Develop Reference

Why Toolbar not showing on iOS display using Xamarin

I want to display very simple Toolbar using xamarin on iOS, but I can't see the toolbar on display.
I use this code:
<?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="Test.MainPage">
<ContentPage.ToolbarItems>
<ToolbarItem Text="Example Item"
IconImageSource="https://img.icons8.com/cute-clipart/64/000000/menu.png"
Order="Primary"
Priority="0" />
</ContentPage.ToolbarItems>
</ContentPage>
There are no errors in the code and the display is empty..
What needs to change to see the toolbar ?

Are you putting your page in NavigationPage? By default ContentPage does not have Navigation bar (Toolbar), you must put your page in NavigationPage, after that Navigation bar will show up with its functionality.
have a look at here : Xamarin.Forms Navigation
So I assume you should do something like this
public App ()
{
MainPage = new NavigationPage (new MainPage());
}

adding map control to xamarin project breaks it

I am new to Xamarin (came from C# and WPF)
I build a Xamarin form application using the template provided (VS created it for me)
I add Xamarin.Forms.Map from the nuget and added it to a page like this:
<?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:d="http://xamarin.com/schemas/2014/forms/design"
xmlns:maps="clr-namespace:Xamarin.Forms.Maps;assembly=Xamarin.Forms.Maps"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
x:Class="XamarinTest.Views.MapPage"
Title="Map"
>
<!--Title="{Binding Title}"-->
<ContentPage.ToolbarItems>
<!--<ToolbarItem Text="Add" Clicked="AddItem_Clicked" />-->
</ContentPage.ToolbarItems>
<StackLayout Spacing="10">
<maps:Map x:Name="map" />
</StackLayout>
</ContentPage>
Now the application doesn't work and I am getting an error which says the code can not be debugged using this debugger. (I am using UWP platform)
When I commented out the map, it would work and there is no problem.
I tested it on Android and I am getting similar errors when reference to map exist.
What is the problem and how I can fix it?

Thanks to comments, I found that I need to initialize the map in each implementation.
For example UWP we should have this line in MainPage.xaml.cs
Xamarin.FormsMaps.Init("INSERT_AUTHENTICATION_TOKEN_HERE");
This is a good document on how to initialise map on different platforms:
Xamarin.Forms Map Initialization and Configuration

Xamarin Start-up

I am a newbie in Xamarin. I created a C# cross-platform project, after the project has been created there were several errors I don't know why these errors occurred. How can I fix these errors? When I click build nothing displays. When I click Play my default app does not display.
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="App1.App">
<Application.Resources>
</Application.Resources>
</Application>
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"
xmlns:local="clr-namespace:App1"
x:Class="App1.MainPage">
<StackLayout>
<!-- Place new controls here -->
<Label Text="Welcome to Xamarin.Forms!"
HorizontalOptions="Center"
VerticalOptions="CenterAndExpand" />
</StackLayout>
</ContentPage>
MainPage.xaml.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Xamarin.Forms;
namespace App1
{
public partial class MainPage : ContentPage
{
public MainPage()
{
InitializeComponent();
}
}
}

Try to reinstall the Xamarin with Visual studio , It seems there has been something missing form installation. You can find the documentation here
https://learn.microsoft.com/en-us/xamarin/cross-platform/get-started/installation/windows
Regards

Right click on your project
Manage Nuuget Packages
Installed tab : Check if Xamarin is intalled, if yes update it, if not install xamarin
Clean and rebuild your project.

XamarinForms: Use a Control from a Custom Renderer in XAML

I created my own custom renderer in Xamarin that looks like so:
namespace TestApp
{
public class CustomEntry : Entry
{
public CustomEntry ()
{
}
}
}
How can I include this in my HomePage.xaml file? I tried this:
<?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:local="clr-namespace:TestApp;assembly:TestApp"
x:Class="TestApp.SubPage">
<ContentPage.Content>
<StackLayout>
<local:CustomEntry></local:CustomEntry>
</StackLayout>
</ContentPage.Content>
</ContentPage>
But it didn't work, saying CustomEntry is not a valid control in the "http://xamarin.com/schemas/2014/forms" namespace. Any ideas?

Try changing <x:local="clr-namespace:TestApp;assembly:TestApp"> into <xmlns:local="clr-namespace:TestApp;assembly:TestApp">
And <x:local:CustomEntry> into <local:CustomEntry>

Nevermind, I found the problem. It seems that the xmlns:local declaration I had was wrong. I had this:
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:local="clr-namespace:TestApp;assembly:TestApp"
x:Class="TestApp.SubPage">
And it was this:
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:local="clr-namespace:TestApp;assembly=TestApp"
x:Class="TestApp.SubPage">
Seems that assembly was assigned with the '=' operator, not the ':' one. The class stayed the same and everything works now.

Xamarin forms navigation

I am having trouble with Xamarin forms navigation, as in, it does not work at all.
My code :
appname.cs
using System;
using Xamarin.Forms;
namespace List
{
public class App : Application {
public App () {
MainPage = new NavigationPage (new HomePage ());
}
}
}
homepage.xaml.cs
using System;
using Xamarin.Forms;
using System.ComponentModel;
using System.Globalization;
namespace List
{
public partial class HomePage : ContentPage {
public HomePage () {
InitializeComponent ();
}
public void OnButtonClicked (object sender, EventArgs args) {
Navigation.PushAsync (new DetailsPage ());
}
}
}
My intention is obviously to open a main page, have a button on there that goes to a second page upon press.
However this happens instead whenever the button is clicked:
error message
Could not load type 'UIKit.UIView_UITextField' from assembly 'Xamarin.Forms.Platform.iOS'.
Can someone tell me what I'm doing wrong here?
Edit - code for DetailsPage, since this could be source of error:
using System;
using System.Collections.Generic;
using Xamarin.Forms;
namespace List
{
public partial class DetailsPage : ContentPage
{
public DetailsPage ()
{
InitializeComponent ();
}
}
}
Edit 2 - code for Xaml pages (thanks for the help everyone, I really appreciate it):
Homepage.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:local="clr-namespace:List" x:Class="List.HomePage">
<ContentPage.Title>
1
</ContentPage.Title>
<Button Text="Click Me!" HorizontalOptions="Center" VerticalOptions="CenterAndExpand" Clicked="OnButtonClicked" />
</ContentPage>
DetailsPage.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="List.DetailsPage">
<Label Text="LOL"/>
</ContentPage>

In your xaml, the first element needs to be a layout (if you have multiple elements). I would try something similar to below and see if anything changes.
HomePage.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:local="clr-namespace:List" x:Class="List.HomePage" Title="1">
<StackLayout>
<Button Text="Click Me!" HorizontalOptions="Center" VerticalOptions="CenterAndExpand" Clicked="OnButtonClicked" />
</StackLayout>
</ContentPage>
DetailsPage.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="List.DetailsPage">
<StackLayout>
<Label Text="LOL"/>
</StackLayout>
</ContentPage>
Also, I noticed you were setting your title like using ContentPage.Title 1 ContentPage.Title. This is unnecessary. Just set the title directly in your ContentPage tag as I showed in the above example.

Well, I was having the same problem as you. I came across this solution of the xamarin guide.
It seems that in app.cs you need to call the using Xamarin.Forms.Xaml;
Right above your namespace insert [assembly:XamlCompilation(XamlCompilationOptions.Compile)]
But I really can't tell why. I'm Looking for the reason. Try to see if it resolves. In my case went well. Sorry about the bad english and the bad edit of the post, kind of new to this. But comparing all your code, it was missing this piece for you too, maybe this is the reason.
EDIT (12/01/2017) - Add
i found this, that might explain why was not working, seems like the function that we are using is part of a new set for Xamarin that helps him to became faster.
I can be wrong, if I am, please correct me someone that knows better.

Navigation.PushModalAsync(new DetailsPage());
Reference: http://developer.xamarin.com/guides/cross-platform/xamarin-forms/introduction-to-xamarin-forms/#Navigation