public class mainActivity extends Activity {
    Button button;
    Button button2;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        button = (Button) findViewById(R.id.btn1);
        button2 = (Button) findViewById(R.id.btn2);
        button.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                timer = new Timer();
                timer.schedule(task, 1000, 1000);
            }
        });
        button2.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                这里该怎么写让他完全停止 再次点击开始的时候不报错


            }
        });
    }

    Timer timer;
    TimerTask task = new TimerTask() {
        @Override
        public void run() {
            System.out.println("a");
        }
    };
}