Xamarin Forms - How to display content from one xaml inside another - xaml

I'm used to Android development, and am having some difficulty accomplishing what I would think is a simple task.
I have a MasterDetailPage (called ContainerView.xaml).
The Master is my navigation bar (called NavbarView.xaml).
The Details is supposed to be a page with a fixed title bar, and a "view" I can can swap per user choices.
The Details page is called MainView.xaml.
The Title I'd like to display at the top and is called TitleBarView.xaml.
Then I have a number of content pages such as Page1View.xaml.
in my ContainerView.xaml:
<MasterDetailPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="MyApp.ContainerView"
IsGestureEnabled="True"
MasterBehavior="Popover"
Title="MasterDetail Page">
<MasterDetailPage.Master>
</MasterDetailPage.Master>
<MasterDetailPage.Detail>
</MasterDetailPage.Detail>
</MasterDetailPage>
in my NavbarView.xaml - this is the Master
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="MyApp.NavBarView"
Title="Nav Bar">
<ContentPage.Content>
<StackLayout Orientation="Vertical">
<Label Text="{Binding Item1}"/>
<Button Text="Options" Command="{Binding Option1Command}"/>
</StackLayout >
</ContentPage.Content>
</ContentPage>
in my MainView.xaml - this is the details
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="MyApp.MainView"
Title="Main View">
<ContentPage.Content>
// what to put here to show the TitleBarView.xaml?
// what to put here to show my content xaml pages?
</ContentPage.Content>
</ContentPage>
in my TitleBarView.xaml
<?xml version="1.0" encoding="UTF-8"?>
<ContentView xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="MyApp.TitleBarView">
<ContentView.Content>
<StackLayout Orientation="Horizontal">
<Label Text="{Binding Item1}"/>
<Button Text="Options" Command="{Binding OptionsCommand}"/>
</StackLayout>
</ContentView.Content>
</ContentView>
and a generic content view, of course there will be many others I want to switch between
<ContentView xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="MyApp.Page1View">
<ContentView.Content>
<StackLayout Orientation="Vertical">
<Label Text="{Binding Info}"/>
<Button Text="Log In" Command="{Binding GoToPage2Command}"/>
</StackLayout >
</ContentView.Content>
</ContentView>
I am using the MVVM model and have this code, but can't seem to get just the basics working.
The Master page displays fine.
If the Details page is just a simple page, it works, but I can't figure out how to insert the TitleBar and swap out the "Content".
ContainerView containerPage = new ContainerView();
ContainerViewModel containerVM = new ContainerViewModel();
containerPage.BindingContext = containerVM;
NavBarView navigationBar = new NavBarView();
navigationBar.Title = "Navigation Bar"; // required, otherwise I get an exception.
NavBarViewModel navigationBarVM = new NavBarViewModel();
navigationBar.BindingContext = navigationBarVM;
MainView mainView = new MainView();
mainView.Title = "MainView";
MainViewModel mainViewVM = new MainViewModel();
mainView.BindingContext = mainViewVM;
TitleBarView titleBar = new TitleBarView();
TitleBarViewModel titleBarVM = new TitleBarViewModel();
titleBar.BindingContext = titleBarVM;
Page1View page1 = new Page1View();
Page1ViewModel page1VM = new Page1ViewModel();
page1.BindingContext = page1VM;
mainView.Content = new StackLayout()
{
Orientation = StackOrientation.Vertical,
Children =
{
new Label { Text = "I'm Content!" },
new Label { Text = "I'm Content!" },
//titleBar.Content,
//loginView.Content
}
};
containerPage.MasterBehavior = MasterBehavior.Popover;
containerPage.Master = navigationBar;
containerPage.Detail = new NavigationPage(mainView);
I'm sure I'm missing a fundamental concept. Any help would be appreciated

Xaml can instantiate any control, defined in code or in Xaml, so in case of TitleBarView, you can instantiate it in any Xaml by
<xmlnsprefix:TitleBarView />
The problem is to set the right xmlnsprefix. Every xaml file define a few xmlns and you can add your own, like this:
xmlns:local="clr-namespace:MyApp"
and it'll mean that the Xml namespace 'local' will reference the clr namespace 'MyApp' in the current assembly.
So you MainView becomes:
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:local="clr-namespace:MyApp"
x:Class="MyApp.MainView"
Title="Main View">
<ContentPage.Content>
<local:TitleBarView />
</ContentPage.Content>
</ContentPage>

Related

How can I display a ContentView in a ContentPage

I created a sftabView, every SfTabItem have a ContentView so I created an other View to display it in this ContentView. so the question is how to make this happened?
This is the ContentView which I wanted to display in the ContentPage
<?xml version="1.0" encoding="utf-8" ?>
<ContentView
xmlns="http://xamarin.com/schemas/2014/forms"
x:Class="App5.Views.Self_Trainig"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
NavigationPage.HasNavigationBar="False">
<ContentView.Resources>
<ResourceDictionary>
............
</ResourceDictionary>
</ContentView.Resources>
<ContentView.Content>
<AbsoluteLayout>
...............
</AbsoluteLayout>
</ContentView.Content>
</ContentView>
and this is my ContentPage:
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:tabView="clr-namespace:Syncfusion.XForms.TabView;assembly=Syncfusion.SfTabView.XForms"
x:Class="App5.Views.Accueil">
<ContentPage.Content>
<tabView:SfTabView OverflowMode="DropDown" VisibleHeaderCount="3" BackgroundColor="White">
<tabView:SfTabItem Title="Self Training">
<tabView:SfTabItem.Content>
""the code to display it here""
</tabView:SfTabItem.Content>
</tabView:SfTabItem>
<tabView:SfTabItem Title="Contacts">
<tabView:SfTabItem.Content>
<Grid BackgroundColor="White" x:Name="ContactsGrid" />
</tabView:SfTabItem.Content>
</tabView:SfTabItem>
</tabView:SfTabView>
</ContentPage.Content>
</ContentPage>
<ContentPage
xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:mynamespace=clr-namespace:App5.Views"
...>
...
<tabView:SfTabItem.Content>
<mynamespace:Self_Trainig ... />
</tabView:SfTabItem.Content>
Explanation:
Add an xmlns:... definition for the namespace your ContentView is in.
Add an element with that namespace and the class name of your ContentView. <mynamespace:Self_Trainig ... />
...: After the class name, you can add any needed attributes. Just like any other ContentView.
If you want your view to have "custom" attributes (as opposed to the standard attributes of ContentView such as BackgroundColor), that can be set in each page's XAML, then in your ContentView's code behind, you'll add BindablePropertys. Doing that correctly is beyond the scope of this answer; there are other Q&As on that topic.
is it possible to display the view form the C# code ?
i mean doing
ContentView x:Name="TheView"
and on the C# code doing something like
TheView = Self_Trainig;
i know that code doesn't work but i'm searching that kind of solution

Xamarin forms Add button in TabbedPage

I have a question. I created the following TabbedPage:
<?xml version="1.0" encoding="utf-8" ?>
<TabbedPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:d="http://xamarin.com/schemas/2014/forms/design"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:views="clr-namespace:MyApp.Views"
mc:Ignorable="d"
x:Class="MyApp.Views.MainPage"
xmlns:android="clr-namespace:Xamarin.Forms.PlatformConfiguration.AndroidSpecific;assembly=Xamarin.Forms.Core"
android:TabbedPage.ToolbarPlacement="Bottom"
BarBackgroundColor="White"
BarTextColor="Black"
android:TabbedPage.BarItemColor="#B2B2B2"
android:TabbedPage.BarSelectedItemColor="#56D7A5"
android:TabbedPage.IsSwipePagingEnabled="False">
<TabbedPage.Children>
<NavigationPage Title="page1" IconImageSource="navbar_page1">
<x:Arguments>
<views:page1 NavigationPage.HasNavigationBar="False" />
</x:Arguments>
</NavigationPage>
<NavigationPage Title="page2" IconImageSource="navbar_page2">
<x:Arguments>
<views:page2 NavigationPage.HasNavigationBar="False" />
</x:Arguments>
</NavigationPage>
<NavigationPage Title="page3" IconImageSource="navbar_page3">
<x:Arguments>
<views:page3 NavigationPage.HasNavigationBar="False" />
</x:Arguments>
</NavigationPage>
</TabbedPage>
Now on every page I have added this custom FabMenu like this:
<c:FloatingMenu Margin="0, 0, 10, 10" BGColor="#56D7A5" OpenIcon="openFab_icon" CloseIcon="closeFab_icon"
AbsoluteLayout.LayoutBounds=".95,.95" AbsoluteLayout.LayoutFlags="PositionProportional">
<c:FloatingButton x:Name="btnAddHomework" BGColor="#59E1FF" IconSrc="add_homework_icon" OnClickCommand="{Binding btnAddHomeworkCommand}" />
<c:FloatingButton x:Name="btnAddDeadline" BGColor="#0FF1A0" IconSrc="add_deadline_icon"/>
<c:FloatingButton x:Name="btnAddTest" BGColor="#5988FF" IconSrc="add_test_icon"/>
</c:FloatingMenu>
The problem is that every page has his own FabMenu, so you see it dissapear and reappear on every page, so my question is: Is there some kind of root view that overlays all the tabs in the TabbedPage?
Please let me know how I do that!
Disclaimer
I came up with a way to create the effect wanted using only pure Xamarin.Forms. Read along and pay attention to the tricky parts of the solution.
Abstract
This solution is achieved implementing AbsoluteLayout, CarouselView, IndicatorView and DataTemplateSelector. Xamarin.Forms 4.8 is supposed in what follows. If a lower version is used, please take into account that features like CarouselView or IndicatorView could be in Preview status.
DataTemplateSelector, CarouselView and IndicatorView are used to simulate a TabbedPage, and AbsoluteLayout is used to provide the Overlay.
So, now with the solution:
Create your Views
Here you create a view for each of the pages you want. In this example i want my application to consist of two pages, so i create two views (code behind remains untouched):
View1.xaml
<ContentView xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="overlayTest.View1"
BackgroundColor="Black">
<ContentView.Content>
<StackLayout>
<Label Text="Welcome to Xamarin.Forms 1!"
TextColor="White"
VerticalOptions="CenterAndExpand"
HorizontalOptions="CenterAndExpand" />
</StackLayout>
</ContentView.Content>
</ContentView>
View2.xaml
<?xml version="1.0" encoding="UTF-8"?>
<ContentView xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="overlayTest.View2">
<ContentView.Content>
<StackLayout>
<Label Text="Welcome to Xamarin.Forms 2!"
VerticalOptions="CenterAndExpand"
HorizontalOptions="CenterAndExpand" />
</StackLayout>
</ContentView.Content>
</ContentView>
Create a DataTemplateSelector
This will be used by the CarouselView in order to select one view or the other depending on the current Position.
using System;
using Xamarin.Forms;
namespace overlayTest
{
class MyTemplateSelector : DataTemplateSelector
{
readonly DataTemplate view1, view2;
public MyTemplateSelector()
{
view1 = new DataTemplate(typeof(View1));
view2 = new DataTemplate(typeof(View2));
}
protected override DataTemplate OnSelectTemplate(object item, BindableObject container)
{
String s = item.ToString();
if(s == "1")
{
return view1;
}
return view2;
}
}
}
Create your Main Page
Page1.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:t="clr-namespace:overlayTest"
x:Class="overlayTest.Page1">
<ContentPage.Resources>
<ResourceDictionary>
<t:MyTemplateSelector x:Key="templateSelector"/>
</ResourceDictionary>
</ContentPage.Resources>
<ContentPage.Content>
<AbsoluteLayout>
<StackLayout AbsoluteLayout.LayoutBounds="0,0,1,1"
AbsoluteLayout.LayoutFlags="All"
Padding="0"
Spacing="0">
<CarouselView ItemTemplate="{StaticResource templateSelector}"
IndicatorView="indicatorView">
<CarouselView.ItemsSource>
<x:Array Type="{x:Type x:String}">
<x:String>1</x:String>
<x:String>2</x:String>
</x:Array>
</CarouselView.ItemsSource>
</CarouselView>
<IndicatorView x:Name="indicatorView">
<IndicatorView.IndicatorTemplate>
<DataTemplate>
<StackLayout HorizontalOptions="FillAndExpand">
<Frame Margin="10">
<Label/>
</Frame>
</StackLayout>
</DataTemplate>
</IndicatorView.IndicatorTemplate>
</IndicatorView>
</StackLayout>
<ContentView
IsVisible="True" VerticalOptions="Start"
AbsoluteLayout.LayoutBounds="0,0,1,1"
AbsoluteLayout.LayoutFlags="All"
BackgroundColor="Transparent">
<Frame CornerRadius="10"
Margin="20"
VerticalOptions="StartAndExpand"
HorizontalOptions="CenterAndExpand" InputTransparent="False">
<StackLayout Padding="0">
<Label
FontSize="Medium"
TextColor="Black"/>
<StackLayout Orientation="Horizontal"
HorizontalOptions="CenterAndExpand">
<Label Text="I am floating here"/>
<Switch IsToggled="True" />
</StackLayout>
<Button Text="Save"
BackgroundColor="Accent"/>
</StackLayout>
</Frame>
</ContentView>
</AbsoluteLayout>
</ContentPage.Content>
</ContentPage>
And in the code behind we set the name of the tabs. Here please put attention in the fact that i am supposing an element tree of a StackLayout -> Frame -> Label. If you change the IndicatorTemplate, you will have to also modify this part of the code!
Page1.xaml.cs
using System.Linq;
using Xamarin.Forms;
using Xamarin.Forms.Xaml;
namespace overlayTest
{
[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class Page1 : ContentPage
{
public Page1()
{
InitializeComponent();
indicatorView.PropertyChanged += (s, a) =>
{
if (a.PropertyName == IndicatorView.HeightProperty.PropertyName)
{
var indicators = indicatorView.IndicatorLayout.Children.ToList();
int counter = 0;
foreach(var indicator in indicators)
{
var indicatorBaseStack = (StackLayout)indicator;
var indicatorFrame = (Frame)indicatorBaseStack.Children[0];
var indicatorFrameLabel = (Label)indicatorFrame.Content;
indicatorFrameLabel.Text = counter == 0 ? "View1" : "View2";
counter++;
}
}
};
}
}
}
Finally set that Page to the MainPage property of App:
public App()
{
InitializeComponent();
MainPage = new Page1();
}
The final result looks like this:
As a workaround, you could set ToolbarItem of each ContentPage (or you can define a base ContentPage).
<ContentPage.ToolbarItems>
<ToolbarItem Text="Example Item"
IconImageSource="xxx.png"
Order="Secondary"
Clicked="{Binding xx}"
Priority="0" />
<ToolbarItem Text="Example Item"
IconImageSource="xxx.png"
Order="Secondary"
Priority="1" />
<ToolbarItem Text="Example Item"
IconImageSource="xxx.png"
Order="Secondary"
Priority="2" />
</ContentPage.ToolbarItems>
I recommend creating a BaseContentPage that includes a static FloatingButton. This allows every page to inherit from BaseContentPage and use the same FloatingButton.
Code
BaseContentPage
abstract class BaseContentPage : ContentPage
{
protected static Button Button { get; } = new Button { Text = $"This button was created at {DateTimeOffset.UtcNow}" }.Invoke(button => button.Clicked += HandleButtonClicked);
static async void HandleButtonClicked(object sender, EventArgs e) =>
await Application.Current.MainPage.DisplayAlert("Button Clicked", "This is the same button on both pages", "OK");
}
Example LabelPage
class LabelPage : BaseButtonPage
{
public LabelPage()
{
Title = "LabelPage";
Content = new StackLayout
{
Children =
{
new Label { Text = "Label Page" }.TextCenter().Center(),
Button
}
}
}
}
Example ButtonPage
class ButtonPage : BaseButtonPage
{
public ButtonPage()
{
Title = "ButtonPage";
Content = Button;
}
}
Example App
public class App : Application
{
public App()
{
Device.SetFlags(new[] { "Markup_Experimental" });
MainPage = new TabbedPage
{
Children =
{
new ButtonPage(),
new LabelPage()
}
};
}
}
Sample App
Here is the sample app used to create the attached GIF:
https://github.com/brminnick/TabbedPageButton/

Xamarin-Get String from TextField and place it in Label

I am new to Xamarin Form Application development and Want to try a simple app that will get string from textfield and place it in label by data binding.
Text field with 20 px margin from both side and vertically center.
Label will be below text field.
When typing in textField, the label will update (MVVM)
UI design will be from XAML.
Thank you.
If you are using Xamarin Forms to achieve this and using DataBinding (MVVM), first in your ViewModel (We will call it MainPageViewModel.cs) you need something like this:
using System.ComponentModel;
using System.Runtime.CompilerServices;
namespace SandboxForms.ViewModels
{
public class MainPageViewModel : INotifyPropertyChanged
{
private string _myTextField;
public string MyTextField
{
get { return _myTextField; }
set
{
_myTextField = value;
OnPropertyChanged(nameof(MyTextField));
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void OnPropertyChanged([CallerMemberName] string propertyName = "")
{
var handler = PropertyChanged;
if (handler != null)
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
Then in our ContentPage (We will call this one MainPage.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"
x:Class="SandboxForms.Pages.MainPage"
xmlns:viewmodels="clr-namespace:SandboxForms.ViewModels;SandboxForms">
<ContentPage.BindingContext>
<viewmodels:MainPageViewModel />
</ContentPage.BindingContext>
<ContentPage.Content>
<StackLayout Padding="20">
<!-- I am applying EndAndExpand to the entry and
StartAndExpand to the label to center them each other -->
<Entry
HorizontalOptions="FillAndExpand"
VerticalOptions="EndAndExpand"
Placeholder="Write here and see the magic!!!"
Text="{Binding MyTextField}"/>
<Label
HorizontalTextAlignment="End"
HorizontalOptions="FillAndExpand"
VerticalOptions="StartAndExpand"
Text="{Binding MyTextField}"/>
</StackLayout>
</ContentPage.Content>
</ContentPage>
Here is a few screenshots of the results:
Application starting,
Entering text on your Entry
Hope this works for you, my best regards!
There are two approaches for data binding each of which has merits depending on the situation. The first is MVVM as mentioned previously. This works well for fields that your ViewModel should know about, such as the text in an entry field but this isn't always the case and it's important to have a complete understanding before choosing the right method for your needs.
MVVM Approach
ViewModel
public class MyPageViewModel : INotifyPropertyChanged
{
private string myTextField;
public string MyTextField
{
get { return myTextField; }
set
{
if( !myTextField.Equals( value ) )
{
myTextField = value;
OnPropertyChanged("MyTextField");
}
}
}
}
View
<?xml version="1.0" encoding="UTF-8"?>
<ContentPage
xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="SandboxForms.Pages.MainPage"
xmlns:viewmodels="clr-namespace:SandboxForms.ViewModels;SandboxForms">
<ContentPage.BindingContext>
<viewmodels:MainPageViewModel />
</ContentPage.BindingContext>
<ContentPage.Content>
<StackLayout Padding="20">
<!-- I am applying EndAndExpand to the entry and
StartAndExpand to the label to center them each other -->
<Entry
HorizontalOptions="FillAndExpand"
VerticalOptions="EndAndExpand"
Placeholder="Write here and see the magic!!!"
Text="{Binding MyTextField}"/>
<Label
HorizontalTextAlignment="End"
HorizontalOptions="FillAndExpand"
VerticalOptions="StartAndExpand"
Text="{Binding MyTextField}"/>
</StackLayout>
</ContentPage.Content>
</ContentPage>
This is generally a preferred approach by most developers as opposed to mixing business logic directly in the code behind of your UI.
There are a number of helpers, and frameworks out there that you can look at if you aren't familiar with this. The following are some of the more popular ones.
MvvmHelpers - James Montemagno
Prism Library (my personal favorite)
Mvvm Cross
Mvvm Light
View Centric Approach
Sometimes it actually would violate the MVVM pattern to directly bind to a property of our ViewModel, and other times we may want to display something in our View without the need of updating a backing field in the ViewModel. As an example we can look at Xamarin's guide to data binding.
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="XamlSamples.SliderBindingsPage"
Title="Slider Bindings Page">
<StackLayout>
<Label Text="ROTATION"
BindingContext="{x:Reference Name=slider}"
Rotation="{Binding Path=Value}"
FontAttributes="Bold"
FontSize="Large"
HorizontalOptions="Center"
VerticalOptions="CenterAndExpand" />
<Slider x:Name="slider"
Maximum="360"
VerticalOptions="CenterAndExpand" />
<Label BindingContext="{x:Reference slider}"
Text="{Binding Value,
StringFormat='The angle is {0:F0} degrees'}"
FontAttributes="Bold"
FontSize="Large"
HorizontalOptions="Center"
VerticalOptions="CenterAndExpand" />
</StackLayout>
</ContentPage>
I should note that one of the most common times I would recommend using this approach is with Context Actions in a ListView, since our ViewModel may contain the Command that we want to execute on the individual cell, however the cell in which we are executing the context action actually is bound to the object from our IEnumerable<T> and not our ViewModel. In this particular case we would do something like the following:
<?xml version="1.0" encoding="UTF-8"?>
<ContentPage xmlns ="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Name="someListPage"
x:Class="MyApp.Views.SomeListPage">
<ListView ItemsSource="{Binding Gear}"
CachingStrategy="RecycleElement"
IsRefreshing="{Binding IsRefreshing}"
IsPullToRefreshEnabled="True"
RefreshCommand="{Binding RefreshCommand}">
<ListView.ItemTemplate>
<DataTemplate>
<TextCell Text="{Binding Description}" Detail="{Binding Detail}">
<TextCell.ContextActions>
<MenuItem Text="Remove"
Command="{Binding BindingContext.RemoveItemCommand,Source={x:Reference someListPage}}"
CommandParameter="{Binding .}"
IsDestructive="True" />
</TextCell.ContextActions>
</TextCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</ContentPage>
You'll notice that for this to work we first give the page itself a name that we can then reference for our binding for the ContextAction Command property. This is only changing where we are looking for this single property. We then resume using the normal binding context for the CommandParameter property and pass in the actual object the cell is bound to with {Binding .}
Hope this helps you better understand your options for binding with Xaml. Happy Coding!

Property Content is null or is not IEnumerable

I have a test page in Xamarin.Forms and it gets me this error, how can I fix this ?
Property Content is null or is not IEnumerable
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" x:Class="Project1.Page1">
<ContentPage.Content>
<Label Text="Page"></Label>
<Editor Text="I am an Editor" />
</ContentPage.Content>
</ContentPage>
The Content property is of type View. You cannot have two views into it. Replace it with
<StackLayout >
<Label Text="Page"></Label>
<Editor Text="I am an Editor" />
<StackLayout>
If anyone else lands here from google and the above wasn't the fix. For me it was because I had a view with a Grid.Row="0" property set even though I accidentally placed it outside the bounds of the actual grid.

Circular referenced IValueConverter in Application.Resources

I'm getting the error :
StaticResource not found for key maxLength
the setup is as follows:
Converter setup in app.xaml, which also contains a datatemplate
<Application.Resources>
<ResourceDictionary>
<ext:MaxLengthStringConverter x:Key="maxLength"/>
....
<DataTemplate x:Key="HotelViewModel">
<tripSegmentPartViews:HotelView
Padding="0"
HeightRequest="60"
BorderWidth="1"
BorderColor="{ext:ColourResource Divider}"
BordersToDraw="{x:Static controls:Borders.Top}"
BackgroundColor="Transparent"/>
</DataTemplate>
....
view in the HotelView.xaml which is in the datatemplate, uses the converter
....
<Label Text="{Binding HotelName, Converter={StaticResource maxLength}, ConverterParameter=10}"
AbsoluteLayout.LayoutFlags="All"
AbsoluteLayout.LayoutBounds="1,0.2,0.62,0.5"
VerticalOptions="End"
HorizontalOptions="Start"
FontSize="20"
/>
....
If I move the converter to HotelView.xaml resource dictionary it works
If I change the reference to a DynamicResource it is not used
Obviously with something as basic as max length (which shortens the string and adds '...' if its over the required length) I want to be able to use it through out the application, and not have to reference it in multiple resource dictionaries.
Is this a bug?
----------------- edit ------------------
OK I have reproduced this errror with a minimum app consisting of:
App1.xaml
<?xml version="1.0" encoding="utf-8" ?>
<Application xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="App1.App"
xmlns:ext="clr-namespace:App1.Extensions;assembly=App1"
xmlns:local="clr-namespace:App1;assembly=App1">
<Application.Resources>
<ResourceDictionary>
<ext:MyConverter x:Key="conv"></ext:MyConverter>
<DataTemplate x:Key="dt">
<local:View1></local:View1>
</DataTemplate>
</ResourceDictionary>
</Application.Resources>
</Application>
Page1.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"
x:Class="App1.Page1"
xmlns:local="clr-namespace:App1;assembly=App1">
<StackLayout>
<Label Text="Page1" VerticalOptions="Center" HorizontalOptions="Center" TextColor="White" />
<ListView ItemTemplate="{StaticResource dt}" ItemsSource="List">
</ListView>
</StackLayout>
</ContentPage>
View1.xaml
<?xml version="1.0" encoding="utf-8" ?>
<ContentView xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="App1.View1"
xmlns:ext="App1.Extensions">
<Label Text="{Binding MainText, Converter={StaticResource conv}" VerticalOptions="Center" HorizontalOptions="Center" TextColor="White"/>
</ContentView>
App1.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Xamarin.Forms;
namespace App1
{
public partial class App : Application
{
public App()
{
InitializeComponent();
// The root page of your application
Page1 p = new Page1();
p.BindingContext = new {
MainText = "test",
List = new List<string>() { "test"}
};
var navContainer = new NavigationPage(p);
navContainer.BarBackgroundColor = Color.Red;
navContainer.BarTextColor = Color.White;
MainPage = navContainer;
}
}
}
The error is thrown at runtime using the VS emulator
From what you mention you want to be able to define a IValueConverter the once, and use it from any Xamarin.Forms ContentPage, without the need to keep specifying the converter in the local XAML page.
This can be achieved by doing the following:-
In your PCL you normally have App.cs.
You will need to delete this, and add a new Forms Xaml Page called App.cs.
This will generate both the App.xaml and related App.cs files.
In this question, (How can I databind an image?), there is a converter called MyByteToImageSourceConverter.
I will illustrate using this:-
App.xaml
<?xml version="1.0" encoding="utf-8" ?>
<Application xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="SampleApp.App"
xmlns:local="clr-namespace:{namespace reference goes here to the converter}"
>
<Application.Resources>
<ResourceDictionary>
<local:MyByteToImageSourceConverter x:Key="kyByteToImageSourceConverter"/>
</ResourceDictionary>
</Application.Resources>
</Application>
So in the above we have defined our converter with a key, that we will then be able to reference from all other Xamarin.Forms ContentPage's.
App.cs
namespace SampleApp
{
public partial class App
: Xamarin.Forms.Application
{
public App()
{
InitializeComponent();
//
this.MainPage = new ByteToImageExample2();
}
}
}
In the code-behind we need to change the default inheritance from ContentPage and specify Xamarin.Forms.Application.
We also specify our launch page, via the this.MainPage = ...
ByteToImageExample2.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"
x:Class="SampleApp.ByteToImageExample2"
>
<StackLayout>
<Image Source="{Binding MyImageAsBytes, Converter={StaticResource kyByteToImageSourceConverter}}"/>
</StackLayout>
</ContentPage>
In our ContentPage we can see above we are referencing the converter that we specified in App.xaml via the StaticResource kyByteToImageSourceConverter.
As that was definied in App.xaml, we can re-use this in all our pages without the need to specify the location of the converter locally.
For completeness the code-behind is:-
ByteToImageExample2.cs:-
public partial class ByteToImageExample2 : ContentPage
{
public ByteToImageExample2()
{
InitializeComponent();
//
byte[] bytImage = { your image as a byte collection }
//
this.BindingContext = new MyImageViewModel()
{
MyImageAsBytes = bytImage
};
}
}
Update 1:-
You can have the following in your App.xaml:-
<DataTemplate x:Key="kyByteToImage3ExampleDataTemplate2">
<ViewCell>
<local2:MyCustomView1/>
</ViewCell>
</DataTemplate>
with local2:MyCustomView1 referencing your custom view, which for this example is defined as:-
<ContentView xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="SampleApp.MyCustomView1">
<Image Source="{Binding MyImage, Converter={StaticResource kyByteToImageSourceConverter}}" Aspect="AspectFit" />
</ContentView>
This custom view still uses a Converter as specified from the App.xaml and does still render, without the need to specify the Converter locally within the ContentView class.