Handler.post()解决非主线程更新UI

在非主线程中调用了showMessage方法，结果报错：Can't create handler inside thread that has not called Looper.prepare()

private void showMessage(String msg) {        Toast toast = Toast.makeText(getApplicationContext(), msg, Toast.LENGTH_SHORT);        toast.setGravity(Gravity.CENTER, 0, 0);        toast.show();    }

原来Android中非主线程不能更新UI，Handler.post()方法可以解决这个问题：于是将showMessage方法稍作修改就可以了：

private void showMessage(String msg) {    mSg = msg;    mHandler.post(new Runnable() {            @Override            public void run() {              Toast toast = Toast.makeText(getApplicationContext(), mSg, Toast.LENGTH_SHORT);                  toast.setGravity(Gravity.CENTER, 0, 0);                  toast.show();            }        });