
package com.exercise.HelloGallery;
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import android.app.Activity;
import android.app.WallpaperManager;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.view.View.OnClickListener;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.Gallery;
import android.widget.ImageView;
import android.widget.Toast;
import android.widget.AdapterView.OnItemClickListener;
public class HelloGallery extends Activity {
 
 Bitmap bitmap;
 
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.main);
  final ImageView imageView = (ImageView)findViewById(R.id.imageview);
  Gallery g = (Gallery) findViewById(R.id.gallery);
  final List<String> SD = ReadSDCard();
  g.setAdapter(new ImageAdapter(this, SD));
  g.setOnItemClickListener(new OnItemClickListener() {
      public void onItemClick(AdapterView<?> parent,
        View v, int position, long id) {
       
       String imageInSD = SD.get(position);
       
       Toast.makeText(HelloGallery.this,
         imageInSD,
            Toast.LENGTH_LONG).show();
       
       bitmap = BitmapFactory.decodeFile(imageInSD);
          imageView.setImageBitmap(bitmap);
       
      }
  });
  imageView.setOnClickListener(new OnClickListener(){
  @Override
  public void onClick(View view) {
   // TODO Auto-generated method stub
   WallpaperManager myWallpaperManager
    = WallpaperManager.getInstance(getApplicationContext());
      try {
       myWallpaperManager.setBitmap(bitmap);
      } catch (IOException e) {
       // TODO Auto-generated catch block
       e.printStackTrace();
      }
  }});
}
private List<String> ReadSDCard()
{
List<String> tFileList = new ArrayList<String>();
//It have to be matched with the directory in SDCard
File f = new File("/sdcard/pictures/");
File[] files=f.listFiles();
for(int i=0; i<files.length; i++)
{
File file = files[i];
//add the selected file type only
String curFile=file.getPath();
String ext=curFile.substring(curFile.lastIndexOf(".")+1,
  curFile.length()).toLowerCase();
if(ext.equals("jpg")||ext.equals("gif")||ext.equals("png"))
tFileList.add(file.getPath());
}
return tFileList;
}
public class ImageAdapter extends BaseAdapter {
  int mGalleryItemBackground;
  private Context mContext;
  private List<String> FileList;
  public ImageAdapter(Context c, List<String> fList) {
      mContext = c;
      FileList = fList;
      TypedArray a = obtainStyledAttributes(R.styleable.Theme);
      mGalleryItemBackground = a.getResourceId(
        R.styleable.Theme_android_galleryItemBackground,
        0);
      a.recycle();
  }
  public int getCount() {
      return FileList.size();
  }
  public Object getItem(int position) {
      return position;
  }
  public long getItemId(int position) {
      return position;
  }
  public View getView(int position, View convertView,
    ViewGroup parent) {
      ImageView i = new ImageView(mContext);
      Bitmap bm = BitmapFactory.decodeFile(
        FileList.get(position).toString());
      i.setImageBitmap(bm);
      i.setLayoutParams(new Gallery.LayoutParams(150, 100));
      i.setScaleType(ImageView.ScaleType.FIT_XY);
      i.setBackgroundResource(mGalleryItemBackground);
      return i;
  }
}
}
* Please note that in order to use WallpaperManager, minimum API level have to be set to 5.
* In order to access system wallpaper, AndroidManifest.xml have t be modified to grant permission of "android.permission.SET_WALLPAPER".
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.exercise.HelloGallery"
    android:versionCode="1"
    android:versionName="1.0">
  <uses-sdk android:minSdkVersion="7" />
  <uses-permission android:name="android.permission.SET_WALLPAPER"></uses-permission>
  <application android:icon="@drawable/icon" android:label="@string/app_name">
      <activity android:name=".HelloGallery"
                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>
 Download the files.
Download the files.














