Window、WindowManager和WindowManagerService
前言
Window表示一个窗口，日常开发时接触的不多。但是在一些场景下会使用到window，比如在桌面显示一个悬浮窗。
Window时一个抽象类，具体实现是PhoneWindow。创建一个Window，通过windowManager即可完成
WindowManager是外界访问Window的入口，Window的具体实现在WindowsManagerService中。
WindowManager和 WindowManagerService 的交互是一个IPC过程
Android 中所有的视图都是通过Window来呈现的，不管是 Activity、Dialog 还是 Toast，它们的视图实际上都是附加在 Window 上的，因此Window 实际是 View 的直接管理者。
Window与WindowManager的简单使用
查看代码
Button extraButton = new Button(this);
extraButton.setText("extraButton");
WindowManager.LayoutParams layoutParams = new WindowManager.LayoutParams(WindowManager.LayoutParams.WRAP_CONTENT,WindowManager.LayoutParams.WRAP_CONTENT,0,0, PixelFormat.TRANSPARENT);
layoutParams.flags = WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL|WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE|WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED;
layoutParams.gravity = Gravity.LEFT|Gravity.TOP;
layoutParams.type = 30;
layoutParams.x = 100;
layoutParams.y = 300;
getWindowManager().addView(extraButton,layoutParams);;LayoutParams中的flags和type这两个参数比较重要，下面对其进行说明。
Flags 参数表示 Window 的属性，它有很多选项，通过这些选项可以控制 Window 的显示特性，这里主要介绍几个比较常用的选项
FLAG_NOT_FOCUSABLE
表示Window不需要获取焦点，也不需要接收各种输入事件，此标记会同时启用FLAG_NOT_TOUCH_MODAL，最终事件会直接传递给下层的具有焦点的Window。
FLAG_NOT_TOUCH_MODAL
在此模式下，系统会将当前 Window 区域以外的单击事件传递给底层的 Window，当前Window 区域以内的单击事件则自己处理。这个标记很重要，一般来说都需要开启此标记，否则其他Window 将无法收到单击事件。
FLAG_SHOW_WHEN_LOCKED
开启此模式可以让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，分别是应用Window、子Window和系统Window。应用类Window对应着一个Activity。子Window不能单独存在，它需要附属在特定的父Window之中，比如常见的一些Dialog就是一个子Window。系统Window是需要声明权限在能创建的Window，比如Toast和系统状态栏这些都是系统Window.
Window 是分层的，每个 Window 都有对应的 z-ordered，层级大的会覆盖在层级小的Window的上面。
应用层级为1~99，子Window层级1000~1999，系统Window层级2000~2999。
如果想要Window位于所有Window最顶层，那么采用较大层级即可。
需要声明权限∶<uses-permission android∶name="android.permission.SYSTEM_ALERT_WINDOW">。
WindowManager 所提供的功能很简单，常用的只有三个方法，即添加 View、更新 View和删除View.这三个方法定义在ViewManager 中，而WindowManager 继承了ViewManager。
Window内部机制
Window是一个抽象的概念，每一个Window都对应着一个View 和一个ViewRootImpl，是以View 的形式存在。从 WindowManager 的定义也可以看出，它提供的三个接口方法addView、updateViewLayout 以及 removeView都是针对 View的。
Window的添加删除更新过程需要通过 WindowManager 的 addView来实现，WindowManager是一个接口，它的真正实现是WindowManagerImpl类。而WindowManagerImpl的代码中，真正调用的是WindowManagerGlobal的代码。WindowManagerGlobal以工厂模式向外提供自己的实例。
Window的添加过程
WindowManagerGlobal
1、检查参数是否合法，如果是子window那么还需要调整一些布局参数
public void addView(View view, ViewGroup.LayoutParams params,
Display display, Window parentWindow, int userId) {
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;
}
}2、创建ViewRootImpl并将View添加到列表中
@UnsupportedAppUsage
private final ArrayList<View> mViews = new ArrayList<View>();
@UnsupportedAppUsage
private final ArrayList<ViewRootImpl> mRoots = new ArrayList<ViewRootImpl>();
@UnsupportedAppUsage
private final ArrayList<WindowManager.LayoutParams> mParams =
new ArrayList<WindowManager.LayoutParams>();
private final ArraySet<View> mDyingViews = new ArraySet<View>();mViews存储的是所有Window 所对应的View，
mRoots 存储的是所有Window 所对应的 ViewRootlmpl，
mParams 存储的是所有Window 所对应的布局参数，
mDyingViews则存储了那些正在被删除的View对象，或者说是那些已经调用removeView方法但是删除操作还未完成的 Window 对象
3、通过VIewRootImpl来更新界面并完成window添加过程
由ViewRootImpl的setView方法来完成。
root = new ViewRootImpl(view.getContext(), display);
view.setLayoutParams(wparams);
mViews.add(view);
mRoots.add(root);
mParams.add(wparams);
// do this last because it fires off messages to start doing things
try {
root.setView(view, wparams, panelParentView, userId);
} catch (RuntimeException e) {
// BadTokenException or InvalidDisplayException, clean up.
if (index >= 0) {
removeViewLocked(index, true);
}
throw e;
}setView内部通过requestLayout完成异步刷新请求，在通过WindowSession完成Window添加过程
public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView,
int userId) {
synchronized (this) {
if (mView == null) {
mView = view;
mAttachInfo.mDisplayState = mDisplay.getState();
mDisplayManager.registerDisplayListener(mDisplayListener, mHandler);
mViewLayoutDirectionInitial = mView.getRawLayoutDirection();
mFallbackEventHandler.setView(view);
mWindowAttributes.copyFrom(attrs);
if (mWindowAttributes.packageName == null) {
mWindowAttributes.packageName = mBasePackageName;
}
mWindowAttributes.privateFlags |=
WindowManager.LayoutParams.PRIVATE_FLAG_USE_BLAST;
attrs = mWindowAttributes;
setTag();
if (DEBUG_KEEP_SCREEN_ON && (mClientWindowLayoutFlags
& WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON) != 0
&& (attrs.flags&WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON) == 0) {
Slog.d(mTag, "setView: FLAG_KEEP_SCREEN_ON changed from true to false!");
}
// Keep track of the actual window flags supplied by the client.
mClientWindowLayoutFlags = attrs.flags;
setAccessibilityFocus(null, null);
if (view instanceof RootViewSurfaceTaker) {
mSurfaceHolderCallback =
((RootViewSurfaceTaker)view).willYouTakeTheSurface();
if (mSurfaceHolderCallback != null) {
mSurfaceHolder = new TakenSurfaceHolder();
mSurfaceHolder.setFormat(PixelFormat.UNKNOWN);
mSurfaceHolder.addCallback(mSurfaceHolderCallback);
}
}
// Compute surface insets required to draw at specified Z value.
// TODO: Use real shadow insets for a constant max Z.
if (!attrs.hasManualSurfaceInsets) {
attrs.setSurfaceInsets(view, false /*manual*/, true /*preservePrevious*/);
}
CompatibilityInfo compatibilityInfo =
mDisplay.getDisplayAdjustments().getCompatibilityInfo();
mTranslator = compatibilityInfo.getTranslator();
// If the application owns the surface, don't enable hardware acceleration
if (mSurfaceHolder == null) {
// While this is supposed to enable only, it can effectively disable
// the acceleration too.
enableHardwareAcceleration(attrs);
final boolean useMTRenderer = MT_RENDERER_AVAILABLE
&& mAttachInfo.mThreadedRenderer != null;
if (mUseMTRenderer != useMTRenderer) {
// Shouldn't be resizing, as it's done only in window setup,
// but end just in case.
endDragResizing();
mUseMTRenderer = useMTRenderer;
}
}
boolean restore = false;
if (mTranslator != null) {
mSurface.setCompatibilityTranslator(mTranslator);
restore = true;
attrs.backup();
mTranslator.translateWindowLayout(attrs);
}
if (DEBUG_LAYOUT) Log.d(mTag, "WindowLayout in setView:" + attrs);
if (!compatibilityInfo.supportsScreen()) {
attrs.privateFlags |= WindowManager.LayoutParams.PRIVATE_FLAG_COMPATIBLE_WINDOW;
mLastInCompatMode = true;
}
mSoftInputMode = attrs.softInputMode;
mWindowAttributesChanged = true;
mAttachInfo.mRootView = view;
mAttachInfo.mScalingRequired = mTranslator != null;
mAttachInfo.mApplicationScale =
mTranslator == null ? 1.0f : mTranslator.applicationScale;
if (panelParentView != null) {
mAttachInfo.mPanelParentWindowToken
= panelParentView.getApplicationWindowToken();
}
mAdded = true;
int res; /* = WindowManagerImpl.ADD_OKAY; */
// Schedule the first layout -before- adding to the window
// manager, to make sure we do the relayout before receiving
// any other events from the system.
requestLayout();
InputChannel inputChannel = null;
if ((mWindowAttributes.inputFeatures
& WindowManager.LayoutParams.INPUT_FEATURE_NO_INPUT_CHANNEL) == 0) {
inputChannel = new InputChannel();
}
mForceDecorViewVisibility = (mWindowAttributes.privateFlags
& PRIVATE_FLAG_FORCE_DECOR_VIEW_VISIBILITY) != 0;
if (mView instanceof RootViewSurfaceTaker) {
PendingInsetsController pendingInsetsController =
((RootViewSurfaceTaker) mView).providePendingInsetsController();
if (pendingInsetsController != null) {
pendingInsetsController.replayAndAttach(mInsetsController);
}
}
try {
mOrigWindowType = mWindowAttributes.type;
mAttachInfo.mRecomputeGlobalAttributes = true;
collectViewAttributes();
adjustLayoutParamsForCompatibility(mWindowAttributes);
controlInsetsForCompatibility(mWindowAttributes);
res = mWindowSession.addToDisplayAsUser(mWindow, mWindowAttributes,
getHostVisibility(), mDisplay.getDisplayId(), userId,
mInsetsController.getRequestedVisibility(), inputChannel, mTempInsets,
mTempControls);
if (mTranslator != null) {
mTranslator.translateInsetsStateInScreenToAppWindow(mTempInsets);
mTranslator.translateSourceControlsInScreenToAppWindow(mTempControls);
}
} catch (RemoteException e) {
mAdded = false;
mView = null;
mAttachInfo.mRootView = null;
mFallbackEventHandler.setView(null);
unscheduleTraversals();
setAccessibilityFocus(null, null);
throw new RuntimeException("Adding window failed", e);
} finally {
if (restore) {
attrs.restore();
}
}
mAttachInfo.mAlwaysConsumeSystemBars =
(res & WindowManagerGlobal.ADD_FLAG_ALWAYS_CONSUME_SYSTEM_BARS) != 0;
mPendingAlwaysConsumeSystemBars = mAttachInfo.mAlwaysConsumeSystemBars;
mInsetsController.onStateChanged(mTempInsets);
mInsetsController.onControlsChanged(mTempControls);
computeWindowBounds(mWindowAttributes, mInsetsController.getState(),
getConfiguration().windowConfiguration.getBounds(), mTmpFrames.frame);
setFrame(mTmpFrames.frame);
if (DEBUG_LAYOUT) Log.v(mTag, "Added window " + mWindow);
if (res < WindowManagerGlobal.ADD_OKAY) {
mAttachInfo.mRootView = null;
mAdded = false;
mFallbackEventHandler.setView(null);
unscheduleTraversals();
setAccessibilityFocus(null, null);
switch (res) {
case WindowManagerGlobal.ADD_BAD_APP_TOKEN:
case WindowManagerGlobal.ADD_BAD_SUBWINDOW_TOKEN:
throw new WindowManager.BadTokenException(
"Unable to add window -- token " + attrs.token
+ " is not valid; is your activity running?");
case WindowManagerGlobal.ADD_NOT_APP_TOKEN:
throw new WindowManager.BadTokenException(
"Unable to add window -- token " + attrs.token
+ " is not for an application");
case WindowManagerGlobal.ADD_APP_EXITING:
throw new WindowManager.BadTokenException(
"Unable to add window -- app for token " + attrs.token
+ " is exiting");
case WindowManagerGlobal.ADD_DUPLICATE_ADD:
throw new WindowManager.BadTokenException(
"Unable to add window -- window " + mWindow
+ " has already been added");
case WindowManagerGlobal.ADD_STARTING_NOT_NEEDED:
// Silently ignore -- we would have just removed it
// right away, anyway.
return;
case WindowManagerGlobal.ADD_MULTIPLE_SINGLETON:
throw new WindowManager.BadTokenException("Unable to add window "
+ mWindow + " -- another window of type "
+ mWindowAttributes.type + " already exists");
case WindowManagerGlobal.ADD_PERMISSION_DENIED:
throw new WindowManager.BadTokenException("Unable to add window "
+ mWindow + " -- permission denied for window type "
+ mWindowAttributes.type);
case WindowManagerGlobal.ADD_INVALID_DISPLAY:
throw new WindowManager.InvalidDisplayException("Unable to add window "
+ mWindow + " -- the specified display can not be found");
case WindowManagerGlobal.ADD_INVALID_TYPE:
throw new WindowManager.InvalidDisplayException("Unable to add window "
+ mWindow + " -- the specified window type "
+ mWindowAttributes.type + " is not valid");
case WindowManagerGlobal.ADD_INVALID_USER:
throw new WindowManager.BadTokenException("Unable to add Window "
+ mWindow + " -- requested userId is not valid");
}
throw new RuntimeException(
"Unable to add window -- unknown error code " + res);
}
if ((res & WindowManagerGlobal.ADD_FLAG_USE_BLAST) != 0) {
mUseBLASTAdapter = true;
}
if (view instanceof RootViewSurfaceTaker) {
mInputQueueCallback =
((RootViewSurfaceTaker)view).willYouTakeTheInputQueue();
}
if (inputChannel != null) {
if (mInputQueueCallback != null) {
mInputQueue = new InputQueue();
mInputQueueCallback.onInputQueueCreated(mInputQueue);
}
mInputEventReceiver = new WindowInputEventReceiver(inputChannel,
Looper.myLooper());
if (ENABLE_INPUT_LATENCY_TRACKING && mAttachInfo.mThreadedRenderer != null) {
InputMetricsListener listener = new InputMetricsListener();
mHardwareRendererObserver = new HardwareRendererObserver(
listener, listener.data, mHandler, true /*waitForPresentTime*/);
mAttachInfo.mThreadedRenderer.addObserver(mHardwareRendererObserver);
}
}
view.assignParent(this);
mAddedTouchMode = (res & WindowManagerGlobal.ADD_FLAG_IN_TOUCH_MODE) != 0;
mAppVisible = (res & WindowManagerGlobal.ADD_FLAG_APP_VISIBLE) != 0;
if (mAccessibilityManager.isEnabled()) {
mAccessibilityInteractionConnectionManager.ensureConnection();
}
if (view.getImportantForAccessibility() == View.IMPORTANT_FOR_ACCESSIBILITY_AUTO) {
view.setImportantForAccessibility(View.IMPORTANT_FOR_ACCESSIBILITY_YES);
}
// Set up the input pipeline.
CharSequence counterSuffix = attrs.getTitle();
mSyntheticInputStage = new SyntheticInputStage();
InputStage viewPostImeStage = new ViewPostImeInputStage(mSyntheticInputStage);
InputStage nativePostImeStage = new NativePostImeInputStage(viewPostImeStage,
"aq:native-post-ime:" + counterSuffix);
InputStage earlyPostImeStage = new EarlyPostImeInputStage(nativePostImeStage);
InputStage imeStage = new ImeInputStage(earlyPostImeStage,
"aq:ime:" + counterSuffix);
InputStage viewPreImeStage = new ViewPreImeInputStage(imeStage);
InputStage nativePreImeStage = new NativePreImeInputStage(viewPreImeStage,
"aq:native-pre-ime:" + counterSuffix);
mFirstInputStage = nativePreImeStage;
mFirstPostImeInputStage = earlyPostImeStage;
mPendingInputEventQueueLengthCounterName = "aq:pending:" + counterSuffix;
}
}
}requestLayout内部通过scheduleTraversals绘制View，WindowSession是一个Binder对象，真正的实现类是Session，也就是Window添加过程是一次IPC调用，Seesion内部通过WindowManagerService实现WIndow添加，通过调用addWindow。
Window的删除过程
略
Window的更新过程
略
WindowManagerService
交互图
要想实现完整的窗口管理器，我们首先要知道与WMS相关联的元素。这里先初略的介绍一下
1、WindowManagerService
充当导演，考虑画面的效果与视觉美感，根据实际安排演员站位。
系统级服务，由SystemServer启动，在这之前的画面由BootAnimation提供
异常可重启，关机才退出。
2、SurfaceFlinger
充当摄像机，负责客观地捕捉当前画面，然后真实地呈现给观众
3、有UI的程序
窗口一般分为三类：系统窗口，应用窗口，子窗口，不同窗口层级不同。
4、InputManagerService
IMS负责接收一切输入，当IMS收到一个按键或触摸，他就需要分发给WMS，WMS是派发系统按键和触摸信息的最佳人选。
5、ActivityManagerService
当AC1启动了AC2，UI上的变化就是AC1逐渐消失，AC2慢慢占据屏幕
6、Binder通信
AMS、SurfaceFlinger等，与WMS通讯都需要Binder。
WindowsManagerService的功能
1、窗口添加和删除
2、启动窗口？
3、窗口动画
4、窗口大小
5、窗口层级
6、事件派发
WMS的启动
WMS是SystemServer.java中众多系统服务的一员
t.traceBegin("StartWindowManagerService");
// WMS needs sensor service ready
mSystemServiceManager.startBootPhase(t, SystemService.PHASE_WAIT_FOR_SENSOR_SERVICE);
wm = WindowManagerService.main(context, inputManager, !mFirstBoot, mOnlyCore,
new PhoneWindowManager(), mActivityManagerService.mActivityTaskManager);
ServiceManager.addService(Context.WINDOW_SERVICE, wm, /* allowIsolated= */ false,
DUMP_FLAG_PRIORITY_CRITICAL | DUMP_FLAG_PROTO);
ServiceManager.addService(Context.INPUT_SERVICE, inputManager,
/* allowIsolated= */ false, DUMP_FLAG_PRIORITY_CRITICAL);
t.traceEnd();WMS基础功能
WMS使用AIDL描述接口
WMS工作方式
在Android4.1之前，是使用WMThread作为线程的。之后是使用wmHandlerThread，使得其他服务可以往线程里投递事件。
调用者使用WM有两种方式，一种是事件投递，一种是直接调用
当wmHandlerThread创建一个WindowManagerService对象后，后者的mH成员变量就可以调用sendMessage方法传递消息给wmHandlerThread所属的消息队列中，完成事件投递。
直接调用略
图
WMS、AMS、Activity的联系
Activity运行在应用程序进程中，而AMS，WMS在系统进程中，他们之间通信需要Binder支持。
Activity
未完待续
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