How can I pass a Tapped event into a XAML template? - xamarin

Question

I code that I use often in my application so I created this template. With a lot of help from the user gannaway the code I have so far is this:
<?xml version="1.0" encoding="utf-8" ?>
<ViewCell xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:local="clr-namespace:Japanese;assembly=Japanese"
x:Class="Japanese.SwitchViewCellTemplate"
x:Name="this">
<Grid VerticalOptions="CenterAndExpand" Padding="20,0" >
<local:StyledLabel Text="{Binding Text, Source={x:Reference this}}" HorizontalOptions="StartAndExpand" />
<local:StyledLabel IsVisible="{Binding IsVisible, Source={x:Reference this}}" TextColor="Gray" HorizontalOptions="End" Text="✓" />
</Grid>
</ViewCell>
Here's the code behind:
using System;
using System.Collections.Generic;
using Xamarin.Forms;
namespace Japanese
{
public partial class SwitchViewCellTemplate : ViewCell
{
public event EventHandler SelectAction;
public SwitchViewCellTemplate()
{
InitializeComponent();
}
public static readonly BindableProperty TextProperty = BindableProperty.Create(nameof(Text), typeof(string), typeof(SwitchViewCellTemplate));
public static readonly BindableProperty IsVisibleProperty = BindableProperty.Create(nameof(IsVisible), typeof(bool), typeof(SwitchViewCellTemplate));
public string Text
{
get { return (string)GetValue(TextProperty); }
set { SetValue(TextProperty, value); }
}
public bool IsVisible
{
get { return (bool)GetValue(IsVisibleProperty); }
set { SetValue(IsVisibleProperty, value); }
}
protected override void OnTapped()
{
base.OnTapped();
this.SelectAction?.Invoke(this, new EventArgs());
}
}
}
and the way I would like to use it:
<template:SwitchViewCellTemplate Text="{Binding [1].Name}"
IsVisible="{Binding [1].IsSelected}"
SelectAction="selectValue" />
Here is the method used to handle toggled:
void Handle_SelectAction(object sender, System.EventArgs e)
{
var viewCell = sender as ViewCell;
if (viewCell == null)
return;
}
Where selectValue is a function in the CS code behind of the pages where I use the template.
The code gives an error:
The type initializer for 'Japanese.SwitchViewCellTemplate' threw an exception.
Can anyone give me advice on what might be wrong that is causing this error.

Answer 1

To solve, an event can be added to the template.
XAML Template
<?xml version="1.0" encoding="utf-8" ?>
<ViewCell xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:local="clr-namespace:Japanese;assembly=Japanese"
x:Class="Japanese.SwitchViewCellTemplate"
x:Name="this">
<Grid VerticalOptions="CenterAndExpand" Padding="20,0" >
<local:StyledLabel Text="{Binding Text, Source={x:Reference this}}" HorizontalOptions="StartAndExpand" />
<local:StyledLabel IsVisible="{Binding IsVisible, Source={x:Reference this}}" TextColor="Gray" HorizontalOptions="End" Text="✓" />
</Grid>
</ViewCell>
Add an event to your template's code-behind:
public partial class SwitchViewCellTemplate : ViewCell
{
public event EventHandler SelectAction;
public SwitchViewCellTemplate()
{
InitializeComponent();
}
public static readonly BindableProperty TextProperty =
BindableProperty.Create(
nameof(Text),
typeof(string),
typeof(SwitchViewCellTemplate),
default(string));
public static readonly BindableProperty IsVisibleProperty =
BindableProperty.Create(
nameof(IsVisible),
typeof(bool),
typeof(SwitchViewCellTemplate),
default(bool));
public string Text
{
get { return (string)GetValue(TextProperty); }
set { SetValue(TextProperty, value); }
}
public bool IsVisible
{
get { return (bool)GetValue(IsVisibleProperty); }
set { SetValue(IsVisibleProperty, value); }
}
protected override void OnTapped()
{
base.OnTapped();
this.SelectAction?.Invoke(this, new EventArgs());
}
}
Page XAML
<template:SwitchViewCellTemplate Text="{Binding [1].Name}"
IsVisible="{Binding [1].IsSelected}"
SelectAction="Handle_SelectAction" />
Page Code-Behind
void Handle_SelectAction(object sender, System.EventArgs e)
{
}