问如何在Xamarin Android(Widget)中动态更改ImageView源代码

EN

[BroadcastReceiver(Label = "HellApp Widget")]
[IntentFilter(new string[] { "android.appwidget.action.APPWIDGET_UPDATE" })]
// The "Resource" file has to be all in lower caps
[MetaData("android.appwidget.provider", Resource = "@xml/appwidgetprovider")]
public class AppWidget : AppWidgetProvider
{
    private static string AnnouncementClick = "AnnouncementClickTag";
    private int test = (int)typeof(Resource.Drawable).GetField("fivePlus").GetValue(null);
    /// <summary>
    /// This method is called when the 'updatePeriodMillis' from the AppwidgetProvider passes,
    /// or the user manually refreshes/resizes.
    /// </summary>
    public override void OnUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds)
    {
        var me = new ComponentName(context, Java.Lang.Class.FromType(typeof(AppWidget)).Name);
        appWidgetManager.UpdateAppWidget(me, BuildRemoteViews(context, appWidgetIds));
    }

    private RemoteViews BuildRemoteViews(Context context, int[] appWidgetIds)
    {
        // Retrieve the widget layout. This is a RemoteViews, so we can't use 'FindViewById'
        var widgetView = new RemoteViews(context.PackageName, Resource.Layout.Widget);

        LoadData(widgetView);
        RegisterClicks(context, appWidgetIds, widgetView);
        return widgetView;
    }


    private void LoadData(RemoteViews widgetView)
    {

        widgetView.SetTextViewText(Resource.Id.widgetMedium, "HelloAppWidget");
        widgetView.SetTextViewText(Resource.Id.widgetSmall, string.Format("Last update: {0:H:mm:ss}", DateTime.Now));

    }

    private void RegisterClicks(Context context, int[] appWidgetIds, RemoteViews widgetView)
    {
        var intent = new Intent(context, typeof(AppWidget));
        intent.SetAction(AppWidgetManager.ActionAppwidgetUpdate);
        intent.PutExtra(AppWidgetManager.ExtraAppwidgetIds, appWidgetIds);

        // Register click event for the Background
        var piBackground = PendingIntent.GetBroadcast(context, 0, intent, PendingIntentFlags.UpdateCurrent);
        widgetView.SetOnClickPendingIntent(Resource.Id.widgetBackground, piBackground);

        // Register click event for the Announcement-icon
        widgetView.SetOnClickPendingIntent(Resource.Id.widgetAnnouncementIcon, GetPendingSelfIntent(context, AnnouncementClick));
    }

    private PendingIntent GetPendingSelfIntent(Context context, string action)
    {
        var intent = new Intent(context, typeof(AppWidget));
        intent.SetAction(action);
        return PendingIntent.GetBroadcast(context, 0, intent, 0);
    }

    /// <summary>
    /// This method is called when clicks are registered.
    /// </summary>
    public override void OnReceive(Context context, Intent intent)
    {
        base.OnReceive(context, intent);

        // Check if the click is from the "Announcement" button
        if (AnnouncementClick.Equals(intent.Action))
        {
            try
            {
                RemoteViews remoteViews = new RemoteViews(context.PackageName, Resource.Layout.Widget);
                remoteViews.SetImageViewResource(Resource.Id.widgetAnnouncementIcon, Resource.Drawable.fivePlus);
                AppWidgetManager appWidgetManager = AppWidgetManager.GetInstance(context);
                ComponentName componentName = new ComponentName(context, Java.Lang.Class.FromType(typeof(AppWidget)).Name);
                appWidgetManager.UpdateAppWidget(componentName, remoteViews);
        }
            catch
            {
                // Something went wrong :)
            }
        }
    }
}