我创建了一个异步任务,可以从网络服务器下载.csv文件。不幸的是,该文件存储在正确的目录中,但它是空的。
这是我的异步任务
public class DownloadTask extends AsyncTask<String, Integer, String> {
private Context context;
private ProgressDialog prgDialog = null;
private PowerManager.WakeLock mWakeLock;
private String fileName;
public DownloadTask(Context context, String fileName) {
this.context = context;
this.fileName = fileName;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
/* Take CPU lock to prevent CPU from going off if the user
presses the power button during download */
PowerManager pm = (PowerManager) context.getSystemService(Context.POWER_SERVICE);
mWakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, getClass().getName());
mWakeLock.acquire();
prgDialog = new ProgressDialog(context);
prgDialog.setMessage(context.getString(R.string.prgDialogMessage));
prgDialog.setCancelable(false); // Not able to cancel until programmatically called
prgDialog.show();
}
@Override
protected String doInBackground(String... sUrl) {
InputStream input = null;
OutputStream output = null;
HttpURLConnection connection = null;
try {
URL url = new URL(sUrl[0]);
connection = (HttpURLConnection) url.openConnection();
connection.connect();
/* Expect HTTP 200 OK, to make sure the app doesn't mistakenly save an error report
instead of the file */
if (connection.getResponseCode() != HttpURLConnection.HTTP_OK) {
return R.string.errorServer + connection.getResponseCode()
+ " " + connection.getResponseMessage();
}
// Download the file
input = connection.getInputStream();
// Get dynamic storage directory
File myFile= new File(Environment.getExternalStorageDirectory(), fileName);
output = new FileOutputStream(myFile);
} catch (Exception e) {
return e.toString();
} finally {
try {
if (output != null)
output.close();
if (input != null)
input.close();
} catch (IOException ignored) {
}
if (connection != null)
connection.disconnect();
}
return null;
}
@Override
protected void onPostExecute(String result) {
mWakeLock.release();
if (prgDialog != null) {
if (prgDialog.isShowing()) {
prgDialog.dismiss();
}
prgDialog = null;
}
if (result != null) {
Toast.makeText(context,R.string.errorDownload + result, Toast.LENGTH_LONG).show();
}
}
}
我没有收到任何错误消息或例外情况,因此我不知道问题出在哪里。我将URL与async任务的execute()函数一起交付。 谢谢你的帮助!