I'm using Xamarin Forms Maps official nuget library, everything works good and I handle finish zooming and scrolling map via this code:
map.PropertyChanged += (sender, args) =>
{
var m = sender as Map;
if (m?.VisibleRegion == null) return;
SearchButton.IsVisible = true;
};
map.PropertyChanging += (sender, args) => { SearchButton.IsVisible = false; };
But I want to do some stuff when user starts scrolling or zooming map!
I didn't find it and also PropertyChanging not called when user is surfing the map, it's calling just before PropertyChanged.
I think in Xamarin.Forms your options are limited, so your best option would be to either create a custom renderer and abstract the gestures into Xamarin.Forms, or create your own custom canvas, render the map onto it and that way you would have full control.
Related
Summary
The Touch event is never raised with the ActionType of SKTouchAction.Moved, but SKTouchAction.Pressed is raised. Why does the .Moved event never get raised?
Detail
I am attempting to create a slider in SkiaSharp. This control will need to update the thumb (the little movable circle) when the user either touches on the slider or drags. This is hosted in a Xamarin Forms app, and I have created a SKCanvasView to draw the slider and to respond to touch events.
I have successfully responded to touch events, so I know the SKCanvasView is receiving some UI events, but the SKTouchAction.Moved is never raised.
Example Code
private SKCanvasView CreateSliderControl()
{
var control = new SKCanvasView();
control.PaintSurface += HandlePaintHeightControl;
control.EnableTouchEvents = true;
control.Touch += (sender, args) =>
{
var pt = args.Location;
switch (args.ActionType)
{
case SKTouchAction.Pressed:
// 1. This code gets hit whenever I touch the canvas
control.InvalidateSurface();
break;
case SKTouchAction.Moved:
// 2. This code never gets hit, even if I push, touch, slide, etc
control.InvalidateSurface();
break;
}
};
control.InputTransparent = false;
return control;
}
As shown above #1 gets hit (I can put a breakpoint there, and my control surface is invalidated). #2 never gets hit ever, but I expect it to get hit when I slide my finger over the control.
What I've Tried
Clean/rebuild to make sure my code actually was being deployed
Upgrade from SkiaSharp 1.60.3 to 1.68.0
All the crazy finger movements I could come up with
Read through https://learn.microsoft.com/en-us/xamarin/xamarin-forms/user-interface/graphics/skiasharp/transforms/touch , but that uses XAML to assign an Effect (which I'm not familiar with) and I don't see a TouchEffect class available anywhere in my code to add it to the parent Grid that contains my SkiaCanvasView.
Found a similar issue on SkiaSharp's Github.
Try telling the OS that you want to "continue receiving touch events" by setting the Handled property in the event's args to true.
private SKCanvasView CreateSliderControl()
{
var control = new SKCanvasView();
control.PaintSurface += HandlePaintHeightControl;
control.EnableTouchEvents = true;
control.Touch += (sender, args) =>
{
var pt = args.Location;
switch (args.ActionType)
{
case SKTouchAction.Pressed:
control.InvalidateSurface();
break;
case SKTouchAction.Moved:
control.InvalidateSurface();
break;
}
// Let the OS know that we want to receive more touch events
args.Handled = true;
};
control.InputTransparent = false;
return control;
}
It´s possible to set an image to be the background of all Pages on my application (for all platforms IOS, Android and WP) ?
Page has a BackgroundImage property, so I can create a base page, set the background and make all my pages extends from it.
I want to know if there is a more appropriate solution, to handle this.
You could use Styles in your App.cs :
public App ()
{
Application.Current.Resources.Add(new Xamarin.Forms.Style(typeof(Page)){
Setters = {
new Xamarin.Forms.Setter { Property = Page.BackgroundImageProperty, Value = "back.png"},
}
});
}
much less preferred or advised but for the sake of showing another option you could attach an event handler to your NavigationPages and set the background from there:
yourRootNavigationPage.Pushed+= (sender, e) => e.Page.BackgroundImage = "back.png";
Is there a (half) generic way to handle rotation/orientation in Xamarin Forms for different views and platforms (Android, iOS, WinPhone)?
The UI does rotate, and that is nice enough, though it wreaks havoc to my layout (absolute layout right now). I suppose with a Stacklayout I could make it a litte more flexible, but would then hit a road block somewhere else when the layout is more intricate.
Can I somehow display different views for portrait and landscape, with the same ViewModel? (I am using XLABs based MVVM.)
Possible solutions I have found:
http://blog.rthand.com/post/2014/07/24/Different-XAML-layouts-for-different-device-orienations-in-XamarinForms.aspx is lacking iOS and I wonder if it will handle MVVM too well, seems good though and I am investigating it right now
http://www.jimbobbennett.io/orientation-with-xamarin-forms/ sounds promising but the sample is iOS only, the linked GIT repository has no documentation at all, it just says "Xamarin Helpers"
http://www.sellsbrothers.com/posts/Details/13740 might also be a possibility for programmatically created views. Though in my tests I did not get a size changed event (though I listened at a different code place) for ios simulator when rotating. (The solution is based on size changed to detect rotation.)
If you are already using XLabs then you could use IXFormsApp and property 'Orientation' and event handler 'Rotation'. You would have to add the native observers per platform and set IXFormsApp's 'Orientation' there which would cause the event handler to invoke.
For example on iOS:
public override bool FinishedLaunching(UIApplication app, NSDictionary options)
{
var xapp = new XFormsAppiOS();
xapp.Init(this);
var resolverContainer = new SimpleContainer();
resolverContainer.Register<IXFormsApp>(xapp);
Resolver.SetResolver(resolverContainer.GetResolver());
var a = new App();
LoadApplication(a);
UIDevice.Notifications.ObserveOrientationDidChange((s, e) =>
{
xapp.Orientation = ... // set orientation here
});
Now you can monitor orientation changes by resolving IXFormsApp:
xapp = Resolver.Resolve<IXFormsApp>();
if (xapp.Orientation == Orientation.Landscape) { ... } else { ... }
xapp.Rotation += (sender, args) =>
{
switch (args.Value)
{
case Orientation.LandscapeLeft:
break;
default:
// etc.
break;
}
};
As for layouts I would imagine RelativeLayout would be the most convenient choice as you could put the orientation inside the Constraint's. On rotation make the layout refresh itself.
I am creating an app that allows the user to drag and drop to put one image on top of another using Xamarin.Forms.
On iOS I managed to hack together a workable gesture recognizer renderer by creating a custom ContentView and a custom renderer for it, which then attaches native gesture recognizers to itself based on the GestureRecognizers elements. To do that I disable the default EventTracker and implement my own, with overridden GetNativeRecognizer method
in the custom renderer:
public InteractiveContentViewRenderer () : base ()
{
AutoTrack = false;
events = new InteractiveEventTracker (this);
}
in the custom event tracker:
public InteractiveEventTracker (IVisualElementRenderer renderer) : base (renderer)
{
this.Renderer = renderer;
}
protected override MonoTouch.UIKit.UIGestureRecognizer GetNativeRecognizer (Xamarin.Forms.IGestureRecognizer recognizer)
{
var gestureRecognizer = base.GetNativeRecognizer (recognizer);
if (gestureRecognizer == null) {
// here I find my own native recognizer and return it
}
}
On Android, however, so far I haven't figured out how to achieve the same thing. There's no EventTracker in Android, I think I'll have to implement some Android View for this to work but I haven't figured it out so far.
Has anyone managed to hack together touch events in Xamarin.Forms for Android? I'd like to know at least the basic structure of the hack?
Read this: http://blog.twintechs.com/cross-platform-compositional-gesture-advanced-xamarin-forms-techniques-for-flexible-and-performant-cross-platform-apps-part-4
There's a lot about custom gestures in Xamarin.Forms
The source is here: https://github.com/twintechs/TwinTechsFormsLib/tree/master/TwinTechsForms/TwinTechsForms.Droid/TwinTechs/Gestures
I have an app in which I have a lot of references and the load time was not acceptable to me. I have removed the splash screen image and created an animated loading screen by having a separate project with no reference to the main application which then navigates to the first page of the rest of the app. It does start up fast now but it's a little lacking still.
I would like to do another animation right before the load screen goes away. The only way I can think of to do this is to actually preload the assemblies needed for the navigation to the next page, do an animation, and then navigate.
I have tried
OnNavigatedFrom but the animation doesn't have time to run since the page will be replaced by the new page very quickly from that point.
OnNavigatingFrom is no help either as it is called as soon as I call NavigationService.Navigate();
Searching the web and Stack Overflow :)
I also considered faking it a bit by having the next page show a duplicate of the load screen and do the last animation there, but it can't match the current state of the load screen animation and is harder to maintain
Thanks for any ideas!
If you want to force the loading of an assembly, just reference a type from this assembly.
For instance, something like Console.WriteLine(typeof(YourAssembly.SomeType)); will force the loading of YourAssembly.
Now for your problem, maybe you can use usercontrols? Put the content of your main page in a user control. Display the loading page, create the usercontrol in the background, let the animation play, then when the animation is done playing replace the page's content with the usercontrol.
It turns out that you can preload by just creating a new instance of the page you are going to navigate to. Unfortunately that has to be done on the UI thread which can cause animation slowdown, at least in my experience.
Here is a sample of how to do an animation, then preload, then do another animation before navigating. :
public partial class LoadScreen : PhoneApplicationPage
{
public LoadScreen()
{
InitializeComponent();
this.Loaded += OnLoaded;
}
private void OnLoaded(object sender, RoutedEventArgs routedEventArgs)
{
var sb = new Storyboard();
// create your animation here
sb.Completed += (sender, args) => PreLoad();
sb.Begin();
}
private void PreLoad()
{
// this is the part that actually takes time and causes things to get loaded
// you may need it in a try/catch block depending on what is in your constructor
var page = new PageToNavigateTo();
// now create an animation at the end of which we navigate away
var sbOut = new Storyboard();
// create your animation here
sbOut.Completed += (sender, args) => NavigateToNextScreen();
sbOut.Begin();
}
private void NavigateToNextScreen()
{
// navigate here
}
protected override void OnNavigatedFrom(System.Windows.Navigation.NavigationEventArgs e)
{
base.OnNavigatedFrom(e);
// remove the loading screen from the backstack so the user doesn't see it again when hitting the back button
NavigationService.RemoveBackEntry();
}
}