【发布时间】：2020-04-23 05:26:48
【问题描述】：
我有一个CarouselPage，有 5 个孩子，每个孩子都有一个水平集合视图。在 Collectionview 中选择项目或滑动页面时，我需要赋予不同的文本颜色，并且需要为所选项目添加下划线。我试过如下：
CarouselHomePage.cs
public partial class CarouselHomePage : CarouselPage
{
public List<Activity> activityList { get; set; }
public CarouselHomePage()
{
InitializeComponent();
activityList = new List<Activity>();
AddActivities();
MessagingCenter.Subscribe<App, string>((App)Xamarin.Forms.Application.Current, "child", (s, child) =>
{
CurrentPage = Children[Int32.Parse(child)];
});
}
private void AddActivities()
{
activityList.Add(new Activity() { Title = "PageNumber1" });
activityList.Add(new Activity() { Title = "PageNumber2" });
activityList.Add(new Activity() { Title = "PageNumber3" });
activityList.Add(new Activity() { Title = "PageNumber4" });
activityList.Add(new Activity() { Title = "PageNumber5" });
AddChild(activityList);
}
public void AddChild(List<Activity> activityList)
{
this.Children.Add(new PageNumber1(activityList));
this.Children.Add(new PageNumber2(activityList));
this.Children.Add(new PageNumber3(activityList));
this.Children.Add(new PageNumber4(activityList));
this.Children.Add(new PageNumber5(activityList));
}
}
Activity.cs
public class Activity
{
public string Title { get; set; }
public bool visibility { get; set; }
public bool Visibility
{
set
{
if (value != null)
{
visibility = value;
NotifyPropertyChanged();
}
}
get
{
return visibility;
}
}
private Color textColor;
public Color TextColor
{
set
{
if (value != null)
{
textColor = value;
NotifyPropertyChanged();
}
}
get
{
return textColor;
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
PageNumber1.xaml
<ContentPage.Content>
<StackLayout Orientation="Vertical">
<CollectionView
SelectionMode="Single"
x:Name="ActivityList"
Margin="5,10,5,10"
SelectionChanged="TagItemTapped"
ItemsLayout="HorizontalList">
<CollectionView.ItemTemplate>
<DataTemplate>
<StackLayout
Orientation="Vertical"
Margin="15">
<Label
TextColor="{Binding TextColor}"
HorizontalTextAlignment="Center"
VerticalTextAlignment="Center"
Text="{Binding Title}">
<Label.FontSize>
<OnIdiom x:TypeArguments="x:Double">
<OnIdiom.Phone>18</OnIdiom.Phone>
<OnIdiom.Tablet>27</OnIdiom.Tablet>
<OnIdiom.Desktop>18</OnIdiom.Desktop>
</OnIdiom>
</Label.FontSize>
</Label>
<BoxView
HeightRequest="2"
IsVisible="{Binding Visibility}"
BackgroundColor="{Binding TextColor}"
HorizontalOptions="CenterAndExpand"
VerticalOptions="Start"/>
</StackLayout>
</DataTemplate>
</CollectionView.ItemTemplate>
<CollectionView.HeightRequest>
<OnIdiom x:TypeArguments="x:Double">
<OnIdiom.Phone>30</OnIdiom.Phone>
<OnIdiom.Tablet>60</OnIdiom.Tablet>
<OnIdiom.Desktop>30</OnIdiom.Desktop>
</OnIdiom>
</CollectionView.HeightRequest>
</CollectionView>
<Label Text="Welcome to PageNumber1"
VerticalOptions="CenterAndExpand"
HorizontalOptions="CenterAndExpand" />
</StackLayout>
</ContentPage.Content>
PageNumber1.xaml.cs
public partial class PageNumber1 : ContentPage
{
public PageNumber1(List<Activity> activityList)
{
InitializeComponent();
if (activityList == null)
{
ActivityList.IsVisible = false;
}
else
{
for (int i = 0; i < activityList.Count; i++)
{
if (activityList[i].Title == "PageNumber1")
{
activityList[i].TextColor = Color.FromHex("#26b4d8");
activityList[i].Visibility = true;
}
else
{
activityList[i].TextColor = Color.Gray;
activityList[i].Visibility = false;
}
}
ActivityList.ItemsSource = activityList;
}
}
public void TagItemTapped(object sender, SelectionChangedEventArgs e)
{
var selectedItem = (e.CurrentSelection.FirstOrDefault() as Activity);
if (selectedItem != null)
{
string childnumber = "";
if (selectedItem.Title == "PageNumber1")
{
childnumber = "0";
}
else if (selectedItem.Title == "PageNumber2")
{
childnumber = "1";
}
else if (selectedItem.Title == "PageNumber3")
{
childnumber = "2";
}
else if (selectedItem.Title == "PageNumber4")
{
childnumber = "3";
}
else if (selectedItem.Title == "PageNumber5")
{
childnumber = "4";
}
MessagingCenter.Send<App, string>((App)Xamarin.Forms.Application.Current, "child", childnumber);
}
}
}
我已经在 if 语句中具有相应标题的所有其他子页面上添加了相同的代码。但是选定的页面标题颜色不起作用并且没有显示下划线。
截图：
另外，如果我选择集合视图中的最后一项，我需要将最后一个子项的集合滚动到最后一项。为此，我使用了 Collectioview 的ScrollTo 功能。但这也行不通。
protected override void OnAppearing()
{
ActivityList.ScrollTo(4);
}
如果我手动滑动页面，上面的代码将起作用。直接点击collectionview项目时，滚动不起作用。
我已经上传了一个示例项目here。
【问题讨论】：
-
感谢分享样本，我会检查的。
-
我发现
CollectionView被创建了多次，应该是没有正确显示的原因。这里建议不要在每个子页面中添加CollectionView。 -
@JuniorJiang-MSFT 我已经上传了一个示例视频here。
-
@JuniorJiang-MSFT 这是我的实际项目画面，每一页我都在展示数据，所以每一页都有collectionview，请看视频。
-
知道了。然后你需要一个
CarouselPage。如果想要实现那个视频的效果，你需要让CarouselPage包含一个CollectionView和CarouselView。
标签： xamarin xamarin.forms uicollectionview carousel