使用AlarmManager和BroadcastReceiver来定时启动后台操作，并在操作完成后重新设置下一次操作的时间。代码示例：

1.在AndroidManifest.xml文件中添加以下权限和服务声明：

2.创建MyService类来执行后台操作：

public class MyService extends Service {

@Override
public void onCreate() {
    super.onCreate();
    // 初始化后台操作
}

@Override
public int onStartCommand(Intent intent, int flags, int startId) {
    // 执行后台操作
    scheduleNext();
    return START_STICKY;
}

@Override
public void onDestroy() {
    super.onDestroy();
    // 停止后台操作
}

private void scheduleNext() {
    AlarmManager alarmMgr = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
    Intent intent = new Intent(this, MyService.class);
    PendingIntent alarmIntent = PendingIntent.getService(this, 0, intent, 0);
    long triggerAtMillis = System.currentTimeMillis() + 1000 * 60 * 60 * 24; // 下一次操作时间
    alarmMgr.set(AlarmManager.RTC_WAKEUP, triggerAtMillis, alarmIntent);
}

@Nullable
@Override
public IBinder onBind(Intent intent) {
    return null;
}

}

3.创建MyBootReceiver类来在系统开机时启动MyService：

public class MyBootReceiver extends BroadcastReceiver {

@Override
public void onReceive(Context context, Intent intent) {
    Intent serviceIntent = new Intent(context, MyService.class);
    context.startService(serviceIntent);
}

}

4.在Activity中启动MyService：

public class MainActivity extends AppCompatActivity {

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

    Intent serviceIntent = new Intent(this, MyService.class);
    startService(serviceIntent);
}

}