将onPostExecute值返回到RecyclerAdapter的onBindViewHolder中

Question

我有聊天屏幕，我正在从FirebaeStorage下载附件。 我有各种格式的文件，可以发送doc，pdf，apk等，每个我有相同的TextViews和ImageViews。

在聊天屏幕的recyclerview适配器我设置本地存储的文件路径，它可以通过运行AsyncTask从Firebase存储中下载文件并返回文件路径来获取。此工作完美，但问题是如何找回文件路径onBindViewHolder上特别是如果其他

这里是我的RecyclerAdapter这里我打电话的AsyncTask和需要结果返回到相同的范围和等到下载完成，然后根据数据集视图返回

public void onBindViewHolder(final Chat_Adapter.ViewHolder holder, int position) { 


if (fileType.equals("pdf")){ 
new DownloadFileFromFS(Download_URL,FileName+".pdf").execute(); 

//HERE I NEED THE RESULT FROM ASYNCTASK AND WAIT TILL DOWNLOAD COMPLETES 
//THEN SET THE VIEWS WITH RETURN RESULT FROM ASYNCTASK 

    if (DownloadFilePath!=null){ 
     File file=new File(DownloadFilePath); 
     long sizeFile=file.length()/1024; //In KB 
     holder.Doc_FileName.setText(DownloadFilePath); 
     holder.Doc_FileSize.setText(String.valueOf(sizeFile)); 
    } 
    else { 
     Log.d(TAG,"DOWNLOAD FILE PATH IS NULL"); 
    } 

} 

的AsyncTask

public class DownloadAttachment extends AsyncTask<Void, String, String> { 
    String DownloadUrl,fileName; 
    File file; 
    Context context; 
    ProgressBar progressBar; 
    public static final String TAG="###Download Attachment"; 

    public DownloadAttachment(Context context, String downloadUrl, String fileName) { 
     DownloadUrl = downloadUrl; 
     this.fileName = fileName; 
     this.context=context; 
    } 


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

    @Override 
    protected String doInBackground(Void... params) { 
     int count; 
     try { 
      File root = android.os.Environment.getExternalStorageDirectory(); 

      Log.d(TAG,"DO IN BACKGROUND RUNNING"); 
      File dir = new File(root.getAbsolutePath() + "/Downloaded Files/"); 
      if (dir.exists() == false) { 
       dir.mkdirs(); 
      } 


      URL url = new URL(DownloadUrl); //you can write here any link 
      file = new File(dir, fileName); 

      long startTime = System.currentTimeMillis(); 
      Log.d(TAG, "download begining"); 
      Log.d(TAG, "download url:" + url); 
      Log.d(TAG, "downloaded file name:" + fileName); 

     /* Open a connection to that URL. */ 
      URLConnection ucon = url.openConnection(); 

      //this will be useful so that you can show a typical 0-100% progress bar 
      int lengthOfFile=ucon.getContentLength(); 
     /* 
     * Define InputStreams to read from the URLConnection. 
     */ 
      InputStream is = ucon.getInputStream(); 
      BufferedInputStream bis = new BufferedInputStream(is); 

     /* 
     * Read bytes to the Buffer until there is nothing more to read(-1). 
     */ 
      ByteArrayOutputStream baf = new ByteArrayOutputStream(5000); 
      int current = 0; 
      long total=0; 
      while ((current = bis.read()) != -1) { 
       baf.write((byte) current); 
       total=total+current; 
       //PUBLISH THE PROGRESS 
       //AFTER THIS onProgressUpdate will be called 
       publishProgress(""+(int)(total*100)/lengthOfFile); 
      } 


     /* Convert the Bytes read to a String. */ 
      FileOutputStream fos = new FileOutputStream(file); 
      fos.write(baf.toByteArray()); 
      fos.flush(); 
      fos.close(); 
      Log.d("DownloadManager", "download ready in " + ((System.currentTimeMillis() - startTime)/1000) + " sec"); 
      Log.d(TAG,"File Path "+file); 

     } catch (IOException e) { 
      Log.d("DownloadManager", "Error: " + e); 
     } 

     return file.toString(); 
    }  

} 

UPDATE作为@Atef野兔建议，我没有在code.its实施工作正常，但如果我有不同的格式。如果从Asynctask获得结果后如何调用特定的cuz代码，建议只在调用pdf时声明。

if (fileType.equals("pdf")){ 
    final String nameFile=UUID.randomUUID().toString(); 
    new DownloadFileFromFS(chat_wrapper.getDocuments(),nameFile).execute(); 

    filePathInterface=new FilePath() { 
     @Override 
     public void LocalFilePath(final String Path) { 
      //HERE I AM GETTING RESULT FROM ASYNCTASK 
      //AND SETTING VIEWS ACCORDING TO IT    
     } 
    }; 


} 
else if (fileType.equals("doc")){ 
//HOW TO GET RESULT FROM ASYNCTASK HERE IF FILETYPE IS "doc" 

} 
else if (fileType.equals("ppt")){ 
//HOW TO GET RESULT FROM ASYNCTASK HERE IF FILETYPE IS "ppt" 
} 

Answer 1

好的使用接口 - 如你所知 - 将实现你所需要的！

只是做这样的：

public interface AsyncTaskCallback { 
    void onSuccess (String filePath); 
} 

和适配器，没有任何数据集的观点，除非你获得了数据从后面的AsyncTask，像这样：

public void onBindViewHolder(final Chat_Adapter.ViewHolder holder, int position) { 

     //Initialize filetype here 

     new DownloadFileFromFS(Download_URL, FileName + "."+ filetype, new AsyncTaskCallback() { 
      @Override 
      public void onSuccess(String filePath) { 
       //HERE I NEED THE RESULT FROM ASYNCTASK AND WAIT TILL DOWNLOAD COMPLETES 
       //THEN SET THE VIEWS WITH RETURN RESULT FROM ASYNCTASK 

       if (filePath != null) { 
        File file = new File(filePath); 
        long sizeFile = file.length()/1024; //In KB 
        holder.Doc_FileName.setText(filePath); 
        holder.Doc_FileSize.setText(String.valueOf(sizeFile)); 
       } else { 
        Log.d(TAG, "DOWNLOAD FILE PATH IS NULL"); 
       } 
      } 
     }).execute(); 
    } 

Answer 2

您可以使用回调。

public interface FileDownloadCallback { 
    void onSuccess (String filePath); 
    void onFailed(); 

} 

将它传递给您的AsyncTask并从onPostExecute调用它。