安卓计时器

创建子线程并创建Message对象，用sendMessage方法向主线程发送消息

Boolean isWork=true;
 new Thread(new Runnable() {
                    @Override
                    public void run() {
                        try {
                            for (int i = 0; i <= 1000; i++) {
                                if (isWork) {
                                    //间隔一秒
                                    Thread.sleep(1000);
                                    Message msg = new Message();
                                    msg.what = i;
                                    handler.sendMessage(msg);
                                }
                            }

                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                    }
                }).start();

主线程接受消息

final Handler handler=new Handler(){
            @Override
            public void handleMessage(@NonNull Message msg) {
                tv_jishiqi.setText("耗时"+msg.what+"秒");
            }
        };

停止的时候将isWork=false即可