title: Android - How to download a file from a webserver
body: <p>In my app I am downloading a <code>kml</code> file from a webserver. I have set the permission for external storage and internet in my android manifest file. I am new to Android, your help is greatly appreciated.</p>
  
  <p><strong>MainActivity.java</strong></p>
  
  <pre class="lang-java prettyprint-override"><code>package com.example.demo;
  
  import java.io.DataInputStream;
  import java.io.File;
  import java.io.FileOutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.net.MalformedURLException;
  import java.net.URL;
  
  import android.app.Activity;
  import android.os.Bundle;
  import android.os.Environment;
  import android.util.Log;
  import android.view.Menu;
  
  public class MainActivity extends Activity {
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);
  
          DownloadFiles();
      }
  
      public void DownloadFiles(){
          try {
              URL u = new URL("http://www.qwikisoft.com/demo/ashade/20001.kml");
              InputStream is = u.openStream();
              DataInputStream dis = new DataInputStream(is);
  
              byte[] buffer = new byte[1024];
              int length;
  
              FileOutputStream fos = new FileOutputStream(new File(Environment.getExternalStorageDirectory() + "/" + "data/test.kml"));
              while ((length = dis.read(buffer)) &gt; 0) {
                  fos.write(buffer, 0, length);
              }
  
          } catch (MalformedURLException mue) {
              Log.e("SYNC getUpdate", "malformed url error", mue);
          } catch (IOException ioe) {
              Log.e("SYNC getUpdate", "io error", ioe);
          } catch (SecurityException se) {
              Log.e("SYNC getUpdate", "security error", se);
          }
      }
  }
  </code></pre>
  
  <p><strong>Android Manifest File</strong></p>
  
  <pre class="lang-xml prettyprint-override"><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="com.example.demo"
      android:versionCode="1"
      android:versionName="1.0" &gt;
  
      &lt;uses-sdk
          android:minSdkVersion="8"
          android:targetSdkVersion="16" /&gt;
      &lt;uses-permission android:name="android.permission.INTERNET"/&gt;
      &lt;uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/&gt;
  
      &lt;application
          android:allowBackup="true"
          android:icon="@drawable/ic_launcher"
          android:label="@string/app_name"
          android:theme="@style/AppTheme" &gt;
  
          &lt;activity
              android:name="com.example.demo.MainActivity"
              android:label="@string/app_name" &gt;
              &lt;intent-filter&gt;
                  &lt;action android:name="android.intent.action.MAIN" /&gt;
  
                  &lt;category android:name="android.intent.category.LAUNCHER" /&gt;
              &lt;/intent-filter&gt;
          &lt;/activity&gt;
      &lt;/application&gt;
  &lt;/manifest&gt;
  </code></pre>
  
  <p><strong>Logcat error:</strong></p>
  
  <blockquote>
    <p>FATAL EXCEPTION: main
        java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.demo/com.example.demo.MainActivity}: android.os.NetworkOnMainThreadException
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
        at android.app.ActivityThread.access$600(ActivityThread.java:123)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:137)
        at android.app.ActivityThread.main(ActivityThread.java:4424)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
        at dalvik.system.NativeStart.main(Native Method)
        Caused by: android.os.NetworkOnMainThreadException
        at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1099)
        at java.net.InetAddress.lookupHostByName(InetAddress.java:391)
        at java.net.InetAddress.getAllByNameImpl(InetAddress.java:242)
        at java.net.InetAddress.getAllByName(InetAddress.java:220)
        at libcore.net.http.HttpConnection.(HttpConnection.java:71)
        at libcore.net.http.HttpConnection.(HttpConnection.java:50)
        at libcore.net.http.HttpConnection$Address.connect(HttpConnection.java:351)
        at libcore.net.http.HttpConnectionPool.get(HttpConnectionPool.java:86)
        at libcore.net.http.HttpConnection.connect(HttpConnection.java:128)
        at libcore.net.http.HttpEngine.openSocketConnection(HttpEngine.java:308)
        at libcore.net.http.HttpEngine.connect(HttpEngine.java:303)
        at libcore.net.http.HttpEngine.sendSocketRequest(HttpEngine.java:282)
        at libcore.net.http.HttpEngine.sendRequest(HttpEngine.java:232)
        at libcore.net.http.HttpURLConnectionImpl.getResponse(HttpURLConnectionImpl.java:273)
        at libcore.net.http.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:168)
        at java.net.URL.openStream(URL.java:462)
        at com.example.demo.MainActivity.DownloadFiles(MainActivity.java:30)
        at com.example.demo.MainActivity.onCreate(MainActivity.java:24)
        at android.app.Activity.performCreate(Activity.java:4465)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)</p>
  </blockquote>
  
  <p><strong>EDIT</strong></p>
  
  <pre class="lang-java prettyprint-override"><code>package com.example.demo;
  
  import java.io.BufferedInputStream;
  import java.io.FileOutputStream;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.net.URL;
  import java.net.URLConnection;
  
  import android.app.Activity;
  import android.app.Dialog;
  import android.app.ProgressDialog;
  import android.os.AsyncTask;
  import android.os.Bundle;
  import android.os.Environment;
  import android.util.Log;
  
  public class MainActivity extends Activity {
  
      private ProgressDialog pDialog;
      public static final int progress_bar_type = 0;
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);
  
          new DownloadFileFromURL().execute("http://www.qwikisoft.com/demo/ashade/20001.kml");
      }
  
      @Override
      protected Dialog onCreateDialog(int id) {
          switch (id) {
              case progress_bar_type: // we set this to 0
                  pDialog = new ProgressDialog(this);
                  pDialog.setMessage("Downloading file. Please wait...");
                  pDialog.setIndeterminate(false);
                  pDialog.setMax(100);
                  pDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
                  pDialog.setCancelable(true);
                  pDialog.show();
                  return pDialog;
              default:
                  return null;
          }
      }
  
      class DownloadFileFromURL extends AsyncTask&lt;String, String, String&gt; {
  
          /**
           * Before starting background thread Show Progress Bar Dialog
           **/
          @Override
          protected void onPreExecute() {
              super.onPreExecute();
              showDialog(progress_bar_type);
          }
  
          /**
           * Downloading file in background thread
           **/
          @Override
          protected String doInBackground(String... f_url) {
              int count;
              try {
                  URL url = new URL(f_url[0]);
                  URLConnection conection = url.openConnection();
                  conection.connect();
  
                  // this will be useful so that you can show a tipical 0-100%
                  // progress bar
                  int lenghtOfFile = conection.getContentLength();
  
                  // download the file
                  InputStream input = new BufferedInputStream(url.openStream(),
                          8192);
  
                  // Output stream
                  OutputStream output = new FileOutputStream(Environment
                          .getExternalStorageDirectory().toString()
                          + "/data/downloadedfile.kml");
  
                  byte data[] = new byte[1024];
  
                  long total = 0;
  
                  while ((count = input.read(data)) != -1) {
                      total += count;
                      // publishing the progress....
                      // After this onProgressUpdate will be called
                      publishProgress("" + (int) ((total * 100) / lenghtOfFile));
  
                      // writing data to file
                      output.write(data, 0, count);
                  }
  
                  // flushing output
                  output.flush();
  
                  // closing streams
                  output.close();
                  input.close();
              } catch (Exception e) {
                  Log.e("Error: ", e.getMessage());
              }
  
              return null;
          }
  
          /**
           * Updating progress bar
           **/
          protected void onProgressUpdate(String... progress) {
              // setting progress percentage
              pDialog.setProgress(Integer.parseInt(progress[0]));
          }
  
          /**
           * After completing background task Dismiss the progress dialog
           **/
          @Override
          protected void onPostExecute(String file_url) {
              // dismiss the dialog after the file was downloaded
              dismissDialog(progress_bar_type);
          }
      }
  }
  </code></pre>
  
  <p>When I run this code in the emulator the code still does not work - the file is not getting downloaded.</p>