runOnUiThread 更新ui

/**
 * Runs the specified action on the UI thread. If the current thread is the UI
 * thread, then the action is executed immediately. If the current thread is
 * not the UI thread, the action is posted to the event queue of the UI thread.
 *
 * @param action the action to run on the UI thread
 */
public final void runOnUiThread(Runnable action) {
    if (Thread.currentThread() != mUiThread) {
        mHandler.post(action);
    } else {
        action.run();
    }
}

在非ui thread中想要更新ui操作，需要使用runOnUiThread来完成。若当前线程是ui thread则立即执行，否则action 会被post到ui thread的event queue中。