我如何让天文计时器在Android中作为倒计时器工作？

import android.os.Bundle;
import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.widget.TextView;

import java.util.Timer;
import java.util.TimerTask;

public class CountdownActivity extends AppCompatActivity {
    private TextView countdownTextView;
    private Timer timer;
    private int totalTime = 60; // 倒计时总时间，单位为秒

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_countdown);

        countdownTextView = findViewById(R.id.countdownTextView);

        timer = new Timer();
        timer.scheduleAtFixedRate(new TimerTask() {
            @Override
            public void run() {
                totalTime--;

                // 更新UI
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        countdownTextView.setText(String.valueOf(totalTime));
                    }
                });

                if (totalTime == 0) {
                    // 倒计时结束，执行所需的操作
                    timer.cancel();
                    // TODO: 在这里执行倒计时结束后的操作
                }
            }
        }, 0, 1000); // 每隔1秒执行一次
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        timer.cancel();
    }
}