如何在 BaseAdapter class 中更新异步任务的 imageView 源 onPostResult

Question

我想在 OnPostExecute 方法 async 方法

中下载后更新图像查看源

这是我的基本适配器的 getView 方法 class

public View getView(int position, View convertView, ViewGroup parent) {
    vi = convertView;
    ViewHolder holder;
    if(convertView==null){

        /****** Inflate tabitem.xml file for each row ( Defined below ) *******/
        vi = inflater.inflate(R.layout.activity_single_message, null);
        /****** View Holder Object to contain tabitem.xml file elements ******/

        holder = new ViewHolder();
        holder.chatText = (TextView) vi.findViewById(R.id.singleMessage);
        holder.imageView=(ImageView)vi.findViewById(R.id.image);
        holder.videoIcon=(ImageView)vi.findViewById(R.id.video_icon);
        holder.singleMessageContainer=(LinearLayout)vi.findViewById(R.id.singleMessageContainer);
        holder.singleMessageImageContainer=(LinearLayout)vi.findViewById(R.id.singleMessageImageContainer);
        holder.dwnld_btn = (Button)vi.findViewById(R.id.download_btn);

        /************  Set holder with LayoutInflater ************/
        vi.setTag( holder );
    }
    else
        holder=(ViewHolder)vi.getTag();

    if(data.size()<=0)
    {
        holder.chatText.setText("Start new conversation!");


    }
    else
    {
        /***** Get each Model object from Arraylist ********/
        tempValues=null;
        tempValues = (ChatMessage) data.get(position);
        //Toast.makeText(activity, "MimeType = " + tempValues.getMessageText(), Toast.LENGTH_LONG).show();
        String path = tempValues.getMediaURL();
        String mediaMIMEType = tempValues.getMediaMIMEType();
        int isDownload = tempValues.getIsDownloaded();
        String senderUserInfoId = tempValues.getSenderUserInfoId();

if(!tempValues.getSenderUserInfoId().equals(loginUserInfoId) && mediaMIMEType.contains("IMAGE"))
        {
            holder.chatText.setPadding(30,10,10,10);
            holder.chatText.setMaxWidth(550);
            holder.chatText.setBackgroundResource(R.drawable.chat_rightpng);
            holder.chatText.setTextColor(Color.parseColor("#FFFFFF"));//.setTextColor(R.color.white);
            holder.chatText.setText(tempValues.getMessageText());

            holder.singleMessageContainer.setGravity(true ? Gravity.LEFT : Gravity.RIGHT);

            try {
                holder.imageView.setVisibility(View.VISIBLE);
                holder.videoIcon.setVisibility(View.GONE);

                if(isDownload == 0) {
                    holder.dwnld_btn.setVisibility(View.VISIBLE);

                    holder.imageView.setPadding(10,10,10,10);
                    holder.imageView.setMaxWidth(450);
                    holder.imageView.setBackgroundColor(Color.parseColor("#005684"));
                    holder.imageView.setImageResource(R.drawable.blur);
                }
                else {
                    holder.dwnld_btn.setVisibility(View.GONE);

                    holder.imageView.setPadding(10,10,10,10);
                    holder.imageView.setMaxWidth(450);
                    holder.imageView.setMaxWidth(550);
                    holder.imageView.setBackgroundColor(Color.parseColor("#005684"));
                    holder.imageView.setImageDrawable(Drawable.createFromPath(path));
                }

                holder.singleMessageImageContainer.setGravity(true ? Gravity.LEFT : Gravity.RIGHT);
            } catch(Exception e) {
                //txtUrl.setText("Error: Exception");
            }
        }


            } catch(Exception e) {
                //txtUrl.setText("Error: Exception");
            }
        }

        /******** Set Item Click Listner for LayoutInflater for each row *******/
        holder.dwnld_btn.setOnClickListener(new OnDownloadBtnClickListener(position));
    }
    return vi;
}

这是我点击下载按钮时的点击功能

private class OnDownloadBtnClickListener  implements View.OnClickListener {
    private int mPosition;

    OnDownloadBtnClickListener(int position){
        mPosition = position;
    }

    @Override
    public void onClick(View arg0) {
        final ChatMessage val = ( ChatMessage ) data.get(mPosition);
        if(isInternetOn()) {
            String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss", Locale.getDefault()).format(new Date());
            downlodedMsgId = val.getId();
            if (val.getMediaMIMEType().contains("IMAGE")) {
                localFileURL = Environment.getExternalStorageDirectory() + File.separator + "/Planetskool/Media/Images/IMG_" + timeStamp + ".png";

                new DownloadFileFromURL().execute(val.getOnlineMediaURL());

        }
    }
}

这是 async 下载文件的方法，其中 OnPostExecute 我想更改 imageview

的来源

class DownloadFileFromURL extends AsyncTask<String, String, String> {

    /**
     * Before starting background thread
     * Show Progress Bar Dialog
     * */
    @Override
    protected void onPreExecute() {
        progressDialog = new ProgressDialog(activity);
        progressDialog.setMessage("Downloading file. Please wait...");
        progressDialog.setIndeterminate(false);
        progressDialog.setMax(100);
        progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
        progressDialog.setCancelable(true);
        progressDialog.show();
        super.onPreExecute();
    }

    /**
     * Downloading file in background thread
     * */
    @Override
    protected String doInBackground(String... f_url) {
        int count;
        try {
            URL url = new URL(f_url[0]);
            URLConnection conection = url.openConnection();
            conection.connect();
            // getting file length
            int lenghtOfFile = conection.getContentLength();

            // input stream to read file - with 8k buffer
            InputStream input = new BufferedInputStream(url.openStream(), 8192);

            // Output stream to write file
            OutputStream output = new FileOutputStream(localFileURL);

            byte data[] = new byte[1024];

            long total = 0;

            while ((count = input.read(data)) != -1) {
                total += count;
                // publishing the progress....
                // After this onProgressUpdate will be called
                publishProgress(""+(int)((total*100)/lenghtOfFile));

                // writing data to file
                output.write(data, 0, count);
            }

            // flushing output
            output.flush();

            // closing streams
            output.close();
            input.close();

        } catch (Exception e) {
            Log.e("Error: ", e.getMessage());
        }

        return null;
    }

    /**
     * Updating progress bar
     * */
    protected void onProgressUpdate(String... progress) {
        progressDialog.setProgress(Integer.parseInt(progress[0]));
    }

    /**
     * After completing background task
     * Dismiss the progress dialog
     * **/
    @Override
    protected void onPostExecute(String file_url) {
        db.updateDownlodedPath(downlodedMsgId, localFileURL);
        updateResults(data);
        localFileURL = "";
        downlodedMsgId = 0;
        progressDialog.dismiss();
    }

}

Answer 1

首先你必须检查你想要显示图像的位置是否在你的列表视图中可见，如果可见则更新它或者将它保存在你想要的任何首选位置（文件或 Lrucache ）。

查看位置是否可见的方法如下

public synchronized void onThumbnailReceived(Bitmap thumnail, String path) {
    if(listview!= null)
    {
    final int numVisibleChildren = listview.getChildCount();
    final int firstVisiblePosition = listiew
            .getFirstVisiblePosition();

    for (int i = firstVisiblePosition; i < firstVisiblePosition + numVisibleChildren; i++) {

        if (data.get(i).get(IMAGEPATH).toString()
                .equals(path)) {
            View view = listview.getChildAt(i - firstVisiblePosition);
            getView(i, view, null);
        }
    }
    }
}

Answer 2

将您的 clickListner 更改为

@Override
    public void onClick(View arg0) {
        final ChatMessage val = ( ChatMessage ) data.get(mPosition);
        if(isInternetOn()) {
            String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss", Locale.getDefault()).format(new Date());
            downlodedMsgId = val.getId();
            if (val.getMediaMIMEType().contains("IMAGE")) {
                localFileURL = Environment.getExternalStorageDirectory() + File.separator + "/Planetskool/Media/Images/IMG_" + timeStamp + ".png";

                new DownloadFileFromURL(position).execute(val.getOnlineMediaURL());

        }
    }

并在 AsyncTask 中创建构造函数

 class DownloadFileFromURL(int mPosition){
         //get your imageViewByPosition here and change the url in OnPostExecute Method
}

如何在 BaseAdapter class 中更新异步任务的 imageView 源 onPostResult

How to update an imageView source onPostResult of async task in BaseAdapter class

android

android-layout

android-adapter

android-adapterview