android - instantiateItem(ViewGroup, int) in PagerAdapter and AddView in ViewPager confusion

Question

So far I've been hacking together examples to get a feel for the APIs the Android SDK as a whole. However, I've hit an impasse.

I'm trying to Inflate a LinearLayout with 2 TextViews from an XML file. These will be then Views that are paged. I simply can't get this to work and realize that I totally don't understand what's going on with the code.

Looking at the source I can see that the method ViewPager.addNewItem calls the InstantiateItem from the supplied adapter. And addNewItem is called in populate(). populate() is called in a number of other places.

Anyway, in the example, I've experienced that when the method is overridden for PagerAdapter one must include a call to addView() on the ViewPager collection that is passed from the ViewPager as an argument.

If I wish to add multiple views I thought this would be a case of calling addView() more than once but as instantiateItem() returns an Object to ViewPager (in the example I had it returns the view that it added) I don't know what to return. I've tried returning the inflated view and a number of other things.

Please, can someone explain what is happening here?

Much appreciated.

@Override
public Object instantiateItem(View collection, int position) {

    layout = inflater.inflate(R.layout.animallayout, null);
    TextView tv = (TextView) layout.findViewById(R.id.textView1);
    tv.setText("1________________>" + position);

    TextView tv2 = (TextView) layout.findViewById(R.id.textView2);
    tv.setText("2________________>" + position);

    ((ViewPager) collection).addView(layout);
    return layout;
}

Answer 1

I've recently implemented this and this is my instantiateItem method (made it a bit minimal for readability.

@Override
public Object instantiateItem(View collection, int position) {
    Evaluation evaluation = evaluations.get(position);

    View layout = inflater.inflate(R.layout.layout_evaluation, null);

    TextView evaluationSummary = (TextView) layout.findViewById(R.id.evaluation_summary);
    evaluationSummary.setText(evaluation.getEvaluationSummary());

    ((ViewPager) collection).addView(layout);

    return layout;
}

@Override
public void destroyItem(View collection, int position, Object view) {
     ((ViewPager) collection).removeView((View) view);
}

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

So for the page that is displayed, I get the data from my evaluations list using the position as the index. Then inflate the Layout which has the views I will add my data too. Then I get the TextView to set the evaluation summary text on. Then the whole Layout is added to the ViewPager. And finally the Layout is also returned.

If you still can't get it post your code.