【发布时间】：2018-12-18 14:58:26
【问题描述】：
我的页面中有 2 个列表视图。第一个列表水平显示类别。第二个列表在单击类别时显示下面的相应产品。第二个列表的每个列表项都包含用于将产品添加到购物车的加号和减号按钮。标签在单击按钮时更新每个产品的计数。第一次完美运行。来自其他类别后，标签在 ui 中未更新。按钮点击正常，调试时，标签值在 viewmodel 中正确更新，但自第二次以来未反映在 ui 中。需要帮助..
xaml:
<ListView x:Name="pdt_list" HasUnevenRows="True" SeparatorVisibility="None" ItemsSource="{Binding Productlist}" BackgroundColor="White" Margin="0,10,0,0" >
<ListView.ItemTemplate>
<DataTemplate >
<ViewCell >
<ViewCell.View>
<Frame HasShadow="False" Margin=" 0,10,0,10" Padding="10,5,10,5" BackgroundColor="#e9e9e9" HeightRequest="80" HorizontalOptions="FillAndExpand" VerticalOptions="CenterAndExpand" >
<Grid>
<!--<StackLayout HorizontalOptions="FillAndExpand" VerticalOptions="CenterAndExpand" Margin="0,10,0,10" >-->
<StackLayout VerticalOptions="FillAndExpand" Margin="0" Padding="10,0,0,0" Orientation="Horizontal" Opacity="{Binding opacity}">
<Image Source="{Binding image}" Aspect="AspectFill" WidthRequest="70" HeightRequest="180" VerticalOptions="FillAndExpand" />
<StackLayout HorizontalOptions="FillAndExpand" Orientation="Vertical" >
<Label Text="{Binding product_name}" Font="Bold" VerticalTextAlignment="Center" FontSize="Medium" TextColor="Black" FontFamily="opensans_light.ttf#opensans_light" Margin="10,20,0,0" />
<StackLayout Orientation="Horizontal" Margin="10,0,0,0" HorizontalOptions="Start" VerticalOptions="Start" >
<Label Text="{Binding rupee}" TextColor="#FA2E27" HeightRequest="90"
FontSize="Medium" HorizontalOptions="Start" VerticalTextAlignment="Start" VerticalOptions="FillAndExpand" />
<Label Text="{Binding selling_price}" Font="Bold" HorizontalOptions="Start" Margin="0" TextColor="#FA2E27" VerticalTextAlignment="Start" FontSize="Medium" FontFamily="opensans_light.ttf#opensans_light" />
</StackLayout>
</StackLayout>
<ImageButton Source="carts.png" BackgroundColor="Transparent" IsVisible="False" HorizontalOptions="EndAndExpand" WidthRequest="40" HeightRequest="40" VerticalOptions="CenterAndExpand" Clicked="Add_cart_Clicked" Margin="0,20,0,0" Aspect="AspectFit" />
<StackLayout Orientation="Horizontal" BackgroundColor="Transparent" HorizontalOptions="EndAndExpand">
<ImageButton Source="minus.png" HorizontalOptions="EndAndExpand" BackgroundColor="Transparent" WidthRequest="25" HeightRequest="25" Clicked="Minus_Tapped" />
//this label is not updating <Label Text="{Binding Num}" VerticalTextAlignment="Center" HorizontalOptions="EndAndExpand" FontSize="Medium" TextColor="Black" FontFamily="opensans_light.ttf#opensans_light" Margin="0,0,0,0" />
<ImageButton Source="plus2.png" HorizontalOptions="EndAndExpand" BackgroundColor="Transparent" WidthRequest="25" HeightRequest="25" Clicked="Plus_Tapped" />
</StackLayout>
</StackLayout>
<StackLayout BackgroundColor="Black" HorizontalOptions="EndAndExpand" VerticalOptions="StartAndExpand" WidthRequest="100" HeightRequest="25" IsVisible="{Binding opaque}" Margin="0,0,0,0" >
<Label Text="Not Available" FontFamily="opensans_light.ttf#opensans_light" TextColor="White" FontAttributes="Bold" HorizontalOptions="Center" VerticalTextAlignment="Center" />
</StackLayout>
</Grid>
</Frame>
</ViewCell.View>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
视图模型：
点击加号按钮后，执行这段代码：
public ObservableCollection<Product_Value2> purchaselist = new ObservableCollection<Product_Value2>();
public void Plus_item(Product_Value2 product_Value2)
{
var list = new ObservableCollection<Product_Value2>(purchaselist);
string id = product_Value2.id;
ProductsRegister reg = new ProductsRegister();
reg.Name_Product = product_Value2.product_name;
App.Database.SaveProducts(reg);
if ((purchaselist.ToList() != null) && (purchaselist.ToList().Any()))
{
// bool alreadyExists = purchaselist.Any(x => x.id.Equals(id));
if (purchaselist.Any(x => x.id.Equals(id)))
{
foreach (Product_Value2 pdt in list)
{
if (pdt.id.Equals(id))
{
pdt.Num++; // here value is updating everytime,but first time only in ui
OnPropertyChanged("Num");
break;
}
}
}
}
DependencyService.Get<IToast>().ShortAlert("Added To Cart");
Number++;
OnPropertyChanged("Number");
}
型号：
public class Product_Value2 : INotifyPropertyChanged
{
public string id { get; set; }
public string image { get; set; }
public string imagepath { get; set; }
public string product_name { get; set; }
public string rupee { get; set; }
public float selling_price { get; set; }
public float price { get; set; }
public string available_qty { get; set; }
public string count { get; set; }
public bool minus_enb { get; set; }
public bool plus_enb { get; set; }
bool Visibility;
public bool visibility
{
set
{
Visibility = value;
OnPropertyChanged("visibility");
}
get
{
return Visibility;
}
}
long num1 ;
public long Num //this is the label text
{
set
{
num1 = value;
OnPropertyChanged("Num");
}
get
{
return num1;
}
}
bool Visible;
public bool visible
{
set
{
Visible = value;
OnPropertyChanged("visible");
}
get
{
return Visible;
}
}
void OnPropertyChanged(string IsVisible)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(IsVisible));
}
public event PropertyChangedEventHandler PropertyChanged;
}
附上下面的截图显示初始：
下面显示第二次：
【问题讨论】：
-
已添加。但不工作..
-
在 pdt.Num++ 下面的 viewmodel 类中添加了这个； OnPropertyChanged("Num");还是不行。。
-
你可以试试这个
Text="{Binding Num, Source={x:Reference Productlist}"可能需要另一个绑定，因为 Lebel 在 viewcell 内 -
我把这个：Text="{Binding Num, Source={x:Reference pdt_list}}"。现在标签文本不首先显示
标签： xamarin mvvm xamarin.forms