I have a Xamarin Forms project using MVVM in which I am attempting to use Fody and the PropertyChanged.Fody package. No matter what I try it simply does not work. I have spent the day searching for examples of projects using PropertyChanged.Fody and can't find any example sample code that actually works. Can someone help me out? Thanks.
I have added both Fody and PropertyChanged.Fody nugets to the project.
I have added the FodyWeavers.xml file to the Forms project which looks like...
<?xml version="1.0" encoding="utf-8"?>
<Weavers>
<PropertyChanged />
</Weavers>
My view is a standard ContentPage...
<ContentPage.BindingContext>
<viewmodels:GetStartedViewModel />
</ContentPage.BindingContext>
<ContentPage.Content>
<StackLayout >
<Entry Text="{Binding TestMessage}" TextColor="Lime" FontSize="20" />
</StackLayout>
</ContentPage.Content>
I have tried implementing PropertyChanged.Fody on the ViewModel in 2 ways, both of which fail to work.
1)
public class GetStartedViewModel : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public string TestMessage { get; set; }
}
2)
[AddINotifyPropertyChangedInterface]
public class GetStartedViewModel
{
public string TestMessage { get; set; }
}
Related
I am a beginner, so this should be an easy fix for someone with experience.
I am a veterinarian trying to build an app for vets to use. I am trying to learn via youtube and previous posts online, but I cannot find a solution for my roadblock:
I am trying to call a method already written in the App class:
Settings form binds a volume of onhand penicillin.
Usage form displays that volume, and asks the user to enter a volume used.
On button click I need the onhand volume to be 'updated' but i can't call the method in the App class (which has a get and set)
I have simplified for easier evaluation:
App code behind:
using Xamarin.Forms;
using Xamarin.Forms.Xaml;
[assembly: XamlCompilation(XamlCompilationOptions.Compile)]
namespace methods
{
public partial class App : Application
{
private const string penicillin = "penicillin";
public App()
{
InitializeComponent();
MainPage = new NavigationPage(new MainPage());
}
public string Penicillin
{
get
{
if (Properties.ContainsKey(penicillin))
{
return Properties[penicillin].ToString();
}
return "";
}
set
{
Properties[penicillin] = value;
}
}
}
}
Settings Form:
<?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="methods.Settings">
<ContentPage.Content>
<StackLayout>
<Label Text="Penicillin Onhand" ></Label>
<Entry Text="{Binding Penicillin}" Keyboard="Numeric" ></Entry>
</StackLayout>
</ContentPage.Content>
</ContentPage>
Settings Code behind:
using Xamarin.Forms;
namespace methods
{
public partial class Settings : ContentPage
{
public Settings()
{
InitializeComponent();
BindingContext = Application.Current;
}
}
}
Usage form:
<?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="methods.Usage">
<ContentPage.Content>
<StackLayout>
<Label Text="Penicillin Held" ></Label>
<Label x:Name="Held" Text="{Binding Penicillin}" ></Label>
<Label Text="Penicillin Used" ></Label>
<Entry x:Name="Using" Placeholder="ml" Keyboard="Numeric" ></Entry>
<Button Text="Use" Clicked="Used_Clicked"></Button>
</StackLayout>
</ContentPage.Content>
</ContentPage>
Usage Code behind:
using Xamarin.Forms;
namespace methods
{
public partial class Usage : ContentPage
{
public Usage()
{
InitializeComponent();
BindingContext = Application.Current;
}
void Used_Clicked(object sender, System.EventArgs e)
{
var VUsed = double.Parse(Using.Text);
var VHeld = double.Parse(Held.Text);
var Remaining = VHeld - VUsed;
//how do i code the following? Error:'App' does not contain definition for Penicillin????
App.Penicillin.value = Remaining;
}
}
}
You don't need to create a new instance of App - Xamarin Forms already maintains a reference to the current instance
((App)Application.Current).Penicillin = Remaining;
I have Template1 that inherits from ContentView. For the purpose of this question I removed a lot of things in the template to make it simple.
<?xml version="1.0" encoding="UTF-8"?>
<ContentView 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.Template1" x:Name="this">
<Label Grid.Column="0" Text="{Binding Text, Source={x:Reference this}}" />
</ContentView>
and the Template1 C# back end
namespace Japanese
{
public partial class Template1 : ContentView
{
public CardOrderTemplate()
{
InitializeComponent();
}
}
}
I would like this template to share bindings in this class and so I tried some different ways to do this but none seem to work. Here's what I was trying. Not sure but I guess I need something like a ViewModel for the template but I am not sure how I could go about implementing this.
namespace Japanese
{
public class SegBase : ContentView
{
public static readonly BindableProperty TextProperty = BindableProperty.Create(nameof(Text), typeof(string), typeof(SegTemplate), default(string));
public string Text
{
get { return (string)GetValue(TextProperty); }
set { SetValue(TextProperty, value); }
}
}
}
Does anyone know how I can do this? I tried making the Template1 class inherit from SegBase but it gives me an error because the XAML is a type ContentView and the C# is not inheriting from ContentView.
Trying to get the new bindable picker to work in Xamarin Forms version 2.3.4.270 with Visual Studio 2017.
I can get the view to load in a list from the view model so when you click the picker, it does show the list of items. I want to set a default item in the picker on screen load though and nothing I have tried is working.
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"
xmlns:local="clr-namespace:BindablePickerTest"
x:Class="BindablePickerTest.MainPage">
<StackLayout>
<Label Text="Welcome to Xamarin Forms!"
VerticalOptions="Center"
HorizontalOptions="Center" />
<Picker Title="Test Picker" ItemsSource="{Binding Names}" SelectedItem="{Binding Name, Mode=TwoWay}" />
</StackLayout>
</ContentPage>
View Code Behind: (the view model is in the code behind for simplicity)
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Xamarin.Forms;
namespace BindablePickerTest
{
public partial class MainPage : ContentPage
{
MainPageViewModel vm;
public MainPage()
{
InitializeComponent();
this.BindingContext = vm = new MainPageViewModel();
}
}
public class MainPageViewModel : INotifyPropertyChanged
{
List<string> names = new List<string>
{
"Doug",
"Fred",
"Steve",
"Tom",
"Victor"
};
public List<string> Names => names;
public string Name = "Steve";
public event PropertyChangedEventHandler PropertyChanged;
}
}
When this runs, the picker is still empty - "Steve" is not selected. When clicking the picker, the list shows correctly and I can choose any name, but it will not set a default selection.
Any help is appreciated!
Name is a field right now. For Binding to work - it needs to be converted to property.
public string Name => "Steve";
In my xamarin forms app using Prism MVVM Framework, How should I use IoC containers?
There are no
Container.Resolve<Interface,Implentation>
I think we need to resolve the IoC and initialize in app.xaml.cs. But I am not able to find proper way to do it.
Can anyone help me out ?
UPDATE:
PAGE:
<?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:prism="clr-namespace:Prism.Mvvm;assembly=Prism.Forms"
prism:ViewModelLocator.AutowireViewModel="True"
x:Class="CoC.Core.Views.MenuPage">
<ContentPage.Content>
<ListView x:Name="info"
SeparatorVisibility="None"
SeparatorColor="Transparent"
HasUnevenRows="false"
RowHeight="50" BackgroundColor="#485366" >
<ListView.ItemTemplate>
<DataTemplate>
<!--<ImageCell Text="{Binding Title}" ImageSource="{Binding IconSource}" /> -->
<ViewCell>
<!--<Label Text="{Binding Title}" />-->
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</ContentPage.Content>
</ContentPage>
ViewModel:
using Prism.Commands;
using Prism.Mvvm;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Collections.ObjectModel;
using Prism.Navigation;
namespace CoC.Core.ViewModels
{
public class MenuPageViewModel : BindableBase , INavigationAware
{
IMenuList _menuList;
public ObservableCollection<MenuItem> ConductList { get; set; }
public void OnNavigatedFrom(NavigationParameters parameters)
{
//throw new NotImplementedException();
}
public void OnNavigatedTo(NavigationParameters parameters)
{
//throw new NotImplementedException();
}
public MenuPageViewModel(IMenuList MenuList)
{
_menuList = MenuList;
ConductList = _menuList.GetMenuList();
}
}
}
APP:
using Prism.Unity;
using CoC.Core.Views;
namespace CoC.Core
{
public partial class App : PrismApplication
{
protected override void OnInitialized()
{
InitializeComponent();
//NavigationService.NavigateAsync("MainPage?title=Hello%20from%20Xamarin.Forms");
NavigationService.NavigateAsync("MenuPage");
}
protected override void RegisterTypes()
{
Container.RegisterTypeForNavigation<MainPage>();
Container.RegisterTypeForNavigation<RootPage>();
Container.RegisterTypeForNavigation<MenuPage>();
}
}
}
When I run this code, I am getting error in Main.cs of IOS pro
Error:
Foundation.MonoTouchException
NSInternalLnconistencyException Reason: Application window are expected to have a root view controller at the end of the application.
What you are looking for is an extension method in Unity. You need to add the using Microsoft.Practices.Unity namespace to your code file. The you can register your services using Container.Register<IService,MyService>().
I created a Prism Unity App (from the prism extension pack - really nice), added 2 new views and set up basic navigation between the views. This all worked fine without any hiccups.
What I really want is to use DryIoc (company policy). So I proceeded to remove the unity packages (Unity and Prism.Unity.Forms) and installed the DryIoc Packages (DryIoc and Prism.DryIoc.Forms). Fixed the App.xaml to use the correct namespace (xmlns:prism="clr-namespace:Prism.DryIoc;assembly=Prism.DryIoc.Forms") and alos fixed all the other references to use DryIoc and not the Unity References.
This all compiles and runs without any exceptions. But when I debug it is clear that the AutoWireup does not work as expected (at least as I expect it to). The breakpoint in the ViewModel's constructor (or any other place) is not hit and the Title bindings does not pull through.
Is there a Configuration/Setup or reference that I am missing?
My Code:
App.xaml:
<?xml version="1.0" encoding="utf-8" ?><prism:PrismApplication xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:prism="clr-namespace:Prism.DryIoc;assembly=Prism.DryIoc.Forms"
x:Class="XamFormsPrism.App"></prism:PrismApplication>
App.xaml.cs:
public partial class App : Prism.DryIoc.PrismApplication
{
public App(IPlatformInitializer initializer = null) : base(initializer) { }
protected override void ConfigureContainer()
{
base.ConfigureContainer();
}
protected override void OnInitialized()
{
this.InitializeComponent();
this.NavigationService.NavigateAsync(NavigationLinks.MainPage);
}
protected override void RegisterTypes()
{
this.Container.RegisterTypeForNavigation<MainPage>();
this.Container.RegisterTypeForNavigation<ViewA>();
this.Container.RegisterTypeForNavigation<ViewB>();
}
}
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:prism="clr-namespace:Prism.Mvvm;assembly=Prism.Forms"
prism:ViewModelLocator.AutowireViewModel="True"
x:Class="XamFormsPrism.Views.MainPage"
Title="MainPage"><StackLayout HorizontalOptions="Center" VerticalOptions="Center">
<Label Text="{Binding Title}" />
<Button Text="{Binding NavigateText}" Command="{Binding NavigateCommand}" /> </StackLayout></ContentPage>
MainPageViewModel.cs:
public class MainPageViewModel : BindableBase, INavigationAware
{
private INavigationService navigationService = null;
private string _title = "Jose Cuervo";
public string Title
{
get { return _title; }
set { SetProperty(ref _title, value); }
}
public DelegateCommand NavigateCommand { get; private set; }
public MainPageViewModel(INavigationService navigationService)
{
this.navigationService = navigationService;
this.NavigateCommand = new DelegateCommand(this.navigate, this.canNavigate);
}
private void navigate()
{
this.navigationService.NavigateAsync("ViewA");
}
private bool canNavigate()
{
return true;
}
public void OnNavigatedFrom(NavigationParameters parameters)
{
}
public void OnNavigatedTo(NavigationParameters parameters)
{
if (parameters.ContainsKey("title"))
Title = (string)parameters["title"] + " and Prism";
}
}
As seen above I use the standard naming convention of PageName & PageNameViewModel with the AutoWireUp set to True.
This all worked fine with Unity but I am missing something in DryIoc...but what escapes me.
I have searched the entire project, there is no reference or trace left of Unity.
Any help is much appreciated.
I finally had time again to have a look at this. If I explicit register the ViewModels in the container everything works fine. So I am guessing that there is either a rule missing for the DryIoC container or when using DryIoC you have to explicitly register the ViewModels.