android_qidian_app/Hello_GudieActivity.java

package com.example.final_project_app;

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

public class Hello_GudieActivity extends AppCompatActivity {
    public TextView djs;
    private android.os.CountDownTimer countDownTimer;
    private long timeLeftInMillis =6000;
    private boolean CountDownTimer;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_hello_gudie);
        djs = findViewById(R.id.djs);
        //启动倒计时
        startCountdown();
    }
    private void startCountdown() {
        countDownTimer =new CountDownTimer(timeLeftInMillis,1000) {
            @Override
            public void onTick(long millisUntilFinished) {
                timeLeftInMillis = millisUntilFinished;
                int secondsRemaining = (int) (millisUntilFinished / 1000);
                djs.setText(secondsRemaining +" s");
            }

            @Override
            public void onFinish() {
                //跳转界面
                startActivity(new Intent(Hello_GudieActivity.this,login.class));
                // 倒计时结束后跳转到哪个界面
                finish();

            }
        }.start();
    }

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