我在绑定我的Xamarin Picker时遇到了一些困难,所以当我更改所选项时,它会触发我表单中的刷新 . 我正在使用XAML代码隐藏 .
这是XAML . 您可以看到Picker已定义 . 数据被很好地绑定,并从我的List加载Name属性 .
它上面有一个Id“Entry”字段,这是不起作用的部分 . 我想要做的是当选择器被“挑选”时,从列表/选择列表项中显示Id字段 .
还有一些我在网上找到的示例代码--Surname和Forename都在输入数据时更新相应的标签 . 所以它必须与picker和SelectedItem绑定或我尝试使用OnPropertyChanged的方式有关 .
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" x:Class="TechsportiseApp.MainUI.Races">
<StackLayout Padding="0,20,0,0">
<Label Text="Race ID" />
<Entry Text="{Binding Id}" />
<Picker ItemsSource="{Binding RaceList}" ItemDisplayBinding="{Binding Name}" SelectedItem="{Binding RacesIndex, Mode=TwoWay}" />
<Label Text="Data Binding 101 Demo" FontAttributes="Bold" HorizontalOptions="Center" />
<Label Text="Forename:" />
<Entry Text="{Binding Forename, Mode=TwoWay}" />
<Label Text="Surname:" />
<Entry Text="{Binding Surname, Mode=TwoWay}" />
<Label Text="Your forename is:" />
<Label Text="{Binding Forename}" />
<Label Text="Your surname is:" />
<Label Text="{Binding Surname}" />
</StackLayout>
</ContentPage>
我正在使用的ViewModel如下所示 .
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Threading.Tasks;
using Newtonsoft.Json;
using RestSharp;
using TechsportiseApp.API.Models;
using Xamarin.Forms;
using TechsportiseApp.API;
namespace TechsportiseApp.MainUI.Models
{
public class RacesViewModel : INotifyPropertyChanged
{
int _id;
public int Id
{
get
{
return _id;
}
set
{
if (_id != value)
{
_id = value;
OnPropertyChanged("Id");
}
}
}
string _name;
public string Name
{
get
{
return _name;
}
set
{
if (_name != value)
{
_name = value;
OnPropertyChanged("Name");
}
}
}
public List<Race> RaceList
{
get
{
var racelist = RacesAPI.GetRaces();
return racelist;
}
}
int _racesIndex;
public int RacesIndex
{
get
{
return _racesIndex;
}
set
{
if (_racesIndex != value)
{
_racesIndex = value;
// trigger some action to take such as updating other labels or fields
OnPropertyChanged("RacesIndex");
}
}
}
string forename, surname;
public string Forename
{
get
{
return forename;
}
set
{
if (forename != value)
{
forename = value;
OnPropertyChanged("Forename");
}
}
}
public string Surname
{
get
{
return surname;
}
set
{
if (surname != value)
{
surname = value;
OnPropertyChanged("Surname");
}
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
{
var changed = PropertyChanged;
if (changed != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
如果需要,这里是我用来填充列表数据的代码,我从API的JSON响应中获取 .
using Newtonsoft.Json;
using RestSharp;
using System;
using System.Collections.Generic;
using System.Text;
using TechsportiseApp.API.Models;
using TechsportiseApp.MainUI;
using Xamarin.Forms;
namespace TechsportiseApp.API
{
public class RacesAPI
{
public static List<Race> GetRaces()
{
var raceList = new List<Race>();
string APIServer = Application.Current.Properties["APIServer"].ToString();
string Token = Application.Current.Properties["Token"].ToString();
var client = new RestClient(APIServer);
var request = new RestRequest("api/race", Method.GET);
request.AddHeader("Content-type", "application/json");
request.AddHeader("Authorization", "Bearer " + Token);
var response = client.Execute(request) as RestResponse;
raceList = JsonConvert.DeserializeObject<List<Race>>(response.Content);
return raceList;
}
}
}
有任何想法吗?我一直试图破解这几天,但似乎无法让它发挥作用 .
1 回答
从我所看到的,你在任何时候都没有设置Id的值 . 可能你想把它放在RacesIndex的setter中 . RacesIndex也应绑定到SelectedIndex,而不是SelectedItem . 我假设Race类有一个Id属性,它是一个int,所以请看下面的内容 . 如果要绑定到selectedItem,则绑定到的属性应与列表中的属性相同