Android How to - Download Binary Data from the web








The following code shows how to Download Binary Data from the web.

Example

Add the following statement to the AndroidManifest.xml file: 

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.java2s.myapplication3.app" >

    <uses-permission android:name="android.permission.INTERNET"/>
    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="java2s.com"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.java2s.myapplication3.app.MainActivity"
            android:label="java2s.com"
            >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

    </application>

</manifest>

Layout xml file

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <ImageView
        android:id="@+id/img"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center" />

</LinearLayout>

Main Activity Java code

package com.java2s.myapplication3.app;
/*from w  w w .  j  a v  a2 s .  co  m*/
import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.widget.ImageView;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;

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

public class MainActivity extends Activity {
    ImageView img;

    private InputStream OpenHttpConnection(String urlString) throws IOException
    {
        InputStream in = null;
        int response = -1;

        URL url = new URL(urlString);
        URLConnection conn = url.openConnection();

        if (!(conn instanceof HttpURLConnection))
            throw new IOException("Not an HTTP connection");
        try{
            HttpURLConnection httpConn = (HttpURLConnection) conn;
            httpConn.setAllowUserInteraction(false);
            httpConn.setInstanceFollowRedirects(true);
            httpConn.setRequestMethod("GET");
            httpConn.connect();
            response = httpConn.getResponseCode();
            if (response == HttpURLConnection.HTTP_OK) {
                in = httpConn.getInputStream();
            }
        }
        catch (Exception ex)
        {
            Log.d("Networking", ex.getLocalizedMessage());
            throw new IOException("Error connecting");
        }
        return in;
    }

    private Bitmap DownloadImage(String URL)
    {
        Bitmap bitmap = null;
        InputStream in = null;
        try {
            in = OpenHttpConnection(URL);
            bitmap = BitmapFactory.decodeStream(in);
            in.close();
        } catch (IOException e1) {
            Log.d("NetworkingActivity", e1.getLocalizedMessage());
        }
        return bitmap;
    }

    private class DownloadImageTask extends AsyncTask<String, Void, Bitmap> {
        protected Bitmap doInBackground(String... urls) {
            return DownloadImage(urls[0]);
        }

        protected void onPostExecute(Bitmap result) {
            ImageView img = (ImageView) findViewById(R.id.img);
            img.setImageBitmap(result);
        }
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        new DownloadImageTask().execute(
                "http://www.java2s.com/style/download.png");
    }
}
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