Xamarin Android垂直ViewPager

Question

I need a vertical ViewPager in Android using Xamarin and the solution doesn't work. I searched some examples in java but there's an object developed by the git community that do all the work. Unfortunately there isn't in Xamarin. So, this is my code, it doesn't give me error, but it displays only a black screen. Nothing more.

I Extended the ViewPager class

public class VerticalViewPager : ViewPager {

    public VerticalViewPager (Context context):base(context) {

        Init ();
    }

    public VerticalViewPager(Context context, IAttributeSet attr):base(context, attr) {

        Init();
    }

    public override bool OnTouchEvent (Android.Views.MotionEvent e) {

        e.SetLocation (e.GetY (), e.GetX ());
        return base.OnTouchEvent (e);
    }

    private void Init()  {

        SetPageTransformer (true, new PagerTransformer());
        OverScrollMode = Android.Views.OverScrollMode.Never;
    }
}

and create my PageTransformer

public class PagerTransformer : Java.Lang.Object, ViewPager.IPageTransformer {

    int pageWidth;
    int pageHeight;
    float yPos;

    public PagerTransformer () {}

    public void TransformPage (View view, float position) {

        pageWidth = view.Width;
        pageHeight = view.Height;

        if (position < -1)  {

            view.Alpha = 0;
        } 
        else if (position <= 1)  {

            view.Alpha = 1;
            // Counteract the default slide transition
            view.TranslationX = (pageWidth * -position);
            //set Y position to swipe in from top
            yPos = position + pageHeight;
            view.TranslationY = yPos;
        } 
        else  {

            // This page is way off-screen to the right.
            view.Alpha = 0;
        }
    }
}

In the MainActivity, onCreate method i set

page = FindViewById<VerticalViewPager> (Resource.Id.vertical_pager);

and obviously page is a VerticalViewPager object.

If I use a normale ViewPager, the app works fine. Any ideas about the reason of the black screen? Any java code is appreciare as well!

Thanks

Answer 1

The reason of black screen is that you set your screen position out of visible bounds. Your visible bounds are from 0 to page height. Try his : "yPos = position * pageHeight;" instead of "yPos = position + pageHeight;"