Android Studio 实现简单倒计时

MainActivity代码：

package com.example.time;

import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.os.CountDownTimer;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    private TextView tvCountdown;
    private CountDownTimer countDownTimer;

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

        tvCountdown = findViewById(R.id.tv_countdown);

        startCountdown();
    }

    private void startCountdown() {
        countDownTimer = new CountDownTimer(60000, 1000) {
            @Override
            public void onTick(long millisUntilFinished) {
                tvCountdown.setText(String.valueOf(millisUntilFinished / 1000));
            }

            @Override
            public void onFinish() {
                tvCountdown.setText("0");
            }
        };
        countDownTimer.start();
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        if (countDownTimer != null) {
            countDownTimer.cancel();
        }
    }
}

activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/tv_countdown"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:textSize="24sp" />

</RelativeLayout>