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使用一个progressbar java/Android下载多个文件

android-progressbar progress-bar android-asynctask android java

Ambreen Khan · 技术社区 · 7 年前

在for()循环的帮助下,我正在一个AsyncTask中下载多个文件。下面的代码工作正常,但每个文件都有自己的单独进度条下载,我只希望所有下载的文件都有一个进度条。

// ProgressDialog for downloading images
@Override
protected Dialog onCreateDialog(int id) {
    switch (id) {
        case progress_bar_type:
            pDialog = new ProgressDialog(this);
            pDialog.setMessage("Downloading file. Please wait...");
            pDialog.setTitle("In progress...");
            pDialog.setIndeterminate(false);
            pDialog.setMax(100);
            pDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
            pDialog.setCancelable(true);
            pDialog.show();
            return pDialog;
        default:
            return null;
    }
}

下面是下载文件的异步任务。。

class DownloadFileFromURL extends AsyncTask<String, Integer, String> {
        /**
     * Before starting background thread Show Progress Bar Dialog
     * */
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        showDialog(progress_bar_type);
    }

    /**
     * Downloading file in background thread
     * */
    @Override
    protected String doInBackground(String... f_url) {
        int count;
        try {

            for (int i = 0; i < f_url.length; i++) {
                URL url = new URL(f_url[i]);
                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);
                System.out.println("Data::" + f_url[i]);
                // Output stream to write file
                OutputStream output = new FileOutputStream(
                        "/sdcard/Images/" + i + ".jpg");

                byte data[] = new byte[1024];

                long total = 0;
                int zarab=20;

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

        return null;
    }

    /**
     * Updating progress bar
     * */
    protected void onProgressUpdate(Integer... progress) {
        // setting progress percentage
        pDialog.setProgress(progress[0]);
    }

    /**
     * After completing background task Dismiss the progress dialog
     * **/
    @Override
    protected void onPostExecute(String file_url) {
        // dismiss the dialog after the file was downloaded
        dismissDialog(progress_bar_type);

        // Displaying downloaded image into image view
        // Reading image path from sdcard
        //String imagePath = Environment.getExternalStorageDirectory()
        //      .toString() + "/downloaded.jpg";
        // setting downloaded into image view
        // my_image.setImageDrawable(Drawable.createFromPath(imagePath));
    }

}

或者,如果Progressbar显示并升级文件数量,而不是长度文件,那么它也将是另一种有用的解决方案。我们将非常感谢您的帮助。

1 回复 | 直到 7 年前

MatPag 7 年前

我认为您有两种选择:

假进度条方法

您提前知道需要下载多少文件,可以设置 ProgressDialog 要下载的文件总数。这对于尺寸较小且相似的文件非常有效,并为用户提供了关于发生了什么的良好反馈。

// you can modify the max value of a ProgressDialog, we modify it
// to prevent unnecessary rounding math.
// In the configuration set the max value of the ProgressDialog to an int with
pDialog.setMax(urls.length);

for (int i = 0; i < urls.length; i++) {
    // launch HTTP request and save the file
    //...
    // your code 
    //...

    //advance one step each completed download
    publishProgress();
}

/**
 * Updating progress bar
 */
protected void onProgressUpdate(Integer... progress) {
    pDialog.incrementProgressBy(1);
}

真正的进度条方法

您需要提前知道需要下载的所有文件的总长度。例如,您可以创建一个单独的REST API,在开始下载每个单独的文件之前先调用它,这样就可以得到总长度(以字节为单位)。通过这种方式,您可以定期更新总数 进度对话框 与已下载的总字节数相对应的长度。