Question

我有一个按钮，开始下载显示进度dailog。进度dailog有一个取消按钮，可以停止下载。但是当点击取消时，下载停止，但整个应用程序崩溃而不保持主要活动 Q）如何阻止这种情况发生并保持主动 2）如何删除部分下载的文件这是进度dailog代码

DownloadFileFromURL cdrt = new DownloadFileFromURL();

@Override
protected Dialog onCreateDialog(int id) {
    switch (id) {
        case progress_bar_type: // we set this to 0
            pDialog = new ProgressDialog(this);
            pDialog.setMessage("Downloading file. Please wait...");
            pDialog.setIndeterminate(false);
            pDialog.setMax(100);
            pDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
            pDialog.setCancelable(true);
            pDialog.setButton("Cancel", new CancelOnClickListener());
            pDialog.show();
            return pDialog;
        default:
            return null;
    }
}
private final class CancelOnClickListener implements DialogInterface.OnClickListener {
    public void onClick(DialogInterface dialog, int which) {
        MainActivity.this.finish();
        dismissDialog(progress_bar_type);
        if(cdrt.getStatus() == AsyncTask.Status.RUNNING){
        cdrt.cancel(true);}
}

的AsyncTask

class DownloadFileFromURL extends AsyncTask<String, String, 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{
            URL url = new URL(f_url[0]);

            URLConnection conection = url.openConnection();
            conection.connect();
            // this will be useful so that you can show a tipical 0-100% progress bar
            int lenghtOfFile = conection.getContentLength();

            // download the file
            InputStream input = new BufferedInputStream(url.openStream(), 8192);

            // Output stream
            OutputStream output = new FileOutputStream("/sdcard/download/downloaded.jpg");

            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) {
        // setting progress percentage
        pDialog.setProgress(Integer.parseInt(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);


    }

}

logcat的

12-12 11:37:10.791 25155 25155 E   AndroidRuntime                               FATAL EXCEPTION: main

12-12 11:37:10.791 25155 25155 E   AndroidRuntime                               Process: com.mycompany.myapp2, PID: 25155

12-12 11:37:10.791 25155 25155 E   AndroidRuntime                               java.lang.IllegalArgumentException: no dialog with id 0 was ever shown via Activity#showDialog

12-12 11:37:10.791 25155 25155 E   AndroidRuntime                               at android.app.Activity.missingDialog(Activity.java:3461)

12-12 11:37:10.791 25155 25155 E   AndroidRuntime                               at android.app.Activity.dismissDialog(Activity.java:3446)
12-12 11:37:10.791 25155 25155 E   AndroidRuntime                               at com.mycompany.myapp2.MainActivity$DownloadFileFromURL.onPostExecute(MainActivity.java:170)
12-12 11:37:10.791 25155 25155 E   AndroidRuntime                               at com.mycompany.myapp2.MainActivity$DownloadFileFromURL.onPostExecute(MainActivity.java)
12-12 11:37:10.791 25155 25155 E   AndroidRuntime                               at android.os.AsyncTask.finish(AsyncTask.java:636)
12-12 11:37:10.791 25155 25155 E   AndroidRuntime                               at android.os.AsyncTask.access$500(AsyncTask.java:177)

Answer 1

删除此行。

public void onClick(DialogInterface dialog, int which) {

来自您的方法.. private final class CancelOnClickListener implements DialogInterface.OnClickListener { public void onClick(DialogInterface dialog, int which) { dismissDialog(progress_bar_type); if (cdrt != null && cdrt.getStatus().equals(AsyncTask.Status.RUNNING)) { cdrt.cancel(true); } }

当你的取消方法被调用时，你正在完成你的活动。它试图处理不存在的视图。所以它应该是这样的。

{{1}}

Answer 2

您正在尝试关闭您无权访问的对话框。关闭AsyncTask类中的对话框。如果您关闭活动中的对话框，那么它将会粉碎

     pDialog = new ProgressDialog(this);
        pDialog.setMessage("Downloading file. Please wait...");
        pDialog.setIndeterminate(false);
        pDialog.setMax(100);
        pDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
        pDialog.setCancelable(true);
        pDialog.setButton("Cancel", new CancelOnClickListener());
        pDialog.show();

应该在AsyncTask类中

按下取消下载按钮时整个应用程序崩溃

2 个答案: