在 Xamarin Forms 中绑定自定义条目

Question

我正在尝试将框架中的此条目提取到 Xamarin 中的自定义元素中，以获得仅在顶部和底部带有边框的可重用条目：

<Frame xmlns="..."
       HasShadow="False"
       CornerRadius="0"
       Padding="0, 1, 0, 1"
       BackgroundColor="#c0c0c0">
    <Entry Padding="20, 10, 20, 10"
           Placeholder="{Binding Placeholder}"
           Text="{Binding Text}"
           BackgroundColor="#ffffff" />
</Frame>

隐藏代码：

public partial class CbSingleEntry : Frame
{
    public static readonly BindableProperty TextProperty = BindableProperty.Create("Text", typeof(string), typeof(CbSingleEntry));
    public static readonly BindableProperty PlaceholderProperty = BindableProperty.Create("Placeholder", typeof(string), typeof(CbSingleEntry));

    public string Text
    {
        get { return (string)GetValue(TextProperty); }
        set { SetValue(TextProperty, value); }
    }

    public string Placeholder
    {
        get { return (string)GetValue(PlaceholderProperty); }
        set { SetValue(PlaceholderProperty, value); }
    }

    public CbSingleEntry()
    {
        InitializeComponent();

        BindingContext = this;
    }
}

当我尝试使用此自定义字段时，占位符和文本属性已正确设置，但我无法将它们绑定到 class:

中的属性

// this one works fine
<local:CbSingleEntry Placeholder="Company" Text="My Company" />
// Placeholder works, but Text is always empty
<local:CbSingleEntry Placeholder="Company" Text="{Binding Company}" />

我可以确认 Company 有一个值，因为使用普通文本字段它可以正常工作：

// This one works as expected, Text is displayed from binded attribute
<Entry Placeholder="Company" Text="{Binding Company}" />

Answer 1

原因：在您的情况下，您在 CbSingleEntry

中设置了 BindingContext

BindingContext = this;

因此 ContentPage 中的绑定将不再起作用。

解法：

您可以修改CbSingleEntry

中的代码

在xaml

<Frame 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:Name="CustomView"  // set the name here
       
             x:Class="xxx">
 
       
           <Entry
             
           Placeholder="{Binding Source={x:Reference CustomView},Path=Placeholder}"
           Text="{Binding Source={x:Reference CustomView},Path=Text}"
           BackgroundColor="#ffffff" />
        
    
</Frame>

在后面的代码中

public partial class CbSingleEntry : Frame
{
    public static readonly BindableProperty TextProperty = BindableProperty.Create("Text", typeof(string), typeof(CbSingleEntry));
    public static readonly BindableProperty PlaceholderProperty = BindableProperty.Create("Placeholder", typeof(string), typeof(CbSingleEntry));

    public string Text
    {
        get { return (string)GetValue(TextProperty); }
        set { SetValue(TextProperty, value); }
    }

    public string Placeholder
    {
        get { return (string)GetValue(PlaceholderProperty); }
        set { SetValue(PlaceholderProperty, value); }
    }

    public CbSingleEntry()
    {
        InitializeComponent();

       // BindingContext = this; don't need to set it any more
    }
}

在 Xamarin Forms 中绑定自定义条目

Binding a custom Entry in Xamarin Forms

c#

xaml

binding

xamarin

xamarin.forms

在xaml

在后面的代码中