Load image from internet, in AsyncTask

This example show how to load image from internet, in background thread using AsyncTask.

Load image from internet

- First of all, to access internet from your app, you have to modify AndroidManifest.xml to add:
<uses-permission android:name="android.permission.INTERNET"/>

- You cannot access Network in main thread, otherwise error of "android.os.NetworkOnMainThreadException" will be reported. That's why we have to implement AsyncTask to load image in background thread.

- Once image loaded, update UI in main thread (or called UI Thread) in onPostExecute() method.

Example code:

package com.example.androidloadimage;

import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;

import android.os.AsyncTask;
import android.os.Bundle;
import android.widget.ImageView;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;

public class MainActivity extends Activity {
 
 String targetUrl = "http://goo.gl/qfGTN3";
 ImageView image1;
 
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  image1 = (ImageView)findViewById(R.id.image1);
  
  /*
   * error Caused by: android.os.NetworkOnMainThreadException
   * if you access internet in Main Thread here!
   */
  //Bitmap bmLoadedImage = loadImageFromUrl(targetUrl);
  //image1.setImageBitmap(bmLoadedImage);
  
  new LoadImageTask(image1).execute(targetUrl);

 }
 
 private class LoadImageTask extends AsyncTask<String, Void, Bitmap>{
  
  ImageView targetImageView;
  
  LoadImageTask(ImageView iv){
   targetImageView = iv;
  }

  @Override
  protected Bitmap doInBackground(String... params) {
   Bitmap bm = loadImageFromUrl(params[0]);
   return bm;
  }

  @Override
  protected void onPostExecute(Bitmap result) {
   targetImageView.setImageBitmap(result);
  }
  
 }
 
 private Bitmap loadImageFromUrl(String targetUrl){
  Bitmap bm = null;
  
  try {
   URL url = new URL(targetUrl);
   URLConnection connection = url.openConnection();
   InputStream inputStream = connection.getInputStream();
   bm = BitmapFactory.decodeStream(inputStream);
  } catch (MalformedURLException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (IOException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
 
  return bm;
 }

}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="android-coding.blogspot.com" />

    <ImageView
        android:id="@+id/image1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</LinearLayout>