android doInBackground

Question

大家好 如何让这段代码等到它完成下载图像

有什么可以替换doInBackground(URL... paths)让它等待下载然后继续其余的代码

private class DownloadImageTask extends AsyncTask<URL, Integer, Bitmap> {
    // This class definition states that DownloadImageTask will take String
    // parameters, publish Integer progress updates, and return a Bitmap
    protected Bitmap doInBackground(URL... paths) {
        URL url;
        try {
            url = paths[0];
            HttpURLConnection connection = (HttpURLConnection) url
                    .openConnection();
            int length = connection.getContentLength();
            InputStream is = (InputStream) url.getContent();
            byte[] imageData = new byte[length];
            int buffersize = (int) Math.ceil(length / (double) 100);
            int downloaded = 0;
            int read;
            while (downloaded < length) {
                if (length < buffersize) {
                    read = is.read(imageData, downloaded, length);
                } else if ((length - downloaded) <= buffersize) {
                    read = is.read(imageData, downloaded, length
                            - downloaded);
                } else {
                    read = is.read(imageData, downloaded, buffersize);
                }
                downloaded += read;
                publishProgress((downloaded * 100) / length);
            }
            Bitmap bitmap = BitmapFactory.decodeByteArray(imageData, 0,
                    length);
            if (bitmap != null) {
                Log.i(TAG, "Bitmap created");
            } else {
                Log.i(TAG, "Bitmap not created");
            }
            is.close();
            return bitmap;
        } catch (MalformedURLException e) {
            Log.e(TAG, "Malformed exception: " + e.toString());
        } catch (IOException e) {
            Log.e(TAG, "IOException: " + e.toString());
        } catch (Exception e) {
            Log.e(TAG, "Exception: " + e.toString());
        }
        return null;

    }

    protected void onPostExecute(Bitmap result) {
        String name = ImageLink.substring(ImageLink
                .lastIndexOf("/") + 1);
        if (result != null) {
            hasExternalStoragePublicPicture(name);
            saveToSDCard(result, name);
            isImage = true;

        } else {
            isImage = false;

        }
    }
}

Answer 1

doInBackground()）在后台执行。 waits for the download和continues with the rest of the code为onPostExecute()的部分。这是你可能要求的功能。

Answer 2

关于AsyncTask的要点是Activity中的主要代码（创建AsyncTask）不等待。异步是异步的缩写 - 这意味着在没有预先确定的时间范围内发生的事情。

如果您希望在其他代码可以执行之前完成下载或多次下载，那么您需要以同步方式执行操作（在Android活动中不太好），或者您需要编写代码以等待回调。