SurfaceView

Surface

Surface继承于Parcelable，内部拥有一系列native方法和一个canvas

private final Canvas mCanvas = new CompatibleCanvas();
private Matrix mCompatibleMatrix

CompatibleCanvas是Surface的内部类，主要包装了Canvas的Matrix方法
SurfaceView继承自View，说明其本质还是个View

SurfaceView

public class SurfaceView extends View {}

在SurfaceView内部有两个Surface

final Surface mSurface = new Surface();
final Surface mNewSurface = new Surface();

还包含Window的相关对象

IWindowSession mSession;
MyWindow mWindow;

IWindowSession是一个aidl文件，是app上层连接底层WindowServiceManager的桥梁
MyWindow是SurfaceView的内部类，继承自BaseIWindow,BaseIWindow又继承自IWindow.Stub

private static class MyWindow extends BaseIWindow{}
public class BaseIWindow extends IWindow.Stub{}

在SurfaceView的onAttachtoWindow中，向父view申请为自己扣个洞

mParent.requestTransparentRegion(this)

在视图发生变化比如可见性发生变化的时候，会调用

updateWindow(false, false);

在updateWindow内部，首先初始化window

mWindow = new MyWindow(this);
mSession.addToDisplayWithoutInputChannel(mWindow, mWindow.mSeq, mLayout,mVisible ? VISIBLE : GONE, display.getDisplayId(), mContentInsets,mStableInsets);

之后申请surface

relayoutResult = mSession.relayout(
                        mWindow, mWindow.mSeq, mLayout, mWidth, mHeight,
                        visible ? VISIBLE : GONE,
                        WindowManagerGlobal.RELAYOUT_DEFER_SURFACE_DESTROY,                           		
                        mWinFrame, mOverscanInsets, mContentInsets,
                        mVisibleInsets, mStableInsets, mConfiguration, mNewSurface);

之后调用SurfaceCallBack销毁当前的Surface

callbacks = getSurfaceCallbacks();
for (SurfaceHolder.Callback c : callbacks) {
	c.surfaceDestroyed(mSurfaceHolder);
}

把新申请的Surface替换为当前的Surface

mSurface.transferFrom(mNewSurface);

最后调用callback的另外两个方法

for (SurfaceHolder.Callback c : callbacks) {
	c.surfaceCreated(mSurfaceHolder);
}

for (SurfaceHolder.Callback c : callbacks) {
	c.surfaceChanged(mSurfaceHolder, mFormat, myWidth, myHeight);
}

其他的View都是利用在activityAttch时生成的PhoneWindow管理Surface，只能在主线程操作，SurfaceView拥有独立的Surface,独立于PhoneWindow,因此不受主线程限制，可以在子线程刷新，同时由于不在View树里面，所以无法进行缩放，旋转等动画