倒计时

public class MainActivity extends AppCompatActivity {

    private int time = 3;
    private TextView text_view;
    private ImageView imageView;
    private Handler handler = new Handler (){
        @Override
        public void handleMessage(Message msg) {
            if (msg.what==0){
                if (time>0){
                    time--;
                    text_view.setText (time+"s");
                    handler.sendEmptyMessageDelayed (0,1000);
                }else {
                    Intent intent=new Intent (MainActivity.this,TwoActivity.class);
                    startActivity (intent);
                    finish ();
                }
            }
        }
    };


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate (savedInstanceState);
        setContentView (R.layout.activity_main);
        text_view = findViewById (R.id.tt);
        handler.sendEmptyMessageDelayed (0,1000);
        //使用倒计时

        //这是使用倒计时的代码

    }
}