Xamarin Forms ListView ItemSelected功能

Question

Here is a function that gets called when an item gets selected from a ListView :

async void detail_clicked(object sender, SelectedItemChangedEventArgs e){
    if (e.SelectedItem == null) {
            return;
    }
    Detail selected = (Detail)e.SelectedItem;
    order_vm.List_of_details.Add(selected);
    await DisplayAlert ("Item Added", 
        String.Format ("{0} added to cart.", selected.detail_name), "Okay");
    ((ListView)sender).SelectedItem = null;
}

I added this function using the ItemSelected event handler

details_list.ItemSelected += detail_clicked;

The first time I click on the Item, the DisplayAlert pops up. After the first click, the DisplayAlert inside detail_clicked no longer pops up. But the other code inside the handler does get called.

Anyone know how to fix this issue? Is it something I am not understanding about event handlers? Is it something about await/async?

Answer 1

The DisplayAlert might be running on a different thread. Try wrapping Display Alert in Device.BeginInvokeOnMainThread . You can ready about that here .

Answer 2

请再次检查方法是否异步，然后在DisplayAlert（）上等待。

Answer 3

Use this following code. It will helps you.

private void OnItemSelected(object sender, SelectedItemChangedEventArgs e)
    {
        if (e.SelectedItem == null)
        {

            return;

        }

        listView.SelectedItem = null;

        DisplayAlert("Alert", e.SelectedItem.ToString(), "Ok");

    }