android: ViewPager and HorizontalScrollVIew

I have a HorizontalScrollView inside my ViewPager. I set requestDisallowInterceptTouchEvent(true); for the HorizontalScrollView but the ViewPager is still sometimes intercepting touch events. Is there another command I can use to prevent a View's parent and ancestors from intercepting touch events?

note: the HorizontalScrollView only occupies half the screen.

Solution 1:

I had the same problem. My solution was:

1. Make a subclass of ViewPager and add a property called childId.
2. Create a setter for the childId property and set the id of the HorizontalScrollView.
3. Override onInterceptTouchEvent() in the subclass of ViewPager and if the childId property is more than 0 get that child and if the event is in HorizontalScrollView area return false.

Code

public class CustomViewPager extends ViewPager {

    private int childId;    

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

    @Override
    public boolean onInterceptTouchEvent(MotionEvent event) {
        if (childId > 0) {
            View scroll = findViewById(childId);
            if (scroll != null) {
                Rect rect = new Rect();
                scroll.getHitRect(rect);
                if (rect.contains((int) event.getX(), (int) event.getY())) {
                    return false;
                }
            }
        }
        return super.onInterceptTouchEvent(event);
    }

    public void setChildId(int id) {
        this.childId = id;
    }
}

In onCreate() method

viewPager.setChildId(R.id.horizontalScrollViewId);
adapter = new ViewPagerAdapter(this);
viewPager.setAdapter(adapter);

Hope this help

Solution 2:

Thanks for the reply. I modified your solution a bit and managed to make nested ViewPagers work:

public class CustomViewPager extends ViewPager {
    private int childId;

    public CustomViewPager(Context context, AttributeSet attrs) {
        super(context, attrs);
    }
     @Override
    public boolean onInterceptTouchEvent(MotionEvent event) {
        if (childId > 0) {          
            ViewPager pager = (ViewPager)findViewById(childId);

            if (pager != null) {           
                pager.requestDisallowInterceptTouchEvent(true);
            }

        }

        return super.onInterceptTouchEvent(event);
    }

    public void setChildId(int id) {
        this.childId = id;
    }
}

Solution 3:

So, I know this question is pretty old, but I've come with a solution which I think has some extra advantages over the one posted here. One situation that could happen is that I could have more than one HorizontalScrollView inside my ViewPager (which I do), and then I would need to provide tons of Ids to the ViewPager so it can always check for child touch conflicts.

I analyzed the source from the ViewPager, and found that they use this method called "canScroll" to determine if a child view can be scrolled. Luckily, it wasn't made static nor final, so I could just override it. Inside that method that the "boolean ViewCompat.canScrollHorizontally(View, int)" was called (the one that always returns false for SDK < 14). My solution then was:

public class CustomViewPager extends ViewPager {

    public CustomViewPager(Context context, AttributeSet attrs) {
        super(context, attrs);
    }
    public CustomViewPager(Context context) {
        super(context);
    }
    protected boolean canScroll(View v, boolean checkV, int dx, int x, int y) {
        return super.canScroll(v, checkV, dx, x, y) || (checkV && customCanScroll(v));
    }
    protected boolean customCanScroll(View v) {
        if (v instanceof HorizontalScrollView) {
            View hsvChild = ((HorizontalScrollView) v).getChildAt(0);
            if (hsvChild.getWidth() > v.getWidth())
                return true;
        }
        return false;
   }
}

So, if you have a different class of View inside your ViewPager that should also receive horizontal drags, just change the customCanScroll(View) so you can return if the touch should not be intercepted or not.

The boolean checkV is true if the current view should also be checked for 'scrollability', that's why we should also check for that.

Hope this helps future issues like this (or if there is a better solution, or an official one from the Android platform, let me know).

Solution 4:

I don't know if you've solved the problem already or not. But none of the answers above work properly. So I think it's necessary for those people who might be searching the solutions with suffering.

In fact, the solution is quite simple if you read the official document about handling touch events in ViewGroup.

First you need to understand the usage of

ViewParent.requestDisallowInterceptTouchEvent(boolean), Call this upon a parent View to indicate that it should not intercept touch events with onInterceptTouchEvent(MotionEvent).

Then you need to intercept the events and make sure that the parent ViewGroup of your HorizontalScrollView won't dispatch the events any further.

So, set an OnToushListener for you HorizontalScrollView. Detecting the touch down and move events, then set the requestDisallowInterceptTouchEvent(true) to it's parent(ViewPager or sth else) to make sure the events would be handled by the HorizontalScrollView.

Of course you could put these code below into your CustomHorizontalScrollView components so that it can be reused.

Hoping it helps. ;-)

horizontalScrollView.setOnTouchListener(new View.OnTouchListener() {
float rawX;
int mTouchSlop =  ViewConfiguration.get(getActivity()).getScaledTouchSlop();

@Override
public boolean onTouch(View v, MotionEvent event) {
    switch (event.getActionMasked()) {
        case MotionEvent.ACTION_DOWN:
            v.getParent().requestDisallowInterceptTouchEvent(true);
            rawX = event.getRawX();
            break;
        case MotionEvent.ACTION_CANCEL:
        case MotionEvent.ACTION_UP:
            v.getParent().requestDisallowInterceptTouchEvent(false);
            rawX = 0f;
            break;
        case MotionEvent.ACTION_MOVE:
            if (Math.abs(rawX - event.getRawX()) > mTouchSlop)
                v.getParent().requestDisallowInterceptTouchEvent(true);
            break;
    }
    return false;
}