通过服务更新 Android 小部件，即执行 http 请求

Question

以下场景的最佳策略是什么：

我的应用程序将定期向服务器运行 PHP 脚本发送和接收 http 请求。 我尝试了由 AlarmManager 触发的服务或直接单击其小部件。设备上的直接操作工作正常（如随机数，请参阅http://www.vogella.com/tutorials/AndroidWidgets/article.html） 当涉及到请求时，这些应该在异步任务中完成。我试图从异步任务的 postexecute 部分更新小部件（remoteView），但它不起作用。

谁能给我一些提示或者sn-ps？

提前谢谢你

更新：

具有异步任务的小部件提供程序类：

public class MyWidgetProvider extends AppWidgetProvider {

private static final String ACTION_CLICK = "ACTION_CLICK";
long ddd;
String dddd;
RemoteViews remoteViews;
TextView tvUpdate;


  private static final String LOG = "de.vogella.android.widget.example";

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

    Log.w(LOG, "onUpdate method called");
    // Get all ids
    ComponentName thisWidget = new ComponentName(context,
        MyWidgetProvider.class);
    int[] allWidgetIds = appWidgetManager.getAppWidgetIds(thisWidget);

    // Build the intent to call the service
    Intent intent = new Intent(context.getApplicationContext(),
        UpdateWidgetService.class);
    intent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_IDS, allWidgetIds);

    // Update the widgets via the service
    context.startService(intent);
  }
 }

具有异步任务的服务类对网站进行 ping 操作（仅用于测试目的，以后的请求将在那里完成） 目的是在小部件中显示 ping：

public class UpdateWidgetService extends Service {
private static final String LOG = "de.vogella.android.widget.example";
long ddd;
String dddd;
RemoteViews remoteViews;
TextView tvUpdate;

@Override
public void onStart(Intent intent, int startId) {
    Log.i(LOG, "Called");
    // create some random data

    AppWidgetManager appWidgetManager = AppWidgetManager.getInstance(this
            .getApplicationContext());

    int[] allWidgetIds = intent
            .getIntArrayExtra(AppWidgetManager.EXTRA_APPWIDGET_IDS);

    ComponentName thisWidget = new ComponentName(getApplicationContext(),
            MyWidgetProvider.class);
    int[] allWidgetIds2 = appWidgetManager.getAppWidgetIds(thisWidget);
    Log.w(LOG, "From Intent" + String.valueOf(allWidgetIds.length));
    Log.w(LOG, "Direct" + String.valueOf(allWidgetIds2.length));

    for (int widgetId : allWidgetIds) {
        // create some random data
        int number = (new Random().nextInt(100));

        remoteViews = new RemoteViews(this
                .getApplicationContext().getPackageName(),
                R.layout.widget_layout);
        Log.w("WidgetExample", String.valueOf(number));
        if (dddd!=null)Log.w("dddd -", dddd);
        new LongOperation().execute("");
        if (dddd!=null)Log.w("dddd +", dddd);
        // Set the text
        remoteViews.setTextViewText(R.id.update,
                "Random: " + String.valueOf(number));

        // Register an onClickListener
        Intent clickIntent = new Intent(this.getApplicationContext(),
                MyWidgetProvider.class);

        clickIntent.setAction(AppWidgetManager.ACTION_APPWIDGET_UPDATE);
        clickIntent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_IDS,
                allWidgetIds);

        PendingIntent pendingIntent = PendingIntent.getBroadcast(
                getApplicationContext(), 0, clickIntent,
                PendingIntent.FLAG_UPDATE_CURRENT);
        remoteViews.setOnClickPendingIntent(R.id.update, pendingIntent);
        appWidgetManager.updateAppWidget(widgetId, remoteViews);
        AlarmManager alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
        Calendar cal = Calendar.getInstance();
        cal.setTimeInMillis(System.currentTimeMillis());
        cal.add(Calendar.SECOND, 5);
        alarmManager.setRepeating(AlarmManager.RTC_WAKEUP,
                cal.getTimeInMillis(), 5 * 1000, pendingIntent);

    }
    stopSelf();

    super.onStart(intent, startId);
}

@Override
public IBinder onBind(Intent intent) {
    return null;
}

private class LongOperation extends AsyncTask<String, Void, String> {
    @Override
    protected void onPreExecute() {
        // TODO Auto-generated method stub
        super.onPreExecute();
    }

    @Override
    protected String doInBackground(String... params) {
        // TODO Auto-generated method stub
        ddd = MainActivity.isURLReachable();

        Log.e("ddd", ddd + "");
        dddd = ddd + " ms";
        Log.e("dddd", dddd);

        return null;
    }

    @Override
    protected void onPostExecute(String result) {
        // TODO Auto-generated method stub
        super.onPostExecute(result);
        Log.e("POST dddd", dddd);
        remoteViews.setTextViewText(R.id.update, dddd);
    }

}

}

问题是无法从执行后的异步任务访问小部件。

更新 2：

如何从 postexecute 方法中获取 WidgetID？

@Override
    protected void onPostExecute(String result) {
        // TODO Auto-generated method stub
        super.onPostExecute(result);
        AppWidgetManager appWidgetManager = AppWidgetManager.getInstance(UpdateWidgetService.this
                .getApplicationContext());

        int[] allWidgetIds = intent
                .getIntArrayExtra(AppWidgetManager.EXTRA_APPWIDGET_IDS);

        ComponentName thisWidget = new ComponentName(getApplicationContext(),
                MyWidgetProvider.class);
        int[] allWidgetIds2 = appWidgetManager.getAppWidgetIds(thisWidget);
        Log.w(LOG, "From Intent" + String.valueOf(allWidgetIds.length));
        Log.w(LOG, "Direct" + String.valueOf(allWidgetIds2.length));

        for (int widgetId : allWidgetIds) {
            // create some random data
            int number = (new Random().nextInt(100));

            remoteViews = new RemoteViews(UpdateWidgetService.this
                    .getApplicationContext().getPackageName(),
                    R.layout.widget_layout);
            Log.w("WidgetExample", String.valueOf(number));
            if (dddd!=null)Log.w("dddd -", dddd);
            new LongOperation().execute("");
            if (dddd!=null)Log.w("dddd +", dddd);
            // Set the text
            remoteViews.setTextViewText(R.id.update,
                    "Random: " + dddd);

            // Register an onClickListener
            Intent clickIntent = new     Intent(UpdateWidgetService.this.getApplicationContext(),
                        MyWidgetProvider.class);

            clickIntent.setAction(AppWidgetManager.ACTION_APPWIDGET_UPDATE);
            clickIntent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_IDS,
                    allWidgetIds);

            PendingIntent pendingIntent = PendingIntent.getBroadcast(
                    getApplicationContext(), 0, clickIntent,
                    PendingIntent.FLAG_UPDATE_CURRENT);
            remoteViews.setOnClickPendingIntent(R.id.update, pendingIntent);
            appWidgetManager.updateAppWidget(widgetId, remoteViews);
        }


    }

Answer 1

问题是无法从执行后的异步任务访问小部件。

不需要。 onPostExecute() 可以get an instance of AppWidgetManager via getInstance() 并调用updateAppWidget() 就可以了。