CODEWITHSUNDEEP
androidandroid-viewpagerandroid-pageradapter
woot
woot

Reputation: 3731

Calling notifyDataSetChanged from instantiateItem()

I have a requirement to show a ViewPager displaying initially just one View. Once this View goes through measure & layout pass, depending on the result of these I might need to change the contents of the adapter. While doing so, I've come across a scenario where the ViewPager will not follow through with it's movement while trying to swipe to the next item from a certain position.
I'm sure I'm doing something wrong in my adapter implementation, yet I can't point my finger at the problem.

For the sake of demonstration I've created a dummy adapter that will mimic what happens on my actual project. In order to reproduce the issue just try to swipe all the way to position 2 (3rd item), result is you can't get past position 1 (2nd item).

Thanks!

public class CustomAdapter extends PagerAdapter {
    int pages = 0;

    @Override
    public int getCount() {
        return pages;
    }

    @Override
    public boolean isViewFromObject(View view, Object o) {
        return view == o;
    }

    public void setPages(int x) {
        this.pages = x;
    }

    @Override
    public Object instantiateItem(ViewGroup container, int position) {
        TextView tv = new TextView(MainActivity.this);
        ViewGroup.LayoutParams lp =
                new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
                        ViewGroup.LayoutParams.WRAP_CONTENT);

        tv.setLayoutParams(lp);
        tv.setText("Position: " + position);

        if (position == 0 && pages == 1) {
            setPages(2);
            notifyDataSetChanged();
        }
        if (position == 1 && pages == 2) {
            setPages(3);
            notifyDataSetChanged();
        }

        container.addView(tv);
        return tv;
    }

    @Override
    public void destroyItem(ViewGroup container, int position, Object object) {
        container.removeView((View) object);
    }
}

Activity (onCreate or so):

    CustomAdapter adapter = new CustomAdapter();
    adapter.setPages(1);
    vp.setAdapter(adapter);
    adapter.notifyDataSetChanged();

Upvotes: 2

Views: 1272

Answers (1)

Ercan
Ercan

Reputation: 3705

instantiateItem item method is wrong place to do it. because it doest work for only one view it works for 3 view at same time.

try moving 

    if (position == 0 && pages == 1) {
        setPages(2);
        notifyDataSetChanged();
    }
    if (position == 1 && pages == 2) {
        setPages(3);
        notifyDataSetChanged();
    }

in setPrimaryItem Method

UPDATE:

Try to call instantiateItem method for the position you want in the setPrimaryItem method. You can do it since instantiateItem is a public method.But i have no idea how it is going to work it is a theory. Just give it a try.

Upvotes: 2

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