Android Example-Set the Wallpaper of Your Device using Bitmap Class

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<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"
    tools:context="in.kantapp.example110.MainActivity">

    <ImageView
        android:id="@+id/img"
        android:layout_width="fill_parent"
        android:layout_height="300dp"
        android:paddingTop="10dp"
        android:layout_gravity="center_horizontal"
        android:src="@drawable/aa" />

    <Button
        android:id="@+id/button"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="SetWallpaper" />

    <HorizontalScrollView
        android:layout_width="match_parent"

        android:layout_height="fill_parent">

        <LinearLayout
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:paddingLeft="5dp"
            android:paddingRight="5dp"
            android:orientation="horizontal">

            <ImageView
                android:id="@+id/img1"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:scaleType="fitXY"
                android:src="@drawable/a" />

            <ImageView
                android:id="@+id/img2"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:paddingLeft="5dp"
                android:scaleType="fitXY"
                android:src="@drawable/b" />

            <ImageView
                android:id="@+id/img3"
                android:layout_width="160dp"
                android:layout_height="160dp"
                android:paddingLeft="5dp"

                android:scaleType="fitXY"
                android:src="@drawable/c" />

            <ImageView
                android:id="@+id/img4"
                android:layout_width="160dp"
                android:layout_height="160dp"
                android:paddingLeft="5dp"
                android:scaleType="fitXY"
                android:src="@drawable/d" />

            <ImageView
                android:id="@+id/img5"
                android:layout_width="160dp"
                android:layout_height="160dp"
                android:paddingLeft="5dp"
                android:scaleType="fitXY"
                
                android:src="@drawable/e" />
        </LinearLayout>
    </HorizontalScrollView>
</LinearLayout>

MainActivity.java

package in.kantapp.example110;

import java.io.IOException;
import java.io.InputStream;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.view.View;
import android.view.Window;
import android.view.WindowManager;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Toast;

public class MainActivity extends Activity implements OnClickListener
{
    ImageView display;
    int tophone;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);

        // to our activity to cover the whole screen
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
                WindowManager.LayoutParams.FLAG_FULLSCREEN);

        setContentView(R.layout.activity_main);
        Button but = (Button) findViewById(R.id.button);
        tophone = R.drawable.aa;
        but.setOnClickListener(this);
        display = (ImageView) findViewById(R.id.img);
        ImageView image1 = (ImageView) findViewById(R.id.img1);
        ImageView image2 = (ImageView) findViewById(R.id.img2);
        ImageView image3 = (ImageView) findViewById(R.id.img3);
        ImageView image4 = (ImageView) findViewById(R.id.img4);
        ImageView image5 = (ImageView) findViewById(R.id.img5);

        image1.setOnClickListener(this);
        image2.setOnClickListener(this);
        image3.setOnClickListener(this);
        image4.setOnClickListener(this);
        image5.setOnClickListener(this);

    }

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        Toast var;
        switch (v.getId()) {
            case R.id.img1:
                display.setImageResource(R.drawable.aa);
                var = Toast.makeText(MainActivity.this, "image changed",
                        Toast.LENGTH_SHORT);

                var.show();

                tophone = R.drawable.aa;
                break;
            case R.id.img2:
                display.setImageResource(R.drawable.bb);
                var = Toast.makeText(MainActivity.this, "image changed",
                        Toast.LENGTH_SHORT);

                var.show();

                tophone = R.drawable.bb;
                break;
            case R.id.img3:
                display.setImageResource(R.drawable.cc);
                var = Toast.makeText(MainActivity.this, "image changed",
                        Toast.LENGTH_SHORT);

                var.show();

                tophone = R.drawable.cc;
                break;
            case R.id.img4:
                display.setImageResource(R.drawable.dd);
                var = Toast.makeText(MainActivity.this, "image changed",
                        Toast.LENGTH_SHORT);

                var.show();

                tophone = R.drawable.dd;
                break;
            case R.id.img5:
                display.setImageResource(R.drawable.ee);
                var = Toast.makeText(MainActivity.this, "image changed",
                        Toast.LENGTH_SHORT);

                var.show();

                tophone = R.drawable.ee;
                break;
            case R.id.button:
                // to set a background we need to use bitmap
                InputStream is = getResources().openRawResource(tophone);
                // to phone is a variable that is updated everytime we click on an
                // ImageView to that imageview resource and by clicking the button
                // we set the phone background to that image.
                Bitmap bm = BitmapFactory.decodeStream(is);
                // decode inputstream is
                try {
                    getApplicationContext().setWallpaper(bm);
                    // to set the wallpaper of the phone background we need to ask
                    // permission from the user so add permission of background from
                    // manifest file

                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                var = Toast.makeText(MainActivity.this, "Wallpaper image changed",
                        Toast.LENGTH_SHORT);

                var.show();

                break;
        }
    }

}

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="in.kantapp.example110">
<uses-permission android:name="android.permission.SET_WALLPAPER"/>
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

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

</manifest>