android - 使用来自互联网的图像更新 android 小部件(使用异步任务)

Question

我有一个简单的 android 小部件，我想用来自 Internet 的图像对其进行更新。我可以在小部件上显示静态图像没问题。有人告诉我，您需要为此使用异步任务，而我对此经验不多。

这是我的小部件:

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

        super.onUpdate(context, appWidgetManager, appWidgetIds);

        for (int i = 0; i < appWidgetIds.length; i++){
            int appWidgetId = appWidgetIds[i];      

            RemoteViews views = new RemoteViews(context.getPackageName(), R.layout.activity_main);

                //Setup a static image, this works fine.
            views.setImageViewResource(R.id.imageView1, R.drawable.wordpress_icon);             

            new DownloadBitmap().execute("MyTestString");       

            appWidgetManager.updateAppWidget(appWidgetId, views);
        }

然后我有一个执行下载的异步任务类。它看起来像这样:

public class DownloadBitmap extends AsyncTask<String, Void, Bitmap> {

    /** The url from where to download the image. */
    private String url = "http://0.tqn.com/d/webclipart/1/0/5/l/4/floral-icon-5.jpg"; 

    @Override
    protected Bitmap doInBackground(String... params) {
        try {
            InputStream in = new java.net.URL(url).openStream();
            Bitmap bitmap = BitmapFactory.decodeStream(in);
            return bitmap;              
            //NOTE:  it is not thread-safe to set the ImageView from inside this method.  It must be done in onPostExecute()
        } catch (Exception e) {
            Log.e("ImageDownload", "Download failed: " + e.getMessage());
        }
        return null;
    }


    @Override
    protected void onPostExecute(Bitmap bitmap) {
        if (isCancelled()) {
            bitmap = null;
        }

           //Here is where I should set the image to the imageview, but how?
    } 
}

我认为我的代码已成功从 Internet 下载图像。

让我感到困惑的是，如何将此图像从我的异步任务类中获取到特定小部件的“ImageView”中。要更新图像，您需要访问 3 个不同的对象:Context、AppWidgetManager 和 AppWidgetId...。但是我如何在该语句中传递所有这些对象:???

new DownloadBitmap().execute("MyTestString");

谢谢!

Answer 1

一个解决方案是将 RemoteViews 作为参数传递给 DownloadBitmap 构造函数，并在 onPostExecute() 中设置图像:

在 onUpdate() 中:

new DownloadBitmap(views).execute("MyTestString");

在 DownloadBitmap 中:

//....
public class DownloadBitmap extends AsyncTask<String, Void, Bitmap> {
    private RemoteViews views;

    public DownloadBitmap(RemoteViews views){
        this.views = views;
    }

    //.....
    public void onPostExecute(Bitmap bitmap){
        views.setImageViewBitmap(R.id.imageView1, bitmap);
    }
}