ViewPager中的4种布局1页

Question

I have a ViewPager with which I want 4 instances of a layout displayed on the screen at a time, and you scroll to look at the next 4. This means I either need to add 4 instances of the layout to a single page, or I need to tell the ViewPager to scroll 4 pages at a time. I'd like to do this without making 4 copies of a layout in the same xml. Here's how I'm handling this now:

@Override
public Object instantiateItem(ViewGroup container, int position)
{   
    LinearLayout toReturn = new LinearLayout(getActivity());
    toReturn.setOrientation(LinearLayout.HORIZONTAL);

    for(int i = position; i < position + 4; i++)
    {
        View layout = getActivity().getLayoutInflater().inflate(R.layout.viewpager_fragment_layout, container, false);

        toReturn.addView(layout);
    }

    container.addView(toReturn);

    return toReturn;
}

The result is the same as though I were adding each layout to the ViewPager 1 at a time instead of grouping them up into a single layout. It displays 4 layouts on the screen at a time, but when you scroll, you only move past 1 layout at a time.

Answer 1

Override getPageWidth() in your PagerAdapter to return the portion of the screen to use for a page. For four pages at a time, returning 0.25 should work.

Here is a sample project demonstrating this. Also here is a blog post outlining this technique and a couple of others.

---

With regards to your current code, I do not know for certain how you are determining that "when you scroll, you only move past 1 layout at a time". After all, since you are not changing anything in the layouts, they all look the same.

Hence, I am going to make two assumptions, that would seem to fit your described symptoms:

1. There is code that you elected not to show between your inflate() call and your addView() call.

2. The code in question is populating the widgets based on position .

Bear in mind that position is the page index , not the layout index .

Let's suppose that you have 12 total layouts. You want to show those in 3 pages in a ViewPager . Hence, getPageCount() should be returning 3. And instead of:

 for(int i = position; i < position + 4; i++) {

I would expect to see:

 for(int layout_offset = 0; layout_offset < 4; layout_offset++) {
    int i=(position*4)+layout_offset;

(though I would have named i to be layout_index or something)