1. 使用AlarmManager和BroadcastReceiver实现在固定时间启动指定Activity的方法。 代码示例如下：

在Activity中设置AlarmManager：

//获取定时时间（例如每天早上8点）
Calendar calendar = Calendar.getInstance();
calendar.setTimeInMillis(System.currentTimeMillis());
calendar.set(Calendar.HOUR_OF_DAY, 8);
calendar.set(Calendar.MINUTE, 0);

//创建Intent
Intent intent = new Intent(this, UnlockActivity.class);
PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);

//设置AlarmManager
AlarmManager alarmManager = (AlarmManager) getSystemService(ALARM_SERVICE);
alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(), AlarmManager.INTERVAL_DAY, pendingIntent);

在BroadcastReceiver中打开Activity：

public class UnlockReceiver extends BroadcastReceiver {
   @Override
   public void onReceive(Context context, Intent intent) {
      Intent unlockIntent = new Intent(context, UnlockActivity.class);
      unlockIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
      context.startActivity(unlockIntent);
   }
}

在AndroidManifest.xml中注册BroadcastReceiver和Activity：

2. 使用JobScheduler实现在固定时间启动指定Activity的方法。

代码示例如下：

在Activity中设置JobScheduler：

//获取JobScheduler
JobScheduler jobScheduler = (JobScheduler) getSystemService(JOB_SCHEDULER_SERVICE);

//设置JobInfo
ComponentName componentName = new ComponentName(this, UnlockJobService.class);
JobInfo jobInfo = new JobInfo.Builder(1, componentName)
      .setRequiredNetworkType(JobInfo.NETWORK_TYPE_ANY)
      .setMinimumLatency(0)
      .setOverrideDeadline(1000)
      .setPersisted(true)
      .build();

//执行JobScheduler
jobScheduler.schedule(jobInfo);

在JobService中打开Activity：

public class UnlockJobService extends JobService {
   @Override
   public boolean onStartJob(JobParameters params) {
      Intent unlockIntent = new Intent(this, UnlockActivity.class);
      unlockIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
      startActivity(unlockIntent