具有可绑定属性的自定义视图在Xamarin.Forms SAP上未正确绑定 [英] Custom View with Bindable Property not binding properly on Xamarin.Forms SAP

问题描述

我有一个复选框，该复选框应该触发按钮的IsEnabled事件.但是不知何故，原本应该执行的命令永远不会被正确绑定并因此而执行.

I have a checkbox that's supposed to fire the IsEnabled event of a button. But somehow the command that's supposed to do that never gets properly binded and therefore executed.

这是CheckBox.xaml.cs(控件)中的可绑定属性:

This is the bindable property in CheckBox.xaml.cs (the control):

public static readonly BindableProperty CheckBoxCommandProperty =
       BindableProperty.Create<CheckBox, ICommand>(
       checkbox =>
           checkbox.CheckBoxCommand,
           null,
           propertyChanged: (bindable, oldValue, newValue) =>
               {
                   CheckBox checkbox = (CheckBox)bindable;
                   EventHandler<bool> eventHandler = checkbox.CheckedChanged;
                   if (eventHandler != null)
                   {
                       eventHandler(checkbox, checkbox.IsChecked);
                   }
               });

   public event EventHandler<bool> CheckedChanged;

   public ICommand CheckBoxCommand
   {
       get { return (ICommand)GetValue(CheckBoxCommandProperty); }
       set { SetValue(CheckBoxCommandProperty, value); }
   }

这就是我在ViewModel上所拥有的:

And this is what I have on the ViewModel:

   public ICommand Next_OnClick { get; set; }
   public ICommand OnCheckBoxTapChanged { get; set; }

   public TermsAndConditionsViewModel()
   {
       Next_OnClick = new Command(NextClicked);
       OnCheckBoxTapChanged = new Command(CheckBoxTapped);
   }

   private void CheckBoxTapped()
   {
       if (IsCheckedChanged)
       {
           Next_IsEnabled = true;
       }
       else
       {
           Next_IsEnabled = false;
       }
   }

CheckBoxTapped方法永远不会执行，因此我要设置的button属性永远不会更改.

The CheckBoxTapped method never gets executed and therefore the button property I wanna set never changes.

在此先感谢大家！

推荐答案

使用Xamarin.Forms.Behavior解决了该问题.它允许对控件进行多次绑定.

Solved it using Xamarin.Forms.Behavior. It allows multiple bindings to controls.

例如>

<Entry Placeholder="Enter password"
             Text= "{Binding TxtFirstPasswordInput}"
             IsPassword="true">
        <b:Interaction.Behaviors>
          <b:BehaviorCollection>
            <b:EventToCommand EventName="Unfocused" Command="{Binding entry_Finished}"/>
            <b:EventToCommand EventName="Focused" Command="{Binding entry_Focused}"/>
          </b:BehaviorCollection>
        </b:Interaction.Behaviors>
      </Entry>

在ViewModel上

And on the ViewModel>

public PasswordInputViewModel()
        {
            entry_Finished = new Command(validateAndContinue);//unfocused
            entry_Focused = new Command(entryFocused); //focused
        }

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