How to Get the Centre of the View

How to get the centre of the view

Swift 4 extension:

extension CGRect {
    var center: CGPoint { .init(x: midX, y: midY) }
}

let someRect = CGRect(x: 10, y: 10, width: 200, height: 40)

let theCenter = someRect.center // {x 110 y 30}

How can i get center x,y of my view in android?

centre of the imageView will be

 centreX=imageView.getX() + imageView.getWidth()  / 2;
 centreY=imageView.getY() + imageView.getHeight() / 2;

but make sure you call it after the imageView created

Get center of any UIView in Swift

Original Answer:

I had reproduce your problem easily (see my comment).
I think it could be a problem of auto layout. So may be you can use constraints instead calculate position ?

func addActivityIndicatorToView(activityIndicator: UIActivityIndicatorView, view: UIView){

    self.view.addSubview(activityIndicator)

    //Don't forget this line
    activityIndicator.setTranslatesAutoresizingMaskIntoConstraints(false)
    view.addConstraint(NSLayoutConstraint(item: activityIndicator, attribute: NSLayoutAttribute.CenterX, relatedBy: NSLayoutRelation.Equal, toItem: view, attribute: NSLayoutAttribute.CenterX, multiplier: 1, constant: 0))
    view.addConstraint(NSLayoutConstraint(item: activityIndicator, attribute: NSLayoutAttribute.CenterY, relatedBy: NSLayoutRelation.Equal, toItem: view, attribute: NSLayoutAttribute.CenterY, multiplier: 1, constant: 0))

    activityIndicator.startAnimating()

}

Updated Code for Swift 5.0:

From edit by Rob
NSLayoutAttribute.CenterX is now NSLayoutConstraint.Attribute.centerX
NSLayoutRelation.Equal is now NSLayoutConstraint.Relation.equal
NSLayoutAttribute.CenterY is now NSLayoutConstraint.Attribute.centerY

func addActivityIndicatorToView(activityIndicator: UIActivityIndicatorView, view: UIView){

    self.view.addSubview(activityIndicator)

    //Don't forget this line
    activityIndicatorView.translatesAutoresizingMaskIntoConstraints = false
    view.addConstraint(NSLayoutConstraint(item: activityIndicator, attribute: NSLayoutConstraint.Attribute.centerX, relatedBy: NSLayoutConstraint.Relation.equal, toItem: view, attribute: NSLayoutConstraint.Attribute.centerX, multiplier: 1, constant: 0))
    view.addConstraint(NSLayoutConstraint(item: activityIndicator, attribute: NSLayoutConstraint.Attribute.centerY, relatedBy: NSLayoutConstraint.Relation.equal, toItem: view, attribute: NSLayoutConstraint.Attribute.centerY, multiplier: 1, constant: 0))

    activityIndicator.startAnimating()

}

How to center a subview of UIView

Objective-C

yourSubView.center = CGPointMake(yourView.frame.size.width  / 2, 
                                 yourView.frame.size.height / 2);

Swift

yourSubView.center = CGPoint(x: yourView.frame.size.width  / 2,
                             y: yourView.frame.size.height / 2)

centering a CGRect in a view

UIView's center is a property, not a method.

You need to calculate the actual location you want to put it in. You can do this by setting the frame of the view, or by setting its center, which is simpler in your case.

You don't say what view you then go make imageView a subview of. If you're putting it inside something called superview, you could do this:

CGPoint superCenter = CGPointMake(CGRectGetMidX([superview bounds]), CGRectGetMidY([superview bounds]));
[imageView setCenter:superCenter];

Make UIView in the center of the screen

Check center property of UIView. You can set your view center to viewControllers root view for example:

yourView.center = self.view.center;

iOS: How to Align The Center of a View With The Bottom of Another View With AutoLayout

There are a lot of ways to do this. I'll just show one of the ways.

OK, Let's do this step by step.

Step 1

First, in order to align the center of the oval image with the bottom of the rectangular image, we need to embed the rectangular view in another view in which we could name as the Container View.

This container view will have the ff attributes:

transparent background color
width is equal to the screen width
height will be twice the height of the rectangular view(Later you

will know why).

For the constraints of the Container View:

Leading is equal to super view's leading
top space to super view is 0
Centered horizontally in super view.
set aspect ratio with self.

Once you are done, the constraints will look like this.

Sample Image

Step 2

Now for the rectangular image view, the constraints would be:

Leading is equal to the container view's leading
Top space to container view is 0
Trailing is equal to container view's trailing.
Set aspect ratio with oval image view
- By setting aspect ratio with the oval image view. The change in size of this rectangular view will be proportional with the change of size of the oval view.

It will look like this:

Sample Image

Step 3

This time, the contraints of the oval view:

centered horizontally in container view
centered vertically also in container view
set aspect ratio with self
• Setting aspect ration with self ensures that when the rectangular view expands in size, the change in size of the oval view will not cause distortion.

This will be the result:

Sample Image

Step 4

There one very important view to add. This view will ensure that the rectangular view will always be half the size of the container view so that the center of the oval view will always be aligned with the bottom of the rectangular view. So, we call this view that we will be adding, the dummy view.

The dummy view will have the ff attributes:

transparent background color
width and height value should only be 1

The dummy view's contraints:

centered vertically in the container view
centered horizontally in the container view
width and height are fixed.
assign vertical spacing with rectangular view

This is how it should be done:

Sample Image

Alright, if you did the steps above you will achieve the effect.

This will be the overview of the constraints:

Sample Image

I hope this helps. :)

Proof that this works!

I ran it in the simulator... :D

iPhone 4:

Sample Image

iPhone 5:

Sample Image

iPhone 6:

Sample Image

iPhone 6 Plus:

Sample Image

How to get center of the displayed area in UIScrollView?

Try this

yourCustomAlert.center = self.view.center;

Inside your scrollView

first get visible Rect of scrollview

CGRect visibleRect = CGRectMake(myScrollView.contentOffset.x, myScrollView.contentOffset.y, myScrollView.bounds.size.width, myScrollView.bounds.size.height)

then get it's center

CGPoint centerPoint = CGPointMake(visibleRect.size.width/2, visibleRect.size.height/2);

then set your alertView's center
```
yourCustomAlert.center = centerPoint;
```

Understanding how subview.center = view.center works and why the getter and setter do different things

So when setting it, it is setting it inside it's superview. When getting the subviews center it gives you the actual views center.

So half of 50 is 25, hence 25,25. You are wanting the subview's center not its parent's center so there is no reason for it to return its parent's center coordinates, just its own.

To be a bit more technical it has to related to Frame and Bounds of a view (the getter is getting the center by using the view's bounds and the setter is using the view's frame). Here is a link that describes what those are and how they are different.

How to Get the Centre of the View