In this tutorial, he uses the OnClickListener a bit different:
buttonSetWallpaper.setOnClickListener(new Button.OnClickListener(){....
Try this, should work:
start.setOnClickListener(new Button.OnClickListener(){
@Override
public void onClick(View arg0) {
WallpaperManager myWallpaperManager = WallpaperManager.getInstance(getApplicationContext());
try {
myWallpaperManager.setResource(R.drawable.shrek);
} catch (IOException e) {
e.printStackTrace();
}
}});
EDIT: Of course you can also just call your method in OnClick instead of handling it directly