点，对非系统应用，队列中最多同时又50个ToastRecord：
// limit the number of outstanding notificationrecords an app can have
//MAX_PACKAGE_NOTIFICATIONS = 50
int count = getNotificationCountLocked(pkg, userId, id, tag);
if (count >= MAX_PACKAGE_NOTIFICATIONS) {
mUsageStats.registerOverCountQuota(pkg);
Slog.e(TAG, "Package has already posted or enqueued " + count
+ " notifications. Not showing more. package=" + pkg);
return false;
}
好了，系统进程看完了。接着看实例化Toast时的创建的TN，我们在上面分析，猜测 这里才是我们想要的WIndow的创建过程，那么往下看吧：
private static class TN extends ITransientNotification.Stub {
private final WindowManager.LayoutParams mParams = new WindowManager.LayoutParams();
private static final int SHOW = 0;
private static final int HIDE = 1;
private static final int CANCEL = 2;
final Handler mHandler;
...
static final long SHORT_DURATION_TIMEOUT = 4000;
static final long LONG_DURATION_TIMEOUT = 7000;
TN(String packageName, @Nullable Looper looper) {
final WindowManager.LayoutParams params = mParams;
...
//window的type：TYPE_TOAST = FIRST_SYSTEM_WINDOW+5，是个系统window
params.type = WindowManager.LayoutParams.TYPE_TOAST;
params.setTitle("Toast");
//window的flags
params.flags = WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON
| WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
| WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE;
mPackageName = packageName;
//这里可知，必须在有looper的线程才能new Toast，为啥呢？因为前面分析NMS中调用TN的show、Hide，因为是IPC过程，实际在App这边执行是在Bind线程池中进行的，所以需要切换到当前发Toast的线程
if (looper == null) {
// Use Looper.myLooper() if looper is not specified.
looper = Looper.myLooper();
if (looper == null) {
throw new RuntimeException(
"Can't toast on a thread that has not called Looper.prepare()");
}
}
mHandler = new Handler(looper, null) {
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case SHOW: {
IBinder token = (IBinder) msg.obj;
handleShow(token);
break;
}
case HIDE: {
handleHide();
// Don't do this in handleHide() because it is also invoked by
// handleShow()
mNextView = null;
break;
}
case CANCEL: {
handleHide();
// Don't do this in handleHide() because it is also invoked by
// handleShow()
mNextView = null;
try {
getService().cancelToast(mPackageName, TN.this);
} catch (RemoteException e) {
}
break;
}
}
}
};
}
/**
* schedule handleShow into the right thread
*/
@Override
public void show(IBinder windowToken) {
if (localLOGV) Log.v(TAG, "SHOW: " + this);
mHandler.obtainMessage(SHOW, windowToken).sendToTarget();
}
/**
* schedule handleHide into the right thread
*/
@Override
public void hide() {
if (localLOGV) Log.v(TAG, "HIDE: " + this);
mHandler.obtainMessage(HIDE).sendToTarget();
}
public void cancel() {
if (localLOGV) Log.v(TAG, "CANCEL: " + this);
mHandler.obtainMessage(CANCEL).sendToTarget();
}
public void handleShow(IBinder windowToken) {
...
if (mView != mNextView) {
// remove the old view if necessary
handleHide();
//mNextView赋值给mView
mView = mNextView;
...
//1.获取WindowManager
mWM = (WindowManager)context.getSystemService(Context.WINDOW_SERVICE);
// the layout direction
final Configuration config = mView.getContext().getResources().getConfiguration();
final int gravity = Gravity.getAbsoluteGravity(mGravity, config.getLayoutDirection());
...
...
try {
//2.windowManager的addView
mWM.addView(mView, mParams);
trySendAccessibilityEvent();
} catch (WindowManager.BadTokenException e) {
/* ignore */
}
}
}
public void handleHide() {
if (localLOGV) Log.v(TAG, "HANDLE HIDE: " + this + " mView=" + mView);
if (mView != null) {
if (mView.getParent() != null) {
if (localLOGV) Log.v(TAG, "REMOVE! " + mView + " in " + this);
//windowManager的removeView
mWM.removeViewImmediate(mView);
}
...
mView = null;
}
}
}
所以，TN才是Toast中真正处理Window创建的地方。
好了，Window讲完啦！
参考： 初步理解 Window 体系 Window, WindowManager和WindowManagerService之间的关系
.
好了，今天就到这里，欢迎留言讨论~
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