I'm developing an app with a ViewPager for lateral scrolling tables, sometimes i need to change the adapter to load a different set of tables. I've tried to do the following:
mViewPager.setAdapter(new pagerAdapterPushed(getSupportFragmentManager()));
mViewPager.getAdapter().notifyDataSetChanged();
indicator.setViewPager(mViewPager);
indicator.invalidate();
mViewPager.invalidate();
but it always reload the previous data. Isn't it possibile to change the adapter of a ViewPager?
Exactly like my APP doing...
For change ViewPagerAdapter, what I did is :
Clear all Fragments inside current adapter
Set current adapter to null
Assign new adpater for ViewPager
/* Clear all Fragments inside current adapter */
public class MyPagerAdapter extends FragmentPagerAdapter
{
private ArrayList<Fragment> fragments = new ArrayList<Fragment>();
//...some stuff
public void clearAll() //Clear all page
{
for(int i = 0; i < fragments.size(); i ++)
fragMan.beginTransaction().remove(fragments.get(i)).commit();
fragments.clear();
}
}
/* Set current adapter to null */
Constants.VP.removeAllViews();
Constants.VP.setAdapter(null);
/* Assign new adpater for ViewPager */
Constants.PAGER = new MyPagerAdapter(getSupportFragmentManager());
Constants.VP.setAdapter(Constants.PAGER);
Hope it helps~
You need to override public int getItemPosition (Object object) in pager adapter. For every element in the viewpager, you need to return POSITION_UNCHANGED (if it is still in the pager) or POSITION_NONE (if it was removed). Otherwise the view pager won't know something has changed. I wouldn't recommend setting a new adapter, just clearing out the data in the old one.
I see that @RRTW way worked for some people but it did not do the trick for me (although it was close). Without commitNow() instead of regular commit() it would not work properly. I did something like that:
private fun changePagerAdapter(newAdapter: PagerAdapter) {
val transaction = supportFragmentManager.beginTransaction()
supportFragmentManager.fragments.forEach {
transaction.remove(it)
}
transaction.commitNow()
view_pager.adapter = newAdapter
}
For those who still have issues, do like what I did. I wish it will save your time. It is in Xamarin.Android, but idea should be same in java and kotlin
Prepare your Adapter classes with ClearFragments method through an abstract class:
public abstract class BaseAdapter : FragmentStateAdapter
{
public BaseAdapter(FragmentManager fm, Lifecycle lifecycle) : base(fm, lifecycle)
{
this.fm = fm;
}
readonly FragmentManager fm;
public override int ItemCount => ITEM_COUNT;
private readonly List<Fragment> fragments = new List<Fragment>();
public override Fragment CreateFragment(int position)
{
var fragment = new MyFragment();
fragments.Add(fragment);
return fragment;
}
public void ClearFragments()
{
if (fragments.Count > 0)
{
var transaction = fm.BeginTransaction();
foreach (var fragment in fragments)
{
transaction.Remove(fragment);
}
if (!fm.IsDestroyed)
{
transaction.CommitNow();
}
//see note of Dispose(disposing)
foreach (var fragment in fragments)
{
fragment.Dispose();
}
fragments.Clear();
}
}
private bool disposedValue = false;
//Important note: Your fragment might use Context. You need to override Dispose(disposing) in your fragment class
//and ensure you do not use Context after you dispose it here
protected override void Dispose(bool disposing)
{
if (!disposedValue)
{
disposedValue = true;
if (disposing)
{
ClearFragments();
}
base.Dispose(disposing);
}
}
}
public Adapter1 : BaseAdapter
{
public Adapter1(FragmentManager fm, Lifecycle lifecycle) : base(fm, lifecycle)
{
}
}
public Adapter2 : BaseAdapter
{
public Adapter2(FragmentManager fm, Lifecycle lifecycle) : base(fm, lifecycle)
{
}
}
Then when you want to change adapter, do like this:
public MainActivity : AppCompatActivity
{
private void UseAdapter2()
{
var oldAdapter = viewPager.Adapter as BaseAdapter;
oldAdapter?.ClearFragments();
viewPager.Adapter = null;
var adapter = new Adapter2(SupportFragmentManager, Lifecycle);
// Do any logic that makes this adapter different from the previous one.
viewPager.Adapter = adapter;
oldAdapter?.Dispose();
}
}
@ibrahim Your recommendation goes against the advice of the ViewPager2 docs. It specifically states do not use that technique for CreateFragment. You must always return a new instance of a fragment. Do not reuse from a list of fragments. See https://developer.android.com/training/animation/vp2-migration
Add this to view pager to reload for next fragment:
viewPager.setCurrentItem()
