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NetworkOnMainThreadException android activity [duplicate]

This question already has answers here:
How can I fix 'android.os.NetworkOnMainThreadException'?
(66 answers)
Closed 6 years ago.
I am using this code to retrieve website data inside android activity.It is throwing android.os.networkonmainthreadexception
try
{
URL url = new URL("https://enigmatic-woodland-35608.herokuapp.com/pager.json");
URLConnection tc = url.openConnection();
BufferedReader in = new BufferedReader(new InputStreamReader(
tc.getInputStream()));
String line, newl = " ";
while ((line = in.readLine()) != null) {
newl += line.trim();
}
System.out.println("newl" + newl.trim());
} catch (Exception e) {
Log.e("exception", e.toString());
}
Please give me a possible solution..

Network oprations/call cannot be done in main thread. You need to run it from another thread , asynchronous task or an intent service
Note : All UI opration shoud be done onPostExecute,onPreExecute
The below code may help you to solve.
Call AsyncTask where you want
new PagerAsyncTask().execute();
class PagerAsyncTask extends AsyncTask<String,Void,String>{
#Override
protected void onPreExecute() {
super.onPreExecute();
}
#Override
protected String doInBackground(String... params) {
StringBuilder sb=null;
BufferedReader reader=null;
String serverResponse=null;
try {
URL url = new URL(""https://enigmatic-woodland-35608.herokuapp.com/pager.json"");
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
connection.setConnectTimeout(5000);
connection.setRequestMethod("GET");
connection.connect();
int statusCode = connection.getResponseCode();
//Log.e("statusCode", "" + statusCode);
if (statusCode == 200) {
sb = new StringBuilder();
reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
String line;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
}
connection.disconnect();
if (sb!=null)
serverResponse=sb.toString();
} catch (Exception e) {
e.printStackTrace();
} finally {
if (reader != null) {
try {
reader.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
return serverResponse;
}
#Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
//All your UI operation can be performed here
//Response string can be converted to JSONObject/JSONArray like
JSONObject response=new JSONObject(s);
System.out.println(s);
}
}

Network operations can involve unpredictable delays. To prevent this
from causing a poor user experience, always perform network operations
on a separate thread from the UI.
Please check the doc.

I am using a NetworkOps util in my projects. Try it:
import android.content.Context;
import android.net.Uri;
import android.util.Log;
import com.csehelper.variables.Constants;
import com.csehelper.variables.Keys;
import com.csehelper.variables.Url;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.HttpURLConnection;
import java.net.ProtocolException;
import java.net.SocketTimeoutException;
import java.net.URL;
import java.util.ArrayList;
public class NetworkOps {
public final String EXCEPTION = "~Exception~";
/****************************
* Method to Grab Source
****************************/
public static String GrabSource(String URL) {
return PostData(URL, null);
}
/**
* *****************************************
* Method to Grab Source code from URL
* Posting Data
* *****************************************
*/
private static String PostData(String url, Uri.Builder uribuilder) {
String Source;
HttpURLConnection.setFollowRedirects(false);
HttpURLConnection urlConnection = null;
try {
urlConnection = (HttpURLConnection) new URL(url).openConnection();
urlConnection.setDoOutput(true);
urlConnection.setConnectTimeout(10000);
if(uribuilder != null) {
String query = uribuilder.build().getEncodedQuery();
OutputStream os = urlConnection.getOutputStream();
BufferedWriter writer = new BufferedWriter(
new OutputStreamWriter(os, "UTF-8"));
writer.write(query);
writer.flush();
writer.close();
os.close();
}
urlConnection.connect();
if (urlConnection.getResponseCode() == HttpURLConnection.HTTP_OK) {
String line;
StringBuilder builder = new StringBuilder();
InputStreamReader isr = new InputStreamReader(
urlConnection.getInputStream());
BufferedReader reader = new BufferedReader(isr);
while ((line = reader.readLine()) != null) {
builder.append(line);
}
Source = builder.toString();
} else {
Source = EXCEPTION + "Server unreachable. Check network connection.";
}
} catch (SocketTimeoutException e) {
Source = EXCEPTION + "Connection timed out.";
} catch (java.net.UnknownHostException e) {
Source = EXCEPTION + Constants.EXCEPTION_NO_NET;
} catch (ArrayIndexOutOfBoundsException e) {
Source = EXCEPTION + "Server error";
} catch (ProtocolException e) {
Source = EXCEPTION + "Protocol error";
} catch (IOException e) {
Source = EXCEPTION + "Server unreachable. Check network connection.";
} catch (Exception e) {
Source = EXCEPTION + "Error:" + e.toString() + " - "
+ e.getMessage();
e.printStackTrace();
} finally {
if (urlConnection != null) urlConnection.disconnect();
}
return Source;
}
}
Call these Static Functions from AsyncTask:
/*********************************
* AsyncTask to GrabSource
********************************/
class AsyncTask_GrabSource extends AsyncTask<Void, Void, Void> {
String Source = null;
String url = "https://enigmatic-woodland-35608.herokuapp.com/pager.json";
#Override
protected void onPreExecute() {
//Runs on Main Thread. You can access your UI elements here.
}
#Override
protected Void doInBackground(Void... params) {
// Don't access any UI elements from this function
Source = NetworkOps.GrabSource(this.url);
return null;
}
#Override
protected void onPostExecute(Void result) {
if (Source != null) {
if (!Source.contains(EXCEPTION)) {
//Show Error Message or do whatever you want
} else {
//Do Whatever with your Grabbed Sourcecode.
// This function runs on UI Thread, so you can update UI elements here
}
}
}
You can also post data with the function PostData. In method doInBackground, add this:
Uri.Builder builder = new Uri.Builder()
.appendQueryParameter("key", "value")
.appendQueryParameter("key2", "value2");
Source = NetworkOps.PostData(getApplicationContext(), url, builder);

Sending data via post without using apache classes

I want to send data to a php server without using http classes if this is possible; ie the org.apache.http package.
My code until now
import android.content.Context;
import android.os.AsyncTask;
import android.widget.Toast;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
public class serverHandler extends AsyncTask<String,Integer,String> {
Context context;
ByteArrayOutputStream content;
public serverHandler(Context context){
this.context = context;
}
#Override
protected String doInBackground(String... params) {
InputStream input = null;
HttpURLConnection connection = null;
try {
URL url = new URL(params[0]);
connection = (HttpURLConnection) url.openConnection();
connection.connect();
// expect HTTP 200 OK, so we don't mistakenly save error report
// instead of the file
if (connection.getResponseCode() != HttpURLConnection.HTTP_OK) {
return "Server returned HTTP " + connection.getResponseCode()
+ " " + connection.getResponseMessage();
}
// this will be useful to display download percentage
// might be -1: server did not report the length
int fileLength = connection.getContentLength();
// download the file
input = connection.getInputStream();
byte buff[] = new byte[4096];
content = new ByteArrayOutputStream();
long total = 0;
int count;
while ((count = input.read(buff)) != -1) {
// allow canceling with back button
content.write(buff,0,count);
total += count;
}
} catch (Exception e) {
return e.toString();
} finally {
try {
if (input != null)
input.close();
} catch (IOException ignored) {
}
if (connection != null)
connection.disconnect();
}
return new String(content.toByteArray());
}
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
String country = "No Country";
if(result.length()==0){
Toast.makeText(context, "No Data", Toast.LENGTH_LONG).show();
return;
}
try{
JSONObject data = new JSONObject(result);
JSONObject address = data.getJSONObject("address");
country = address.getString("country");
}
catch(JSONException e){
e.printStackTrace();
}
Toast.makeText(context,country,Toast.LENGTH_LONG).show();
}
}
I know that sending POST data for sure will need some HTTP service. What I'm asking for is if it's possible to send the data without importing any of the org.apache.http packages. All the SO answers and the examples I found on the internet are using this package. And I, for some reason, don't want to use it if this is possible.

You can use square's retrofit library for POST data to server.

Android: Download from URL

i follow more explain in this site for download mp3 or picture from URL , I follow more method and try to write my method but when i run application it stop.
I make method to query download when click
also put permission for INTERNET & WRITE_EXTERNAL_STORAGE
put the problem is still
this method is download
public static void downloadMain(){
File fileToSave = null;
String scrPath ="http://***";
BufferedInputStream bis;
BufferedOutputStream bos;
fileToSave = new File(Environment.getExternalStorageDirectory().getPath() +"/"+ "A"+"/");
if (!fileToSave.exists())
fileToSave.mkdirs();
fileToSave = new File(Environment.getExternalStorageDirectory().getPath() +"/"+ "A" +"/" + "h"+"/");
if (!fileToSave.exists())
fileToSave.mkdirs();
File file = new File (fileToSave,"***.mp3");
try{
URL url = new URL(scrPath+"***.mp3");
URLConnection ucon = url.openConnection();
ucon.connect();
bis=new BufferedInputStream(ucon.getInputStream());
bos = new BufferedOutputStream(new FileOutputStream(file));
bis=new BufferedInputStream(url.openStream());
byte[] data = new byte[1024];
int a =0;
while(true){
int k = bis.read(data);
if(k==-1){
bis.close();
bos.flush();
bos.close();
break;
}
bos.write(data, 0, k);
a+=k;
}
}catch(IOException e){}
}

I have three main perplexity about your program:
Do you run the following code in an asynctask? (this must run asincronusly otherwise it will block)
Why it loop infinitly?
You couldn't open an url or a file named with a '*' inside of it
Edit:
You must run the download method asincronusly otherwise it wouldn't work, interaction with filesystem and network couldn't be done in the main thread
Edit2:
AsyncTask should be something like this
private class DownloadTask extends AsyncTask<String, Integer, String> {
private Context context;
public DownloadTask(Context context) {
this.context = context;
}
#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, so we don't mistakenly save error report
// instead of the file
if (connection.getResponseCode() != HttpURLConnection.HTTP_OK) {
return "Server returned HTTP " + connection.getResponseCode()
+ " " + connection.getResponseMessage();
}
// download the file
input = connection.getInputStream();
output = new FileOutputStream("/sdcard/file_name.extension");//put here your path and your mkdirs
byte data[] = new byte[4096];
long total = 0;
int count;
while ((count = input.read(data)) != -1) {
total += count;
output.write(data, 0, count);
}
} 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) {
if (result != null)
Toast.makeText(context,"Download error: "+result, Toast.LENGTH_LONG).show();
else
Toast.makeText(context,"File downloaded", Toast.LENGTH_SHORT).show();
}
}
And you shoould call it like this
DownloadTask downloadTask = new DownloadTask(YourActivity.this);
downloadTask.execute("the url to the file you want to download");
You could also have a look at this answer

HttpURLConnection : Server return HTTP 403 Forbidden

I want to download a file with his url.
I use an AsyncTask with HttpURLConnection but when I get response code, server return error 403.
I use the HttpURLConnection in doInBackground.
Code :
#Override
protected String doInBackground(String... sUrl) {
InputStream input = null;
OutputStream output = null;
HttpURLConnection connection = null;
try {
ext = FilenameUtils.getExtension(sUrl[0]);
fileName = FilenameUtils.getBaseName(sUrl[0]);
Log.i("Brieg", "storage : /storage/emulated/0/" + fileName + "." + ext);
URL url = new URL(sUrl[0]);
connection = (HttpURLConnection) url.openConnection();
connection.connect();
if (connection.getResponseCode() != HttpURLConnection.HTTP_OK) {
return "Server returned HTTP " + connection.getResponseCode() + " " + connection.getResponseMessage();
}
int fileLength = connection.getContentLength();
input = connection.getInputStream();
output = new FileOutputStream("/storage/emulated/0/" + fileName + "." + ext);
byte data[] = new byte[4096];
long total = 0;
int count;
while ((count = input.read(data)) != -1) {
if (isCancelled()) {
input.close();
return null;
}
total += count;
if (fileLength > 0)
publishProgress((int) (total * 100 / fileLength));
output.write(data, 0, count);
}
}
catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
finally {
try {
if (output != null)
output.close();
if (input != null)
input.close();
}
catch (IOException ignored) {
}
if (connection != null)
connection.disconnect();
}
return null;
}
Where is the problem ?
Knowing that when I get URL in a browser, the download file starts up.
Thank you in advance.

The cause should be you are not setting User-Agent:
connection = (HttpURLConnection) url.openConnection();
connection.addRequestProperty("User-Agent", "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:221.0) Gecko/20100101 Firefox/31.0"); // add this line to your code
connection.connect();

HTTP 403 Forbidden
Where is the problem
Error code says it clearly - you are forbidden from accessing the resource on the server. Maybe you need to authenticate first, maybe you are simply banned. Many possibilities.

How to retry in the async task downloader?

public class PreviewDownload extends AsyncTask<String, Void, String> {
public static final String TAG = "PreviewDownload";
public String inputPath = null;
public String outputFolder = null;
public IRIssue issue = null;
#Override
protected String doInBackground(String... parms) {
InputStream input = null;
OutputStream output = null;
HttpURLConnection connection = null;
issue = Broker.model.issueDataStore.getIRIssue(parms[0]);
outputFolder = IRConstant.issueFolder(issue.year, issue.month, issue.day, issue.pubKey);
try {
inputPath = IRConstant.downloadFile(issue.year, issue.month, issue.day, issue.pubKey, "preview", "0");
URL url = new URL(inputPath);
Log.d (TAG,"input: " + inputPath);
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(outputFolder + "/preview.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 outputFolder;
}
#Override
protected void onPostExecute(String outputFolder) {
// TODO Auto-generated method stub
super.onPostExecute(outputFolder);
if (outputFolder != null) {
File zipFile = new File (outputFolder + "/preview.zip");
if (Utils.unzip(outputFolder,outputFolder + "/preview.zip" )) {
zipFile.delete();
issue.isThumbDownloaded = 1;
} else {
issue.isThumbDownloaded = 0;
}
} else {
Toast.makeText(Broker.launcherActivity.getBaseContext(), R.string.wordCantDownload, Toast.LENGTH_LONG).show();
issue.isThumbDownloaded = 0;
}
issue.updateProgress(issue.progress);
}
}
Here is the downloader I implemented , the problem is , when the network lost, the output become null and show error message, however, if I would like to retry two times before showing error message, are there any way to do this? If I perfer not to pass in an object instead of string ,is it not recommended? thanks

What prevents you from re-instanciating and re-executing a "Downloader" from your catch blocks in case of errors ?
You could use a single common shared object between dowloader instances to count the attempts, or better, pass a parameter to each of them. In the catch block, you would then retry if you didn't reach the limit, and increase the value passed to a new downloader... Something recursive.

int expectedLength = connection.getContentLength();
can you compare with the expectedLength & downloaded length and retry?