根据所选类别在列表中显示产品的首页。最初显示第一类产品。第一类的API响应为空，但计数正确，仅显示空白帧。从其他类别切换后，产品将正确显示。等待任务。我认为问题出在异步等待调用上。需要帮助纠正这一点。
private async Task InitializeAsync()
{
await Get_categories(); //calling method
}
public Task Initialization { get; private set; }
public Grid_vm() //constructor
{
Initialization = InitializeAsync();
}
public async Task Get_categories()
{
var items = await restClient.Get_categories();
Categorylist = new List<Category_value>();
foreach (Category_data cat in items.data)
{
Category_value category = new Category_value();
if (cat.category_id=="6")
{
category.category_id = cat.category_id;
category.category_name = cat.category_name;
Categorylist.Add(category);
}
else
{
category.category_id = cat.category_id;
category.category_name = cat.category_name;
Categorylist.Add(category);
}
}
await Get_branch_products("6") ; // calling first category
}
public async Task Get_branch_products (string category_id)
{
RestClient restClient = new RestClient();
var items=await restClient.Get_branch_products2(category_id);//calling restAPI
Productlist = new List<Product_Value2>();//var items null initially
foreach (Product_Data p in items.data)
{
Product_Value2 val = new Product_Value2();
val.available_qty = p.available_qty;
if (p.status == "1")
{
val.visible = true ;
OnPropertyChanged("visible");
val.visibility = false;
OnPropertyChanged("visibility");
Productlist.Add(val);
}
else
{
val.visible = true ;
OnPropertyChanged("visible");
val.visibility = false;
OnPropertyChanged("visibility");
val.opacity = 0.25;
OnPropertyChanged("opacity");
Productlist.Add(val);
}
}
}
}
public async Task<ProductDetails> Get_branch_products2(string cat_id)
{
var formcontent = new FormUrlEncodedContent(new[]
{
new KeyValuePair<string,string>("category_id",cat_id)
});
var response = await client.PostAsync(base_url + "listbranchproduct", formcontent).ConfigureAwait(false);//execution returns null from here
var result = await response.Content.ReadAsStringAsync();//executed later
var status = JsonConvert.DeserializeObject<ProductDetails>(result);
return status;
}
<ListView x:Name="pdt_list" HasUnevenRows="True" SeparatorVisibility="None" ItemsSource="{Binding Productlist}" BackgroundColor="White" Margin="0,0,0,0">
<ListView.ItemTemplate>
<DataTemplate >
<ViewCell >
<ViewCell.View>
<Frame HasShadow="False" Margin=" 0,10,0,10" Padding="10,0,10,5" BackgroundColor="#f1f1f1" HeightRequest="80" HorizontalOptions="FillAndExpand" VerticalOptions="CenterAndExpand" >
<Grid Padding="0">
<!--<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 Name}" Font="Bold" VerticalTextAlignment="Center" FontSize="Small" 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 sellingprice_default}" Font="Bold" HorizontalOptions="Start" Margin="0" TextColor="#FA2E27" VerticalTextAlignment="Start" FontSize="Small" FontFamily="opensans_light.ttf#opensans_light" />
<Label Text="QAR" TextColor="#FA2E27" HeightRequest="90" FontSize="Small" HorizontalOptions="Start" VerticalTextAlignment="Start" VerticalOptions="FillAndExpand" />
</StackLayout>
</StackLayout>
<ImageButton Source="carts.png" BackgroundColor="Transparent" IsVisible="{Binding visible}" HorizontalOptions="EndAndExpand" WidthRequest="40" HeightRequest="40" VerticalOptions="CenterAndExpand" Clicked="Add_cart_Clicked" Margin="0,20,0,0" Aspect="AspectFit">
</ImageButton>
<StackLayout Orientation="Horizontal" BackgroundColor="Transparent" IsVisible="{Binding visibility}" HorizontalOptions="EndAndExpand">
<ImageButton Source="minus.png" HorizontalOptions="End" VerticalOptions="Center" Aspect="Fill" BackgroundColor="Transparent" WidthRequest="20" HeightRequest="20" Clicked="Minus_Tapped" />
<Label Text="{Binding Number2}" VerticalTextAlignment="Center" HorizontalOptions="EndAndExpand" FontSize="Medium" TextColor="Black" FontFamily="opensans_light.ttf#opensans_light" Margin="0,0,0,0" />
<ImageButton Source="plus2.png" HorizontalOptions="End" Aspect="Fill" VerticalOptions="Center" BackgroundColor="Transparent" WidthRequest="20" HeightRequest="20" 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>
答案 0 :(得分：1)
Get_branch_products (string category_id)方法的else块中提供的opacity为0.25。
val.opacity = 1;
OnPropertyChanged("opacity");
。