我无法使用 Xamarin 窗体中的命令更新屏幕

Question

我正在尝试制作一个ImageButton，当我单击它时，可以看到其他按钮。默认情况下，其他ImageButton是不可见的。

我知道我必须刷新屏幕，但我不知道该怎么做；INotifyPropertyChanged"；但它不起作用。

主页.xaml:

MainPage.xaml(我无法粘贴代码，我不知道为什么(

ViewModel.cs:

public class ViewModel
{
public string ImageSource { get; set; }
public string ButtonColor { get; set; }

public string IsVisible2 { get; set; }
public string Website { get; set; }
// public Command<string> OpenAppCommand { get; set; }
public Command OpenAppCommand { get; }
public Command OpenFloating { get; }

public ViewModel()
{
OpenAppCommand = new Command(launcWeb);
OpenFloating = new Command(openFloatingButton);
IsVisible2 = "false";          
ImageSource = "share256white.png";
ButtonColor = "red";
}


public void launcWeb()
{
Website = "https://facebook.com";
Device.OpenUri(new Uri(Website));
}
//===============================

Boolean firstStart = true;
Boolean nextClick = true;
public void openFloatingButton()
{

if (firstStart)
{
IsVisible2 = "true";
firstStart = false;

}
else
{

if (nextClick)
{
IsVisible2 = "false";
nextClick = false;
}
else
{
IsVisible2 = "true";
nextClick = true;
}

}
}
}

Answer 1

首先，IsVisible2属性应该是bool

例如

public bool IsVisible2 { get; set; }

其次，没有证据表明您的INotifyPropertyChanged实现可能是它不起作用的原因。关于如何实现它的文档可以在这里找到

您需要在ViewModel类上实现该接口。

类似于：

public class ViewModel : INotifyPropertyChanged
{
private bool isVisible2;
public bool IsVisible2
{
get => isVisible2;
set
{
isVisible2 = value;
NotifyPropertyChanged();
}
}
public event PropertyChangedEventHandler PropertyChanged;  
// This method is called by the Set accessor of each property.  
// The CallerMemberName attribute that is applied to the optional propertyName  
// parameter causes the property name of the caller to be substituted as an argument.  
private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")  
{  
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
} 
}