Android 用户进程绘制过程

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1、Android用户进程绘制过程下面我们来看下这个函数，它先调用了Surface的lockCanvas获取一个Canvas，然后再调用surface.unlockCanvasAndPost来表示绘制结束。[cpp]viewplaincopy在CODE上查看代码片派生到我的代码片privatebooleandrawSoftware(Surfacesurface,AttachInfoattachInfo,intxoff,intyoff,booleanscalingRequired,Rectdirty){//Drawwithsoftwarerenderer.fi

2、nalCanvascanvas;try{finalintleft=dirty.left;finalinttop=dirty.top;finalintright=dirty.right;finalintbottom=dirty.bottom;canvas=mSurface.lockCanvas(dirty);//获取一个Canvas......finally{try{surface.unlockCanvasAndPost(canvas);//绘制结束}catch(IllegalArgumentExceptione){Log.e(TAG,"Couldnotu

3、nlocksurface",e);mLayoutRequested=true;//askwmforanewsurfacenexttime.//noinspectionReturnInsideFinallyBlockreturnfalse;}if(LOCAL_LOGV){Log.v(TAG,"Surface"+surface+"unlockCanvasAndPost");}}returntrue;}一、应用进程申请buffer我们先来看Surface的lockCanvas函数，其调用了native函数nativeLockCanvas[cpp]viewpla

4、incopy在CODE上查看代码片派生到我的代码片publicCanvaslockCanvas(RectinOutDirty)throwsSurface.OutOfResourcesException,IllegalArgumentException{synchronized(mLock){checkNotReleasedLocked();if(mLockedObject!=0){//Ideally,nativeLockCanvas()wouldthrowinthissituationandpreventthe//double-lock,butthatw

5、on'thappenifmNativeObjectwasupdated.Wecan't//abandontheoldmLockedObjectbecauseitmightstillbeinuse,soinstead//wejustrefusetore-locktheSurface.thrownewIllegalArgumentException("Surfacewasalreadylocked");}mLockedObject=nativeLockCanvas(mNativeObject,mCanvas,inOutDirty);returnmCanvas

6、;}}这个函数在android_view_Surface.cpp中，这个函数内容很多，我们先调用了Surface的lock函数来申请buffer，然后新建了一个SkBitmap，设置了内存地址，并且把这个bitmap放入了Canvas中。[cpp]viewplaincopy在CODE上查看代码片派生到我的代码片staticjlongnativeLockCanvas(JNIEnv*env,jclassclazz,jlongnativeObject,jobjectcanvasObj,jobjectdirtyRectObj){spsurfac

7、e(reinterpret_cast(nativeObject));if(!isSurfaceValid(surface)){doThrowIAE(env);return0;}RectdirtyRect;Rect*dirtyRectPtr=NULL;if(dirtyRectObj){dirtyRect.left=env->GetIntField(dirtyRectObj,gRectClassInfo.left);dirtyRect.top=env->GetIntField(dirtyRectObj,gRectClassInfo.top

8、);dirtyRect.right=env->GetIntField(dirty