使用sharedPreferenceChange中的pendingIntent重新计划不准确的重复警报(Reschedule inexactRepeating alarm with pendingIntent from sharedPreferenceChange)

 我正在开发一个测试应用程序来学习Android，我需要定期启动服务来更新一些数据。 我正在使用带有BroadcastReceiver的AlarmManager来设置警报，并且它使用默认间隔成功更新数据，但我希望将此间隔作为用户定义的值。 
 我目前有以下代码来注册警报： 
 
 在清单中： 
 
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>
<receiver android:name=".BootReceiver">
    <intent-filter>
         <action android:name="android.intent.action.BOOT_COMPLETED"/>
    </intent-filter>
</receiver>
 
 收件人： 
 
public class BootReceiver extends BroadcastReceiver {
    private static final String TAG = BootReceiver.class.getSimpleName();

    @Override
    public void onReceive(Context context, Intent intent) {
        Log.d(TAG,"onReceive method");
        AlarmCreator.setAlarm(context, intent);

    }
}
 
 实际报警： 
 
public static void setAlarm(Context context, Intent intent){
    Log.d(TAG, "Setting alarm");
    // I need the context here
    context.startService(new Intent(context, RefreshService.class));

    SharedPreferences prefs = PreferenceManager
            .getDefaultSharedPreferences(context);
    long interval = Long.parseLong(prefs.getString("interval",
            Long.toString(DEFAULT_INTERVAL)));
    // Here
    PendingIntent operation = PendingIntent.getService(context, -1,
            new Intent(context, RefreshService.class),
            PendingIntent.FLAG_UPDATE_CURRENT);

    // And here
    AlarmManager alarmManager = (AlarmManager) context
            .getSystemService(Context.ALARM_SERVICE);

    if (interval == 0) {
        alarmManager.cancel(operation);
        Log.d(TAG, "Cancelling alarm");
    } else {
        alarmManager.setInexactRepeating(AlarmManager.RTC,
                System.currentTimeMillis(), interval, operation);
        Log.d(TAG, "Setting alarm with interval: " + interval);
    }
}
 

 
 我试过的 
 
 我知道使用onSharedPreferenceChanged我可以在更新首选项时执行代码，问题是为了设置警报，我需要有一个Preference类没有提供的Context 。 我知道getActivity().getApplicationContext()的问题是它们可以返回null，具体取决于Preference活动的生命周期。 
 
public class SettingsFragment extends PreferenceFragment implements OnSharedPreferenceChangeListener{
    private SharedPreferences prefs;
    @Override 
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.settings);
    }

    @Override
    public void onStart() {
        super.onStart();
        prefs = PreferenceManager.getDefaultSharedPreferences(getActivity());
        prefs.registerOnSharedPreferenceChangeListener(this);
    }
    @Override
    public void onSharedPreferenceChanged(SharedPreferences prefs, String key) {
        if (key.equals("interval")){
                // Since I'm not using the intent I can just simply pass null.
                AlarmCreator.setAlarm(??,null);
            }

    }

}
 
 这个问题 
 
 我应该将什么传递给AlarmCreator.setAlarm(Content,intent)以便正确取消或更新警报？ 它甚至可能吗？ 也许有一种我错过的更好的方法。 
 
 附加信息 
 
 我刚刚开始学习Android开发，但我花了很多时间阅读文档，而我却无法弄清楚如何去做。 有一个类似的问题有助于我走上正轨，但我发现答案对我目前的理解来说太模糊了。 
 
 任何想法，将不胜感激。 
 干杯。 

I'm developing a test app to learn Android in which I need to fire up a service periodically to update some data. I'm using the AlarmManager with a BroadcastReceiver to set the alarm and it successfully updates the data with the default interval but I'd like to have this interval as a user defined value.
 I currently have the following code to register the alarm:
 
In the manifest:
 
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>
<receiver android:name=".BootReceiver">
    <intent-filter>
         <action android:name="android.intent.action.BOOT_COMPLETED"/>
    </intent-filter>
</receiver>
 
The receiver:
 
public class BootReceiver extends BroadcastReceiver {
    private static final String TAG = BootReceiver.class.getSimpleName();

    @Override
    public void onReceive(Context context, Intent intent) {
        Log.d(TAG,"onReceive method");
        AlarmCreator.setAlarm(context, intent);

    }
}
 
The actual alarm:
 
public static void setAlarm(Context context, Intent intent){
    Log.d(TAG, "Setting alarm");
    // I need the context here
    context.startService(new Intent(context, RefreshService.class));

    SharedPreferences prefs = PreferenceManager
            .getDefaultSharedPreferences(context);
    long interval = Long.parseLong(prefs.getString("interval",
            Long.toString(DEFAULT_INTERVAL)));
    // Here
    PendingIntent operation = PendingIntent.getService(context, -1,
            new Intent(context, RefreshService.class),
            PendingIntent.FLAG_UPDATE_CURRENT);

    // And here
    AlarmManager alarmManager = (AlarmManager) context
            .getSystemService(Context.ALARM_SERVICE);

    if (interval == 0) {
        alarmManager.cancel(operation);
        Log.d(TAG, "Cancelling alarm");
    } else {
        alarmManager.setInexactRepeating(AlarmManager.RTC,
                System.currentTimeMillis(), interval, operation);
        Log.d(TAG, "Setting alarm with interval: " + interval);
    }
}
 

 
What I've tried
 
I know that using the onSharedPreferenceChanged I can execute code when a preference is updated, the problem is that in order to set the alarm I need to have a Context which the Preference class doesn't provide. I am aware of getActivity().getApplicationContext() the problem is that they can return null depending on the life cycle of the Preference activity.
 
public class SettingsFragment extends PreferenceFragment implements OnSharedPreferenceChangeListener{
    private SharedPreferences prefs;
    @Override 
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.settings);
    }

    @Override
    public void onStart() {
        super.onStart();
        prefs = PreferenceManager.getDefaultSharedPreferences(getActivity());
        prefs.registerOnSharedPreferenceChangeListener(this);
    }
    @Override
    public void onSharedPreferenceChanged(SharedPreferences prefs, String key) {
        if (key.equals("interval")){
                // Since I'm not using the intent I can just simply pass null.
                AlarmCreator.setAlarm(??,null);
            }

    }

}
 
The question
 
What should I pass to AlarmCreator.setAlarm(Content,intent) so that the alarm gets correctly canceled or updated? Is it even possible? Maybe there's a better approach that I'm missing.
 
Additional info
 
I just started learning Android development but I've spent a good amount of time reading the documentation and I just couldn't figure out how to do it. There was a similar question which helped to get me on track but I found the answer too vague for my understanding at the moment.
 
Any Ideas would be appreciated. 
 Cheers.

原文：https://stackoverflow.com/questions/24406899