让我们一起看看代码吧！

首先，CalledFromWrongThreadException这个异常是有下面的代码抛出的：

void checkThread() {

if (mThread != Thread.currentThread()) {

throw new CalledFromWrongThreadException(

"Only the original thread that created a view hierarchy can touch its views.");

}

}

该段代码出自 framework/base/core/java/android/view/ViewRoot.java

其次，看看RootView的构造函数：

public ViewRoot(Context context) {

super();

if (MEASURE_LATENCY && lt == null) {

lt = new LatencyTimer(100, 1000);

}

// For debug only

//++sInstanceCount;

// Initialize the statics when this class is first instantiated. This is

// done here instead of in the static block because Zygote does not

// allow the spawning of threads.

getWindowSession(context.getMainLooper());

mThread = Thread.currentThread();

mLocation = new WindowLeaked(null);

mLocation.fillInStackTrace();

mWidth = -1;

mHeight = -1;

mDirty = new Rect();

mTempRect = new Rect();

mVisRect = new Rect();

mWinFrame = new Rect();

mWindow = new W(this, context);

mInputMethodCallback = new InputMethodCallback(this);

mViewVisibility = View.GONE;

mTransparentRegion = new Region();

mPreviousTransparentRegion = new Region();

mFirst = true; // true for the first time the view is added

mAdded = false;

mAttachInfo = new View.AttachInfo(sWindowSession, mWindow, this, this);

mViewConfiguration = ViewConfiguration.get(context);

mDensity = context.getResources().getDisplayMetrics().densityDpi;

}

最后，我们看看ViewRoot.checkThread的调用顺序：