handling scrolling in android scrollview

Question

I am using this library to create a floating action button in my android application. What I need is to hide the floating action button when I scroll down, and show it again when I scroll up. The problem is I have a FrameLayout and a ScrollView that doesn't contain a setOnScrollListener()!

I read this solution, but supposedly it is laggy.

Can anyone tell me how to reach get the functionality I'm looking for without losing performance?

score 1 · Accepted Answer · answered Aug 11 '15 at 20:14

1

Try this library.

It provides a floating action button that disappears when you scroll down :-)

answered Aug 11 '15 at 20:14

Alex Crist

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score 1 · Answer 2 · answered Aug 11 '15 at 20:14

One option is to create an ObservableScrollView that has a scroll listener. Google uses this approach in the IOSched14 app. One way of creating this might be:

public class ObservableScrollView extends ScrollView {
    private boolean mScrollingEnabled = true;
    private ArrayList<Callbacks> mCallbacks = new ArrayList<Callbacks>();

    public ObservableScrollView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @Override
    protected void onScrollChanged(int l, int t, int oldl, int oldt) {
        super.onScrollChanged(l, t, oldl, oldt);
        for (Callbacks c : mCallbacks) {
            c.onScrollChanged(l - oldl, t - oldt);
        }
    }

    @Override
    public int computeVerticalScrollRange() {
        return super.computeVerticalScrollRange();
    }

    public void addCallbacks(Callbacks listener) {
        if (!mCallbacks.contains(listener)) {
            mCallbacks.add(listener);
        }
    }

    public static interface Callbacks {
        public void onScrollChanged(int deltaX, int deltaY);
    }



    public void setScrollingEnabled(boolean scrollingEnabled) {
        mScrollingEnabled = scrollingEnabled;
    }

//    @Override
//    public boolean onTouchEvent(MotionEvent ev) {
//        if (!mScrollingEnabled) return false;
//        return super.onTouchEvent(ev);
//    }

}

Simply add this instead of your ScrollView and then attach a listener using the addCallbacks method:

ObservableScrollView scrollView = new ObservableScrollView(context);
scrollView.addCallbacks(this);

handling scrolling in android scrollview

2 Answers2