I have XAML code to create program output in frame. I can change content of frame in case I used "MyFrame.Navigate(typeof(Setup))". Is there any way to initialize content of frame in XAML code?
XAML code fragment:
</SplitView.Pane>
<SplitView.Content>
<Frame Name="MyFrame" ?any reference to view to first time intiilaization? />
</SplitView.Content>
Thanks for help
You can use SourcePageType
It can set in xaml ,the code is
<Frame Name="MyFrame" SourcePageType="Setup"></Frame>
The frame will navigate to Setup
I think you can use the control above in the Frame when you enter the page ,you can set it Visibility and you can set is hidden when load complete.
Related
I tried to get the same large title behavior like the settings app on iOS when the user scrolls down. The transition between the large title and the small title is smooth. But on Xamarin Forms the header snaps.
In my NavigationPage i set PrefersLargeTitles="true". In the embedded content page i set LargeTitleDisplay="Always" and UseSafeArea="true". The content in the page looks like this:
<ContentPage.Content>
<AbsoluteLayout>
<ListView />
<Frame x:Name="LoadingFrame" /> <!-- Only visible until ListView is loaded -->
</AbsoluteLayout>
</ContentPage.Content>
I tried setting NavigationPage.IsNavigationBarTranslucent="True". Then it works, but only if i disable SafeArea (Page.UseSafeArea="False") in the ContentPage. Disabling SafeArea is not what i want, because now the content is behind the notch.
I had the same issue.
The trick was to change top constraint of list to superView instead of safe area which only works on Native.
extendedLayoutIncludesOpaqueBars = true;
On Xamarin.Forms, I tried these solutions:
Use a custom renderer to set the LayoutConstraints of the scrollable view (Doesn't work)
Create a UITableViewController in a custom renderer then convert the Xamarin TableView element to a UITableView and set it to the TableView property of the UITableViewController then PushViewController to the new UITableViewController. (work)
You can raise the problem on github for better support：
https://github.com/xamarin/Xamarin.Forms/issues
I'm new to Xamarin.
When I try to insert a Button or a BoxView I can set the "HeightRequest" and "WidthRequest" Parameters but the elements are just filling the whole screen.
What am I doing wrong?
You have done nothing wrong, but you missed some key procedure. you did not set LayoutOptions of Button or BoxView. The following code could make element size effected.
<Button Text="click me"
HeightRequest="44"
WidthRequest="60"
VerticalOptions="Start"
HorizontalOptions="Start"/>
As you know, the button control is inherited from the View. The default value of VerticalOptions dependency property is LayoutOptions.Fill. And it also works for HorizontalOptions. So if you did not set value for VerticalOptions and HorizontalOptions, the control will fill the whole screen.
I want to setup a background image for a page. Right now I am using
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="M.LaunchPage"
Title ="M" BackgroundImage="Mars.jpg">
<ContentPage.Content>
<StackLayout Padding="10,0,10,10" >
<Button VerticalOptions="CenterAndExpand" Text="Sign Up" TextColor="White" Clicked="OnSignUp" BackgroundColor="Maroon" />
<StackLayout Padding="10,0,10,10" Orientation="Horizontal" VerticalOptions="EndAndExpand" />
</StackLayout>
</ContentPage.Content>
</ContentPage>
This works well but the image is being filled multiple times to fit the screen. Cn anyone suggest better code so that I can fit the image on the page perfectly?
Thanks.
This is platform dependent, for example on iOS the following is used in the Form's iOS's PageRender:
View.BackgroundColor = UIColor.FromPatternImage(UIImage.FromBundle(bgImage));
The View.BackgroundColor will end up tiling your image when it is smaller the UIController's View dimensions as FromPatternImage is designed to be used with a small repeating pattern (for memory and draw performance reasons) and not full screen/page images.
In order for this auto-tiling not to happen, you would be to assign the background image in code based upon the device's screen resolution and page size at runtime and not statically assign it in XAML.
Note: You could bind the BackgroundImage property in a ViewModel where the calculations of which image to use could be done.
You should use each platform specifications, for example in iOS you need to have Mars#2x.jpg and Mars#3x.jpg,in our platform project in Forms you can specify from "Mars" it will pick the correct one.
On Android set the image in the correct dpi folder.
In the Universal Windows Platform API, how do I use x:Bind inside of a User Control (intended to be the layout for a GridView's ItemTemplate) to bind to instance properties of a GridView's ItemSource?
Background
I'm trying to re-create the layout found in Windows 10 stock apps like Sports, News, Money, etc.
I'm using a two GridViews for the main area of the app; one for "featured articles" (2 large photos w/ headlines) and one for all the other articles (smaller photos w/ headlines).
I'm able to bind to a data source that I supply in the code behind (a List where NewsItem is a POCO with a Image and Headline property) Here's the pertinent parts of the MainPage.xaml:
<Page ...
xmlns:data="using:NewsApp.Models" />
....
<GridView Name="FeaturedItems" Grid.Row="0">
<GridView.ItemTemplate>
<DataTemplate x:DataType="data:NewsItem">
<Grid Name="mainPanel" HorizontalAlignment="Stretch" Width="500" >
<Image Source="{x:Bind Image}" HorizontalAlignment="Stretch" />
<TextBlock Text="{x:Bind Headline}" />
</Grid>
</DataTemplate>
</GridView.ItemTemplate>
</GridView>
....
The Image and Headline bind just fine (even though they've not been styled correctly). However, instead I think I need to bind to a User Control to get the styling options I want, control over resizing esp. when using Visual State Triggers and to simplify the XAML in general (at least, this was the technique suggested to me.)
So, I added a new User Control to the project (FeaturedItemControl.xaml), and copied in the DataTemplate's child Grid:
<UserControl ... >
<Grid Name="mainPanel" HorizontalAlignment="Stretch" Width="500" >
<Image Source="{x:Bind Image}" HorizontalAlignment="Stretch" />
<TextBlock Text="{x:Bind Headline}" />
</Grid>
</UserControl>
And then back in the MainPage.xaml, I change the DataTemplate to reference the new FeaturedItemControl:
<GridView Name="FeaturedItems" Grid.Row="0">
<GridView.ItemTemplate>
<DataTemplate x:DataType="data:NewsItem">
<local:FeaturedItemControl HorizontalAlignment="Stretch" VerticalAlignment="Stretch" />
</DataTemplate>
</GridView.ItemTemplate>
</GridView>
However, I get the error message for both Image and Headline properties: Invalid binding path 'Headline': Property 'Headline' can't be found on type 'FeaturedItemControl'.
I've tried a few things but am flailing just throwing code at the problem without understanding what I'm doing. Any help would be greatly appreciated.
Thank you for your kind attention.
Using Depechie's answer, I formulated this little cheat cheat for posterity:
Do note that you MUST use this technique to utilize the VisualStateManager with items inside your data bound controls' (GridView, ListView) data templates.
1) Create a User Control.
2) Cut the content of the DataTemplate in your page and paste it into the User Control replacing the template's Grid.
3) Reference the User Control from inside the Data Template:
4) Modify the contents of the User Control changing x:Bind statements to utilize object.property notation:
<UserControl>
<StackPanel>
<Image Source="{x:Bind NewsItem.LeadPhoto}" />
<TextBlock Text="{x:Bind NewsItem.Headline}" />
<TextBlock Text="{x:Bind NewsItem.Subhead}" />
</StackPanel>
</UserControl>
5) Add this in the User Control's Code Behind:
public Models.NewsItem NewsItem { get { return this.DataContext as Models.NewsItem; } }
public ContactTemplate()
{
this.InitializeComponent();
this.DataContextChanged += (s, e) => Bindings.Update();
}
Well it's possible to use x:Bind in user controls, but you'll need to add some extra code behind.
I encountered the same problem in my project, you can see the result here : https://github.com/AppCreativity/Kliva/tree/master/src/Kliva/Controls
So what you need to do is, create a property in the code behind of your user control that points to the correct DataContext.
If you do that, you can use properties of that DataContext in the xaml of your control: for example:
Do note that in the constructor of your control you do need to add: DataContextChanged += (sender, args) => this.Bindings.Update(); because the datacontext will change depending on the page where your control is used!
Then on the page where you are placing this control, you'll also need to do the same to enable the x:bind to work.
You'll see this in my example on the MainPage.DeviceFamily-Mobile.xaml and MainPage.xaml.cs files.
Hope this helps.
x:Bind isn't really hierarchical like Binding/DataContext is. Additionally when you're not directly inside a DataTemplate (such as inside your user control) the object that x:Bind tries to use is 'this' rather than 'this.DataContext'. My current line of thinking on how to solve this sort of issue is to try not to use UserControls anywhere. Instead preferring DataTemplates contained within a ResourceDictionary. There are some pretty strong caveats to this approach though, you will for example crash the xaml compiler if you use x:Bind inside a data template that was created from the ResourceDictionary item template (add new item). you can find a pretty complete example here https://github.com/Microsoft/Windows-universal-samples/tree/master/Samples/XamlBind its important to note in the sample where they show the ResourceDictionary being used that its not actually just a ResourceDictionary.xaml its also a ResourceDictionary.xaml.cs (this is where the generated code from x:Bind ends up)
Another option is to add Headline and Image as properties on your user control and x:Bind them from the template, then inside the user control x:Bind as you are currently doing, but now the x:Bind generated path 'this.Headline' will exist. Unfortunately the order things are actually bound means that the x:Bind's you have inside your user control will have to be OneWay rather than the default OneTime. this is because x:Bind OneTime does the bind inside the InitializeComponent call, and any set of properties/DataContext stuff doesn't get done until after that has already run.
So to sum this up, you have two options, use data templates everywhere, or bind to properties that are directly on the user control.
I have the following code in which I hide a WebView just under the main Grid (LayoutRoot) so I can do a sliding animation later:
<Page...>
<Grid x:Name="LayoutRoot">
...
<Grid x:Name="ContentRoot">
...
</Grid>
<WebView...>
<WebView.RenderTransform>
<CompositeTransform TranslateY="{Binding ElementName=LayoutRoot,
Path=ActualHeight}"/> <!--Does not work-->
</WebView.RenderTransform>
</WebView>
</Grid>
</Page>
When I first type the {Binding ElementName=...} line into the designer, the WebView appears just below the Grid like it should. However, when I rebuild the solution or run the app, the WebView simply obscures the whole LayoutRoot.
This will happen regardless of what I am binding to/whatever the control is; however, binding to the exact same expression will show up properly in the designer and in the phone. To demonstrate what I am saying:
<Button Width="{Binding ElementName=LayoutRoot, Path=ActualHeight}"> <!--Works perfectly, both on designer and phone-->
<Button.RenderTransform>
<CompositeTransform SomeProperty={Binding ElementName=SomeElement, Path=SomePath}"/> <!--This does not work-->
</Button.RenderTransform>
</Button>
Is there any way to bind to LayoutRoot.ActualHeight short of writing C# code for this?
One problem you have is you are trying to bind to ActualHeight which is not a dependency property nor an observable (INotifyPropertyChanged) property, so the binding is only evaluated once when it's first created.