Is there a ScrollView event in xamarin that is triggered when the user forces scroll up and scroll is already at top? Many apps uses this as the "command" to update the page.
Currently, there is no PullToRefresh property or RefreshCommand for a ScrollView built into Xamarin.Forms. However, It does exist on ListView as shown in the docs, which you might be able to use instead depending on your needs.
Also, it does look like there is a PullToRefreshLayout opensource project created by James Montemagno you might be able to use to easily implement pull to refresh with a ScrollView, but it has been a while since it's last been updated.
You can use the Scrolled event handler. If the ScrollView is already positioned at the top of the contents and the user "pulls down" then Y amount will be either 0 or negative (I know this will work on Android and iOS, not sure about UWP and others).
scroll.Scrolled += (object sender, ScrolledEventArgs e) =>
{
if (e.ScrollY <= 0)
{
// scrolled when already at top of list
}
};
Related
.NET Maui CarouselView. In certain situations I want my app to take the user to the next card automatically. If I update CarouselView.Position or CarouselView.CurrentItem in code behind, it "jumps" to the next card immediately, no animation. Is it possible to imitate user's swipe? Or as a workaround, maybe somehow apply non-native-CarouselView animation manually to the CarouselView. Please advise.
The CarouselView contains a ScrollTo method that will animate the scroll for you. You either scroll to an index or a specific item.
Give your CarouselView a name in the XAML, and then in the code behind call the ScrollTo.
To scroll to an index:
carouselView.ScrollTo(6);
To scroll to a specific item:
var viewModel = BindingContext as MyViewModel;
var item = viewModel.Items.FirstOrDefault(m => m.Name == "TheBest");
carouselView.ScrollTo(item);
These methods have to be called from the code behind, so if you're using a MVVM approach, you'll need to fire an event or command from your VM for your code behind to act on.
For additional info, take a look at the ScrollTo method docs from Microsoft.
I have simple Click event and want to navigate between views, but I get annoying slide up animation even that I have "false" as a parameter for animation in function. Is there any way to turn of animation effect when browsing between views in Xamarin Forms?
Thank you!
void Button_Clicked_Signup(System.Object sender, System.EventArgs e)
{
Navigation.PushModalAsync(new Signup(), false);
}
Your app is doing exactly what you're asking it to do. That annoying slide up animation is called Pushing a Modal which is happening since you are using the PushModalAsync function.
You need to the documentation and understand Hierarchical Navigation.
To fix it, you need to
Create a NavigationPage first
Pass in your current page into that
Use Navigation.PushAsync instead of Navigation.PushModalAsync
I have a listView and when the receive a message, the listview should scroll to the end only, if it already in the end.
To make it clear, if the user is seeing old message, the listview shouldn't scroll to the end automatically, but if the is already on the on the listview when receiving a message the listview should automatically scroll to the end.
So I have to get the actual position of the ListView, I didn't see any property or method similar to get this position on the API.
So I was thinking if is possible to override an event like OnScroll, so I can save the current position of the ListView without using custom render.
This can be done using XamarinForms?
ListView doesn't fire Scrolled events like ScrollView does, but it does fire ItemAppearing and ItemDisappearingevents that you may be able to use to keep track of which items are currently visible.
First, SelectedIndex is not exposed in markup, so you have to do it in code behind, right?
Second, I have set the binding in code behind:
Binding binding = new Binding("Main.PanoSelectedIndex.ObservedObject");
binding.Mode = BindingMode.TwoWay;
rootPano.SetBinding(Panorama.SelectedIndexProperty, binding);`
(ObservedObject implements iNotifyChanged)
The binding path points to my Main view model, and I can see that the PanoramaItem is updating the binding. However,the panorama does not respond when something else (a MVVM Light command) changes the binding. Any ideas?
Thanks,
Roger
To quote from the Windows Phone Developer FAQ
Panorama is designed so the user is in control, there fore you cannot set SelectedIndex programmatically, or force a navigation to a panorama item.
You can set the DefaultItem so that when your panorama is first launched, the panorama navigates to that item, but you can’t navigate programmatically beyond that. DefaultItem can also be used so that a back navigation feels like the item where the user was at did not change.
UPDATE: You can use the DefaultItem to save/restore the selection for a Panorama as shown below (code from Jeff Prosise's recent blog post):
protected override void OnNavigatedFrom(NavigationEventArgs e)
{
// Save the Panorama control's SelectedIndex in page state
State["Index"] = PanoramaControl.SelectedIndex;
}
protected override void OnNavigatedTo(NavigationEventArgs e)
{
// Restore the Panorama control's SelectedIndex
if (State.ContainsKey("Index"))
PanoramaControl.DefaultItem = PanoramaControl.Items[(int)State["Index"]];
}
As far as I know SelectedIndex is a readonly property in Panorama ( Weired why WP7 SDK made it readonly). So you will get only UI change back to your VM, and you cant update UI through the VM propertychange.
And DefaultItem is the property which used to set the index programatically.
Again the issue of programatically setting an already instantiated Panorama is that, the alignment of the Title and Panoramaitem wont be in sync. Anyway I am not discouraging but there is still some chance of hack there.
I have a Pivot Control in my WP7 app that by nature responds to left and right swipes to move between the pivot items.
I then want to use the Flick Gesture on a UserControl (a small UI segment on my page) for something else.
My user control does handle the event but so does the Pivot control, so it navigates to the next item. I have not figured out how to stop the event when the usercontrol handles it.
Is it possible to use a sub control with the flick gesture within a WP7 Pivot Control?
eg:
private void glBlinds_Flick(object sender, FlickGestureEventArgs e)
{
//do stuff
e.Handled = true;
}
This solution posted recently seems to be working out for people for dealing with gesture conflicts on pano / pivot. You might like to check it out.
Preventing the Pivot or Panorama controls from scrolling
The short answer is don't put a control which supports a gesture on top of another control which also supports the same gesture.
Please see this answer to a very similar question for a slightly longer response: WP7 Toggle switch in a Pivot control?
I found this works well for incorporating a slider on a pivot item:
LayoutRoot
Pivot
PivotItem
Grid
Scrollviewer
[Content goes here, I use another grid]
Slider
If I skip the grid and place the slider inside the scrollviewer it doesn't work. I stumbled upon this solution as I wanted to support landscape and still have the slider visible / usable.
You might be able to place your small UI segment for the gesture similar to where I placed my slider.