问题描述
我为 PagerAdapter
开设了这门课:
public class MyPagerAdapter : PagerAdapter
{
private List<string> tab_names = new List<string>();
int[] page = { Resource.Layout.page0,Resource.Layout.page1,Resource.Layout.page2,Resource.Layout.page3,Resource.Layout.page4 };
public Action OnAllPagesAdded = delegate { };
public override java.lang.Object InstantiateItem(ViewGroup container,int page_offset)
{
var view = LayoutInflater.From(container.Context).Inflate(page[page_offset],container,false);
container.AddView(view);
if (page_offset == page.Length - 1)
OnAllPagesAdded();
return view;
}
public MyPagerAdapter(List<string> tab_names)
{
this.tab_names = tab_names;
}
public override int Count => tab_names.Count;
public override bool IsViewFromObject(View view,java.lang.Object obj) => view == obj;
public string GetTabName(int position) => tab_names[position];
public override void DestroyItem(ViewGroup container,int position,java.lang.Object obj)
=> container.RemoveView((View)obj);
}
当所有页面都已实例化并准备好使用时,我需要触发一个事件。我即兴触发了 OnAllPagesAdded
事件:
if (page_offset == page.Length - 1)
OnAllPagesAdded();
在实例化最后一页时触发。我已经设置:
view_pager.OffscreenPageLimit = 100;
所以所有页面都将从一开始就实例化。
是否有更好/更安全的方法来触发事件 OnAllPagesAdded
?
解决方法
您可以在ViewPager的PageScrolled
方法中添加页面数据,它会检测是否显示最后一页。
例如:
MyPagerAdapter myPagerAdapter = ...
...
viewPager.PageScrolled += ViewPager_PageScrolled;
private void ViewPager_PageScrolled(object sender,ViewPager.PageScrolledEventArgs e)
{
if(e.Position == page.Length - 1){
// add page data
myPagerAdapter.OnAllPagesAdded();
}
}