连接断开后,异步任务下载器将失败 [英] Async task downloader will fail when the connection lost
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问题描述
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import android.os.AsyncTask;
import android.util.Log;
public class IssueDownload extends AsyncTask<IRPack, Void, IRPack> {
public static final String TAG = "IssueDownload";
public String path = null;
public IRIssue issue = null;
@Override
protected IRPack doInBackground(IRPack... parms) {
InputStream input = null;
OutputStream output = null;
HttpURLConnection connection = null;
issue = Broker.model.issueDataStore.getIRIssue(parms[0].pubKey);
try {
File downloadFile = new File(IRConstant.issueFolder(issue.year, issue.month, issue.day, issue.pubKey) + "/" + parms[0].currPage + ".zip");
if (!downloadFile.exists()) {
path = IRConstant.downloadFile(issue.year, issue.month, issue.day, issue.pubKey, "content", ""
+ parms[0].currPage);
URL url = new URL(path);
Log.d (TAG,"input: " + path);
connection = (HttpURLConnection) url.openConnection();
connection.connect();
if (connection.getResponseCode() != HttpURLConnection.HTTP_OK)
return null;
// return "Server returned HTTP " + connection.getResponseCode()
// + " " + connection.getResponseMessage();
// download the file
input = connection.getInputStream();
output = new FileOutputStream(IRConstant.issueFolder(issue.year, issue.month, issue.day, issue.pubKey) + "/" + parms[0].currPage + ".zip");
Log.d (TAG,"output: " + output);
byte data[] = new byte[1024];
int count;
while ((count = input.read(data)) != -1) {
output.write(data, 0, count);
}
}
} catch (Exception e) {
// return e.toString();
return null;
} finally {
try {
if (output != null)
output.close();
if (input != null)
input.close();
} catch (IOException ignored) {
}
if (connection != null)
connection.disconnect();
}
return parms[0];
}
@Override
protected void onPostExecute(IRPack pack) {
// TODO Auto-generated method stub
super.onPostExecute(pack);
pack.downloadPackComplete(); // Unzip completed pack
}
}
我目前正在使用此下载文件class,问题是,当我失去连接时,它只会失败并退出应用程序,请尝试以任何方式包含try and error:如果失败则重试连接,如果重试2次后连接未成功,则进行祝酒。谢谢
I am currently using this download class , the problem is , when I lost connection it simply fail and exit the apps, please are there any way to include try and error : retry connection if fail , if connect is not success after retry 2 times., then make a toast. Thanks
推荐答案
要做的第一件事是在发出请求之前检查连接性。
the first thing to do is check connectivity before making requests.
ConnectivityManager connMgr = (ConnectivityManager)
getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();
if (networkInfo != null && networkInfo.isConnected()) {
// fetch data
} else {
// display error
}
第二个:
private String downloadUrl(String myurl) throws IOException {
InputStream is = null;
// Only display the first 500 characters of the retrieved
// web page content.
int len = 500;
try {
URL url = new URL(myurl);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setReadTimeout(10000 /* milliseconds */);
conn.setConnectTimeout(15000 /* milliseconds */);
conn.setRequestMethod("GET");
conn.setDoInput(true);
// Starts the query
conn.connect();
int response = conn.getResponseCode();
Log.d(DEBUG_TAG, "The response is: " + response);
is = conn.getInputStream();
// Convert the InputStream into a string
String contentAsString = readIt(is, len);
return contentAsString;
// Makes sure that the InputStream is closed after the app is
// finished using it.
} finally {
if (is != null) {
is.close();
}
}
}
包含部分代码如上所示抛出IOException
Make the part of your code throw an IOException as shown above
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