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iosswiftstoryboardnslayoutconstraint

how can I apply the NSLayoutConstraints to the element so that it is always in the middle of the element below him?

In my storyboard I have a MapView stretched to the borders of my screen. But there's a possibility to show up the keyboard, so then I update the constraints and the map shrinks in height.

This is my method responsible for that:

func keyboardWillChangeFrame(notification: NSNotification) {
    let endFrame = (notification.userInfo![UIKeyboardFrameEndUserInfoKey] as! NSValue).CGRectValue()

    if(isKeyboardShown == true)
    {
        bottomConstraint.constant = CGRectGetHeight(view.bounds) - endFrame.origin.y+49
        self.view.layoutIfNeeded()
        isKeyboardShown = false
    } else {
        bottomConstraint.constant = CGRectGetHeight(view.bounds) - endFrame.origin.y
        self.view.layoutIfNeeded()
        isKeyboardShown = true
    }
}

It works fine. Now I want to add the UIImageView that is always centered on the map, no matter if the keyboard is visible or not. I thought it's enough to center the image in the perfect center of the map.

It so far looks like this:

enter image description here

I managed to add somehow the constraint on the Y axis:

enter image description here

but what about X?

I tried adding it here:

enter image description here

but the align option is greyed out...

How can I add constraints so that the image is always centered no matter how the map is shrinked?

Solution

  • Try Ctrl+dragging from the image view to the map, and clicking Center Horizontally.

    You also might have a conflict with your Top Space to: Top Layout... constraint and your Align Center Y to: Map View constraint. It sounds like you just want the center Y constraint, since when your map grows / shrinks your image won't always be 192 from the top if it's centered on the map.