How to download image from url and save on SD card in android.

The path to SD Card can be retrieved using
Environment.getExternalStorageDirectory();

Then compress and write to SD Card by:
outStream = new FileOutputStream(file);
bm.compress(Bitmap.CompressFormat.PNG, 100, outStream);
outStream.flush();
outStream.close();

In order to premit the App to access internet and write to SD Card, we need "android.permission.INTERNET" and "android.permission.WRITE_EXTERNAL_STORAGE".
Modify AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.exercise.AndroidWebImage"
    android:versionCode="1"
    android:versionName="1.0">
  <application android:icon="@drawable/icon" android:label="@string/app_name">
      <activity android:name=".AndroidWebImage"
                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>
  <uses-sdk android:minSdkVersion="4" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
</manifest>


main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  >
<TextView
  android:layout_width="fill_parent"
  android:layout_height="wrap_content"
  android:text="@string/hello"
  />
<Button
  android:id="@+id/save"
  android:layout_width="fill_parent"
  android:layout_height="wrap_content"
  android:text="Save"
  />
<ImageView
  android:id="@+id/image"
  android:scaleType="center"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
/>
</LinearLayout>


AndroidWebImage.java
package com.exercise.AndroidWebImage;

import java.io.File;
import java.io.FileNotFoundException;
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 java.net.URLConnection;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.os.Environment;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Toast;

public class AndroidWebImage extends Activity {

String image_URL=
 "http://chart.apis.google.com/chart?chs=200x200&cht=qr&chl=http%3A%2F%2Fandroid-er.blogspot.com%2F";

String extStorageDirectory;

Bitmap bm;

  /** Called when the activity is first created. */
  @Override
  public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.main);
   
      Button buttonSave = (Button)findViewById(R.id.save);

      ImageView bmImage = (ImageView)findViewById(R.id.image);
   BitmapFactory.Options bmOptions;
   bmOptions = new BitmapFactory.Options();
   bmOptions.inSampleSize = 1;
   bm = LoadImage(image_URL, bmOptions);
   bmImage.setImageBitmap(bm);
 
   extStorageDirectory = Environment.getExternalStorageDirectory().toString();

   buttonSave.setText("Save to " + extStorageDirectory + "/qr.PNG");
   buttonSave.setOnClickListener(buttonSaveOnClickListener);
  }

  private Bitmap LoadImage(String URL, BitmapFactory.Options options)
  {    
   Bitmap bitmap = null;
   InputStream in = null;    
      try {
          in = OpenHttpConnection(URL);
          bitmap = BitmapFactory.decodeStream(in, null, options);
          in.close();
      } catch (IOException e1) {
      }
      return bitmap;            
  }

private InputStream OpenHttpConnection(String strURL) throws IOException{
 InputStream inputStream = null;
 URL url = new URL(strURL);
 URLConnection conn = url.openConnection();

 try{
  HttpURLConnection httpConn = (HttpURLConnection)conn;
  httpConn.setRequestMethod("GET");
  httpConn.connect();

  if (httpConn.getResponseCode() == HttpURLConnection.HTTP_OK) {
   inputStream = httpConn.getInputStream();
  }
 }
 catch (Exception ex)
 {
 }
 return inputStream;
}

Button.OnClickListener buttonSaveOnClickListener
 = new Button.OnClickListener(){

  @Override
  public void onClick(View arg0) {
   // TODO Auto-generated method stub
   OutputStream outStream = null;
   File file = new File(extStorageDirectory, "er.PNG");
   try {
    outStream = new FileOutputStream(file);
    bm.compress(Bitmap.CompressFormat.PNG, 100, outStream);
    outStream.flush();
    outStream.close();
 
    Toast.makeText(AndroidWebImage.this, "Saved", Toast.LENGTH_LONG).show();
 
   } catch (FileNotFoundException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
    Toast.makeText(AndroidWebImage.this, e.toString(), Toast.LENGTH_LONG).show();
   } catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
    Toast.makeText(AndroidWebImage.this, e.toString(), Toast.LENGTH_LONG).show();
   }

  }

};

}