Dragging (when zoomed) in ViewPager not working as expected

[peshkira]

I have a few pdfs displayed in a view pager. When I zoom one and try to drag to the left/right, the pdf does not pan, but the view pager immediately takes hold of the scrolling and switches to the next page.

If I first drag up/down and then (without lifting my finger) drag left/right, it seems to work as expected.

Any ideas, how I can pass the touch events first to the PDFView and then to the view pager?

[dabele91]

Same problem here. Would be nice if someone has an idea how to resolve this issue.

[MoQ93]

That's because canScrollHorizontally(int direction) is not implemented, which is already requested in issue #19

[paperrose]

Had the same problem, but fixed it with overriding VP canScroll method

[dabele91]

@paperrose can you write an example how you've implemented the canScroll functionality?

[paperrose]

@dabele91

public class PDFViewPager extends ViewPager {

    public PDFViewPager(Context context) {
        super(context);

    }

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

    @Override
    protected boolean canScroll(View v, boolean checkV, int dx, int x, int y) {
        if (v instanceof ViewGroup) {
            final ViewGroup group = (ViewGroup) v;
            final int scrollX = v.getScrollX();
            final int scrollY = v.getScrollY();
            final int count = group.getChildCount();
            for (int i = count - 1; i >= 0; i--) {
                final View child = group.getChildAt(i);
                if (x + scrollX >= child.getLeft() && x + scrollX < child.getRight() &&
                        y + scrollY >= child.getTop() && y + scrollY < child.getBottom()) {
                    if ((child instanceof PDFView && isNotHorizontalBounds((PDFView)child, dx)) || canScroll(child, true, dx, x + scrollX - child.getLeft(),
                            y + scrollY - child.getTop()))
                        return true;
                }
            }
        }

        return checkV && false;
    }

    private boolean isNotHorizontalBounds(PDFView view, int dx) {
        final float zoom = view.getZoom();
        final float pageWidth = view.getWidth()*zoom;
        final float offset = view.getCurrentXOffset();
        if (offset + pageWidth <= getWidthScreen() + 1 && dx < 0) return false;
        if (offset >= -1 && dx > 0) return false;
        return true;
    }

    private int getWidthScreen(){
        WindowManager wm = (WindowManager) getContext().getSystemService(Context.WINDOW_SERVICE);
        Display display = wm.getDefaultDisplay();
        Point size = new Point();
        display.getSize(size);
        return size.x;
    }
} 

[dabele91]

@paperrose works lke a charm. thanks ;-)

[hustyichi]

Thank you , it works

[paperrose]

Just find a small bug in my code above. In landscape orientation right-to-left swipe doesn't change page
Solved by replacing
final float pageWidth = view.getWidth()*zoom;
to
final float pageWidth = view.getOptimalPageWidth()*zoom;

[MonaHammad]

How to use this approach, I can't find ViewPager class?

[peshkira]

Hi @MonaHammad!

The ViewPager is part of the android support library: https://developer.android.com/reference/android/support/v4/view/ViewPager.html

It is not related to this PDF library. This issue here is relevant if you show multiple PDFs inside a view pager. Hope this helps.

best

[MonaHammad]

Hi @peshkira
Ok, thanks.
But how to use it here to improve the paging while zooming in this library?
I couldn't figure out how to use PDFViewPager?