refer to: https://stackoverflow.com/a/10881215/2771869
File f = new File(Environment.getExternalStorageDirectory(), "1.jpg");
String path = f.getAbsolutePath();
File f1 = new File(path);
if(f1.exists()) {
Bitmap bmp = BitmapFactory.decodeFile(path);
BitmapDrawable bitmapDrawable = new BitmapDrawable(bmp);
WallpaperManager m=WallpaperManager.getInstance(this);
try {
m.setBitmap(bmp);
} catch (IOException e) {
e.printStackTrace();
}
}
Open Androidmanifest.xml file and add permission like..
<uses-permission android:name="android.permission.SET_WALLPAPER" />
Try this and let me know what happen..