I don't need a MasterDetail until I've navigated through two regular ContentPages first, where I collect information that the MasterDetail will need. The ContentPages make use of the INavigationParameters sent to OnNavigatedTo and OnNavigatedFrom for that collected information.
The the SecondPage viewmodel handles a button command wherein the handler calls the MasterDetail:
NavigationService.NavigateAsync("CompareSelectionsMasterDetail/CompareSelectionsNavigationPage/RangeCircle",
parameters);
Sure enough, the RangeCircleViewModel.OnNavigatedTo receives the parameters. However, when I go back (like with the Android back button), its OnNavigatedFrom is not called, thereby sending null parameters back leaving my ContentPages with no idea what their state was.
The viewmodel for CompareSelectionMasterDetail doesn't do anything and the viewmodel for CompareSelectionsNavigationPage just does this:
public class CompareSelectionsNavigationPage : NavigationPage, INavigationPageOptions
{
public bool ClearNavigationStackOnNavigation => false;
}
I'm not sure what it means to have a NavigationPage in the MasterDetailPage XAML and the separate CompareSelectionsNavigationPage that I call with Prism but if I remove the XAML one, the RangeCircle page doesn't render. If I only have the XAML one and change the Prism navigation to CompareSelectionsMasterDetail/NavigationPage/RangeCircle then I get the same behavior as using both NavigationPages.
My MasterDetail XAML is simple.
> <MasterDetailPage.Master>
> <NavigationPage Title="Required Foo" Icon="hamburger_icon.png">
> <x:Arguments>
> <ContentPage Title="Menu">
> <StackLayout Padding="40">
> <!-- TODO: // Update the Layout and add some real menu items -->
> <Label Text="Hello John"/>
> <Button Text="Range Circle" Command="{Binding NavigateToRangeCircleCommand}" CommandParameter="ViewA" />
> </StackLayout>
> </ContentPage>
> </x:Arguments>
> </NavigationPage> </MasterDetailPage.Master>
Every example I can find of Master Detail (especially with Prism) starts off the app with Master Detail page. I'm not sure if my usage is what breaks OnNavigatedFrom? (Basically ContentPage(Page1)->ContentPage(Page2)->MasterDetail->NavigationPage->NavigationPage->ContentPage(RangeCircle))
The individual ContentPages don't have a problem calling OnNavigatedFrom.
Related
Good morning
I have a TabbedPage in my application. Due to restictions I would like to display one more tab on Android than on iOS.
My current TabbedPage look like:
<TabbedPage>
...
<ContentPage x:Name="Page1"/>
<ContentPage x:Name="Page2"/>
<ContentPage x:Name="Page3"/>
<ContentPage x:Name="Page4"/>
</TabbedPage>
I have decided to render Page3 only for Android. I changed my code into:
<TabbedPage>
...
<ContentPage x:Name="Page1"/>
<ContentPage x:Name="Page2"/>
<OnPlatform x:TypeArguments="Page">
<On Platform="Android">
<On.Value>
<ContentPage x:Name="Page3"/>
</On.Value>
</On>
</OnPlatform>
<ContentPage x:Name="Page4"/>
</TabbedPage>
This leads to runtime exception when entering into this TabbedPage:
An error occurred: 'Value cannot be null. Parameter name: item'.
Callstack: ' at
Xamarin.Forms.ObservableWrapper`2[TTrack,TRestrict].Add (TRestrict
item) [0x00008] in D:\a\1\s\Xamarin.Forms.Core\ObservableWrapper.cs:27
I tried to remove x:Name but did not work. Any ideas?
PS. As a workaround I am always able to:
Constructor()
{
if(Runtime.IsIOS)
{
this.Children.Remove(this.Page3)
}
}
However would be better to not render it at all and have it at XAML level.
Unless someone comes up with a way to do this in XAML, this is the best you can do (building on Jason's comment):
xaml:
<ContentPage x:Name="Page1"/>
<ContentPage x:Name="Page2"/>
<!-- no Page3 in XAML -->
<ContentPage x:Name="Page4"/>
c#:
private ContentPage page3;
Constructor()
{
InitializeComponent();
if (Runtime.IsAndroid)
{
page3 = new ContentPage();
// After pages 1 and 2.
Children.Insert(2, page3);
}
}
// Elsewhere in code-behind.
if (page3 != null)
{
...refer to page3...
}
This has the advantage of not constructing the page at all on iOS.
It also makes it easy to test whether page3 is there (page3 != null).
In practice, the other pages will typically be their own classes. Given partial class Page3 : ContentPage elsewhere:
private Page3 page3;
...
page3 = new Page3();
According to this,xaml is an alternative to programming code for instantiating and initializing objects, and organizing those objects in parent-child hierarchies.If you add one additional tab on android it will cause a NullReferenceException on ios.So you may want to do it in codebehind with Device.RuntimePlatform.
Here is my test you can refer to:
switch (Device.RuntimePlatform)
{
case Device.Android:
Children.Add(page1);
Children.Add(page2);
break;
case Device.iOS:
Children.Add(page1);
break;
case Device.UWP:
Children.Add(page1);
break;
}
I am using the Shell template from VS2019 in a Xamarin Forms app.I have two pages listed in the shell flyout.
<FlyoutItem Title="Home" Icon="icon_about.png">
<ShellContent Route="HomePage" ContentTemplate="{DataTemplate local:HomePage}" />
</FlyoutItem>
<FlyoutItem Title="Logoff time" Icon="icon_about.png">
<ShellContent Route="SecondPage" ContentTemplate="{DataTemplate
local:SecondPage}" />
</FlyoutItem>
Using the hamburger menu I navigate away from the Homepage to another page SecondPage. I have a button on the SecondPage which perform an action and from that action I want to navigate back to the HomePage. When I use this code:
var route = $"{nameof(HomePage)}";
await Shell.Current.GoToAsync(route);
The HomePage shows but there is a back button instead of the hamburger menu. If I tap the hamburger icon the page navigates back to the SecondPage.
How do I navgate from SecondPage to HomePage and show the hamburger icon?
With so little information (not knowing the details of how your navigation is implemented) it's hard to help you. But the first things that come to mind are the following you could try.
Try one of the following for popping the SecondPage and navigating back to:
await Shell.Current.Navigation.PopAsync();
or
await Shell.Current.Navigation.PopModalAsync();
And if you have a navigation bar with a back button that you don't want then try this in the HomePage.xaml
NavigationPage.HasNvaigationBar="False"
or
Shell.NavBarIsVisible="False"
The two
//
before the route will accomplish my aims.This resets the root page apparently so HomePage once again become the root page.
var route = $"//{nameof(HomePage)}"
I have solved this issue in my own project; I wanted this page to show up at the start of the application, using the navigation class to push the screen and then pop it when the user clicks a button. I had the same issue of a back button showing up, instead of the hamburger icon, when moving the user to the HomePage. I hope this helps someone in the future.
Classes are as follows:
public partial class AppShell : Xamarin.Forms.Shell {
public AppShell() {
InitializeComponent();
Routing.RegisterRoute(nameof(ItemDetailPage), typeof(ItemDetailPage));
Routing.RegisterRoute(nameof(NewItemPage), typeof(NewItemPage));
Routing.RegisterRoute(nameof(HomePage), typeof(HomePage));
Routing.RegisterRoute(nameof(NewUserPage), typeof(NewUserPage));
this.Navigation.PushAsync(new NewUserPage());
}
}
[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class NewUserPage : ContentPage {
public NewUserPage() {
InitializeComponent();
this.BindingContext = new NewUserViewModel();
Shell.SetNavBarIsVisible(this, false);
}
}
class NewUserViewModel : BaseViewModel {
public NewUserViewModel() {
NewUserClickedCommand = new Command(OnNewUserClicked);
}
public Command NewUserClickedCommand { get; }
private async void OnNewUserClicked() {
await Shell.Current.Navigation.PopAsync();
}
}
And the XAML file for NewUserPage:
<?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="Project.Views.NewUserPage">
<ContentPage.Content>
<StackLayout>
<Label Text="This is a page for new users"
VerticalOptions="CenterAndExpand"
HorizontalOptions="CenterAndExpand" />
<Button Text="Click for New User" BackgroundColor="{StaticResource Primary}" Command="{Binding NewUserClickedCommand}"></Button>
</StackLayout>
</ContentPage.Content>
</ContentPage>
I am using ReactiveTabbedPage 'HomeTabbedPage' which has 4 view as shown
<rxui:ReactiveTabbedPage x:Class="HomeTabbedPage"
xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:rxui="clr-namespace:ReactiveUI.XamForms;assembly=ReactiveUI.XamForms"
xmlns:views="clr-namespace:MeasuringPoint.Views;assembly=MeasuringPoint"
xmlns:controls="clr-namespace:MeasuringPoint.Controls;assembly=MeasuringPoint"
xmlns:resx="clr-namespace:MeasuringPoint.Resources;assembly=MeasuringPoint"
xmlns:page="clr-namespace:MeasuringPoint.Pages"
xmlns:vms="clr-namespace:MeasuringPoint.ViewModels"
x:TypeArguments="vms:HomeTabbedViewModel" BackgroundColor="White">
<views:CreateView x:Name="createView" Title="Create"/>
<views:HistoryView x:Name="historyView" Title="History"/>
<views:SyncView x:Name="syncView" Title="Sync"/>
<views:SettingsView x:Name="settingsView" Title="Settings" />
</rxui:ReactiveTabbedPage>
By default Createview is the one shown. I need to navigate to another 'Page' and come back to another child view 'SettingsView'
If I call
HostScreen
.Router
.Navigate
.Execute(new SettingsViewModel())
.Subscribe();
The SettingsView is displayed but the tabs disappear.
If I can navigate back to the HomeTabbedPage
HostScreen
.Router
.Navigate
.Execute(new HomeTabbedViewModel())
.Subscribe();
Then the CreateView is displayed.
Am I missing something here?
I'm using Prism.Forms 6.3 in a Xamarin.Forms 2.3.4.247 project. I'm having a hard time tracking why the back arrow button isn't visible when I navigate to a details page within a Master/Detail setup.
I can navigate to the Pages just fine, but the back-button never shows up. Instead, the hamburger menu icon is always visible. This is my "Master" page.
<?xml version="1.0" encoding="utf-8" ?>
<MasterDetailPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:local="clr-namespace:FloatSink.Apps.Mobile.Views.ValueConverters"
xmlns:prism="clr-namespace:Prism.Mvvm;assembly=Prism.Forms"
prism:ViewModelLocator.AutowireViewModel="True"
x:Class="FloatSink.Apps.Mobile.Views.MainPage"
BackgroundColor="Blue">
<MasterDetailPage.Master>
<ContentPage Title="Menu">
<StackLayout Padding="40">
<Label Text="Hello" />
<Button Text="Feed" Command="{Binding NavigateCommand}" CommandParameter="NavigationPage/FeedPage" />
<Button Text="Options" Command="{Binding NavigateCommand}" CommandParameter="NavigationPage/OptionsPage" />
</StackLayout>
</ContentPage>
</MasterDetailPage.Master>
</MasterDetailPage>
This is two of my Detail pages.
<?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="FloatSink.Apps.Mobile.Views.FeedPage">
<Label Text="Hello from Feed Page!" />
</ContentPage>
<?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="FloatSink.Apps.Mobile.Views.OptionsPage">
<Label Text="Hello from Options Page!" />
</ContentPage>
I navigate to it using the CommandParameter specified in my Master page, using the navigation service in the MainPageViewModel.
private void NavigateToPage(string uri)
{
this.navigationService.NavigateAsync(uri);
}
I've setup my NavigationPage like this during the startup of the app so I land on the FeedPage first, then I can navigate to the OptionsPage.
public class App : PrismApplication
{
public App(IPlatformInitializer dependencyRegister) : base(dependencyRegister) { }
protected override void OnInitialized()
{
base.NavigationService.NavigateAsync("MainPage/NavigationPage");
}
protected override void RegisterTypes()
{
var builder = new ContainerBuilder();
builder.RegisterModule<NavigationRegistration>();
builder.RegisterModule<ServicesRegistration>();
base.Container.RegisterTypeForNavigation<NavigationPage>();
// This is deprecated but we have to wait for Prism.Autofac to update itself
builder.Update(base.Container);
}
}
The DI registrations associated with navigation are done in this module:
internal class NavigationRegistration : Module
{
/// <summary>
/// Load the navigation related types into the given builder.
/// </summary>
/// <param name="builder">Container Builder that will be turned into the final IOC Container</param>
protected override void Load(ContainerBuilder builder)
{
// Register the NavigationPage in Xamarin with the Prism Navigation system.
//builder.RegisterType<NavigationPage>().AsSelf();
//PageNavigationRegistry.Register(nameof(NavigationPage), typeof(NavigationPage));
// Get all of the Types that represent a View in our assembly for DI and navigation registration
// If start-up time ever becomes an issue, we can replace this assembly scan with explicit registrations.
Type[] viewTypes = base.ThisAssembly.GetTypes().Where(type => type.IsAssignableTo<Page>()).ToArray();
// Iterate over each discovered View Type and register it with the navigation system and DI container.
for(int index = 0; index < viewTypes.Length; index++)
{
Type viewType = viewTypes[index];
builder.RegisterType(viewType).Named<Page>(viewType.Name);
// If we ever need to disconnect a view name from its Type name, we can do so here.
// We would build a custom attribute to decorate the view with, pull the attribute from the Type
// and register the Type with the attribute value.
PageNavigationRegistry.Register(viewType.Name, viewType);
}
}
}
Again I can each one of my detail pages without problem, the hamburger menu exists and I can open the Master page to view my buttons used for navigating. I just can't navigate backwards once I'm there. Is that something I'm supposed to wire up myself?
I'm not sure I'm reading your question right but it sounds like this is normal behavior. In my (short) experience with XF/Prism, every navigation from the master is a beginning of the stack. If you were to add another page, e.g. from Master->PageA->PageB, I would expect Page A to have the hamburger menu but going to PageB would give you the back arrow.
For using NavigationPage inside uri you should register it for navigation in the App.xaml.cs:
protected override void RegisterTypes()
{
// your registrations
Container.RegisterTypeForNavigation<NavigationPage>();
}
I most cases it is the reason.
To Navigate To Master Page
"/MasterPage/NavigationPage/ViewA"
To Navigate out of Master Page from ViewA and with back button
"ViewB"
You need to start your app with MainPage = new NavigationPage(new StartPage()); That is how it is solved in normal situation. So maybe try to register your MainPage wrapped in a NavigationPage.
I am trying a new approach i.e. XAML to make application in xamarin.forms. At this time i am facing an issue to reuse my stack layout which is having a image and label. How i can reuse my layout in different pages using XAML.
You can actually define your custom component in a separate XAML file and then just link the component wherever you need it.
For example a label with image can be grouped together in a dedicated XAML file:
<?xml version="1.0" encoding="utf-8" ?>
<StackLayout xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="UserControls.ImageWithTitle"
VerticalOptions="Center" HorizontalOptions="Center" >
<Label HorizontalOptions="Center"
x:Name="TitleLabel" />
<Image Source="noimage.png" />
</StackLayout>
On the .cs file I've defined a binding for the TitleLabel
public string TitleName
{
get { return TitleLabel.Text; }
set { TitleLabel.Text = value; }
}
So when you include the component on another layout, you can assign the label value directly (or via a binding):
<usercontrols:ImageWithTitle TitleName="Home"/>