android - Detecting the scrolling direction in the adapter (up/down)

Question

I am trying to mimic the Google Plus application in my project, as it seems to be the reference now.

The listview effect when scrolling is really nice and I would like to do something similar.

I have started with the LayoutAnimationController http://android-er.blogspot.be/2009/10/listview-and-listactivity-layout.html

LayoutAnimationController controller 
   = AnimationUtils.loadLayoutAnimation(
     this, R.anim.list_layout_controller);
  getListView().setLayoutAnimation(controller);

and that seems bad, as not all the elements are animated:

So I ended up by using the getView of the adapter and using this:

        AnimationSet set = new AnimationSet(true);

        Animation animation = new AlphaAnimation(0.0f, 1.0f);
        animation.setDuration(800);
        set.addAnimation(animation);

        animation = new TranslateAnimation(
            Animation.RELATIVE_TO_SELF, 0.0f,Animation.RELATIVE_TO_SELF, 0.0f,
            Animation.RELATIVE_TO_SELF, 1.0f,Animation.RELATIVE_TO_SELF, 0.0f
        );
        animation.setDuration(600);
        set.addAnimation(animation);

        row.startAnimation(set);

The result is awesome and I am really happy with it!

Unfortunately, it only works when I scroll from top to bottom of the list!

I want to make it work when scrolling on the other side, I need to change a little bit the TranslateAnimation.

So my question, is there a way to detect if I scroll upwards or downwards in my adapter?

Answer 1

Assign an OnScrollListener to your ListView. Create a flag which indicates whether the user is scrolling up or down. Set an appropriate value to the flag by checking if the current first visible item position equals to more or less than the previous first visible item position. Put that check inside onScrollStateChanged().

Sample code:

private int mLastFirstVisibleItem;
private boolean mIsScrollingUp;

public void onScrollStateChanged(AbsListView view, int scrollState) {
    final ListView lw = getListView();

    if (view.getId() == lw.getId()) {
        final int currentFirstVisibleItem = lw.getFirstVisiblePosition();

        if (currentFirstVisibleItem > mLastFirstVisibleItem) {
            mIsScrollingUp = false;
        } else if (currentFirstVisibleItem < mLastFirstVisibleItem) {
            mIsScrollingUp = true;
        }

        mLastFirstVisibleItem = currentFirstVisibleItem;
    } 
}

Check if mIsScrollingUp is true or false in getView(), and assign the animations accordingly.