some example code

public class myPage extends Activity {


    private Gallery g =null;
    private Context mContext = null;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.cheongfun);

        if (g==null)
        {
            Gallery g = (Gallery) findViewById(R.id.gallery);
            g.setAdapter(new ImageAdapter(this));
            g.setOnItemClickListener(new OnItemClickListener() {
                public void onItemClick(AdapterView parent, View v, int position, long id) {
                    Toast.makeText(myPage.this, "" + position, Toast.LENGTH_SHORT).show();
                }
            });

            g.setSelection(3);

        }
    }

    @Override
    public void onPause()
    {
        super.onPause();
        g = null;
        finish();
    }

    @Override
    public void onStop()
    {
        super.onStop();
        g = null;
        finish();
    }




    public class ImageAdapter extends BaseAdapter {
        int mGalleryItemBackground;
        private Context mContext;

        private Integer[] mImageIds = {
                R.drawable.cheongfun1,
                R.drawable.cheongfun2,
                R.drawable.cheongfun3,
                R.drawable.cheongfun4,
                R.drawable.cheongfun5,
                R.drawable.cheongfun6,
                R.drawable.cheongfun7
        };

        public ImageAdapter(Context c) {
            mContext = c;
            TypedArray a = obtainStyledAttributes(R.styleable.DefaultGallery);
            mGalleryItemBackground = a.getResourceId(
                    R.styleable.DefaultGallery_android_galleryItemBackground, 0);
            a.recycle();
        }

        public int getCount() {
            return mImageIds.length;
        }

        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);

            i.setImageResource(mImageIds[position]);
            i.setLayoutParams(new Gallery.LayoutParams(300, 200));
            i.setScaleType(ImageView.ScaleType.FIT_XY);
            i.setBackgroundResource(mGalleryItemBackground);

            return i;
        }
    }

    public void onResume() {
        super.onResume();
        setContentView(R.layout.cheongfun);
        if (g==null)
        {
            Gallery g = (Gallery) findViewById(R.id.gallery);
            g.setAdapter(new ImageAdapter(this));
            g.setOnItemClickListener(new OnItemClickListener() {
                public void onItemClick(AdapterView parent, View v, int position, long id) {
                    Toast.makeText(myPage.this, "" + position, Toast.LENGTH_SHORT).show();
                }
            });

            g.setSelection(3);

        }


    }
    public void onConfigurationChanged(Configuration newConfig) {
        super.onConfigurationChanged(newConfig);
        setContentView(R.layout.cheongfun);
        if (g==null)
        {
            Gallery g = (Gallery) findViewById(R.id.gallery);
            g.setAdapter(new ImageAdapter(this));
            g.setOnItemClickListener(new OnItemClickListener() {
                public void onItemClick(AdapterView parent, View v, int position, long id) {
                    Toast.makeText(myPage.this, "" + position, Toast.LENGTH_SHORT).show();
                }
            });

            g.setSelection(3);

        }
    }