Android之Window底層原理

1.概述

Window是一個抽象類夏醉,他的實現(xiàn)是PhoneWindow爽锥。Window通過WindowManager創(chuàng)建,是訪問Window的入口畔柔。Window的具體實現(xiàn)位于WindowManagerService中氯夷,WIndowManager與WindowManagerService的交互是一個IPC的過程。
WindowManager中的Layoutparam中的Type表示W(wǎng)indow的類型靶擦,Window有三種類型腮考,分別是應(yīng)用Window、子Window和系統(tǒng)Window玄捕。應(yīng)用類Window對應(yīng)著一個Activity踩蔚。子Window不能單獨存在,他需要附屬在特定的父Window枚粘,例如Dialog馅闽。系統(tǒng)Window是需要在聲明權(quán)限在能創(chuàng)建Window,比如Toast九串。
Window的層級范圍是1-99堡掏,子Window的層級范圍是1000-1999锦茁,系統(tǒng)Window的層級范圍是2000-2999臂拓。對應(yīng)著LayoutParams的type參數(shù)野芒。層級大的會覆蓋在層級小的Window上面脑又。
Layoutparams
public static final int FIRST_SUB_WINDOW = 1000;
public static final int FIRST_SYSTEM_WINDOW = 2000;

2.Window的內(nèi)部實現(xiàn)機制

2.1Window文留、PhoneWindow题禀、DecorView

window是一個抽象類搬设,提供一組通用的繪制窗口API穴店,可抽象理解為一個載體,各種View在這個載體上顯示
PhoneWindow是window類的實現(xiàn)拿穴,類內(nèi)部包含一個DecorView
DecorView是一個FragmeLayout的子類泣洞,該DecorView對象時所有應(yīng)用窗口的根View
Activity的setContentView調(diào)用到PhoneView的setConteView,如果沒有DecorView默色,那么就創(chuàng)建他球凰,將View添加到DecorView的mContentParent中,回調(diào)Activity的onContentChanged方法通知Activity視圖已經(jīng)發(fā)生改變

@Override  
  public void setContentView(int layoutResID) {  
  // Note: FEATURE_CONTENT_TRANSITIONS may be set in the process of installing the window  
  // decor, when theme attributes and the like are crystalized. Do not check the feature  
  // before this happens.  
  if (mContentParent == null) {  
  installDecor();//創(chuàng)建DecorView  
  } else if (!hasFeature(FEATURE_CONTENT_TRANSITIONS)) {//所以Activity可以多次的setContetView-  
  mContentParent.removeAllViews();  
  }  
  
  if (hasFeature(FEATURE_CONTENT_TRANSITIONS)) {  
  final Scene newScene = Scene.getSceneForLayout(mContentParent, layoutResID,  
  getContext());  
  transitionTo(newScene);  
  } else {  
  mLayoutInflater.inflate(layoutResID, mContentParent);  
  }  
  mContentParent.requestApplyInsets();  
  final Callback cb = getCallback();  
  if (cb != null && !isDestroyed()) {  
  cb.onContentChanged();  
  }  
  }  
private void installDecor() {  
if (mDecor == null) {  
mDecor = generateDecor();  
mDecor.setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS);  
mDecor.setIsRootNamespace(true);  
if (!mInvalidatePanelMenuPosted && mInvalidatePanelMenuFeatures != 0) {  
mDecor.postOnAnimation(mInvalidatePanelMenuRunnable);  
}  
}  
if (mContentParent == null) {  
mContentParent = generateLayout(mDecor);  
  
// Set up decor part of UI to ignore fitsSystemWindows if appropriate.  
mDecor.makeOptionalFitsSystemWindows();  
  
final DecorContentParent decorContentParent = (DecorContentParent) mDecor.findViewById(  
R.id.decor_content_parent);  
  
if (decorContentParent != null) {  
mDecorContentParent = decorContentParent;  
mDecorContentParent.setWindowCallback(getCallback());  
if (mDecorContentParent.getTitle() == null) {  
mDecorContentParent.setWindowTitle(mTitle);  
}  
  
final int localFeatures = getLocalFeatures();  
for (int i = 0; i < FEATURE_MAX; i++) {  
if ((localFeatures & (1 << i)) != 0) {  
mDecorContentParent.initFeature(i);  
}  
}  
  
mDecorContentParent.setUiOptions(mUiOptions);  
  
if ((mResourcesSetFlags & FLAG_RESOURCE_SET_ICON) != 0 ||  
(mIconRes != 0 && !mDecorContentParent.hasIcon())) {  
mDecorContentParent.setIcon(mIconRes);  
} else if ((mResourcesSetFlags & FLAG_RESOURCE_SET_ICON) == 0 &&  
mIconRes == 0 && !mDecorContentParent.hasIcon()) {  
mDecorContentParent.setIcon(  
getContext().getPackageManager().getDefaultActivityIcon());  
mResourcesSetFlags |= FLAG_RESOURCE_SET_ICON_FALLBACK;  
}  
if ((mResourcesSetFlags & FLAG_RESOURCE_SET_LOGO) != 0 ||  
(mLogoRes != 0 && !mDecorContentParent.hasLogo())) {  
mDecorContentParent.setLogo(mLogoRes);  
}  
  
// Invalidate if the panel menu hasn't been created before this.  
// Panel menu invalidation is deferred avoiding application onCreateOptionsMenu  
// being called in the middle of onCreate or similar.  
// A pending invalidation will typically be resolved before the posted message  
// would run normally in order to satisfy instance state restoration.  
PanelFeatureState st = getPanelState(FEATURE_OPTIONS_PANEL, false);  
if (!isDestroyed() && (st == null || st.menu == null) && !mIsStartingWindow) {  
invalidatePanelMenu(FEATURE_ACTION_BAR);  
}  
} else {  
mTitleView = (TextView)findViewById(R.id.title);  
if (mTitleView != null) {  
mTitleView.setLayoutDirection(mDecor.getLayoutDirection());  
if ((getLocalFeatures() & (1 << FEATURE_NO_TITLE)) != 0) {  
View titleContainer = findViewById(  
R.id.title_container);  
if (titleContainer != null) {  
titleContainer.setVisibility(View.GONE);  
} else {  
mTitleView.setVisibility(View.GONE);  
}  
if (mContentParent instanceof FrameLayout) {  
((FrameLayout)mContentParent).setForeground(null);  
}  
} else {  
mTitleView.setText(mTitle);  
}  
}  
}  
  
if (mDecor.getBackground() == null && mBackgroundFallbackResource != 0) {  
mDecor.setBackgroundFallback(mBackgroundFallbackResource);  
}  
  
// Only inflate or create a new TransitionManager if the caller hasn't  
// already set a custom one.  
if (hasFeature(FEATURE_ACTIVITY_TRANSITIONS)) {  
if (mTransitionManager == null) {  
final int transitionRes = getWindowStyle().getResourceId(  
R.styleable.Window_windowContentTransitionManager,  
0);  
if (transitionRes != 0) {  
final TransitionInflater inflater = TransitionInflater.from(getContext());  
mTransitionManager = inflater.inflateTransitionManager(transitionRes,  
mContentParent);  
} else {  
mTransitionManager = new TransitionManager();  
}  
}  
  
mEnterTransition = getTransition(mEnterTransition, null,  
R.styleable.Window_windowEnterTransition);  
mReturnTransition = getTransition(mReturnTransition, USE_DEFAULT_TRANSITION,  
R.styleable.Window_windowReturnTransition);  
mExitTransition = getTransition(mExitTransition, null,  
R.styleable.Window_windowExitTransition);  
mReenterTransition = getTransition(mReenterTransition, USE_DEFAULT_TRANSITION,  
R.styleable.Window_windowReenterTransition);  
mSharedElementEnterTransition = getTransition(mSharedElementEnterTransition, null,  
R.styleable.Window_windowSharedElementEnterTransition);  
mSharedElementReturnTransition = getTransition(mSharedElementReturnTransition,  
USE_DEFAULT_TRANSITION,  
R.styleable.Window_windowSharedElementReturnTransition);  
mSharedElementExitTransition = getTransition(mSharedElementExitTransition, null,  
R.styleable.Window_windowSharedElementExitTransition);  
mSharedElementReenterTransition = getTransition(mSharedElementReenterTransition,  
USE_DEFAULT_TRANSITION,  
R.styleable.Window_windowSharedElementReenterTransition);  
if (mAllowEnterTransitionOverlap == null) {  
mAllowEnterTransitionOverlap = getWindowStyle().getBoolean(  
R.styleable.Window_windowAllowEnterTransitionOverlap, true);  
}  
if (mAllowReturnTransitionOverlap == null) {  
mAllowReturnTransitionOverlap = getWindowStyle().getBoolean(  
R.styleable.Window_windowAllowReturnTransitionOverlap, true);  
}  
if (mBackgroundFadeDurationMillis < 0) {  
mBackgroundFadeDurationMillis = getWindowStyle().getInteger(  
R.styleable.Window_windowTransitionBackgroundFadeDuration,  
DEFAULT_BACKGROUND_FADE_DURATION_MS);  
}  
if (mSharedElementsUseOverlay == null) {  
mSharedElementsUseOverlay = getWindowStyle().getBoolean(  
R.styleable.Window_windowSharedElementsUseOverlay, true);  
}  
}  
}  
}  

2.2WindowManager腿宰、WindowManagerGlobal呕诉、ViewRootImpl、WindowManagerService

  1. WindowManagerImpl是客戶端WindowManager管理接口的實現(xiàn)吃度,WindowManagerImpl內(nèi)部維護一個單例的WindowManagerGlobal對象甩挫,WindowManagerImpl通過該對象轉(zhuǎn)發(fā)客戶端的窗口管理請求〈幻浚客戶端在創(chuàng)建窗口時首先調(diào)用getWindowManager獲得本地窗口管理對象伊者,并調(diào)用其addView、removeView间护、UpdateViewLayout為窗口進行布局控制
  2. ViewManagerImp是Viewmanager的實現(xiàn)亦渗,該類并沒有直接實現(xiàn)Window的操作,而是由WindowmanagerGlobal進行操作汁尺。
  3. WindowManagerGlobal對象內(nèi)部維護一個ViewRootImpl實例數(shù)組和一個View視圖對象數(shù)組法精,WindowmanagerGlobal的addView函數(shù)首先查看要添加的視圖是否已經(jīng)存在,若不存在則實例化一個ViewRootImpl對象均函,并把view和ViewRootImpl對象及布局參數(shù)保存到本地數(shù)組中,接著調(diào)用ViewRootImpl對象的setView函數(shù)菱涤;removeView通過調(diào)用ViewRootImpl的die方法進行苞也,最終調(diào)用dispatchDetachedFromWindow進行移除;updateViewLayout首先更新View的LayoutParams并替換掉老的LayoutParams,接著更新ViewRootImpl的Layoutparams,通過調(diào)用scheduleTraversals對View重新布局
private final ArrayList<View> mViews = new ArrayList<View>();  
  private final ArrayList<ViewRootImpl> mRoots = new ArrayList<ViewRootImpl>();  
  private final ArrayList<WindowManager.LayoutParams> mParams =  
  new ArrayList<WindowManager.LayoutParams>();  
  private final ArraySet<View> mDyingViews = new ArraySet<View>();  
public void addView(View view, ViewGroup.LayoutParams params,  
Display display, Window parentWindow) {  
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;  
  
synchronized (mLock) {  
// Start watching for system property changes.  
if (mSystemPropertyUpdater == null) {  
mSystemPropertyUpdater = new Runnable() {  
@Override public void run() {  
synchronized (mLock) {  
for (int i = mRoots.size() - 1; i >= 0; --i) {  
mRoots.get(i).loadSystemProperties();  
}  
}  
}  
};  
SystemProperties.addChangeCallback(mSystemPropertyUpdater);  
}  
  
int index = findViewLocked(view, false);  
if (index >= 0) {  
if (mDyingViews.contains(view)) {  
// Don't wait for MSG_DIE to make it's way through root's queue.  
mRoots.get(index).doDie();  
} else {  
throw new IllegalStateException("View " + view  
+ " has already been added to the window manager.");  
}  
// The previous removeView() had not completed executing. Now it has.  
}  
  
// If this is a panel window, then find the window it is being  
// attached to for future reference.  
if (wparams.type >= WindowManager.LayoutParams.FIRST_SUB_WINDOW &&  
wparams.type <= WindowManager.LayoutParams.LAST_SUB_WINDOW) {  
final int count = mViews.size();  
for (int i = 0; i < count; i++) {  
if (mRoots.get(i).mWindow.asBinder() == wparams.token) {  
panelParentView = mViews.get(i);  
}  
}  
}  
  
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);  
} catch (RuntimeException e) {  
// BadTokenException or InvalidDisplayException, clean up.  
synchronized (mLock) {  
final int index = findViewLocked(view, false);  
if (index >= 0) {  
removeViewLocked(index, true);  
}  
}  
throw e;  
}  
}  
public void updateViewLayout(View view, ViewGroup.LayoutParams params) {  
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;  
  
view.setLayoutParams(wparams);  
  
synchronized (mLock) {  
int index = findViewLocked(view, true);  
ViewRootImpl root = mRoots.get(index);  
mParams.remove(index);  
mParams.add(index, wparams);  
root.setLayoutParams(wparams, false);  
}  
}  

[java] view plain copy
public void removeView(View view, boolean immediate) {  
  if (view == null) {  
  throw new IllegalArgumentException("view must not be null");  
  }  
  
  synchronized (mLock) {  
  int index = findViewLocked(view, true);  
  View curView = mRoots.get(index).getView();  
  removeViewLocked(index, immediate);  
  if (curView == view) {  
  return;  
  }  
  
  throw new IllegalStateException("Calling with view " + view  
  + " but the ViewAncestor is attached to " + curView);  
  }  
  }  
  private void removeViewLocked(int index, boolean immediate) {  
  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());  
  }  
  }  
  boolean deferred = root.die(immediate);  
  if (view != null) {  
  view.assignParent(null);  
  if (deferred) {  
  mDyingViews.add(view);  
  }  
  }  
  }  
  1. ViewRootImpl是視圖處理類粘秆,是客戶端視圖的處理類如迟,客戶端的視圖通過該類與窗口管理服務(wù)交互,因此ViewRootImpl是一個中介類。ViewRootImpl內(nèi)部包含一個從IWindow.Stub派生的內(nèi)部類(ViewRootImpl.W)殷勘,窗口管理服務(wù)通過該對象可以與客戶端反向通訊此再。
    setView內(nèi)部通過requestLayout來完成異步刷新請求,scheduleTraversals實際是View繪制的入口玲销,通過調(diào)用performTraversals對View進行measure输拇、layout、draw贤斜,最后通過pokeDrawLockIfNeeded進行IPC策吠。
 public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView) {  
 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;  
 }  
 attrs = mWindowAttributes;  
 // 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);  
 }  
 }  
  
 // Compute surface insets required to draw at specified Z value.  
 // TODO: Use real shadow insets for a constant max Z.  
 if (!attrs.hasManualSurfaceInsets) {  
 final int surfaceInset = (int) Math.ceil(view.getZ() * 2);  
 attrs.surfaceInsets.set(surfaceInset, surfaceInset, surfaceInset, surfaceInset);  
 }  
  
 CompatibilityInfo compatibilityInfo = mDisplayAdjustments.getCompatibilityInfo();  
 mTranslator = compatibilityInfo.getTranslator();  
  
 // If the application owns the surface, don't enable hardware acceleration  
 if (mSurfaceHolder == null) {  
 enableHardwareAcceleration(attrs);  
 }  
  
 boolean restore = false;  
 if (mTranslator != null) {  
 mSurface.setCompatibilityTranslator(mTranslator);  
 restore = true;  
 attrs.backup();  
 mTranslator.translateWindowLayout(attrs);  
 }  
 if (DEBUG_LAYOUT) Log.d(TAG, "WindowLayout in setView:" + attrs);  
  
 if (!compatibilityInfo.supportsScreen()) {  
 attrs.privateFlags |= WindowManager.LayoutParams.PRIVATE_FLAG_COMPATIBLE_WINDOW;  
 mLastInCompatMode = true;  
 }  
  
 mSoftInputMode = attrs.softInputMode;  
 mWindowAttributesChanged = true;  
 mWindowAttributesChangesFlag = WindowManager.LayoutParams.EVERYTHING_CHANGED;  
 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();  
 if ((mWindowAttributes.inputFeatures  
 & WindowManager.LayoutParams.INPUT_FEATURE_NO_INPUT_CHANNEL) == 0) {  
 mInputChannel = new InputChannel();  
 }  
 try {  
 mOrigWindowType = mWindowAttributes.type;  
 mAttachInfo.mRecomputeGlobalAttributes = true;  
 collectViewAttributes();  
 res = mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes,  
 getHostVisibility(), mDisplay.getDisplayId(),  
 mAttachInfo.mContentInsets, mAttachInfo.mStableInsets,  
 mAttachInfo.mOutsets, 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);  
 } finally {  
 if (restore) {  
 attrs.restore();  
 }  
 }  
  
 if (mTranslator != null) {  
 mTranslator.translateRectInScreenToAppWindow(mAttachInfo.mContentInsets);  
 }  
 mPendingOverscanInsets.set(0, 0, 0, 0);  
 mPendingContentInsets.set(mAttachInfo.mContentInsets);  
 mPendingStableInsets.set(mAttachInfo.mStableInsets);  
 mPendingVisibleInsets.set(0, 0, 0, 0);  
 if (DEBUG_LAYOUT) Log.v(TAG, "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 this type already exists");  
 case WindowManagerGlobal.ADD_PERMISSION_DENIED:  
 throw new WindowManager.BadTokenException(  
 "Unable to add window " + mWindow +  
 " -- permission denied for this window 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 is not valid");  
 }  
 throw new RuntimeException(  
 "Unable to add window -- unknown error code " + res);  
 }  
  
 if (view instanceof RootViewSurfaceTaker) {  
 mInputQueueCallback =  
 ((RootViewSurfaceTaker)view).willYouTakeTheInputQueue();  
 }  
 if (mInputChannel != null) {  
 if (mInputQueueCallback != null) {  
 mInputQueue = new InputQueue();  
 mInputQueueCallback.onInputQueueCreated(mInputQueue);  
 }  
 mInputEventReceiver = new WindowInputEventReceiver(mInputChannel,  
 Looper.myLooper());  
 }  
  
 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;  
 }  
 }  
 }  
      
@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();  
 }  
 }  

在die方法內(nèi)部只是簡單做了判斷,如果是異步刪除瘩绒,那個發(fā)送MSG_DIE的消息猴抹,ViewRootImpl中的Handle會處理并調(diào)用doDie,如果為同步直接調(diào)用doDie,doDie內(nèi)部會調(diào)用dispatchDetachedFromWIndow锁荔,進行IPC

/** 
* @param immediate True, do now if not in traversal. False, put on queue and do later. 
* @return True, request has been queued. False, request has been completed. 
*/  
boolean die(boolean immediate) {  
// Make sure we do execute immediately if we are in the middle of a traversal or the damage  
// done by dispatchDetachedFromWindow will cause havoc on return.  
if (immediate && !mIsInTraversal) {  
doDie();  
return false;  
}  
  
if (!mIsDrawing) {  
destroyHardwareRenderer();  
} else {  
Log.e(TAG, "Attempting to destroy the window while drawing!\n" +  
" window=" + this + ", title=" + mWindowAttributes.getTitle());  
}  
mHandler.sendEmptyMessage(MSG_DIE);  
return true;  
}  
  
void doDie() {  
checkThread();  
if (LOCAL_LOGV) Log.v(TAG, "DIE in " + this + " of " + mSurface);  
synchronized (this) {  
if (mRemoved) {  
return;  
}  
mRemoved = true;  
if (mAdded) {  
dispatchDetachedFromWindow();  
}  
  
if (mAdded && !mFirst) {  
destroyHardwareRenderer();  
  
if (mView != null) {  
int viewVisibility = mView.getVisibility();  
boolean viewVisibilityChanged = mViewVisibility != viewVisibility;  
if (mWindowAttributesChanged || viewVisibilityChanged) {  
// If layout params have been changed, first give them  
// to the window manager to make sure it has the correct  
// animation info.  
try {  
if ((relayoutWindow(mWindowAttributes, viewVisibility, false)  
& WindowManagerGlobal.RELAYOUT_RES_FIRST_TIME) != 0) {  
mWindowSession.finishDrawing(mWindow);  
}  
} catch (RemoteException e) {  
}  
}  
  
mSurface.release();  
}  
}  
  
mAdded = false;  
}  
WindowManagerGlobal.getInstance().doRemoveView(this);  
}  
  
void dispatchDetachedFromWindow() {  
if (mView != null && mView.mAttachInfo != null) {  
mAttachInfo.mTreeObserver.dispatchOnWindowAttachedChange(false);  
mView.dispatchDetachedFromWindow();  
}  
  
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 {  
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();  
}  
  
void unscheduleTraversals() {  
if (mTraversalScheduled) {  
mTraversalScheduled = false;  
mHandler.getLooper().getQueue().removeSyncBarrier(mTraversalBarrier);  
mChoreographer.removeCallbacks(  
Choreographer.CALLBACK_TRAVERSAL, mTraversalRunnable, null);  
}  
}  
  1. Session對象也是一個服務(wù)端的樁對象蟀给,用來為客戶端提供交互接口(IWindowSession),包括窗口的創(chuàng)建阳堕、銷毀跋理、布局等接口。每個與窗口管理服務(wù)交互的進程通常都需要打開一個Session對象來實現(xiàn)交互嘱丢,用來保證一個Session會話期間窗口狀態(tài)的一致薪介。Session對象在一個進程新建第一個視圖時使用窗口管理服務(wù)的的openSession接口函數(shù)創(chuàng)建,第一個視圖新建期間也創(chuàng)建一個SurfaceSession對象用來實現(xiàn)視圖的繪制操作越驻。SurfaceSession對象用來與SurfaceFliger服務(wù)建立連接汁政,實現(xiàn)視圖及包含的子視圖在顯示硬件上的實際輸出工作。
  2. WindowManagerService服務(wù)是一個系統(tǒng)服務(wù)類缀旁,是整個窗口管理機制實現(xiàn)的核心记劈。

3.Window的創(chuàng)建

View是Android中的視圖的呈現(xiàn)方式,但是View不能單獨存在并巍,必須依賴于Window這個抽象的概念上目木,因此有視圖的地方就有Window。

3.1應(yīng)用Window-Activity的創(chuàng)建

1)ActivityThread的performLaunchActivity

private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {  
 // System.out.println("##### [" + System.currentTimeMillis() + "] ActivityThread.performLaunchActivity(" + r + ")");  
  
 ActivityInfo aInfo = r.activityInfo;  
 if (r.packageInfo == null) {  
 r.packageInfo = getPackageInfo(aInfo.applicationInfo, r.compatInfo,  
 Context.CONTEXT_INCLUDE_CODE);  
 }  
  
 ComponentName component = r.intent.getComponent();  
 if (component == null) {  
 component = r.intent.resolveActivity(  
 mInitialApplication.getPackageManager());  
 r.intent.setComponent(component);  
 }  
  
 if (r.activityInfo.targetActivity != null) {  
 component = new ComponentName(r.activityInfo.packageName,  
 r.activityInfo.targetActivity);  
 }  
  
 Activity activity = null;  
 try {  
 java.lang.ClassLoader cl = r.packageInfo.getClassLoader();  
 activity = mInstrumentation.newActivity(  
 cl, component.getClassName(), r.intent);  
 StrictMode.incrementExpectedActivityCount(activity.getClass());  
 r.intent.setExtrasClassLoader(cl);  
 r.intent.prepareToEnterProcess();  
 if (r.state != null) {  
 r.state.setClassLoader(cl);  
 }  
 } catch (Exception e) {  
 if (!mInstrumentation.onException(activity, e)) {  
 throw new RuntimeException(  
 "Unable to instantiate activity " + component  
 + ": " + e.toString(), e);  
 }  
 }  
  
 try {  
 Application app = r.packageInfo.makeApplication(false, mInstrumentation);  
  
 if (localLOGV) Slog.v(TAG, "Performing launch of " + r);  
 if (localLOGV) Slog.v(  
 TAG, r + ": app=" + app  
 + ", appName=" + app.getPackageName()  
 + ", pkg=" + r.packageInfo.getPackageName()  
 + ", comp=" + r.intent.getComponent().toShortString()  
 + ", dir=" + r.packageInfo.getAppDir());  
  
 if (activity != null) {  
 Context appContext = createBaseContextForActivity(r, activity);  
 CharSequence title = r.activityInfo.loadLabel(appContext.getPackageManager());  
 Configuration config = new Configuration(mCompatConfiguration);  
 if (DEBUG_CONFIGURATION) Slog.v(TAG, "Launching activity "  
 + r.activityInfo.name + " with config " + config);  
 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);  
  
 if (customIntent != null) {  
 activity.mIntent = customIntent;  
 }  
 r.lastNonConfigurationInstances = null;  
 activity.mStartedActivity = false;  
 int theme = r.activityInfo.getThemeResource();  
 if (theme != 0) {  
 activity.setTheme(theme);  
 }  
  
 activity.mCalled = false;  
 if (r.isPersistable()) {  
 mInstrumentation.callActivityOnCreate(activity, r.state, r.persistentState);  
 } else {  
 mInstrumentation.callActivityOnCreate(activity, r.state);  
 }  
 if (!activity.mCalled) {  
 throw new SuperNotCalledException(  
 "Activity " + r.intent.getComponent().toShortString() +  
 " did not call through to super.onCreate()");  
 }  
 r.activity = activity;  
 r.stopped = true;  
 if (!r.activity.mFinished) {  
 activity.performStart();  
 r.stopped = false;  
 }  
 if (!r.activity.mFinished) {  
 if (r.isPersistable()) {  
 if (r.state != null || r.persistentState != null) {  
 mInstrumentation.callActivityOnRestoreInstanceState(activity, r.state,  
 r.persistentState);  
 }  
 } else if (r.state != null) {  
 mInstrumentation.callActivityOnRestoreInstanceState(activity, r.state);  
 }  
 }  
 if (!r.activity.mFinished) {  
 activity.mCalled = false;  
 if (r.isPersistable()) {  
 mInstrumentation.callActivityOnPostCreate(activity, r.state,  
 r.persistentState);  
 } else {  
 mInstrumentation.callActivityOnPostCreate(activity, r.state);  
 }  
 if (!activity.mCalled) {  
 throw new SuperNotCalledException(  
 "Activity " + r.intent.getComponent().toShortString() +  
 " did not call through to super.onPostCreate()");  
 }  
 }  
 }  
 r.paused = true;  
  
 mActivities.put(r.token, r);  
  
 } catch (SuperNotCalledException e) {  
 throw e;  
  
 } catch (Exception e) {  
 if (!mInstrumentation.onException(activity, e)) {  
 throw new RuntimeException(  
 "Unable to start activity " + component  
 + ": " + e.toString(), e);  
 }  
 }  
  
 return activity;  
 }  

2) Activity的attach

final void attach(Context context, ActivityThread aThread,  
 Instrumentation instr, IBinder token, int ident,  
 Application application, Intent intent, ActivityInfo info,  
 CharSequence title, Activity parent, String id,  
 NonConfigurationInstances lastNonConfigurationInstances,  
 Configuration config, String referrer, IVoiceInteractor voiceInteractor) {  
 attachBaseContext(context);  
  
 mFragments.attachHost(null /*parent*/);  
  
 mWindow = new PhoneWindow(this);  
 mWindow.setCallback(this);  
 mWindow.setOnWindowDismissedCallback(this);  
 mWindow.getLayoutInflater().setPrivateFactory(this);  
 if (info.softInputMode != WindowManager.LayoutParams.SOFT_INPUT_STATE_UNSPECIFIED) {  
 mWindow.setSoftInputMode(info.softInputMode);  
 }  
 if (info.uiOptions != 0) {  
 mWindow.setUiOptions(info.uiOptions);  
 }  
 mUiThread = Thread.currentThread();  
  
 mMainThread = aThread;  
 mInstrumentation = instr;  
 mToken = token;  
 mIdent = ident;  
 mApplication = application;  
 mIntent = intent;  
 mReferrer = referrer;  
 mComponent = intent.getComponent();  
 mActivityInfo = info;  
 mTitle = title;  
 mParent = parent;  
 mEmbeddedID = id;  
 mLastNonConfigurationInstances = lastNonConfigurationInstances;  
 if (voiceInteractor != null) {  
 if (lastNonConfigurationInstances != null) {  
 mVoiceInteractor = lastNonConfigurationInstances.voiceInteractor;  
 } else {  
 mVoiceInteractor = new VoiceInteractor(voiceInteractor, this, this,  
 Looper.myLooper());  
 }  
 }  
  
 mWindow.setWindowManager(  
 (WindowManager)context.getSystemService(Context.WINDOW_SERVICE),  
 mToken, mComponent.flattenToString(),  
 (info.flags & ActivityInfo.FLAG_HARDWARE_ACCELERATED) != 0);  
 if (mParent != null) {  
 mWindow.setContainer(mParent.getWindow());  
 }  
 mWindowManager = mWindow.getWindowManager();  
 mCurrentConfig = config;  
 }  

3) Window創(chuàng)建完成后懊渡,通過setContentView將視圖附加在Window上

public void setContentView(@LayoutRes int layoutResID) {  
 getWindow().setContentView(layoutResID);  
 initWindowDecorActionBar();  
 }  

4) 雖然在attach方法中Window就已經(jīng)被創(chuàng)建刽射,但這個時候還未被Windowmanager識別。在ActivityThread的handleResumeActvity中剃执,調(diào)用了Activity的performResume方法誓禁,接著調(diào)用Activity的makeVisible方法。此時肾档,DecorView才真正的被添加和顯示摹恰。

final void handleResumeActivity(IBinder token,  
 boolean clearHide, boolean isForward, boolean reallyResume) {  
 // If we are getting ready to gc after going to the background, well  
 // we are back active so skip it.  
 unscheduleGcIdler();  
 mSomeActivitiesChanged = true;  
  
 // TODO Push resumeArgs into the activity for consideration  
 ActivityClientRecord r = performResumeActivity(token, clearHide);  
  
 if (r != null) {  
 final Activity a = r.activity;  
  
 if (localLOGV) Slog.v(  
 TAG, "Resume " + r + " started activity: " +  
 a.mStartedActivity + ", hideForNow: " + r.hideForNow  
 + ", finished: " + a.mFinished);  
  
 final int forwardBit = isForward ?  
 WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION : 0;  
  
 // If the window hasn't yet been added to the window manager,  
 // and this guy didn't finish itself or start another activity,  
 // then go ahead and add the window.  
 boolean willBeVisible = !a.mStartedActivity;  
 if (!willBeVisible) {  
 try {  
 willBeVisible = ActivityManagerNative.getDefault().willActivityBeVisible(  
 a.getActivityToken());  
 } catch (RemoteException e) {  
 }  
 }  
 if (r.window == null && !a.mFinished && willBeVisible) {  
 r.window = r.activity.getWindow();  
 View decor = r.window.getDecorView();  
 decor.setVisibility(View.INVISIBLE);  
 ViewManager wm = a.getWindowManager();  
 WindowManager.LayoutParams l = r.window.getAttributes();  
 a.mDecor = decor;  
 l.type = WindowManager.LayoutParams.TYPE_BASE_APPLICATION;  
 l.softInputMode |= forwardBit;  
 if (a.mVisibleFromClient) {  
 a.mWindowAdded = true;  
 wm.addView(decor, l);  
 }  
  
 // If the window has already been added, but during resume  
 // we started another activity, then don't yet make the  
 // window visible.  
 } else if (!willBeVisible) {  
 if (localLOGV) Slog.v(  
 TAG, "Launch " + r + " mStartedActivity set");  
 r.hideForNow = true;  
 }  
  
 // Get rid of anything left hanging around.  
 cleanUpPendingRemoveWindows(r);  
  
 // The window is now visible if it has been added, we are not  
 // simply finishing, and we are not starting another activity.  
 if (!r.activity.mFinished && willBeVisible  
 && r.activity.mDecor != null && !r.hideForNow) {  
 if (r.newConfig != null) {  
 r.tmpConfig.setTo(r.newConfig);  
 if (r.overrideConfig != null) {  
 r.tmpConfig.updateFrom(r.overrideConfig);  
 }  
 if (DEBUG_CONFIGURATION) Slog.v(TAG, "Resuming activity "  
 + r.activityInfo.name + " with newConfig " + r.tmpConfig);  
 performConfigurationChanged(r.activity, r.tmpConfig);  
 freeTextLayoutCachesIfNeeded(r.activity.mCurrentConfig.diff(r.tmpConfig));  
 r.newConfig = null;  
 }  
 if (localLOGV) Slog.v(TAG, "Resuming " + r + " with isForward="  
 + isForward);  
 WindowManager.LayoutParams l = r.window.getAttributes();  
 if ((l.softInputMode  
 & WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION)  
 != forwardBit) {  
 l.softInputMode = (l.softInputMode  
 & (~WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION))  
 | forwardBit;  
 if (r.activity.mVisibleFromClient) {  
 ViewManager wm = a.getWindowManager();  
 View decor = r.window.getDecorView();  
 wm.updateViewLayout(decor, l);  
 }  
 }  
 r.activity.mVisibleFromServer = true;  
 mNumVisibleActivities++;  
 if (r.activity.mVisibleFromClient) {  
 r.activity.makeVisible();  
 }  
 }  
  
 if (!r.onlyLocalRequest) {  
 r.nextIdle = mNewActivities;  
 mNewActivities = r;  
 if (localLOGV) Slog.v(  
 TAG, "Scheduling idle handler for " + r);  
 Looper.myQueue().addIdleHandler(new Idler());  
 }  
 r.onlyLocalRequest = false;  
  
 // Tell the activity manager we have resumed.  
 if (reallyResume) {  
 try {  
 ActivityManagerNative.getDefault().activityResumed(token);  
 } catch (RemoteException ex) {  
 }  
 }  
  
 } else {  
 // If an exception was thrown when trying to resume, then  
 // just end this activity.  
 try {  
 ActivityManagerNative.getDefault()  
 .finishActivity(token, Activity.RESULT_CANCELED, null, false);  
 } catch (RemoteException ex) {  
 }  
 }  
 }  
  
 void makeVisible() {  
 if (!mWindowAdded) {  
 ViewManager wm = getWindowManager();  
 wm.addView(mDecor, getWindow().getAttributes());  
 mWindowAdded = true;  
 }  
 mDecor.setVisibility(View.VISIBLE);  
 }  

3.2 子Window-Dialog的創(chuàng)建

1)初始化

Dialog(@NonNull Context context, @StyleRes int themeResId, boolean createContextThemeWrapper) {  
  if (createContextThemeWrapper) {  
  if (themeResId == 0) {  
  final TypedValue outValue = new TypedValue();  
  context.getTheme().resolveAttribute(R.attr.dialogTheme, outValue, true);  
  themeResId = outValue.resourceId;  
  }  
  mContext = new ContextThemeWrapper(context, themeResId);  
  } else {  
  mContext = context;  
  }  
  
  mWindowManager = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);  
  
  final Window w = new PhoneWindow(mContext);  
  mWindow = w;  
  w.setCallback(this);  
  w.setOnWindowDismissedCallback(this);  
  w.setWindowManager(mWindowManager, null, null);  
  w.setGravity(Gravity.CENTER);  
  
  mListenersHandler = new ListenersHandler(this);  
  }  

2)設(shè)置View

/** 
 * Set the screen content to an explicit view. This view is placed 
 * directly into the screen's view hierarchy. It can itself be a complex 
 * view hierarchy. 
 * 
 * @param view The desired content to display. 
 */  
 public void setContentView(View view) {  
 mWindow.setContentView(view);  
 }  

3)顯示

/** 
  * Start the dialog and display it on screen. The window is placed in the 
  * application layer and opaque. Note that you should not override this 
  * method to do initialization when the dialog is shown, instead implement 
  * that in {@link #onStart}. 
  */  
  public void show() {  
  if (mShowing) {  
  if (mDecor != null) {  
  if (mWindow.hasFeature(Window.FEATURE_ACTION_BAR)) {  
  mWindow.invalidatePanelMenu(Window.FEATURE_ACTION_BAR);  
  }  
  mDecor.setVisibility(View.VISIBLE);  
  }  
  return;  
  }  
  
  mCanceled = false;  
  
  if (!mCreated) {  
  dispatchOnCreate(null);  
  }  
  
  onStart();  
  mDecor = mWindow.getDecorView();  
  
  if (mActionBar == null && mWindow.hasFeature(Window.FEATURE_ACTION_BAR)) {  
  final ApplicationInfo info = mContext.getApplicationInfo();  
  mWindow.setDefaultIcon(info.icon);  
  mWindow.setDefaultLogo(info.logo);  
  mActionBar = new WindowDecorActionBar(this);  
  }  
  
  WindowManager.LayoutParams l = mWindow.getAttributes();  
  if ((l.softInputMode  
  & WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION) == 0) {  
  WindowManager.LayoutParams nl = new WindowManager.LayoutParams();  
  nl.copyFrom(l);  
  nl.softInputMode |=  
  WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION;  
  l = nl;  
  }  
  
  try {  
  mWindowManager.addView(mDecor, l);  
  mShowing = true;  
  
  sendShowMessage();  
  } finally {  
  }  
  }  

4)取消

void dismissDialog() {  
  if (mDecor == null || !mShowing) {  
  return;  
  }  
  
  if (mWindow.isDestroyed()) {  
  Log.e(TAG, "Tried to dismissDialog() but the Dialog's window was already destroyed!");  
  return;  
  }  
  
  try {  
  mWindowManager.removeViewImmediate(mDecor);  
  } finally {  
  if (mActionMode != null) {  
  mActionMode.finish();  
  }  
  mDecor = null;  
  mWindow.closeAllPanels();  
  onStop();  
  mShowing = false;  
  
  sendDismissMessage();  
  }  
  }  

3.3 系統(tǒng)Window-Toast的創(chuàng)建

Toast屬于系統(tǒng)Window辫继,內(nèi)部的視圖有2種指定方式,一種是系統(tǒng)默認樣式俗慈,另外一種是通過setView方法來指定一個自定義的View姑宽。由于Toast具有定時取消的功能,所以系統(tǒng)采用了Handler闺阱。Toast的顯示及隱藏都是通過NotificationmanagerService進行控制

/** 
 * Show the view for the specified duration. 
 */  
 public void show() {  
 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 {  
 service.enqueueToast(pkg, tn, mDuration);  
 } catch (RemoteException e) {  
 // Empty  
 }  
 }  
  
 /** 
 * Close the view if it's showing, or don't show it if it isn't showing yet. 
 * You do not normally have to call this. Normally view will disappear on its own 
 * after the appropriate duration. 
 */  
 public void cancel() {  
 mTN.hide();  
  
 try {  
 getService().cancelToast(mContext.getPackageName(), mTN);  
 } catch (RemoteException e) {  
 // Empty  
 }  
 }  

主要在TN中進行Window操作

private static class TN extends ITransientNotification.Stub {  
 final Runnable mShow = new Runnable() {  
 @Override  
 public void run() {  
 handleShow();  
 }  
 };  
  
 final Runnable mHide = new Runnable() {  
 @Override  
 public void run() {  
 handleHide();  
 // Don't do this in handleHide() because it is also invoked by handleShow()  
 mNextView = null;  
 }  
 };  
  
 private final WindowManager.LayoutParams mParams = new WindowManager.LayoutParams();  
 final Handler mHandler = new Handler();  
  
 int mGravity;  
 int mX, mY;  
 float mHorizontalMargin;  
 float mVerticalMargin;  
  
  
 View mView;  
 View mNextView;  
  
 WindowManager mWM;  
  
 TN() {  
 // XXX This should be changed to use a Dialog, with a Theme.Toast  
 // defined that sets up the layout params appropriately.  
 final WindowManager.LayoutParams params = mParams;  
 params.height = WindowManager.LayoutParams.WRAP_CONTENT;  
 params.width = WindowManager.LayoutParams.WRAP_CONTENT;  
 params.format = PixelFormat.TRANSLUCENT;  
 params.windowAnimations = com.android.internal.R.style.Animation_Toast;  
 params.type = WindowManager.LayoutParams.TYPE_TOAST;  
 params.setTitle("Toast");  
 params.flags = WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON  
 | WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE  
 | WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE;  
 }  
  
 /** 
 * schedule handleShow into the right thread 
 */  
 @Override  
 public void show() {  
 if (localLOGV) Log.v(TAG, "SHOW: " + this);  
 mHandler.post(mShow);  
 }  
  
 /** 
 * schedule handleHide into the right thread 
 */  
 @Override  
 public void hide() {  
 if (localLOGV) Log.v(TAG, "HIDE: " + this);  
 mHandler.post(mHide);  
 }  
  
 public void handleShow() {  
 if (localLOGV) Log.v(TAG, "HANDLE SHOW: " + this + " mView=" + mView  
 + " mNextView=" + mNextView);  
 if (mView != mNextView) {  
 // remove the old view if necessary  
 handleHide();  
 mView = mNextView;  
 Context context = mView.getContext().getApplicationContext();  
 String packageName = mView.getContext().getOpPackageName();  
 if (context == null) {  
 context = mView.getContext();  
 }  
 mWM = (WindowManager)context.getSystemService(Context.WINDOW_SERVICE);  
 // We can resolve the Gravity here by using the Locale for getting  
 // the layout direction  
 final Configuration config = mView.getContext().getResources().getConfiguration();  
 final int gravity = Gravity.getAbsoluteGravity(mGravity, config.getLayoutDirection());  
 mParams.gravity = gravity;  
 if ((gravity & Gravity.HORIZONTAL_GRAVITY_MASK) == Gravity.FILL_HORIZONTAL) {  
 mParams.horizontalWeight = 1.0f;  
 }  
 if ((gravity & Gravity.VERTICAL_GRAVITY_MASK) == Gravity.FILL_VERTICAL) {  
 mParams.verticalWeight = 1.0f;  
 }  
 mParams.x = mX;  
 mParams.y = mY;  
 mParams.verticalMargin = mVerticalMargin;  
 mParams.horizontalMargin = mHorizontalMargin;  
 mParams.packageName = packageName;  
 if (mView.getParent() != null) {  
 if (localLOGV) Log.v(TAG, "REMOVE! " + mView + " in " + this);  
 mWM.removeView(mView);  
 }  
 if (localLOGV) Log.v(TAG, "ADD! " + mView + " in " + this);  
 mWM.addView(mView, mParams);  
 trySendAccessibilityEvent();  
 }  
 }  
  
 private void trySendAccessibilityEvent() {  
 AccessibilityManager accessibilityManager =  
 AccessibilityManager.getInstance(mView.getContext());  
 if (!accessibilityManager.isEnabled()) {  
 return;  
 }  
 // treat toasts as notifications since they are used to  
 // announce a transient piece of information to the user  
 AccessibilityEvent event = AccessibilityEvent.obtain(  
 AccessibilityEvent.TYPE_NOTIFICATION_STATE_CHANGED);  
 event.setClassName(getClass().getName());  
 event.setPackageName(mView.getContext().getPackageName());  
 mView.dispatchPopulateAccessibilityEvent(event);  
 accessibilityManager.sendAccessibilityEvent(event);  
 }  
  
 public void handleHide() {  
 if (localLOGV) Log.v(TAG, "HANDLE HIDE: " + this + " mView=" + mView);  
 if (mView != null) {  
 // note: checking parent() just to make sure the view has  
 // been added... i have seen cases where we get here when  
 // the view isn't yet added, so let's try not to crash.  
 if (mView.getParent() != null) {  
 if (localLOGV) Log.v(TAG, "REMOVE! " + mView + " in " + this);  
 mWM.removeView(mView);  
 }  
  
 mView = null;  
 }  
 }  
 }  

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