Why `PagerAdapter::notifyDataSetChanged` is Not Updating the View?

Why `PagerAdapter::notifyDataSetChanged` is Not Updating the View?

22 May 2024 Stephan Petzl Leave a comment Tech-Help

When working with Android’s ViewPager and PagerAdapter, developers often encounter a common challenge: updating the ViewPager with a new set of views. Even after calling notifyDataSetChanged(), the views may remain unchanged. This article provides a comprehensive guide on how to effectively update the ViewPager, ensuring that your changes are reflected accurately.

Understanding the Issue

In many cases, developers attempt various methods like calling notifyDataSetChanged() on the adapter, invalidating the ViewPager, or even creating a new adapter instance. Despite these efforts, the views often do not update as expected.

Effective Solutions

Here are two primary approaches to address this issue:

1. Overriding getItemPosition()

One of the most straightforward solutions involves overriding the getItemPosition() method in your PagerAdapter. By returning POSITION_NONE, the ViewPager will remove all views and reload them, achieving the desired update effect.

public int getItemPosition(Object object) {
    return POSITION_NONE;

This approach is simple but can be inefficient, especially if you have a large number of views. It forces the ViewPager to recreate all views, which might not be optimal in scenarios with complex or numerous views.

2. Using Tags for Efficient Updates

A more efficient method, especially for applications with many views or complex updates, involves using the setTag() method in instantiateItem() and findViewWithTag() for updates. This approach allows you to update specific views without recreating the entire set.

public Object instantiateItem(View collection, int position) {
    TextView view = new TextView(ctx);
    ((ViewPager) collection).addView(view);
    return view;

public void updateViewPager() {
    for (int i = 0; i < data.size(); i++) {
        TextView view = (TextView) myViewPager.findViewWithTag(i);
        if (view != null) {

This method is more flexible and performant, as it prevents unnecessary recreation of views that haven’t changed.


Choosing the right approach depends on your specific requirements. If your application only needs a simple refresh feature, the first approach might be sufficient. However, for applications requiring frequent or complex updates, the second approach using tags is recommended for its efficiency and flexibility.

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