我的 StateButton 状态没有更新我的视图

Question

我正在尝试使用 Xamarin.CustomControls 中的 StateButtons

我有 2 个状态按钮，我希望它们以二分法的方式工作。

我的视图模型是这样的：

        private bool _btn1Active { get; set; }

        public bool Btn1Active
        {
            get
            {
                return _btn1Active;
            }
            set
            {
                if(_btn1Active != value)
                {
                    _btn1Active = value;

                    NotifyPropertyChanged("Btn1Active");
                }
            }
        }

        private bool _btn2Active { get; set; }

        public bool Btn2Active
        {
            get
            {
                return _btn2Active;
            }
            set
            {
                if(_btn2Active != value)
                {
                    _btn2Active = value;

                    NotifyPropertyChanged("Btn2Active");
                }
            }
        }

我已经绑定了这样的状态按钮：

Btn1.SetBinding(StateButton.IsPressedProperty, "Btn1Active");
Btn2.SetBinding(StateButton.IsPressedProperty, "Btn2Active");

而我的 button_clicked 处理程序是：

private void Btn_Clicked(object sender, EventArgs e)
        {
            var myViewModel = BindingContext as BtnsViewModel;

            myViewModel.Btn1Active= !myViewModel.Btn1Active;
            myViewModel.Btn2Active= !myViewModel.Btn2Active;

        }

我已经调试了很长时间，我看到每个属性都得到了正确的通知和更改，但是视图没有更新。

Answer 1

我创建了一个演示来测试您的代码，它可以正常工作。 主要代码如下：

  public class TestModel2: INotifyPropertyChanged
{
    public TestModel2()
    {
        Btn1Active = false;
        Btn2Active = false;
    }

    private bool _btn1Active;
    public bool Btn1Active
    {
        set { SetProperty(ref _btn1Active, value); }
        get { return _btn1Active; }
    }

    private bool _btn2Active;
    public bool Btn2Active
    {
        set { SetProperty(ref _btn2Active, value); }
        get { return _btn2Active; }
    }



    bool SetProperty<T>(ref T storage, T value, [CallerMemberName] string propertyName = null)
    {
        if (Object.Equals(storage, value))
            return false;

        storage = value;
        OnPropertyChanged(propertyName);
        return true;
    }

    protected void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }

    public event PropertyChangedEventHandler PropertyChanged;
}

MyPage.xaml

<statebutton:StateButton Text="Rotate1" x:Name="Btn1" IsPressed="{Binding Btn1Active}"   RotateImages="true" ActiveTextColor="White" ActiveBackgroundColor="Teal" TextColor="Black" BackgroundColor="Green" ActiveBorderColor="Black" LeftImage="arrowRight" ActiveLeftImage="arrowDown" RightImage="arrowRight" HeightRequest="60"  />
<statebutton:StateButton Text="Rotate2" x:Name="Btn2" IsPressed="{Binding Btn2Active}"   RotateImages="true" ActiveTextColor="White" ActiveBackgroundColor="Teal" TextColor="Black" BackgroundColor="Green" ActiveBorderColor="Black" LeftImage="arrowRight" ActiveLeftImage="arrowDown" RightImage="arrowRight" HeightRequest="60"  />

<statebutton:StateButton Text="click(StateButton)" HeightRequest="60"  Clicked="StateButton_Clicked"/>
<Button  Text="click(Button)" HeightRequest="60" Clicked="Button_Clicked"/>

MyPage.xaml.cs

public partial class MyPage : ContentPage
{
    TestModel2 myViewModel;

    public MyPage ()
    {
        InitializeComponent ();
        myViewModel = new TestModel2();
        BindingContext = myViewModel;           
    }

    private void Button_Clicked(object sender, EventArgs e)
    {
        myViewModel.Btn1Active = !myViewModel.Btn1Active;
        myViewModel.Btn2Active = !myViewModel.Btn2Active;
    }
    private void StateButton_Clicked(object sender, EventArgs e)
    {
        myViewModel.Btn1Active = !myViewModel.Btn1Active;
        myViewModel.Btn2Active = !myViewModel.Btn2Active;
    }
} 

更新

我为StateButtons 添加了一个点击事件，它也可以正常工作。 您可以查看更新后的代码。

结果是：

注意：

1.修改如下代码：

private bool _btn1Active { get; set; }
private bool _btn2Active { get; set; }

到：

 private bool _btn1Active;
 private bool _btn2Active;

2。你使用的绑定方式不正确，你可以试试这个：

Btn1.SetBinding(StateButton.IsPressedProperty, new Binding("Btn1Active"));
Btn2.SetBinding(StateButton.IsPressedProperty, new Binding("Btn2Active"));

或绑定xaml

<statebutton:StateButton Text="Rotate1" x:Name="Btn1" IsPressed="{Binding Btn1Active}"     />
<statebutton:StateButton Text="Rotate2" x:Name="Btn2" IsPressed="{Binding Btn2Active}"     />

3.注意你的BindingContext，你可以这样做：

BtnsViewModel myViewModel;

myViewModel = new BtnsViewModel();
BindingContext = myViewModel;   

更多细节可以查看我的演示代码。

Answer 2

在您的代码中，您的问题在于您的绑定。

改成

Btn1.SetBinding(StateButton.IsPressedProperty, new Binding("Btn1Active"));
Btn2.SetBinding(StateButton.IsPressedProperty, new Binding("Btn2Active"));

它应该可以工作。

这是因为BtnsViewModel 不是按钮的Context，而是按钮所在的整个页面的Context。

一个建议，您的私有字段不需要是属性。我的意思是

private bool _btn1Active { get; set; }
private bool _btn2Active { get; set; }

可以改成

private bool _btn1Active;
private bool _btn2Active;

希望这会有所帮助。-