如何在XAML页面中执行SetBinding和BindingContext？

Question

我目前正在尝试开发基于 Xamarin Forms 选项卡式页面的应用程序。起初，该应用程序只有一个用 C# 编写的内容页面。我现在要做的是将这个现有的内容页面实现到选项卡页面的选项卡之一中。

我正在用 XAML 编写标签页，但我不知道如何用这种语言执行 "SetBinding" 或 "BindingContext"。

这是我想从 C# 翻译成 XAML:

    public MyPage()
    {

        this.BindingContext = new MyPageViewModel();

        Picker pickerBluetoothDevices = new Picker() { Title = "Select a bth device" };
        pickerBluetoothDevices.SetBinding(Picker.ItemsSourceProperty, "ListOfDevices");
        pickerBluetoothDevices.SetBinding(Picker.SelectedItemProperty, "SelectedBthDevice");
        pickerBluetoothDevices.SetBinding(VisualElement.IsEnabledProperty, "IsPickerEnabled");

        Entry entrySleepTime = new Entry() {Keyboard = Keyboard.Numeric, Placeholder = "Sleep time" };
        entrySleepTime.SetBinding(Entry.TextProperty, "SleepTime");

        Button buttonConnect = new Button() { Text = "Connect" };
        buttonConnect.SetBinding(Button.CommandProperty, "ConnectCommand");
        buttonConnect.SetBinding(VisualElement.IsEnabledProperty, "IsConnectEnabled");

        Button buttonDisconnect = new Button() { Text = "Disconnect" };
        buttonDisconnect.SetBinding(Button.CommandProperty, "DisconnectCommand");
        buttonDisconnect.SetBinding(VisualElement.IsEnabledProperty, "IsDisconnectEnabled");

        Button buttonSend = new Button() { Text = "Send" };
        buttonSend.SetBinding(Button.CommandProperty, "SendCommand");
        buttonSend.SetBinding(VisualElement.IsEnabledProperty, "IsSendEnabled");

        StackLayout slButtons = new StackLayout() {Orientation = StackOrientation.Horizontal, Children = {buttonDisconnect, buttonConnect, buttonSend } };

        ListView lv = new ListView();
        lv.SetBinding(ListView.ItemsSourceProperty, "ListOfBarcodes");
        lv.ItemTemplate = new DataTemplate(typeof(TextCell));
        lv.ItemTemplate.SetBinding(TextCell.TextProperty, ".");

        int topPadding = 0;
        if (Device.RuntimePlatform == Device.iOS)
            topPadding = 20;

        StackLayout sl = new StackLayout { Children = { pickerBluetoothDevices, entrySleepTime, slButtons, lv }, Padding = new Thickness(0,topPadding,0,0) };
        Content = sl;
    }

XAML 中这段 C# 代码的等效项是什么？

我是这样开始的：

<?xml version="1.0" encoding="utf-8" ?>
<TabbedPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="TestBth.MyTabbedPage">
  <!--Pages can be added as references or inline-->
  <ContentPage Title="Connect">



        <ContentPage.Content>
            <StackLayout VerticalOptions="Center" HorizontalOptions="Center">

                <Picker x:Name="pickerBluetoothDevices" Title="Select a bth device"/>

                <Button x:Name="buttonConnect" Text="Connect"/>
                <Button x:Name="buttonDisconnect" Text="Disconnect"/>
                <Button x:Name="buttonSend" Text="Send"/>

                <ListView x:Name="lv"/>

            </StackLayout>

        </ContentPage.Content>

  </ContentPage>

Answer 1

您想在代码中创建绑定的原因是什么？您还可以在代码中进行绑定，例如将命令绑定到按钮，您可以使用：

<Button Command="{Binding ButtonCommand}"/>

在视图的构造函数中，您需要设置上下文：

 public View()
  {
        InitializeComponent();
        this.BindingContext = this; // or instance of your ViewModel
  }

并且您还需要在 BindingContext 实例中定义您的命令：

public ICommand ButtonCommand { get; set; }

Answer 2

你的做法是正确的，只需将 c# 绑定属性更改为 Xaml 属性。

与 c# 中的 ItemSourceProperty 一样，xaml 绑定是 ItemSource

<StackLayout VerticalOptions="Center" HorizontalOptions="Center">

            <Picker x:Name="pickerBluetoothDevices" ItemsSource="{Binding ListOfDevices}" Title="Select a bth device" SelectedItem="{Binding SelectedBthDevice}" IsEnable="{Binding IsPickerEnabled}"/>

            <Button x:Name="buttonConnect" Text="Connect" Command="{Binding ConnectCommand}"/>
            <Button x:Name="buttonDisconnect" Text="Disconnect" Command="{Binding DisconnectCommand}"/>
            <Button x:Name="buttonSend" Text="Send" Command="{Binding SendCommand}"/>

            <ListView x:Name="lv" ItemSource="{Binding ListOfBarcodes}"/>

        </StackLayout>

如何在XAML页面中执行SetBinding和BindingContext？

How to perform SetBinding and BindingContext in a XAML page?

c#

xaml

binding

xamarin

tabbedpage