如何同时doInBackground在AsyncTask的运行对话框辞退？

问题描述

我尝试了doInBackGround的AsyncTask方法运行时从mainthread取消对话框。当我下载一张照片，一个进度对话框弹出，当它完成下载我dismis（）在onPostExecute对话框。如果连接速度慢，该对话框了一段时间，直到有一个超时错误或完成下载我不能取消它。如何使用后退按钮所以主线程可以访问。这里是我的code样子：

 私有类DownloadImageTask扩展的AsyncTask＆LT;弦乐，太虚，位图＆GT; {
    在preExecute保护无效（）{
        //这块code似乎不工作
        progressDialog = ProgressDialog.show（上下文，，
                图像加载，真正的）;
    }    保护位图doInBackground（字符串的URL ...）{
        尝试{
            在的InputStream =新的java.net.URL（urldisplay）.openStream（）;
            mIcon11 = BitmapFactory.de codeStream（中）;
        }赶上（例外五）{
            Log.e（错误，e.getMessage（））;
            e.printStackTrace（）;
        }
        返回mIcon11;
    }    保护无效onPostExecute（位图结果）{
        //bmImage.setImageBitmap(result）;
        progressDialog.dismiss（）;
        的someMethod（结果）;    }
}
 

解决方案

使用一个撤销的进度对话框，传递一个取消监听器的进度对话框和方法中取消任务，例如：

 上preExecute保护无效（）{
    progressDialog = ProgressDialog.show（活动，搜索文件，扫描...，真实的，真实的，
            新DialogInterface.OnCancelListener（）{
                @覆盖
                公共无效onCancel（DialogInterface对话）{
                    //当取消对话框，需要明确取消任务，否则它在后台继续运行
                    取消（真）;
                }
            }
    ）;    progressDialog.setProgressStyle（ProgressDialog.STYLE_SPINNER）;
}
 

I am trying to cancel a dialog from the mainthread while the 'doInBackGround' method of AsyncTask is running. While I am downloading a photo, a progress dialog pops up and when it is finished downloading I dismis() the dialog in onPostExecute. If the connection is slow, the dialog is up for a while and I cannot cancel it until there is a timeout error or it finishes downloading. How do I use the back-button so the main thread can access. Here is what my code looks like:

private class DownloadImageTask extends AsyncTask<String, Void, Bitmap> {


    protected void onPreExecute() {
        //this piece code doesn't seem to work
        progressDialog = ProgressDialog.show(context, "",
                "Image loading", true);
    }

    protected Bitmap doInBackground(String... urls) {
        try {
            InputStream in = new java.net.URL(urldisplay).openStream();
            mIcon11 = BitmapFactory.decodeStream(in);
        } catch (Exception e) {
            Log.e("Error", e.getMessage());
            e.printStackTrace();
        }
        return mIcon11;
    }

    protected void onPostExecute(Bitmap result) {
        //bmImage.setImageBitmap(result);
        progressDialog.dismiss();
        someMethod(result);

    }
}

解决方案

Use a cancellable progress dialog, pass in a cancel listener to the progress dialog and cancel the task within that method, eg

protected void onPreExecute() {
    progressDialog = ProgressDialog.show(activity, "Searching files", "Scanning...", true, true,
            new DialogInterface.OnCancelListener() {
                @Override
                public void onCancel(DialogInterface dialog) {
                    // When dialog in cancelled, need to explicitly cancel task otherwise it keeps on running
                    cancel(true);
                }
            }
    );

    progressDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
}

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