Android SmartFragmentStatePagerAdapter that intelligently caches the Fragments in the ViewPager

SmartFragmentStatePagerAdapter.java

/* 
   Extension of FragmentStatePagerAdapter which intelligently caches 
   all active fragments and manages the fragment lifecycles. 
   Usage involves extending from SmartFragmentStatePagerAdapter as you would any other PagerAdapter.
*/
public abstract class SmartFragmentStatePagerAdapter extends FragmentStatePagerAdapter {
	// Sparse array to keep track of registered fragments in memory
	private SparseArray<Fragment> registeredFragments = new SparseArray<Fragment>();

	public SmartFragmentStatePagerAdapter(FragmentManager fragmentManager) {
		super(fragmentManager);
	}

	// Register the fragment when the item is instantiated
	@Override
	public Object instantiateItem(ViewGroup container, int position) {
		Fragment fragment = (Fragment) super.instantiateItem(container, position);
		registeredFragments.put(position, fragment);
		return fragment;
	}

	// Unregister when the item is inactive
	@Override
	public void destroyItem(ViewGroup container, int position, Object object) {
		registeredFragments.remove(position);
		super.destroyItem(container, position, object);
	}

	// Returns the fragment for the position (if instantiated)
	public Fragment getRegisteredFragment(int position) {
		return registeredFragments.get(position);
	}
}

Cool have been looking for this

thank you very mutch... work like a charm

Nice!!!!!

I would make a little change and use generics so we don't need to cast when getting the fragment:

public abstract class SmartFragmentStatePagerAdapter<T extends Fragment> extends FragmentStatePagerAdapter {

    private SparseArray<T> registeredFragments = new SparseArray<T>();

    public SmartFragmentStatePagerAdapter(FragmentManager fragmentManager) {
        super(fragmentManager);
    }

    // Register the fragment when the item is instantiated
    @Override
    public Object instantiateItem(ViewGroup container, int position) {
        T fragment = (T) super.instantiateItem(container, position);
        registeredFragments.put(position, fragment);
        return fragment;
    }

    // Unregister when the item is inactive
    @Override
    public void destroyItem(ViewGroup container, int position, Object object) {
        registeredFragments.remove(position);
        super.destroyItem(container, position, object);
    }

    // Returns the fragment for the position (if instantiated)
    public T getRegisteredFragment(int position) {
        return registeredFragments.get(position);
    }
}

Now, when you extends this class, specify your fragment type:

public class MyPageAdapter extends SmartFragmentStatePagerAdapter<MyFragment> {
....

Nice, it help me a lot for understanding a cache for fragment

Can you please give me a small example how I can manage my Fragments (with AsyncTasks) of ViewPager inside a Fragment by using this adapter?

This will lose its state on configuration change. The FragmentStatePagerAdapter will restore its cached fragment instances, and this object will have no registered instances.

@hashbrown yep!

It helped so much ! 👍 👍

Is there anyway to refresh current fragment?

@gustavogianordoli

Hi thank you very much,
How can i use getRegisteredFragment method on SmartFragmentStatePagerAdapter deployed viewPager ? is it for check caching fragment?

firstly thanks you! hoping it is useful to me,