单击 ListView 事件后 searchBar 不更改占位符 listview_ItemSelected

Question

我在我的 MainPage 上设置了一个 searchBar 和 ListView：

              <StackLayout>  
                    <SearchBar
                       BackgroundColor="#d3d3d3"
                       x:Name="searchBar"
                       Placeholder="Enter city"
                       PlaceholderColor="#919191"
                       TextChanged="SearchBar_TextChanged"
                       SearchButtonPressed="Btn_Search">
                    </SearchBar>

                   <Frame CornerRadius="15"
                           OutlineColor="#919191" 
                           Padding="2"
                           Margin="3">
                         
                       <Label  BackgroundColor="#dedede"
                               TextColor="#919191"
                               Font="Bold"
                               FontSize="20"
                               Text="Списък с населени места"
                               YAlign="Center"
                               XAlign="Center"
                               LineBreakMode="TailTruncation" />
                </Frame>
          
                      <ListView
                        BackgroundColor="#d3d3d3"
                        ItemTapped="ListView_ItemTapped"
                        ItemSelected="listView_ItemSelected"
                        HeightRequest="88"
                        x:Name="listView" >  
                        <ListView.ItemTemplate>  
                            <DataTemplate>  
                                <TextCell Text="{Binding Place}"/>
                            </DataTemplate>  
                        </ListView.ItemTemplate>  
                    </ListView>      
               </StackLayout>

之后我创建了 class 联系人，字符串为“Place” -> get;设置；

public class Contacts
        {
            public string Place { get; set; }
        }

然后打开数据库连接以执行一个查询并像这样填写我的列表：

 IEnumerable<Contacts> GetContacts(string searchText = null)
    {
        
        server = "ip-to-db";
        database = "db-name";
        uid = "user";
        password = "pass";
        string connectionString;
        connectionString = "SERVER=" + server + ";" + "DATABASE=" +
        database + ";" + "UID=" + uid + ";" + "PASSWORD=" + password + ";";
        connection = new MySqlConnection(connectionString);
        connection.Open();
        var cmd = new MySqlCommand();
        cmd.Connection = connection;

        //save from database data
        var contacts = new List<Contacts>();

        //cut first four strings from selected query
        MySqlCommand command = new MySqlCommand($"SELECT SUBSTRING(place,  4, 35), code AS ExtractString FROM places ORDER BY place", connection);

        using (MySqlDataReader reader = command.ExecuteReader())
        {
            while (reader.Read())
            {
                var place = new Contacts
                {
                    Place = reader[0].ToString() + " - " + reader[1].ToString()
                };

                contacts.Add(place);       

            }
            connection.Close();
        }

        if (string.IsNullOrEmpty(searchText))
            return contacts;
        return contacts.Where(p => p.Place.StartsWith(searchText));
    }


    private void ListView_Refreshing(object sender, EventArgs e)
    {
        listView.ItemsSource = GetContacts();
        
        listView.EndRefresh();
    }

    void SearchBar_TextChanged(System.Object sender, Xamarin.Forms.TextChangedEventArgs e)
    {
        listView.ItemsSource = data.Where(p => p.Place.StartsWith(e.NewTextValue));
    }

现在我想在单击某些 ListView 元素时更改 searchBar 上的占位符，但是当我调试此文本下的最后一个代码时，我看到了来自 listView.SelectedItem.ToString(); 的字符串，但是当我想要显示我在显示屏上没有看到带有此代码的字符串：

 void listView_ItemSelected(System.Object sender, Xamarin.Forms.SelectedItemChangedEventArgs e)
    {

        LabelClick.Text = listView.SelectedItem.ToString();

        searchBar.Placeholder = LabelClick.Text;
}

这是当我单击某个 listView 元素时搜索栏上准确显示的屏幕截图。 searchBar after clicked on ListView

Answer 1

ToString 的默认行为是 return class 的名称。这正是正在发生的事情。如果你想显示 Place 属性你需要指定

searchBar.Placeholder = ((Contacts)listView.SelectedItem).Place;

单击 ListView 事件后 searchBar 不更改占位符 listview_ItemSelected

searchBar not change the Placeholder after clicked on ListView event listview_ItemSelected

c#

xamarin.forms

xamarin.forms.listview