Getting StateLayout with CustomState to show image thumbnail - xamarin

Question

In my Xamarin Forms 5 app, I have a form users will fill out to create a post -- similar to Facebook posts.
The effect I'm trying to create is this:
There's an "Add Image" button that allows user to upload an image. Once the image is uploaded, I want to no longer display the button but display a thumbnail version of the uploaded image.
Here's what my XAML looks like:
<StackLayout
xct:StateLayout.CurrentState="{Binding MainState.None}"
xct:StateLayout.CurrentCustomStateKey="{Binding PostImageState}">
<xct:StateLayout.StateViews>
<xct:StateView StateKey="Custom" CustomStateKey="Image set">
<Image
Grid.Row="0"
Grid.Column="0"
Source="{Binding PostImageUrl}"
WidthRequest="30"
HeightRequest="30"/>
</xct:StateView>
</xct:StateLayout.StateViews>
<Button
Text="Add Image"
Command="{Binding AddImageCommand}"
BackgroundColor="{StaticResource SecondaryBackground}"
WidthRequest="100"
HeightRequest="35"
HorizontalOptions="Start"
Margin="10,0,0,0"/>
</StackLayout>
Here's an abbreviated version of my view model:
public class MyViewModel : BaseViewModel
{
public LayoutState _mainState;
string postImageUrl { get; set; }
string postImageState { get; set; } = "No image";
public MyViewModel()
{
Title = string.Empty;
IsBusy = true;
MainState = LayoutState.None;
AddImageCommand = new AsyncCommand(Add_Image_Tapped);
}
public LayoutState MainState
{
get => _mainState;
set => SetProperty(ref _mainState, value);
}
public string PostImageUrl
{
get => postImageUrl;
set
{
if (postImageUrl == value)
return;
postImageUrl = value;
OnPropertyChanged();
}
}
public string PostImageState
{
get => postImageState;
set
{
if (postImageState == value)
return;
postImageState = value;
OnPropertyChanged();
}
}
async Task Add_Image_Tapped()
{
// Upload image
// Once upload is done
PostImageUrl = uploadedFileUrl;
PostImageState = "Image set";
}
}
I haven't been able to get this to work. Currently, it's not even showing the "Add Image" button. Where am I making a mistake?

Answer 1

There are several problems with your code.
1.Since you use Binding for xct:StateLayout.CurrentState, we should bind it to a variable in ViewModel, here we should use MainState not MainState.None:
xct:StateLayout.CurrentState="{Binding MainState}"
2.Based on your requirement, we can use the value from LayoutState enumeration(for example StateKey="Success"),, we don't need add custom states.
3.If we want to hidden the button once uploading the image, we can bind MainState to property IsVisible of button , but need use Converter StateToBooleanConverter to convert State to bool.
Based on your code ,I created a simple demo, and it works properly on my side.
You can refer to the following code:
MyPage.Xaml
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:xct="http://xamarin.com/schemas/2020/toolkit"
xmlns:viewmodel="clr-namespace:FormApp0314.ViewModel"
x:Class="FormApp0314.TestPage1">
<ContentPage.BindingContext>
<viewmodel:MyViewModel></viewmodel:MyViewModel>
</ContentPage.BindingContext>
<ContentPage.Resources>
<xct:StateToBooleanConverter x:Key="StateToBooleanConverter" />
</ContentPage.Resources>
<StackLayout
xct:StateLayout.CurrentState="{Binding MainState}">
<xct:StateLayout.StateViews>
<xct:StateView StateKey="Success" CustomStateKey="Image set">
<Image
Grid.Row="0"
Grid.Column="0"
Source="{ Binding PostImageUrl}"
WidthRequest="60"
HeightRequest="60"/>
</xct:StateView>
</xct:StateLayout.StateViews>
<Button
Text="Add Image"
Command="{Binding AddImageCommand}"
IsVisible="{Binding MainState, Converter={StaticResource StateToBooleanConverter}, ConverterParameter={x:Static xct:LayoutState.None}}"
WidthRequest="100"
HeightRequest="35"
HorizontalOptions="Start"
Margin="10,0,0,0" />
</StackLayout>
</ContentPage>
MyViewModel.cs
public class MyViewModel: BaseViewModel
{
public LayoutState _mainState;
string postImageUrl;
string postImageState = "No image";
public ICommand AddImageCommand { get; }
public MyViewModel()
{
MainState = LayoutState.None;
PostImageUrl = "bell.png";
AddImageCommand = CommandFactory.Create(Add_Image_Tapped);
}
async Task Add_Image_Tapped()
{
MainState = LayoutState.Success;
await Task.Delay(3000);
MainState = LayoutState.None;
}
public LayoutState MainState
{
get => _mainState;
set => SetProperty(ref _mainState, value);
}
public string PostImageUrl
{
get => postImageUrl;
set => SetProperty(ref postImageUrl, value);
}
public string PostImageState
{
get => postImageState;
set => SetProperty(ref postImageState, value);
}
}