Android - How to download a file from a webserver
AndroidWebserverKmlAndroid Problem Overview
In my app I am downloading a kml 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.
MainActivity.java
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)) > 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);
}
}
}
Android Manifest File
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.demo"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="16" />
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.example.demo.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
Logcat error:
> 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.
EDIT
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<String, String, String> {
/**
* 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);
}
}
}
When I run this code in the emulator the code still does not work - the file is not getting downloaded.
Android Solutions
Solution 1 - Android
Using Async task
call when you want to download file : new DownloadFileFromURL().execute(file_url);
public class MainActivity extends Activity {
// Progress Dialog
private ProgressDialog pDialog;
public static final int progress_bar_type = 0;
// File url to download
private static String file_url = "http://www.qwikisoft.com/demo/ashade/20001.kml";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
new DownloadFileFromURL().execute(file_url);
}
/**
* Showing Dialog
* */
@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;
}
}
/**
* Background Async Task to download file
* */
class DownloadFileFromURL extends AsyncTask<String, String, String> {
/**
* 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 connection = url.openConnection();
connection.connect();
// this will be useful so that you can show a tipical 0-100%
// progress bar
int lenghtOfFile = connection.getContentLength();
// download the file
InputStream input = new BufferedInputStream(url.openStream(),
8192);
// Output stream
OutputStream output = new FileOutputStream(Environment
.getExternalStorageDirectory().toString()
+ "/2011.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);
}
}
}
if not working in 4.0 then add:
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
Solution 2 - Android
Simple kotlin version
fun download(link: String, path: String) {
URL(link).openStream().use { input ->
FileOutputStream(File(path)).use { output ->
input.copyTo(output)
}
}
}
> is there anyway to get the download progress or downloaded size from this method ?
This is the same realization as defined in InputStream.copyTo, but with progress
/*inline*/ fun download(link: String, path: String, progress: ((Long, Long) -> Unit)? = null): Long {
val url = URL(link)
val connection = url.openConnection()
connection.connect()
val length = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) connection.contentLengthLong else
connection.contentLength.toLong()
url.openStream().use { input ->
FileOutputStream(File(path)).use { output ->
val buffer = ByteArray(DEFAULT_BUFFER_SIZE)
var bytesRead = input.read(buffer)
var bytesCopied = 0L
while (bytesRead >= 0) {
output.write(buffer, 0, bytesRead)
bytesCopied += bytesRead
progress?.invoke(bytesCopied, length)
bytesRead = input.read(buffer)
}
return bytesCopied
}
}
}
An example of usage:
val handler = object : Handler(Looper.getMainLooper()) {
override fun handleMessage(msg: Message) {
// length may be negative because it is based on http header
val (progress, length) = msg.obj as Pair<Long, Long>
}
}
// call this outside of main thread
val totalSize = download("http://example.site/path/to/file", "path/to/file") { progress, length ->
// handling the result on main thread
handler.sendMessage(handler.obtainMessage(0, progress to length))
}
Solution 3 - Android
I would recommend using Android DownloadManager
DownloadManager downloadmanager = (DownloadManager) getSystemService(Context.DOWNLOAD_SERVICE);
Uri uri = Uri.parse("http://www.example.com/myfile.mp3");
DownloadManager.Request request = new DownloadManager.Request(uri);
request.setTitle("My File");
request.setDescription("Downloading");
request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
request.setVisibleInDownloadsUi(false);
request.setDestinationUri(Uri.parse("file://" + folderName + "/myfile.mp3"));
downloadmanager.enqueue(request);
Solution 4 - Android
Download File Usind Download Manager
DownloadManager downloadmanager = (DownloadManager) getSystemService(Context.DOWNLOAD_SERVICE);
Uri uri = Uri.parse("https://www.globalgreyebooks.com/content/books/ebooks/game-of-life.pdf");
DownloadManager.Request request = new DownloadManager.Request(uri);
request.setTitle("My File");
request.setDescription("Downloading");//request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS,"game-of-life");
downloadmanager.enqueue(request);
Solution 5 - Android
It is bad practice to perform network operations on the main thread, which is why you are seeing the NetworkOnMainThreadException. It is prevented by the policy. If you really must do it for testing, put the following in your OnCreate:
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
Please remember that is is very bad practice to do this, and should ideally move your network code to an AsyncTask or a Thread.
Solution 6 - Android
Mr.Iam4fun your code answer here..You will use thread...
findViewById(R.id.download).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
new Thread(new Runnable() {
public void run() {
DownloadFiles();
}
}).start();
And,then..
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))>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);
}
}
}
Solution 7 - Android
use AsyncTask and
put your download file code in doinbackground of it..
android don't allow anymore to do heavy tasks on main thread to avoid ANR(Application not responding) error
Solution 8 - Android
You should use an AsyncTask (or other way to perform a network operation on background).
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//create and execute the download task
MyAsyncTask async = new MyAsyncTask();
async.execute();
}
private class MyAsyncTask extends AsyncTask<Void, Void, Void>{
//execute on background (out of the UI thread)
protected Long doInBackground(URL... urls) {
DownloadFiles();
}
}
More info about AsyncTask on Android documentation
Hope it helps.
Solution 9 - Android
Run these codes in thread or AsyncTask. In order to avoid duplicated callings of same _url(one time for getContentLength(), one time of openStream()), use IOUtils.toByteArray of Apache.
void downloadFile(String _url, String _name) {
try {
URL u = new URL(_url);
DataInputStream stream = new DataInputStream(u.openStream());
byte[] buffer = IOUtils.toByteArray(stream);
FileOutputStream fos = mContext.openFileOutput(_name, Context.MODE_PRIVATE);
fos.write(buffer);
fos.flush();
fos.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
return;
} catch (IOException e) {
e.printStackTrace();
return;
}
}
Solution 10 - Android
Apart from using AsyncTask you can put the operation in runnable-
Runnable r=new Runnable()
{
public void run()
{
///-------network operation code
}
};
//--------call r in this way--
Thread t=new Thread(r);`enter code here`
t.start();
Also put the UI work in a handler..such as updating a textview etc..
Solution 11 - Android
Here is the code help you to download file from server at the same time you can see the progress of downloading on your status bar.
See the functionality in below image of my code:
STEP - 1 : Create on DownloadFileFromURL.java class file to download file content from server. Here i create an asynchronous task to download file.
public class DownloadFileFromURL extends AsyncTask<String, Integer, String> {
private NotificationManager mNotifyManager;
private NotificationCompat.Builder build;
private File fileurl;
int id = 123;
OutputStream output;
private Context context;
private String selectedDate;
private String ts = "";
public DownloadFileFromURL(Context context, String selectedDate) {
this.context = context;
this.selectedDate = selectedDate;
}
protected void onPreExecute() {
super.onPreExecute();
mNotifyManager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
build = new NotificationCompat.Builder(context);
build.setContentTitle("Download")
.setContentText("Download in progress")
.setChannelId(id + "")
.setAutoCancel(false)
.setDefaults(0)
.setSmallIcon(R.drawable.ic_menu_download);
// Since android Oreo notification channel is needed.
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
NotificationChannel channel = new NotificationChannel(id + "",
"Social Media Downloader",
NotificationManager.IMPORTANCE_HIGH);
channel.setDescription("no sound");
channel.setSound(null, null);
channel.enableLights(false);
channel.setLightColor(Color.BLUE);
channel.enableVibration(false);
mNotifyManager.createNotificationChannel(channel);
}
build.setProgress(100, 0, false);
mNotifyManager.notify(id, build.build());
String msg = "Download started";
//CustomToast.showToast(context,msg);
}
@Override
protected String doInBackground(String... f_url) {
int count;
ts = selectedDate.split("T")[0];
try {
URL url = new URL(f_url[0]);
URLConnection conection = url.openConnection();
conection.connect();
int lenghtOfFile = conection.getContentLength();
InputStream input = new BufferedInputStream(url.openStream(),
8192);
// Output stream
output = new FileOutputStream(Environment
.getExternalStorageDirectory().toString()
+ Const.DownloadPath + ts + ".pdf");
fileurl = new File(Environment.getExternalStorageDirectory()
+ Const.DownloadPath + ts + ".pdf");
byte[] data = new byte[1024];
long total = 0;
while ((count = input.read(data)) != -1) {
total += count;
int cur = (int) ((total * 100) / lenghtOfFile);
publishProgress(Math.min(cur, 100));
if (Math.min(cur, 100) > 98) {
try {
Thread.sleep(500);
} catch (InterruptedException e) {
Log.d("Failure", "sleeping failure");
}
}
Log.i("currentProgress", "currentProgress: " + Math.min(cur, 100) + "\n " + cur);
output.write(data, 0, count);
}
output.flush();
output.close();
input.close();
} catch (Exception e) {
Log.e("Error: ", e.getMessage());
}
return null;
}
protected void onProgressUpdate(Integer... progress) {
build.setProgress(100, progress[0], false);
mNotifyManager.notify(id, build.build());
super.onProgressUpdate(progress);
}
@Override
protected void onPostExecute(String file_url) {
build.setContentText("Download complete");
build.setProgress(0, 0, false);
mNotifyManager.notify(id, build.build());
} }
Note: If you want code with import package then Click Here
Now Step 2: You need to call above ayncronous task on your click event. for example i have set on pdf image icon. To call AsyncTask use below code:
new DownloadFileFromURL(fContext,filename).execute(serverFileUrl);
Note: Here You can see filename variable in file parameter. This is the name which i use to save my downloaded file in local device. currently i am downloading only pdf file but you can use you url in serverFileUrl parameter.
Solution 12 - Android
When you click on download button, first you have to create local storage path where you want to save it, we should put download file functionality into ExecutorService(that is used instead of AsyncTask because AsyncTask is deprecated).
// Create bamchik folder if not created yet
val folder = File(context?.getExternalFilesDir(null)?.absoluteFile, "MusicTrack")
val check = folder.mkdirs()
Log.v(mTAG, "check: $check")
var path = context?.getExternalFilesDir(null)?.absolutePath + "/MusicTrack/music." + fileExt
val SDK_INT = Build.VERSION.SDK_INT
if (SDK_INT > 8) {
val policy: StrictMode.ThreadPolicy = StrictMode.ThreadPolicy.Builder().permitAll().build()
StrictMode.setThreadPolicy(policy)
val executor: ExecutorService = Executors.newSingleThreadExecutor()
val handler = object : Handler(Looper.getMainLooper()) {
override fun handleMessage(msg: Message) {
// Length is the total size of file and progress is how much file have been downloaded, now you can show progress according to this
val (progress, length) = msg.obj as Pair<Long, Long>
Log.v(mTAG, "Progress: $progress, Length: $length")
}
}
executor.execute {
//Background work here
download(link, path) { progress, length ->
// handling the result on main thread
handler.sendMessage(handler.obtainMessage(0, progress to length))
}
handler.post {
//UI Thread work here
}
}
}
Function of download file from url
fun download(link: String, path: String, progress: ((Long, Long) -> Unit)? = null): Long {
val url = URL(link)
val connection = url.openConnection()
connection.connect()
val length = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) connection.contentLengthLong else connection.contentLength.toLong()
url.openStream().use { input ->
FileOutputStream(File(path)).use { output ->
val buffer = ByteArray(DEFAULT_BUFFER_SIZE)
var bytesRead = input.read(buffer)
var bytesCopied = 0L
while (bytesRead >= 0) {
output.write(buffer, 0, bytesRead)
bytesCopied += bytesRead
progress?.invoke(bytesCopied, length)
bytesRead = input.read(buffer)
}
return bytesCopied
}
}
}
Solution 13 - Android
This is how I download using retrofit, save and return a file to the viewmodel :)
interface FileDownloader { companion object { private val instance: FileDownloader by lazy {
val loggingInterceptor = HttpLoggingInterceptor()
loggingInterceptor.level = HttpLoggingInterceptor.Level.HEADERS
val client = OkHttpClient.Builder()
.connectTimeout(120, TimeUnit.SECONDS)
.readTimeout(300, TimeUnit.SECONDS)
.callTimeout(300, TimeUnit.SECONDS)
.addInterceptor(loggingInterceptor)
.build()
val downloaderApi = Retrofit.Builder()
.baseUrl("https://exmaple.com")
.addConverterFactory(GsonConverterFactory.create())
.client(client)
.build()
.create(FileDownloader::class.java)
downloaderApi
}
suspend fun downloadAndSaveFile(
url: String
): File {
val file = getPdfFile()
val responseBody = try {
instance.downloadFile(url)
} catch (e: Exception) {
throw FileDownloadException(url, e)
}
@Suppress("BlockingMethodInNonBlockingContext")
try {
FileOutputStream(file).use { outputStream ->
responseBody.byteStream().use { inputStream ->
inputStream.copyTo(outputStream)
}
}
} catch (e: Exception) {
throw FileDownloadException(url, e)
}
return file
}
}
@GET
@Streaming
suspend fun downloadFile(@Url utl: String): ResponseBody
}
fun getPdfFile(): File {
File(App.appContext.filesDir, "pdfs").apply { mkdirs() }
return File(App.appContext.filesDir, "tempPDF.pdf")
}
class FileDownloadException(url: String, e: Exception) : Throwable()
Solution 14 - Android
Starting from api level 11 or Honeycomb doing network operations on main thread is forbidden. Use thread or asynctask. For more info visit https://developer.android.com/reference/android/os/NetworkOnMainThreadException.html