Android里子线程真的不能刷新UI吗？

如果你在网上搜索CalledFromWrongThreadException：Only the original thread that created a view hierarchy can touch its views. 那么你肯定能看到很多文章说Android里子线程不能刷新UI。这句话不能说错，只是有些不太严谨。其实线程能否刷新UI的关键在于ViewRoot是否属于该线程。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：

com.david.test.helloworld.MainActivity$TestThread2.run -> android.widget.TextView.setText -> android.widget.TextView.checkForRelayout -> android.view.View.invalidate -> android.view.ViewGroup.invalidateChild -> android.view.ViewRoot.invalidateChildInParent -> android.view.ViewRoot.invalidateChild -> android.view.ViewRoot.checkThread