ViewRootImple里的 WindowSeesion是WindowManagerService的proxy， 通过这个句柄来调用WMS的功能
而W是 wms用来控制app window的句柄， 比如dispatch各种事件，focus，move，resize等， 都是由wms控制w来完成android 按键触屏分发大致的流程：· WMS所在的SystemServer进程接收到按键事件。· WMS找到UI位于屏幕顶端的进程所对应的IWindow对象，这是一个Bp端对象。· 调用这个IWindow对象的dispatchKey。IWindow对象的Bn端位于ViewRoot中，ViewRoot再根据内部View的位置信息找到真正处理这个事件的View，最后调用dispatchKey函数完成按键的处理。 activity resume时：ViewRootImpl:
setView()->:(1)mView = view; //decorView(2)requestLayout();(3)mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes, //mWindow 即W， 把W句柄给wms getHostVisibility(), mDisplay.getDisplayId(), mAttachInfo.mContentInsets, mInputChannel);
requestLayout()->scheduleTraversals()->TraversalRunnable::doTraversal()->performTraversals():
(1)relayoutResult = relayoutWindow(params, viewVisibility, insetsPending);int relayoutResult = mWindowSession.relayout( mWindow, mSeq, params, (int) (mView.getMeasuredWidth() * appScale + 0.5f), (int) (mView.getMeasuredHeight() * appScale + 0.5f), viewVisibility, insetsPending ? WindowManagerGlobal.RELAYOUT_INSETS_PENDING : 0, mWinFrame, mPendingOverscanInsets, mPendingContentInsets, mPendingVisibleInsets, mPendingConfiguration, mSurface);|Binder|WindowManagerService:relayoutWindow()->: ... //在wms进程中创建surface并且拷贝到app进程中去 //createSurfaceLocked() --JNI--> nativeCreate, nativeSetXXX 等在c++层实现 -> SurfaceComposerClient::createSurface ①SurfaceControl surfaceControl = winAnimator.createSurfaceLocked(); -> new SurfaceControl() --JNI--> nativeCreate() -> SurfaceComposerClient::createSurface -> ②if (surfaceControl != null) { outSurface.copyFrom(surfaceControl); //把surface对象从wms进程拷贝到app进程， java层的surface对象都只是对native对象的封装，包含一个native surface的指针 if (SHOW_TRANSACTIONS) Slog.i(TAG, " OUT SURFACE " + outSurface + ": copied"); } else { // For some reason there isn't a surface. Clear the // caller's object so they see the same state. outSurface.release(); } ...(2)performMeasure()->mView.measure(childWidthMeasureSpec, childHeightMeasureSpec); //测量长宽(3)performLayout()->host.layout(0, 0, host.getMeasuredWidth(), host.getMeasuredHeight()); //确定位置(4)performDraw()->draw(fullRedrawNeeded) //画图①Surface surface = mSurface;...②drawSoftware(surface, attachInfo, yoff, scalingRequired, dirty)) canvas = mSurface.lockCanvas(dirty); ... mView.draw(canvas); ... surface.unlockCanvasAndPost(canvas);