Xamarin 表单更新 listView itemSource [英] Xamarin form update listView itemSource

问题描述

好的，我有一个 ListView 对象，它有一个 List 作为 ItemSource，我想刷新 ItemSource 每当对象列表发生变化时.ListView 有一个个性化的 ItemTemplate现在我已经这样做了:

Ok I have a ListView object which have a List<Filiale> as ItemSource and I'd like to refresh the ItemSource whenever the list of object change. The ListView has a personalized ItemTemplate For now I have done this:

public NearMe ()
{
    list=jM.ReadData ();
    listView.ItemsSource = list;
    listView.ItemTemplate = new DataTemplate(typeof(FilialeCell));
    searchBar = new SearchBar {
        Placeholder="Search"
    };
    searchBar.TextChanged += (sender, e) => {
        TextChanged(searchBar.Text);
    };
    var stack = new StackLayout { Spacing = 0 };
    stack.Children.Add (searchBar);
    stack.Children.Add (listView);
    Content = stack;
}

public void TextChanged(String text){
        //DOSOMETHING
        list=newList;
}

正如您在 TextChanged 方法中看到的，我为前一个列表分配了一个新列表，但视图中没有任何变化.在我创建的 ViewCell 中，我使用 SetBinding

As you can see in the TextChanged method I assign a new list to the previous one but there are no changes in the view. In the ViewCell that I created I assign the Text field of the Labels with the SetBinding

推荐答案

好的，这是我解决问题的方法，首先我创建了一个包装器"，它为我的列表实现了 INotifyPropertyChanged像这样作为 ItemSource :

Ok here is how I solved the problem, first of all I created a "wrapper" that implement INotifyPropertyChanged for the list that I was taking as ItemSource like this :

public class Wrapper : INotifyPropertyChanged
    {
        List<Filiale> list;
        JsonManager jM = new JsonManager ();//retrieve the list

        public event PropertyChangedEventHandler PropertyChanged;
        public NearMeViewModel ()
        {
            list = (jM.ReadData ()).OrderBy (x => x.distanza).ToList();//initialize the list
        }

        public List<Filiale> List{ //Property that will be used to get and set the item
            get{ return list; }

            set{ 
                list = value;
                if (PropertyChanged != null)
                {
                    PropertyChanged(this, 
                        new PropertyChangedEventArgs("List"));// Throw!!
                }
            }
        }

        public void Reinitialize(){ // mymethod
            List = (jM.ReadData ()).OrderBy (x => x.distanza).ToList();
        }

然后在 NearMe 类中:

Then in the NearMe class:

Wrapper nearMeVM = new Wrapper();
public NearMe ()
        {

            Binding myBinding = new Binding("List");
            myBinding.Source = nearMeVM;
            myBinding.Path ="List";
            myBinding.Mode = BindingMode.TwoWay;
            listView.SetBinding (ListView.ItemsSourceProperty, myBinding); 
            listView.ItemTemplate = new DataTemplate(typeof(FilialeCell));
            searchBar = new SearchBar {
                Placeholder="Search"
            };
            searchBar.TextChanged += (sender, e) => {
                TextChanged(searchBar.Text);
            };
            var stack = new StackLayout { Spacing = 0 };
            stack.Children.Add (searchBar);
            stack.Children.Add (listView);
            Content = stack;
        }
public void TextChanged(String text){
            if (!String.IsNullOrEmpty (text)) {
                text = text [0].ToString ().ToUpper () + text.Substring (1);
                var filterSedi = nearMeVM.List.Where (filiale => filiale.nome.Contains (text));
                var newList = filterSedi.ToList ();
                nearMeVM.List = newList.OrderBy (x => x.distanza).ToList ();
            } else {
                nearMeVM.Reinitialize ();
            }

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