Updating app widget using AlarmManager

Question

I am trying to update a Widget more frequently than the 30 minute restriction imposed by the 1.6docs. After reading nearly every post in SO, and the developer docs, and various other sources, I thought I had got to a point where i could implement it. And so, I tried, and failed. Since then, I have trawled yet more forums and solutions, and I cannot seem to get it to update.

I have an Update class that sets the AlarmManager:

public class Update extends Service{

    @Override
    public void onStart(Intent intent, int startId) {
          String currentTemp = Battery.outputTemp;
          String currentLevel = Battery.outputLevel;
          String currentCard = Battery.outputCard;
          String currentInternal = Battery.memory;
          String currentRam = String.valueOf(Battery.outputRam).substring(0, 3) + "MB";

          // Change the text in the widget
          RemoteViews updateViews = new RemoteViews( 
          this.getPackageName(), R.layout.main);
          //update temp
          updateViews.setTextViewText(R.id.batteryTemp, currentTemp); 
          //update %
          updateViews.setTextViewText(R.id.batteryLevel, currentLevel);     
          //update level
          updateViews.setTextViewText(R.id.sdCard, currentCard);
          //update internal memory
          updateViews.setTextViewText(R.id.internal, currentInternal);
          //update ram
          updateViews.setTextViewText(R.id.ram, currentRam);

          ComponentName thisWidget = new ComponentName(this, Widget.class);
          AppWidgetManager manager = AppWidgetManager.getInstance(this);
          manager.updateAppWidget(thisWidget, updateViews);

    }
    @Override
    public IBinder onBind(Intent intent) {
        // no need to bind
        return null;
    }

}

This has caused my onReceive in my widget class to fire frequently (i have a toast to see when it fires), yet it carries no intent (the toast is meant to display this as they are received but it is blank).

I cannot figure it out (i'm a relative newb-2 months of slow android dev), and appreciate any insight you guys have.

heres my widget class for reference:

    public class Widget extends AppWidgetProvider {


    @Override
    public void onUpdate(Context context, AppWidgetManager appWidgetManager,
            int[] appWidgetIds) {

        AlarmManager alarmManager;
        Intent intent = new Intent(context, Update.class);
        PendingIntent pendingIntent = PendingIntent.getBroadcast(context, 0,
                intent, PendingIntent.FLAG_UPDATE_CURRENT);
        alarmManager = (AlarmManager) context
                .getSystemService(Context.ALARM_SERVICE);
        Calendar cal = Calendar.getInstance();
        cal.setTimeInMillis(System.currentTimeMillis());
        cal.add(Calendar.SECOND, 10);
        alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, cal
                .getTimeInMillis(), 5 * 1000, pendingIntent);

        String currentTemp = Battery.outputTemp;
        String currentLevel = Battery.outputLevel;
        String currentCard = Battery.outputCard;
        String currentInternal = Battery.memory;
        String currentRam = String.valueOf(Battery.outputRam).substring(0, 3)
                + "MB";

        // Change the text in the widget
        RemoteViews updateViews = new RemoteViews(context.getPackageName(),
                R.layout.main);
        // update temp
        updateViews.setTextViewText(R.id.batteryTemp, currentTemp);
        appWidgetManager.updateAppWidget(appWidgetIds, updateViews);
        // update %
        updateViews.setTextViewText(R.id.batteryLevel, currentLevel);
        appWidgetManager.updateAppWidget(appWidgetIds, updateViews);
        // update level
        updateViews.setTextViewText(R.id.sdCard, currentCard);
        appWidgetManager.updateAppWidget(appWidgetIds, updateViews);
        // update internal memory
        updateViews.setTextViewText(R.id.internal, currentInternal);
        appWidgetManager.updateAppWidget(appWidgetIds, updateViews);
        // update ram
        updateViews.setTextViewText(R.id.ram, currentRam);
        appWidgetManager.updateAppWidget(appWidgetIds, updateViews);
        super.onUpdate(context, appWidgetManager, appWidgetIds);

    }

    public void onReceive(Context context, Intent intent) {

        super.onReceive(context, intent);
        Toast
                .makeText(context, intent.getAction() + context,
                        Toast.LENGTH_LONG).show();
        Bundle extras = intent.getExtras();
        if (extras != null) {
            AppWidgetManager appWidgetManager = AppWidgetManager
                    .getInstance(context);
            ComponentName thisAppWidget = new ComponentName(context
                    .getPackageName(), Widget.class.getName());
            int[] appWidgetIds = appWidgetManager
                    .getAppWidgetIds(thisAppWidget);

            onUpdate(context, appWidgetManager, appWidgetIds);
        }

    }
}

Answer 1

I have an Update class that sets the AlarmManager:

No, you don't. AlarmManager appears nowhere in the code snippet.

You do have a reference to AlarmManager in the second code snippet. Problems there include:

• You are setting a new repeating alarm every time the app widget updates

• You are setting a 5 second frequency on the alarm, which is utter insanity

• You are setting a 5 second frequency on a _WAKEUP alarm, which I think is grounds for your arrest in some jurisdictions

• You have a pointless onReceive() method, even ignoring the temporary Toast

• You are assuming that there will be an action string on the Intent in your Toast, but you do not specify an action string when you create the Intent that you put in the PendingIntent for the alarm

• Your code refers to what I presume are static data members on a Battery class, but it is rather likely those are all empty/null... or at least they would be, if you had a sane frequency on the alarm

Answer 2

This is my solution, how to automatically update widget more frequently than the 30 minutes. I use AlarmManager. Before you use AlarmManager for refreshing appwidget, make sure you know what you do, because this technique could drain the device's battery.

Read more about widget update in Android doc - especially about updatePeriodMillis parameter.

This is part of my Manifest.xml. I define custom action AUTO_UPDATE.

<receiver android:name=".appwidget.AppWidget" >
    <intent-filter>
        <action android:name="android.appwidget.action.APPWIDGET_UPDATE" />
    </intent-filter>
    <intent-filter>
        <action android:name="AUTO_UPDATE" />
    </intent-filter>
    <meta-data android:name="android.appwidget.provider" android:resource="@xml/appwidget_info" />
</receiver>

This is part of my AppWidget.java. In onReceive method, I handle my custom action AUTO_UPDATE. In onEnabled and onDisabled methods, I start/stop alarm.

public class AppWidget extends AppWidgetProvider
{
    public static final String ACTION_AUTO_UPDATE = "AUTO_UPDATE";

    @Override
    public void onReceive(Context context, Intent intent)
    {
        super.onReceive(context, intent);

        if(intent.getAction().equals(ACTION_AUTO_UPDATE))
        {
            // DO SOMETHING
        }

        ...
    }

    @Override
    public void onEnabled(Context context)
    {
        // start alarm
        AppWidgetAlarm appWidgetAlarm = new AppWidgetAlarm(context.getApplicationContext());
        appWidgetAlarm.startAlarm();
    }

    @Override
    public void onDisabled(Context context)
    {
        // stop alarm only if all widgets have been disabled
        AppWidgetManager appWidgetManager = AppWidgetManager.getInstance(context);
        ComponentName thisAppWidgetComponentName = new ComponentName(context.getPackageName(),getClass().getName());
        int[] appWidgetIds = appWidgetManager.getAppWidgetIds(thisAppWidgetComponentName);
        if (appWidgetIds.length == 0) {
            // stop alarm
            AppWidgetAlarm appWidgetAlarm = new AppWidgetAlarm(context.getApplicationContext());
            appWidgetAlarm.stopAlarm();
    }

    }

    ...
}

This is my AppWidgetAlarm.java, which starts/stops alarm. Alarm manager sends broadcast to AppWidget.

public class AppWidgetAlarm
{
    private final int ALARM_ID = 0;
    private final int INTERVAL_MILLIS = 10000;

    private Context mContext;


    public AppWidgetAlarm(Context context)
    {
        mContext = context;
    }


    public void startAlarm()
    {
        Calendar calendar = Calendar.getInstance();
        calendar.add(Calendar.MILLISECOND, INTERVAL_MILLIS);

        Intent alarmIntent=new Intent(mContext, AppWidget.class);
        alarmIntent.setAction(AppWidget.ACTION_AUTO_UPDATE);
        PendingIntent pendingIntent = PendingIntent.getBroadcast(mContext, ALARM_ID, alarmIntent, PendingIntent.FLAG_CANCEL_CURRENT);

        AlarmManager alarmManager = (AlarmManager) mContext.getSystemService(Context.ALARM_SERVICE);
        // RTC does not wake the device up
        alarmManager.setRepeating(AlarmManager.RTC, calendar.getTimeInMillis(), INTERVAL_MILLIS, pendingIntent);
    }


    public void stopAlarm()
    {
        Intent alarmIntent = new Intent(AppWidget.ACTION_AUTO_UPDATE);
        PendingIntent pendingIntent = PendingIntent.getBroadcast(mContext, ALARM_ID, alarmIntent, PendingIntent.FLAG_CANCEL_CURRENT);

        AlarmManager alarmManager = (AlarmManager) mContext.getSystemService(Context.ALARM_SERVICE);
        alarmManager.cancel(pendingIntent);
    }
}