從BaseAdapter內的QuickBlox Server下載圖像-Android

Question

嗨，我正在使用QuickBlox SDK開發聊天應用程序。 到目前為止，我在這里已經進行了文字聊天。 現在，我正在發送附件（僅適用於圖像）。 首先，我將圖像上傳到quickblox內容部分，成功上傳后，我將使用AsyncTask在BaseAdapter的子類中下載相同的圖像。 這里發生了什么，doInBackground（）的return語句沒有執行，所以我在這里想要，我在這里做錯了什么。 請幫幫我 。

這是BaseAdapter子類的代碼片段，我正在其中嘗試從quickblox服務器下載圖像。

BaseAdapter子類的getView（）

     @Override
public View getView(int position, View convertView, ViewGroup parent) {
   final ViewHolder holder;
    QBChatMessage chatMessage = getItem(position);
    LayoutInflater vi = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

    int type = getItemViewType(position) ;
    if (convertView == null) {
        convertView = vi.inflate(R.layout.list_item_image, parent, false);
        holder = createViewHolder(convertView);
        convertView.setTag(holder);
    } else {
        holder = (ViewHolder) convertView.getTag();
    }

    QBUser currentUser = ChatService.getInstance().getCurrentUser();
    boolean isOutgoing = chatMessage.getSenderId() == null || chatMessage.getSenderId().equals(currentUser.getId());
    setAlignment(holder, isOutgoing);

    Collection<QBAttachment> attachments =  chatMessage.getAttachments();

    //attachments.
    if ( attachments != null && attachments.size() > 0) {
        String imageid="" ;
        for(QBAttachment attachment :attachments){
            imageid = attachment.getId();
        }
        //Here is the AsyncTask where I am trying to download image
        new BackgroundOperation(holder ,imageid).execute(); 
    } 

    return convertView;
}

BaseAdapter子類內的BackgroundOperation

    class BackgroundOperation extends AsyncTask<InputStream , Void , InputStream>{

       ViewHolder holder ;
       int imageid ;
       InputStream inputStream;

       BackgroundOperation(ViewHolder holder , String imageid){
           this.holder = holder ;
           this.imageid = Integer.parseInt(imageid);
       }

       @Override
       protected void onPreExecute() {
           super.onPreExecute();
       }

       @Override
       protected InputStream doInBackground(InputStream... params) {

           Handler mHandler = new Handler(Looper.getMainLooper());
               mHandler.post(new Runnable() {
                   public void run() {
                       QBContent.downloadFileTask(imageid, new QBEntityCallbackImpl<InputStream>() {
                           @Override
                           public void onSuccess(InputStream inputS, Bundle params) {

                               inputStream = inputS ;

                               //ImageView img =   holder.image_attachment ; //.setImageDrawable(d);
                               //Toast.makeText(context, "Image download Sucess", Toast.LENGTH_SHORT).show();

                           }

                           @Override
                           public void onError(List<String> errors) {
                               Log.d("Image Download Error : ", errors.toString());
                               //Toast.makeText(context, "Image Download Error ", Toast.LENGTH_SHORT).show();
                           }
                       }, new QBProgressCallback() {
                           @Override
                           public void onProgressUpdate(int progress) {
                               //Toast.makeText(context, "Image Download Progress ", Toast.LENGTH_SHORT).show();
                           }
                       });
                   }
               });

           return inputStream;
       }

       @Override
       protected void onPostExecute(InputStream s) {
           super.onPostExecute(s);

           if(s != null){
               Log.d("InputStream Value :", "****************************"+s.toString()+"******************");
               Bitmap bmp = BitmapFactory.decodeStream(s);
               Drawable d = new BitmapDrawable(context.getResources(), bmp);
               if(holder.image_attachment != null)
                   holder.image_attachment.setImageDrawable(d);
           }
       }
   }

Answer 1

我認為您在異步任務中使用了異步代碼。 顯然，您應該在主UI線程中使用調用QB回調，或者如果您想從后台線程運行此異步代碼，則必須創建一個特殊的處理程序。 參見此處以獲取說明： http : //quickblox.com/developers/Android#Sync_vs_Async