一个活动有一个Button和一个ListView。最初,只有Button是可见的。按下按钮时,将显示ListView。显示时,是否可以将某个特定项目显示为选中/聚焦?
一个用例可能是,假设它是一个语言设置列表,当该列表打开时,当前选择的语言必须突出显示。
如果我知道项目的索引,如何将其设置为焦点显示?
发布于 2016-04-03 05:38:58
我使用的是Adapter,并不想设置自定义的背景颜色,而是在可绘制的xml中使用android:state_selected。SetSelection对我不起作用,但也许这也是因为我需要SetNotifyDataChanged,它表明所选状态不是持久的。
我还发现ListView中某项的选中状态不是持久的,因为SetNotifyDataChanged会导致更新ListView布局,从而将它们全部清除。在适配器的GetView中将项目设置为Selected也太快了。
最后,在listview的布局更改之后,我为所选项目的视图设置了Selected状态,这是在触发LayoutChange事件时(在Java语言中,它可能会将附加到ListView的OnLayoutChangeListener )。
为了方便起见,我将所选项目的视图存储为Adapter的SelectedItemView。在ListView的LayoutChange事件处理程序中,我只是将适配器的SelectedItemView.Selected设置为true。
下面是我的活动中的代码,其中我为ListView设置了适配器,还订阅了LayoutChange (或者在Java an OnLayoutChangeListener中)
ringTonesListView.Adapter = ringTonesListAdapter;
ringTonesListView.LayoutChange += (s, layoutChangeArgs) => {
//At this stage the layout has been updated and the Selected can be set to true for the view of the selected item. This will result in android:state_selected logic to be applied as desired and styling can be completely done per layout in Resources.
ringTonesListAdapter.SelectedItemView.Selected = true;
};下面是我的Adapter代码:
public class RingTonesListAdapter : BaseAdapter<RingToneItem>
{
List<RingTone> Items { get; set; }
public override View GetView(int position, View convertView, ViewGroup parent)
{
View view = convertView;
// re-use an existing view, if one is available
// otherwise create a new one
if (view == null)
{
view = Context.LayoutInflater.Inflate(Resource.Layout.AlertSoundItem, parent, false);
view.Click += SelectRingTone;
}
RingTone ringTone = this[position];
if (ringTone.Selected)
{
//==> Important
//Store this view since it's the view for the Selected Item
SelectedItemView = view;
//Setting view.Selected to true here doesn't help either, since Selected will be cleared after.
}
return view;
}
private void SelectRingTone(object sender, EventArgs args)
{
View view = (View)sender;
string title = view.FindViewById<TextView>(Resource.Id.ringToneTitle).Text;
RingToneItem ringToneItem = Items.First(rt => rt.Title == title);
if (!ringToneItem.Selected)
{
//The RingTone was not selected and is selected now
//Deselect Old and Select new
foreach (RingToneItem oldItem in Items.Where(rt => rt.Selected))
{
oldItem.Selected = false;
}
// Select New RingTone
ringToneItem.Selected = true;
//Update the ListView.
//This will result in removal of Selected state for all Items when the ListView updates it's layout
NotifyDataSetChanged();
}
//Now play the test sound
NotifierService.TestSound(Context, ringToneItem);
}
public View SelectedItemView { get; set; }
}https://stackoverflow.com/questions/3888015
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