[英]Access elements of a DataTemplate from code
我想找到一种从 c# 访问ButtonImage
元素的方法。 DataTemplate
中包含的所有内容都不能从 c# 调用。
<CarouselView
x:Name="FrasiView"
RelativeLayout.WidthConstraint="{ConstraintExpression
Type=RelativeToParent,
Property=Width,
Factor=1}"
RelativeLayout.YConstraint="{ConstraintExpression
Type=Constant,
Constant=45}"
PeekAreaInsets="18"
HeightRequest="370">
<CarouselView.ItemsLayout>
<LinearItemsLayout Orientation="Horizontal" SnapPointsType="MandatorySingle" SnapPointsAlignment="Center"/>
</CarouselView.ItemsLayout>
<CarouselView.ItemTemplate>
<DataTemplate>
<RelativeLayout>
<RelativeLayout x:Name="FrontView">
<RelativeLayout.GestureRecognizers>
<TapGestureRecognizer Tapped="FlipToBack_Tapped"/>
</RelativeLayout.GestureRecognizers>
<ImageButton
x:Name="CuoreVuoto"
RelativeLayout.YConstraint="{ConstraintExpression
Type=Constant,
Constant=22}"
RelativeLayout.XConstraint="{ConstraintExpression
Type=Constant,
Constant=275}"
Source="IconHeart"
WidthRequest="24"
Clicked="CuoreVuoto_Clicked"
BackgroundColor="Transparent"/>
<ImageButton
x:Name="CuorePieno"
RelativeLayout.YConstraint="{ConstraintExpression
Type=Constant,
Constant=22}"
RelativeLayout.XConstraint="{ConstraintExpression
Type=Constant,
Constant=275}"
Source="IconHeart"
WidthRequest="24"
Clicked="CuorePieno_Clicked"
IsVisible="False"
BackgroundColor="Transparent"/>
</RelativeLayout>
</RelativeLayout>
</DataTemplate>
</CarouselView.ItemTemplate>
</CarouselView>
在 c# 我想回忆一下CuorePieno
元素我该怎么办?
更好的方法是将datatemplate
移动到单独的文件中。 我假设您共享的文件名为CarouselPage.xaml并且类型为ContentPage
:
<ContentPage.Resource>
<DataTemplate x:Key="FrasiViewItemTemplate">
<yournamespace:FrasiViewItemTemplate>
</DataTemplate>
</ContentPage.Resource>
<CarouselView
x:Name="FrasiView"
RelativeLayout.WidthConstraint="{ConstraintExpression
Type=RelativeToParent,
Property=Width,
Factor=1}"
RelativeLayout.YConstraint="{ConstraintExpression
Type=Constant,
Constant=45}"
PeekAreaInsets="18"
HeightRequest="370"
ItemTemplate={DynamicResource FrasiViewItemTemplate}>
<CarouselView.ItemsLayout>
<LinearItemsLayout Orientation="Horizontal" SnapPointsType="MandatorySingle" SnapPointsAlignment="Center"/>
</CarouselView.ItemsLayout>
</CarouselView>
创建一个新的ContentView
文件(xaml+code-behind),将其命名为FrasiViewItemTemplate.xaml覆盖它:
<RelativeLayout x:Class="yournamespace.FrasiViewItemTemplate"
xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml">
<RelativeLayout x:Name="FrontView">
<RelativeLayout.GestureRecognizers>
<TapGestureRecognizer Tapped="FlipToBack_Tapped"/>
</RelativeLayout.GestureRecognizers>
<ImageButton
x:Name="CuoreVuoto"
RelativeLayout.YConstraint="{ConstraintExpression
Type=Constant,
Constant=22}"
RelativeLayout.XConstraint="{ConstraintExpression
Type=Constant,
Constant=275}"
Source="IconHeart"
WidthRequest="24"
Clicked="CuoreVuoto_Clicked"
BackgroundColor="Transparent"/>
<ImageButton
x:Name="CuorePieno"
RelativeLayout.YConstraint="{ConstraintExpression
Type=Constant,
Constant=22}"
RelativeLayout.XConstraint="{ConstraintExpression
Type=Constant,
Constant=275}"
Source="IconHeart"
WidthRequest="24"
Clicked="CuorePieno_Clicked"
IsVisible="False"
BackgroundColor="Transparent"/>
</RelativeLayout>
</RelativeLayout>
您可以在FrasiViewItemTemplate.xaml.cs代码隐藏中访问DataTemplate
的元素(不要忘记命名空间):
(注意它的基础 class 它不再是ContentView
)
public partial class FrasiViewItemTemplate : RelativeLayout
{
public FrasiViewItemTemplate()
{
BindingContext = this;
InitializeComponent();
}
private void FlipToBack_Tapped(object sender, System.EventArgs e)
{
}
private void CuoreVuoto_Clicked(object sender, System.EventArgs e)
{
CuoreVuoto.IsVisible = false;
CuorePieno.IsVisible = true;
}
private void CuorePieno_Clicked(object sender, System.EventArgs e)
{
CuoreVuoto.IsVisible = true;
CuorePieno.IsVisible = false;
}
private void TapGestureRecognizer_Tapped(object sender, System.EventArgs e)
{
}
}
我希望当用户按下 ImageButton 时,IsVisible 属性会发生变化
我同意 Jason 的回复,您可以使用 Binding 来更改 ImageButton IsVisible 属性,我做了一个示例,您可以看看:
<RelativeLayout>
<CarouselView
x:Name="FrasiView"
HeightRequest="370"
ItemsSource="{Binding lists}"
PeekAreaInsets="18"
RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent,
Property=Width,
Factor=1}"
RelativeLayout.YConstraint="{ConstraintExpression Type=Constant,
Constant=45}">
<CarouselView.ItemsLayout>
<LinearItemsLayout
Orientation="Horizontal"
SnapPointsAlignment="Center"
SnapPointsType="MandatorySingle" />
</CarouselView.ItemsLayout>
<CarouselView.ItemTemplate>
<DataTemplate>
<RelativeLayout x:Name="FrontView">
<Label Text="{Binding str}" />
<ImageButton
x:Name="CuoreVuoto"
BackgroundColor="Transparent"
Clicked="CuoreVuoto_Clicked"
IsVisible="{Binding Vuoto}"
RelativeLayout.XConstraint="{ConstraintExpression Type=Constant,
Constant=275}"
RelativeLayout.YConstraint="{ConstraintExpression Type=Constant,
Constant=22}"
Source="c1.png"
WidthRequest="24" />
<ImageButton
x:Name="CuorePieno"
BackgroundColor="Transparent"
Clicked="CuorePieno_Clicked"
IsVisible="{Binding Pieno}"
RelativeLayout.XConstraint="{ConstraintExpression Type=Constant,
Constant=275}"
RelativeLayout.YConstraint="{ConstraintExpression Type=Constant,
Constant=22}"
Source="check.png"
WidthRequest="24" />
</RelativeLayout>
</DataTemplate>
</CarouselView.ItemTemplate>
</CarouselView>
</RelativeLayout>
代码隐藏
public partial class Page1 : ContentPage
{
public ObservableCollection<carouselmodel> lists { get; set; }
public Page1()
{
InitializeComponent();
lists = new ObservableCollection<carouselmodel>()
{
new carouselmodel(){str="test 1",Vuoto=true,Pieno=false},
new carouselmodel(){str="test 2",Vuoto=true,Pieno=false},
new carouselmodel(){str="test 3",Vuoto=true,Pieno=false},
new carouselmodel(){str="test 4",Vuoto=true,Pieno=false},
new carouselmodel(){str="test 5",Vuoto=true,Pieno=false},
new carouselmodel(){str="test 6",Vuoto=true,Pieno=false}
};
this.BindingContext = this;
}
private void CuoreVuoto_Clicked(object sender, EventArgs e)
{
var button = sender as ImageButton;
var model = button.BindingContext as carouselmodel;
if(model.Vuoto==true)
{
model.Vuoto = false;
model.Pieno = true;
}
}
private void CuorePieno_Clicked(object sender, EventArgs e)
{
var button = sender as ImageButton;
var model = button.BindingContext as carouselmodel;
if (model.Pieno == true)
{
model.Pieno = false;
model.Vuoto = true;
}
}
}
public class carouselmodel : ViewModelBase
{
public string str { get; set; }
private bool _Vuoto;
public bool Vuoto
{
get { return _Vuoto; }
set
{
_Vuoto = value;
RaisePropertyChanged("Vuoto");
}
}
private bool _Pieno;
public bool Pieno
{
get
{ return _Pieno; }
set
{
_Pieno = value;
RaisePropertyChanged("Pieno");
}
}
}
ViewModelBase class 继承INotifyPropertyChanged接口,对 nofity 数据进行了更改。
public class ViewModelBase : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public void RaisePropertyChanged(string propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
}
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