public class MainActivity extends Activity {

    /** The images. */
    public ArrayList<String> images;


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

        GridView gallery = (GridView) findViewById(R.id.galleryGridView);

        gallery.setAdapter(new ImageAdapter(this));

        gallery.setOnItemClickListener(new AdapterView.OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> arg0, View arg1, int position, long arg3) {
                if (null != images && !images.isEmpty())
                    Toast.makeText(
                            getApplicationContext(),
                            "position " + position + " " + images.get(position),
                            300).show();
                ;

            }
        });

    }

   }
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public class ImageAdapter extends BaseAdapter {

    private Activity context;
    public ArrayList<String> images;



    public ImageAdapter(Activity localContext) {
        context = localContext;
        this.images = getAllShownImagesPath(context);
    }

    public int getCount() {
        return images.size();
    }

    public Object getItem(int position) {
        return position;
    }

    public long getItemId(int position) {
        return position;
    }

    public View getView(final int position, View convertView, ViewGroup parent) {

        ImageView picturesView;

        if (convertView == null){
            picturesView = new ImageView(context);
            picturesView.setScaleType(ImageView.ScaleType.FIT_CENTER);
            picturesView.setLayoutParams(new GridView.LayoutParams(325, 325));
        } else {
            picturesView = (ImageView) convertView;
        }

        Glide.with(context).load(images.get(position)).placeholder(R.drawable.ic_launcher).centerCrop().into(picturesView);
        return picturesView;
    }


    private ArrayList<String> getAllShownImagesPath(Activity activity) {

        Uri uri;
        Cursor cursor;
        int column_index_data, column_index_folder_name;
        ArrayList<String> listOfAllImages = new ArrayList<String>();
        String absolutePathOfImage = null;
        uri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;

        String[] projection = {MediaStore.MediaColumns.DATA, MediaStore.Images.Media.BUCKET_DISPLAY_NAME};

        cursor = activity.getContentResolver().query(uri, projection, null, null, null);

        column_index_data = cursor.getColumnIndexOrThrow(MediaStore.MediaColumns.DATA);
        column_index_folder_name = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.BUCKET_DISPLAY_NAME);

        while (cursor.moveToNext()){
            absolutePathOfImage = cursor.getString(column_index_data);

            listOfAllImages.add(absolutePathOfImage);
        }
        return listOfAllImages;
    }

}