I have a InfiniteListView which extend ListView from Xamarin Forms.
I know when you on the last item in the list but how can i figure out if the user scrolled to the top of the list ?
Unfortunately, the Xamarin Forms ListView does not expose a Scrolled event or Position property. So your only option is to use the ItemAppearing and ItemDisappearing events.
When you subscribe to these events, you can figure out if the first cell is appearing again, after it disappeared first. This does not actually give you a 100% correct outcome, since it can happen that only a part of the first cell is shown.
If you want a perfect check that you are at the absolute top, you will have to resort to a custom renderer:
On iOS you can make use of the tableView.contentOffset.y property on the UITableView.
On Android it's a little bit more involved, as there are multiple (but no straightforward) ways to achieve this. See this answer for one possibility. This approach is originally meant for saving and restoring scroll position, so adjust it to your needs.
Other platforms have similar ideas. Check which native control the Xamarin Forms renderer creates, and then search the internet for possible solutions for that specific platform.
Related
I use the same DataTemplate to populate some of the views inside my CarouselView: a XAML file with a ContentView. I assign a custom class list to ItemsSource of the carouselview AND use bindings inside the template layout fields to fill them with the properties of my custom class. Everything is working fine. Here comes the wierd part: Let's say there's a button in the template and when you click it on the screen, a Label with "Well Done" text is added to the current Stacklayout of the shown carouselview. This is done by the codebehind of my template XAML. This is ok, too, but I expect this "Well Done" to disappear after I swipe back and forth enough. Because it's not part of the template. It does not disappear, instead I see it on other carousels once in every 4 swipes and it is replaced, I mean it appears on different carousels if I swipe back and forth. To make it disappear completely I have to swipe away from the views that share the same DataTemplate. I cannot understand the mechanics behind this behaviour. I can create another field inside the template to put the "Well Done" text there and show it when the time comes, I know. But I want to understand the mechanics. Thank you.
Asking the right question about a problem is the key to any solution..
After the realization that I've mentioned at the Update comment, I've searched for DataTemplate Caching and found this issue post on Xamarin.Forms Github: https://github.com/xamarin/Xamarin.Forms/issues/9200
There you can find an explanation to how CollectionView was designed and understand the mechanics behind the behaviour. No bug. It's by design.
I do not want to the collectionView to Scroll but only want it to display as a list as its height.
But it seems there is no property to close the function.
Can anyone help?
The CollectionView is currently a preview, and lacks some of its planned functionality. In addition, the API may change as the implementation is completed.
So ,as Денис Чорный said, thought you just want it display just like a list.You can replace it with listview .
for more detail about collectview you can refer here
I need to find what key the user pressed on a keyboard using xamarin.forms, ideally inside an AbsoluteLayout. I've come up with a few ways myself, but can't get any of them working.
As there isn't an event for this on the AbsoluteLayout control, i tried a little cheat, which was putting an entry field (textbox) on the screen, but hiding it above, so it can't be seen and using the result from that, but it loses focus when someone presses the screen or a button on the screen. so i tried adding an event to each button which refocuses the textbox once i've handled the press and this seemed ok at first, however, if they press anywhere else on the screen, it also loses focus.
I also tried adding a TapGestureRecognizer to the screen, and focusing the button when they press anywhere on the screen, however, there were 2 issues with this, the first being that it appears to only fire when something inside it is touched, and secondly, when i call the focus method for the second time (if they click the screen twice) it un-focuses the entry field, even if i check "isfocused" first (think this is a bug).
I'm only concerned about windows 8 and android apps so far. iOS may come later, but for now im just trying to get it working for these OS's. so maybe i could code it in the windows and android projects (inside my shared project solution), however, i have absolutely no idea where to even begin doing that. I mean, if this is the best way, how can i pass my AbsoluteLayout to the windows project and get it to know what it is, and convert it into a control which i can then add the event to.
Any help or advice, or ideas would be much appreciated. I cant find anything in NuGet which will help me with this. Any ideas?
Many thanks
James
I have a List component from which I'd like to be able to remove items using drag & drop, but without having a specific target. If you use the mac, the behaviour I'm looking for is something like what the Dock uses; when you drag something out of the bounds of the control it should get an icon that indicates that it'll be deleted (OSX uses a cloud or something?) and then if you release it it will be removed from the list.
How can I do this?
(If I need to provide a more clear description, please comment; I'll fill in what I can)
In my experience with drag/drop in Flex, you cannot simply drag something out and handle that. There is no dragOut event (unfortunately), so that would leave you up to the task of writing dragOver and dragDrop listeners on all the containers surrounding your dragInitiator and handling the process accordingly.
It's more time consuming and can become complicated if any of these controls already have specific dragOver and dragDrop event handlers.
Hope this helps.
Having no Flex experience all I can offer is some psuedo code which resembles how I implemented a similar effect in JavaScript, but hopefully it will get you started.
Essentially what you'll want to do is during your drag event measure the current coordinates of the object you're dragging to see if they intersect the original container and when they fall outside of its bounds call the logic to update the icon in order to indicate it will be removed. Then, on the drop event, check the coordinates once more and delete the item if needed.
I have a bit of doubt regarding my application which is being created using Mate framework. The first thing user has to do is to log in, so I created Login.mxml view. After a successful login I need to display the main view with applicationControlBar at the top and a workspace below. At the moment I have two separate views, so if I understand correctly it makes sense using ViewStack.
Thing is, I'd like also to display some kind of panel with buttons on top of the workspace after login - here is screenshot. After clicking on a button the panel should dissapear. To complicate things a little bit more, there is a possibility for this panel to change state. Clicking on a specific button may result in showing progress bar at the bottom of panel.
I feel I should create separate view, MenuDialog.mxml and put there buttons, progress bar and states, but how to display it on the top of the workspace? I hope my problem is clear enough :)
I would make the panel a popUp, with the main application (or the ViewStack's parent container) as the parent of the popUp. You can use the PopUpManager Class to close it based on user actions within the Panel.
Assuming that perhaps you do not want a modal login style panel (which many apps these days eschew) then you should absolutely use states rather than ViewStacks.
States are a much cleaner way to distinguish the various, uh, states that your UI can be in -LOGGED_IN, LOGGED_OUT, etc.
It may take a little to get used to working with states, but once you do, you'll never go back. :-)