Main.java

items.add(Environment.getExternalStorageDirectory() + "/DCIM/Camera/20140706_170122.jpg");
items.add(Environment.getExternalStorageDirectory() + "/DCIM/Camera/20140822_123456.jpg");
items.add(Environment.getExternalStorageDirectory() + "/DCIM/Camera/20140706_152135.jpg");

  for (int count = 0; count < items.size(); count++) {
      BitmapFactory.Options options = new BitmapFactory.Options();
      options.inJustDecodeBounds = true;
      try {
        BitmapFactory.decodeFile(items.get(count), options);
        float width;
        float height;

        if (options.outWidth > getWindowManager().getDefaultDisplay().getWidth()) {
          width = pager.getLayoutParams().width;
        } else {
            width = options.outWidth;
        }

        if (options.outHeight > getWindowManager().getDefaultDisplay().getHeight()) {
            height = getWindowManager().getDefaultDisplay().getHeight();
        } else {
            height = options.outHeight;
        }

        Log.i("Display", "Width : " + width + ", Height : " + height);

        info.add(new PhotoInfo(height, width));

        if ((count + 1) == items.size()) {
            pager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {

                private PhotoInfo previousItem = new PhotoInfo();
                private PhotoInfo currentItem = new PhotoInfo();
                private PhotoInfo nextItem = new PhotoInfo();
                private boolean isScrolling = false;
                private int previousPosition;
                private int currentPosition;
                private int nextPosition;

                @Override
                public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
                    ViewGroup.LayoutParams lp = pager.getLayoutParams();

                    Log.i("OnPageListener", "Position : " + position + ", Position Offset : " + positionOffset + ", Position Offset Pixels : " + positionOffsetPixels);

                    if (positionOffsetPixels <= 0.1) {
                        previousPosition = position - 1;
                        currentPosition = position;
                        nextPosition = position + 1;

                        Log.d("IDLE", "Previous Position : " + previousPosition + ", Current Position : " + currentPosition + ", Next Position : " + nextPosition);
                    }

                    if (position == 0) {
                        if (null == info) {
                            Log.e("OnPageScrolled", "NULL");
                        }
                        currentItem = info.get(currentPosition);
                        nextItem = info.get(nextPosition);

                        lp.width = (int) nextItem.getWidth();
                        lp.height = (int) nextItem.getHeight();
                    } else if (position == items.size()) {
                        previousItem = info.get(previousPosition);
                        currentItem = info.get(currentPosition);

                        lp.width = (int) previousItem.getWidth();
                        lp.height = (int) previousItem.getHeight();
                    } else {
                        previousItem = info.get(previousPosition);
                        currentItem = info.get(currentPosition);
                        nextItem = info.get(nextPosition);

                        if (position == previousPosition) {
                            lp.width = (int) previousItem.getWidth();
                            lp.height = (int) previousItem.getHeight();
                        } else if ((position == currentPosition) && positionOffsetPixels != 0) {
                            lp.width = (int) nextItem.getWidth();
                            lp.height = (int) nextItem.getHeight();
                        } else {
                            lp.width = (int) currentItem.getWidth();
                            lp.height = (int) currentItem.getHeight();
                        }
                    }

                    pager.setLayoutParams(lp);
                }

                @Override
                public void onPageSelected(int position) {}
                
                @Override
                public void onPageScrollStateChanged(int state) {
                    switch (state) {
                        case ViewPager.SCROLL_STATE_DRAGGING:
                            isScrolling = true;
                            Log.d("OnPageListener", "Scroll Start");
                            break;

                        case ViewPager.SCROLL_STATE_IDLE:
                            isScrolling = false;
                            Log.d("OnPageListener", "Scroll Stop");
                            break;

                        default:
                            isScrolling = false;
                            Log.d("OnPageListener", "Default");
                            break;
                    }
                }

            });

        }
    } catch (Exception e) {
        e.printStackTrace();
    }
}