更新异步任务中的列表视图行答案

【问题标题】：Update listview row in asynctask更新异步任务中的列表视图行
【发布时间】：2014-07-15 06:18:51
【问题描述】：

我有一个带有基本适配器的列表视图。我的列表视图中的每一行都包含图像、标题、下载和查看按钮以及进度条。最初进度条和视图按钮的可见性已消失。当用户按下下载按钮时，应该可以看到进度条。下载完成后，下载按钮应该消失，查看按钮应该可见。

我的问题是：我无法从 asynctask 更改视图的可见性。

这是我的代码。

public class PdfListAdapter extends BaseAdapter {

    ArrayList<PdfDetails> arylstPdf = new ArrayList<PdfDetails>();
    Context context;
    String extStorageDirectory;
    ViewHolder holder;
    Activity activity;


    public PdfListAdapter(Context context, ArrayList<PdfDetails> arylstPdf) {
        super();
        this.arylstPdf = arylstPdf;
        this.context = context;

        extStorageDirectory = Environment.getExternalStorageDirectory()
                .toString();
        holder = new ViewHolder();
    }

    @Override
    public int getCount() {
        return arylstPdf.size();
    }

    @Override
    public Object getItem(int position) {
        return position;
    }

    @Override
    public long getItemId(int position) {
        return position;
    }


    @Override
    public View getView(final int position, View convertView, ViewGroup parent) {
        LayoutInflater mInflater = LayoutInflater.from(context);
        activity = (Activity) context;

        if (convertView == null) {
            convertView = mInflater.inflate(R.layout.layout_pdf_list, null);

            holder.tvPdfTitle = (TextView) convertView
                    .findViewById(R.id.tvPdfTitle);

            holder.imgPdfImage = (ImageView) convertView
                    .findViewById(R.id.imgPdfImage);

            holder.btnDownload = (Button) convertView
                    .findViewById(R.id.btnDownload);

            holder.btnView = (Button) convertView.findViewById(R.id.btnView);

            holder.pbDownload = (ProgressBar) convertView
                    .findViewById(R.id.pbDownload);

            holder.tvProgress = (TextView) convertView.findViewById(R.id.tvProgress);

            holder.llProgress = (LinearLayout) convertView.findViewById(R.id.llProgress);

            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }

        File file = new File(extStorageDirectory + "/pdf", arylstPdf.get(
                position).getPostTitle()
                + ".pdf");

        if (file.exists()) {
            holder.btnDownload.setVisibility(View.GONE);
            holder.btnView.setVisibility(View.VISIBLE);
        } else {
            holder.btnDownload.setVisibility(View.VISIBLE);
            holder.btnView.setVisibility(View.GONE);
        }


        holder.tvPdfTitle.setText(arylstPdf.get(position).getPostTitle());

        ImageLoader objImageLoader = new ImageLoader(context);
        objImageLoader.DisplayImage(arylstPdf.get(position).getAttachedImage(),
                holder.imgPdfImage);

        holder.btnDownload.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {

                 // NOT WORKING
                holder.llProgress.setVisibility(View.VISIBLE);
                Async async = new Async();
                async.execute(Integer.toString(position));

            }
        });

        holder.btnView.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                readPDF(arylstPdf.get(position).getPostTitle());
            }
        });

        return convertView;
    }

    class ViewHolder {
        ImageView imgPdfImage;
        TextView tvPdfTitle, tvProgress;
        Button btnDownload;
        Button btnView;
        ProgressBar pbDownload;
        LinearLayout llProgress;
    }



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

        File file, folder;

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

            folder = new File(extStorageDirectory, "pdf");
            folder.mkdir();
        }

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

            String fileName = arylstPdf.get(Integer.parseInt(params[0]))
                    .getPostTitle();

            file = new File(folder, fileName + ".pdf");

            try {
                file.createNewFile();
            } catch (IOException e1) {
                e1.printStackTrace();
            }

            int count;

            try {
                URL url = new URL(arylstPdf.get(Integer.parseInt(params[0]))
                        .getAttachedPdf());
                URLConnection conection = url.openConnection();
                conection.connect();

                int lenghtOfFile = conection.getContentLength();

                InputStream input = new BufferedInputStream(url.openStream(),
                        8192);
                OutputStream output = new FileOutputStream(file);

                byte data[] = new byte[1024];

                long total = 0;

                while ((count = input.read(data)) != -1) {
                    total += count;

                    publishProgress(Integer
                            .toString((int) ((total * 100) / lenghtOfFile)));


                    output.write(data, 0, count);
                }

                output.flush();
                output.close();
                input.close();

            } catch (NumberFormatException e) {
                e.printStackTrace();
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }

            return null;
        }

        @Override
        protected void onProgressUpdate(String... progress) {
            holder.tvProgress.setText(progress[0]);
            holder.pbDownload.setProgress(Integer.parseInt(progress[0]));
        }

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

            // NOT WORKING
            holder.btnDownload.setVisibility(View.GONE);
            holder.btnDownload.setVisibility(View.VISIBLE);
            Toast.makeText(context, "Downloaded", Toast.LENGTH_SHORT).show();
        }

    }

}

【问题讨论】：

标签： android android-layout android-listview android-asynctask

【解决方案1】：

在PdfDetails 类更改下载中添加一个布尔标志，并在getView 方法中查看按钮可见性。

所以只需在 arraylist 位置更改该特定行的布尔标志。

和用户adapter.notifyDataStateChanged();

在 PdfDetails 类中添加 getter setter 方法。

在getView()方法中

使用

PdfDetails detailBin = list.get(position);

if(detailBin.isDownloaded)
   // view button visible and download button hide
else 
  // download button visible and view button hide

在 postExecute() 中

list.get(position).setDownload(true);
adapter.notifyDataStateChanged();

【讨论】：

嘿@Sanket 谢谢.. 它有效！但请解决我的另一个问题。我也想在下载时显示进度条.. 上面的代码，我不能这样做
是的，对于正在进行下载过程的每一行
您应该需要从 AsyncTask 通知您的列表视图。
您能提供一些示例代码或与此相关的任何链接吗？

【解决方案2】：

除了在 Adapter 类本身中创建 holder 之外，您还可以让它在 getView 本身中并将其传递给 AsyncTask 构造函数。

public class PdfListAdapter extends BaseAdapter {

ArrayList<PdfDetails> arylstPdf = new ArrayList<PdfDetails>();
Context context;
String extStorageDirectory;
Activity activity;


public PdfListAdapter(Context context, ArrayList<PdfDetails> arylstPdf) {
    super();
    this.arylstPdf = arylstPdf;
    this.context = context;

    extStorageDirectory = Environment.getExternalStorageDirectory()
            .toString();
}

@Override
public int getCount() {
    return arylstPdf.size();
}

@Override
public Object getItem(int position) {
    return position;
}

@Override
public long getItemId(int position) {
    return position;
}


@Override
public View getView(final int position, View convertView, ViewGroup parent) {
    LayoutInflater mInflater = LayoutInflater.from(context);
    activity = (Activity) context;
    final ViewHolder holder= null;

    if (convertView == null) {
        convertView = mInflater.inflate(R.layout.layout_pdf_list, null);
        holder = new ViewHolder();

        holder.tvPdfTitle = (TextView) convertView
                .findViewById(R.id.tvPdfTitle);

        holder.imgPdfImage = (ImageView) convertView
                .findViewById(R.id.imgPdfImage);

        holder.btnDownload = (Button) convertView
                .findViewById(R.id.btnDownload);

        holder.btnView = (Button) convertView.findViewById(R.id.btnView);

        holder.pbDownload = (ProgressBar) convertView
                .findViewById(R.id.pbDownload);

        holder.tvProgress = (TextView) convertView.findViewById(R.id.tvProgress);

        holder.llProgress = (LinearLayout) convertView.findViewById(R.id.llProgress);

        convertView.setTag(holder);
    } else {
        holder = (ViewHolder) convertView.getTag();
    }

    File file = new File(extStorageDirectory + "/pdf", arylstPdf.get(
            position).getPostTitle()
            + ".pdf");

    if (file.exists()) {
        holder.btnDownload.setVisibility(View.GONE);
        holder.btnView.setVisibility(View.VISIBLE);
    } else {
        holder.btnDownload.setVisibility(View.VISIBLE);
        holder.btnView.setVisibility(View.GONE);
    }


    holder.tvPdfTitle.setText(arylstPdf.get(position).getPostTitle());

    ImageLoader objImageLoader = new ImageLoader(context);
    objImageLoader.DisplayImage(arylstPdf.get(position).getAttachedImage(),
            holder.imgPdfImage);

    holder.btnDownload.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {

             // NOT WORKING
            holder.llProgress.setVisibility(View.VISIBLE);
            Async async = new Async(holder);
            async.execute(Integer.toString(position));

        }
    });

    holder.btnView.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            readPDF(arylstPdf.get(position).getPostTitle());
        }
    });

    return convertView;
}

class ViewHolder {
    ImageView imgPdfImage;
    TextView tvPdfTitle, tvProgress;
    Button btnDownload;
    Button btnView;
    ProgressBar pbDownload;
    LinearLayout llProgress;
}



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

    File file, folder;
    ViewHolder holder;

    public Async(ViewHolder holder) {
        this.holder=holder;
    }

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

        folder = new File(extStorageDirectory, "pdf");
        folder.mkdir();
    }

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

        String fileName = arylstPdf.get(Integer.parseInt(params[0]))
                .getPostTitle();

        file = new File(folder, fileName + ".pdf");

        try {
            file.createNewFile();
        } catch (IOException e1) {
            e1.printStackTrace();
        }

        int count;

        try {
            URL url = new URL(arylstPdf.get(Integer.parseInt(params[0]))
                    .getAttachedPdf());
            URLConnection conection = url.openConnection();
            conection.connect();

            int lenghtOfFile = conection.getContentLength();

            InputStream input = new BufferedInputStream(url.openStream(),
                    8192);
            OutputStream output = new FileOutputStream(file);

            byte data[] = new byte[1024];

            long total = 0;

            while ((count = input.read(data)) != -1) {
                total += count;

                publishProgress(Integer
                        .toString((int) ((total * 100) / lenghtOfFile)));


                output.write(data, 0, count);
            }

            output.flush();
            output.close();
            input.close();

        } catch (NumberFormatException e) {
            e.printStackTrace();
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        return null;
    }

    @Override
    protected void onProgressUpdate(String... progress) {
        holder.tvProgress.setText(progress[0]);
        holder.pbDownload.setProgress(Integer.parseInt(progress[0]));
    }

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

        // NOT WORKING
        holder.btnDownload.setVisibility(View.GONE);
        holder.btnDownload.setVisibility(View.VISIBLE);
        Toast.makeText(context, "Downloaded", Toast.LENGTH_SHORT).show();
    }

}

}

【讨论】：

在将 asynctask 更新计数设置为 viewholders textview android 后

【解决方案3】：

您不能在主 ui 线程以外的其他线程（Asynctasks）中对 UserInterface(UI) 进行任何更改。所以你需要遵循这个

           runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
        //Any UI changes can be done here            
        holder.btnDownload.setVisibility(View.GONE);
        holder.btnView.setVisibility(View.VISIBLE);
                    }
                });

【讨论】：

他在 onPostExecute 中做的，所以没有任何问题
Ya ur crct..post 执行在主 UI 线程上运行...我认为它在 DoinBackground 上完成