问题描述

android.view.ViewRoot$CalledFromWrongThreadException 异常

我想从服务器中下载图片后并显示出来，当进行下载时，会显示一个进度对话框。使用一个 asynctask 类。运用下面的代码：

    private void startDownload() {    new DownloadFileAsync().execute(imageUrl);    image.setImageBitmap(bitmap);} @Override    protected Dialog onCreateDialog(int id) {        switch (id) {            case DIALOG_DOWNLOAD_PROGRESS:                dialog = new ProgressDialog(this);                dialog.setTitle(""Loading"");                dialog.setMessage(""Please wait..."");                dialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);                dialog.setCancelable(false);                dialog.show();                return dialog;            default:                return null;        }    } class DownloadFileAsync extends AsyncTask<String String String> {     int count;     URL myFileUrl;        @Override        protected void onPreExecute() {            super.onPreExecute();            showDialog(DIALOG_DOWNLOAD_PROGRESS);        }        @Override        protected String doInBackground(String... aurl) {            try {                myFileUrl = new URL(imageUrl);                HttpURLConnection conn = (HttpURLConnection) myFileUrl                        .openConnection();                int lenghtOfFile = conn.getContentLength();                //conn.setDoInput(true);                conn.setConnectTimeout(10000);                conn.setReadTimeout(10000);                conn.connect();                InputStream is = conn.getInputStream();                bmImg = BitmapFactory.decodeStream(is);                bitmap = BitmapFactory.decodeStream((InputStream) new URL(imageUrl)                        .getContent());                bitmap = Bitmap.createScaledBitmap(bitmap 70 70 true);                  byte data[] = new byte[1024];                  System.out.println(""mmmmmmmmmmmm"");                    long total = 0;                    System.out.println(""nnnnnnnnnn"");                    while ((count = ((InputStream) new URL(imageUrl)                    .getContent()).read(data)) != -1) {                        total += count;                        publishProgress(""""+(int)((total*100)/lenghtOfFile));                        for(int l=0;l<4;l++){                        if(listObject.get(l).getImage()!="""")                       image.setImageBitmap(bitmap);                    }}            }            catch(Exception e){                System.out.println(e);}        return null;        }        protected void onProgressUpdate(String... progress) {            dialog.setProgress(Integer.parseInt(progress[0]));        }        @Override        protected void onPostExecute(String unused) {            image.setImageBitmap(bitmap);            dismissDialog(DIALOG_DOWNLOAD_PROGRESS);        }        }

却给出下面的异常：

android.view.ViewRoot$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views. 

我找不出错误所在，请大家帮忙改正。

解决方案

继承自AsyncTask，注意AsyncTask最后的最后一个类型为Bitmap，然后 protected Bitmap doInBackground(String... aurl)函数返回获得的图片
最后在

@Override protected void onPostExecute(Bitmap image) {            image.setImageBitmap(image);            dismissDialog(DIALOG_DOWNLOAD_PROGRESS);        }

还有image.setImageBitmap()不能放到doInBackground()中，因为doInBackground()不是运行在主线程。

解决方案二：
image.setImageBitmap()不能放到doInBackground()中，因为doInBackground()不是运行在主线程中的。