我为具有两种类型的行的ListView创建了一个适配器。 ListView有4行。最后一行有不同的布局,这就是为什么我在getview中使用GetItemViewType方法的原因了解ViewHolder模式
我想了解该模式如何工作。我看着这样的: https://www.youtube.com/watch?v=bWsWe9T9HJw,以获得更好的理解 回收是如何工作的
什么,我不明白的是:当我在我的列表视图向下滚动,在convertview 总是空。当我再次滚动备份时,convertview不是null并且是可重用的。
不应该convertview为null只为列表中的第一个项目?我不明白为什么 它为每个新项目为空?只有在列表中的第一项
public override View GetView (int position, View convertView, ViewGroup parent)
{
BaseBundelVO bundle = _bundles [position];
DSBundleListItem bundleHolder = null;
DSBundleArchiveItem archiveHolder = null;
int type = GetItemViewType(position);
if (convertView == null)
{
bundleHolder = new DSBundleListItem (_activity);
archiveHolder = new DSBundleArchiveItem (_activity);
switch (type)
{
case 0:
convertView = _activity.LayoutInflater.Inflate (Resource.Layout.dsBundleListItem, null);
bundleHolder.IconIv = convertView.FindViewById<ImageView> (Resource.Id.iconIv);
bundleHolder.CoverIv = convertView.FindViewById<ImageView> (Resource.Id.coverIv);
bundleHolder.CoverTitleTv = convertView.FindViewById<TextView> (Resource.Id.coverTitleTv);
bundleHolder.CoverSubTitleTv = convertView.FindViewById<TextView> (Resource.Id.coverSubTitleTv);
bundleHolder.BundleProgress = convertView.FindViewById<ProgressBar> (Resource.Id.bundleProgress);
convertView.Tag = bundleHolder;
break;
case 1:
convertView = _activity.LayoutInflater.Inflate (Resource.Layout.dsBundleArchiveItem, null);
archiveHolder.ArchiveTitleTv = convertView.FindViewById<TextView> (Resource.Id.archiveTitleTv);
archiveHolder.ArchiveSubTitleTv = convertView.FindViewById<TextView> (Resource.Id.archiveSubTitleTv);
convertView.Tag = archiveHolder;
break;
}
}
else
{
switch (type)
{
case 0:
bundleHolder = (DSBundleListItem)convertView.Tag;
Console.WriteLine (bundleHolder.IsDisposed());
bundleHolder.RemoveImageLoaderCallBack();
break;
case 1:
archiveHolder = (DSBundleArchiveItem)convertView.Tag;
Console.WriteLine (archiveHolder.IsDisposed());
archiveHolder.RemoveImageLoaderCallBack();
break;
}
}
switch (type)
{
case 0:
bundleHolder.CoverTitleTv.Text = bundle.Title;
bundleHolder.CoverSubTitleTv.Text = bundle.SubTitle;
bundleHolder.LoadImage(bundle.CoverImageLocation,bundle.Icon);
break;
case 1:
archiveHolder.ArchiveTitleTv.Text = "Archief";
archiveHolder.ArchiveSubTitleTv.Text = "Bekijk onze eerder verschenen publicaties";
break;
}
return convertView;
}
如果你的屏幕可以适合说2个视图,那么android会加载视图,2 visibile视图,并在底部的下一个视图,所以它至少需要4个views.This解释了为什么它不只是首先convertview null。顺便说一句,你应该检查与Api 21新的RecyclerView。 –