CODEWITHSUNDEEP
xamarin.ios
Siddharth Kumar
Siddharth Kumar

Reputation: 353

Monotouch - programming for Swipe Gesture

I am developing a control for an IPAD application (My first time doing Apple development). Its a simple control that mimics a grid - consists of a collection of UIViews (each of which represents a cell) all added to a parent UIView (in a grid like fashion).

One of the requirements is to implement a swipe gesture - the users swipe across the grid to activate/inactivate the cell - this corresponds to a 1/0 in the database.

I create a UISwipeGesture and added it to each of my UIView which represents a cell. That appears to be an incorrect approach as it fires the event for the UIView in which the swipe originated but not across all the UIViews.

My understanding would be that i need to implement the SwipeGesture across the parent UIView which contains all these children UIView. However if i do that how will i know which child UIView has been swiped over? Or any other approach which would make sense?

Upvotes: 2

Views: 2278

Answers (3)

Chuck Savage
Chuck Savage

Reputation: 11955

I know this thread is fairly old, but I created a Swipe extension method that might have helped.

View.Swipe(UISwipeGestureRecognizerDirection.Right).Event += Swipe_Event;

void Swipe_Event(ViewExtensions.SwipeClass sender, UISwipeGestureRecognizer recognizer)
{
    View view = sender.View; // do something with view that was swiped.
}

Upvotes: 4

StephenAshley.developer
StephenAshley.developer

Reputation: 1064

I think you're correct that the gesture recognizer has to be attached to the parent view. In the action method associated with the gesture recognizer I think you can use the Monotouch equivalent of CGRectContainsPoint() to determine whether the swipe occurred in a particular subview. I imagine you would have to iterate through the subviews until you found the one in which the swipe occurred. I'm not aware of a method that would immediately identify the swiped subview.

Upvotes: 0

Anuj
Anuj

Reputation: 3134

This may not answer your question, but I can speak to the approach I've taken here with a similar use case:

1) I would abandon UIScrollView and use UITableView. You'll notice that UITableView inherits from UIScrollView and has all the performance benefits of virtualization and cell / view re-use. Which you'll find terribly useful as you work towards optimizing your app for performance on device.

2) Utilize the UITableViewCell's ContentView to create custom "Grid" cells. Or better yet, utilize MonoTouch.Dialog if you're not required to create Grid rows ad-hoc.

3) Use this awesome class (props to @praeclarum) to setup gestures in MonoTouch. You essentially provide a UIGestureRecognizer as a generic argument. You can then utilize the LocationInView method to grab the point in the UITableView where the gesture occurred

public void HandleSwipe(UISwipeGestureRecognizer recognizer)
{
    if(recognizer.State == UIGestureRecognizerState.Ended) {

        var point = recognizer.LocationInView(myTableView);
        var indexPath = myTableView.IndexPathForRowAtPoint(point);

        // do associated calculations here
    }
}

Upvotes: 2

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