无法在ListView中绑定属性

问题描述

我正在编写天气预报应用程序，无法在ListView中绑定对象的属性。

集合由WeatherModel对象组成，它们具有字符串属性“ Temperature”

Xaml可以看到该集合并将其输出，但是找不到对象属性“温度”。

如何绑定属性“温度”？

这是我的XAML

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:d="http://xamarin.com/schemas/2014/forms/design"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             mc:Ignorable="d"
             x:Class="IMAP.View.Weather"
             xmlns:local="clr-namespace:IMap.viewmodel;assembly=IMAP">

    <ContentPage.Resources>
        <local:ForecastWeatherviewmodel x:Key="vm"/>
    </ContentPage.Resources>
    <ContentPage.Content>
        <ListView ItemsSource="{Binding items,Source={StaticResource vm}}">
            <ListView.ItemTemplate>
                <DataTemplate>
                    <ViewCell>
                        <StackLayout Orientation="Horizontal" Padding="2,15">

                            <Label Text="{Binding Temperature}"/>

                        </StackLayout>
                    </ViewCell>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>
    </ContentPage.Content>
</ContentPage>

这是我的viewmodel

namespace IMap.viewmodel
{
    public class ForecastWeatherviewmodel : viewmodel
    {
        public ObservableCollection<WeatherModel> WeatherList { get; set; }

        public ObservableCollection<WeatherModel> items
        {
            get
            {
                return WeatherList;
            }
        }



        public ForecastWeatherviewmodel()
        {
            WeatherList = new ObservableCollection<WeatherModel>();

            WeatherList.Add(new WeatherModel()
                {
                    Temperature = SomeTemp
                });

            WeatherList.Add(new WeatherModel()
                {
                    Temperature = SomeTemp
                });

            OnPropertyChange();

        }
    }
}

这是我的模特

namespace IMAP.Model
{
    public class WeatherModel
    {
        public string Temperature;
    }
}

解决方法

首先，您不能绑定到字段，而应使用属性代替。

public class WeatherModel
{
    public string Temperature { get; set; }
}

然后，您可以在视图模型中修复集合管理。同样具有以下命名规则：财产用大写字母，领域用小写字母。现在，您具有同一个集合的两个公共属性，让我们制作一个。

public class ForecastWeatherViewModel : ViewModel
{
    // backing field,never interact with it outside of the property getter/setter
    private ObservableCollection<WeatherModel> items;

    // public property,bind here,interact with it
    public ObservableCollection<WeatherModel> Items
    {
        get => items; // same as "get { return items; }" but shorter
        set
        {
            items = value;
            OnPropertyChange();
        }
    }

    public ForecastWeatherViewModel()
    {
        Items = new ObservableCollection<WeatherModel>();

        Items.Add(new WeatherModel()
        {
            Temperature = SomeTemp
        });

        Items.Add(new WeatherModel()
        {
            Temperature = SomeTemp
        });
    }
}

<ListView ItemsSource="{Binding Items,Source={StaticResource vm}}">