我正在为横向滚动表开发一个带有 ViewPager 的应用程序，有时我需要更改适配器以加载一组不同的表。我尝试执行以下操作：
mViewPager.setAdapter(new pagerAdapterPushed(getSupportFragmentManager()));
mViewPager.getAdapter().notifyDataSetChanged();
indicator.setViewPager(mViewPager);
indicator.invalidate();
mViewPager.invalidate();
但它总是重新加载以前的数据。是不是可以更改 ViewPager 的适配器？
就像我的APP做的一样...
对于更改 ViewPagerAdapter，我所做的是：
清除当前适配器内的所有 Fragment
将当前适配器设置为空
为 ViewPager 分配新的适配器
/* 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);
希望有帮助~
您需要public int getItemPosition (Object object)在寻呼机适配器中覆盖。对于视图分页器中的每个元素，您需要返回POSITION_UNCHANGED（如果它仍在分页器中）或POSITION_NONE（如果它已被删除）。否则视图寻呼机将不知道发生了什么变化。我不建议设置新适配器，只需清除旧适配器中的数据即可。
我看到@RRTW 方式对某些人有用，但对我没有用（尽管它很接近）。如果没有commitNow()代替常规commit()，它将无法正常工作。我做了这样的事情：
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 您的建议与 ViewPager2 文档的建议背道而驰。它特别声明不要将该技术用于 CreateFragment。您必须始终返回片段的新实例。不要从片段列表中重复使用。见https://developer.android.com/training/animation/vp2-migration
将此添加到查看寻呼机以重新加载下一个片段：
viewPager.setCurrentItem()