我的 android 应用程序在下载文件时总是卡住，直到下载完成。但是，下载线程是从 AyncTask 继承的，它在后台。任何人都可以看看有什么问题，我该如何修改代码以使其正常工作？
private class DownloadFileTask extends AsyncTask<String, Integer, String> {
File destFile;
private boolean openAfterDownload;
private Exception failure;
public DownloadFileTask(boolean openAfterDownload) {
this.openAfterDownload = openAfterDownload;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
downloadDialog.setMessage(getString(R.string.downloading));
downloadDialog.show();
}
@Override
protected String doInBackground(String... params) {
try {
String url = params[0];
LOG.debug("Downloading: " + url);
String fileName = url.substring(url.lastIndexOf('/') + 1);
HttpParams httpParams = new BasicHttpParams();
DefaultHttpClient client = new DefaultHttpClient(httpParams);
client.getCredentialsProvider().setCredentials(
new AuthScope(null, -1),
new UsernamePasswordCredentials(user, password));
HttpGet get = new HttpGet(url);
HttpResponse response = client.execute(get);
if (response.getStatusLine().getStatusCode() == 200) {
File destFolder = new File(config.getDownloadsFolder());
if (!destFolder.exists()) {
destFolder.mkdirs();
}
/**
* Make sure we always store downloaded files as .epub,
* so they show up in scans later on.
*/
if ( ! fileName.endsWith(".epub") ) {
fileName = fileName + ".epub";
}
destFile = new File(destFolder, URLDecoder.decode(fileName));
if (destFile.exists()) {
destFile.delete();
}
// lenghtOfFile is used for calculating download progress
long lenghtOfFile = response.getEntity().getContentLength();
if(lenghtOfFile>=config.getAvailableSpace())
{
this.failure = new Exception("not enough space");
return null;
}
// this is where the file will be seen after the download
FileOutputStream f = new FileOutputStream(destFile);
try {
// file input is from the url
InputStream in = response.getEntity().getContent();
// here's the download code
byte[] buffer = new byte[1024];
int len1 = 0;
long total = 0;
while ((len1 = in.read(buffer)) > 0) {
// Make sure the user can cancel the download.
if (isCancelled()) {
return null;
}
total += len1;
publishProgress((int) ((total * 100) / lenghtOfFile));
f.write(buffer, 0, len1);
}
} finally {
f.close();
}
} else {
this.failure = new RuntimeException(response
.getStatusLine().getReasonPhrase());
LOG.error("Download failed: "
+ response.getStatusLine().getReasonPhrase());
}
} catch (Exception e) {
Toast.makeText(getActivity(), e.getMessage() + "1",
Toast.LENGTH_LONG).show();
LOG.error("Download failed.", e);
this.failure = e;
}
return null;
}