java - 应使用 PowerManager 唤醒设备多长时间以确保显示使用 BroadcastReceiver 创建的 Activity ？

Question

我有我的 AlarmManager，它会在任何时间后连接到我的 BroadcastReceiver。因此，设备当然可以处于 IDLE( sleep )模式，包括密码锁定。我想知道使用 PowerManager 是否是好的做法和必要的，因为 https://developer.android.com/training/scheduling/wakelock.html#java说

"Creating and holding wake locks can have a dramatic impact on the host device's battery life. Thus you should use wake locks only when strictly necessary and hold them for as short a time as possible. For example, you should never need to use a wake lock in an activity. As described above, if you want to keep the screen on in your activity, use FLAG_KEEP_SCREEN_ON."

为了更好地理解:最后它应该是默认 Android 闹钟的副本。

list :

    <receiver android:name=".AlarmReceiver">
        <intent-filter>
            <category
            android:name="android.intent.category.DEFAULT" />
        </intent-filter>
    </receiver>

    <activity android:name=".RingtoneAlarm">
    </activity>

广播接收者:

public class AlarmReceiver extends BroadcastReceiver {
@Override
    public void onReceive(Context context, Intent intent) {
PowerManager powerManager = (PowerManager) context.getSystemService(POWER_SERVICE);
PowerManager.WakeLock wakeLock = powerManager.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK,"MyApp::MyWakelockTag");
wakeLock.acquire(10*60*1000L /*10 minutes*/);

intent.setClassName(context, "com.example.myName.myWork.RingtoneAlarm");
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
context.startActivity(intent);
}
}

按 Intent 打开的 Activity :

public class RingtoneAlarm extends AnyOfMyActivitynamesIGuess{
 @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_ringtonealarm);
 getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON
|WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED
|WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON);
   //(setShowWhenLocked(true);setTurnScreenOn(true); My sidenote: both methods are too new for most required API levels)
   //Remember to implement: PowerManager.WakeLock wakeLock = powerManager.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK,"MyApp::MyWakelockTag"); wakeLock.release();
[...]
}
}

这是我可以让设备在手机处于空闲( sleep )模式并使用密码锁定的准确时间唤醒的唯一方法。如果我将 PowerManager 放入 RingtoneAlarm Activity 中，它不会工作，因为没有创建 Activity，因此 getWindow().addFlags(....); 是没有激活。在没有 PowerManager 的情况下，我无法找到使它工作的方法(如前所述:文档说这不是好的做法)。更重要的是，感觉 PowerManager 只是一种解决方法，因为我只在 BroadcastReceiver 和创建 RingtoneAlarm Activity 之间的那段时间需要它，并且它可能在未来被弃用像 FLAG_TURN_SCREEN_ON。

那么wakeLock.acquire(X)中应该是多少秒；在 BroadcastReceiver 中？ 3 秒太短而且不起作用，10 分钟可能有点矫枉过正......或者没有 PowerManager 有更好的解决方案吗？

Answer 1

根据 Restrictions to background activity starts documentation ，在 Android Q (API 29) 和更高版本的设备上运行时，根本不允许从后台启动 Activity 。

如 that documentation 中所述:

In nearly all cases, apps that are in the background should create notifications to provide information to the user instead of directly starting an activity.

In specific cases, your app might need to get the user's attention urgently, such as an ongoing alarm or incoming call. You might have previously configured your app to launch a background activity for this purpose.

自 API 11 以来，当 setFullScreenIntent添加了 API(在 NotificationCompat 中也可用)。这允许您向通知添加一个 Intent，如果设备的屏幕关闭，该 Intent 会自动启动一个 Activity，这是闹钟应用的推荐做法。