handler.postDelayed 不生效

在项目使用 Handler.postDelayed() 延时执行任务，却发现无效，代码如下：

private Handler mHandler = new Handler();
boolean ret = mHandler.postDelayed(new Runnable() {
                                        @Override
                                        public void run() {
                                            
                                        }
                                    }, delay);
Log.d("Nat", "postDelayed:" + ret);

修改后的代码如下：

private Handler mHandler = new Handler(Looper.getMainLooper());
boolean ret = mHandler.postDelayed(new Runnable() {
                                        @Override
                                        public void run() {
                                            
                                        }
                                    }, delay);
Log.d("Nat", "postDelayed:" + ret);

总结：需要给Handler设置一个主线程的 looper。