i got a UICollectionView with (3*3 Grid), so when i scroll up and down, is there a way i can detect if the collection view cell is displaying more than 50% of its height on the screen?
let visibleRect = CGRect(origin: collectionView.contentOffset, size: collectionView.bounds.size)
let visiblePoint = CGPoint(x: visibleRect.minX, y: visibleRect.midY)
let visibleIndexPath = collectionView.indexPathForItem(at: visiblePoint)
I have tried this but it doesn't seems to work. Does anyone has solution for this?
You can ask for
#property(nonatomic) CGPoint contentOffset;
of UIScrollView because UICollectionView's inherits from them.
and don't forget your Cell's have a CALayer that knows the visible Rectangle as well.
CGRect visiblerect = cell.layer.visibleRect;
if (visiblerect.size.height > (cell.frame.size.height * 0.5)) {
// do stuff when cell is more visible then half its size
}
I have two methods:
private func showPicker() {
UIView.animate(withDuration: 0.3,
animations: {
var pickerFrame = self.vPickerWrapper.frame
pickerFrame.origin.y = self.view.frame.size.height - 300.0
self.vPickerWrapper.frame = pickerFrame
self.bIsShowingPicker = true
self.view.layoutIfNeeded()
self.view.updateConstraintsIfNeeded()
})
}
private func closeThePicker() {
UIView.animate(withDuration: 0.3,
animations: {
var pickerFrame = self.vPickerWrapper.frame
pickerFrame.origin.y = self.view.frame.size.height + 1
self.vPickerWrapper.frame = pickerFrame
self.bIsShowingPicker = false
self.view.layoutIfNeeded()
self.view.updateConstraintsIfNeeded()
})
....
the first method is called when the user touches a text field that requires them to populate from the pickerview. The second method is called when either the close or select button is touched within the wrapper.
The wrapper is created in storyboard and has constraints (trailing, leading bottom) to position it off screen. I initially made the bottom constraint a IBOutlet and wanted to change its constant to handle the animation. (Which I do with other objects in this VC). I then tried to work with CGAffineTransform.translate and .identity and finally dropped down to working with the frame. In all three cases the wrapper will display but not close (move back off screen).
Here's the value of vPickerWrapper after I set its frame to pickerFrame:
pickerFrame CGRect (origin = (x = 0, y = 668), size = (width = 375, height = 300))
which is what I am expecting, just not any animation in the sim. The view never moves. Any idea why the display is not showing it in the new coordinates?
I have a UIView inside a UIViewm and I want the inner UIView to be always centered inside the outer one, without it having to resize the width and height.
I've set the struts and springs so that it's on top/left/right/bottom without setting the resize. But it still doesn't center. Any idea?
You can do this and it will always work:
child.center = [parent convertPoint:parent.center fromView:parent.superview];
And for Swift:
child.center = parent.convert(parent.center, from:parent.superview)
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)
Before we'll begin, let's just remind that origin point is the Upper Left corner CGPoint of a view.
An important thing to understand about views and parents.
Lets take a look at this simple code, a view controller that adds to it's view a black square:
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
createDummyView()
super.view.backgroundColor = UIColor.cyanColor();
}
func createDummyView(){
var subView = UIView(frame: CGRect(x: 15, y: 50, width: 50 , height: 50));
super.view.addSubview(subView);
view.backgroundColor = UIColor.blackColor()
}
}
This will create this view:
the black rectangle origin and center does fit the same coordinates as it's parent
Now let's try to add subView another SubSubView, and giving subSubview same origin as subView, but make subSubView a child view of subView
We'll add this code:
var subSubView = UIView();
subSubView.frame.origin = subView.frame.origin;
subSubView.frame.size = CGSizeMake(20, 20);
subSubView.backgroundColor = UIColor.purpleColor()
subView.addSubview(subSubView)
And this is the result:
Because of this line:
subSubView.frame.origin = subView.frame.origin;
You expect for the purple rectangle's origin to be same as it's parent (the black rectangle) but it goes under it, and why is that?
Because when you add a view to another view, the subView frame "world" is now it's parent BOUND RECTANGLE, if you have a view that it's origin on the main screen is at coords (15,15) for all it's sub views, the upper left corner will be (0,0)
This is why you need to always refer to a parent by it's bound rectangle, which is the "world" of it's subViews, lets fix this line to:
subSubView.frame.origin = subView.bounds.origin;
And see the magic, the subSubview is now located exactly in it's parent origin:
So, you like "ok I only wanted to center my view by my parents view, what's the big deal?"
well, it isn't big deal, you just need to "translate" the parent Center point which is taken from it's frame to parent's bounds center
by doing this:
subSubView.center = subView.convertPoint(subView.center, fromView: subSubView);
You're actually telling him "take parents view center, and convert it into subSubView world".
And you'll get this result:
I would use:
self.childView.center = CGPointMake(CGRectGetMidX(self.parentView.bounds),
CGRectGetMidY(self.parentView.bounds));
I like to use the CGRect options...
SWIFT 3:
self.childView.center = CGPoint(x: self.parentView.bounds.midX,
y: self.parentView.bounds.midY);
1. If you have autolayout enabled:
Hint: For centering a view on another view with autolayout you can use same code for any two views sharing at least one parent view.
First of all disable child views autoresizing
UIView *view1, *view2;
[childview setTranslatesAutoresizingMaskIntoConstraints:NO];
If you are UIView+Autolayout or Purelayout:
[view1 autoAlignAxis:ALAxisHorizontal toSameAxisOfView:view2];
[view1 autoAlignAxis:ALAxisVertical toSameAxisOfView:view2];
If you are using only UIKit level autolayout methods:
[view1 addConstraints:({
#[ [NSLayoutConstraint
constraintWithItem:view1
attribute:NSLayoutAttributeCenterX
relatedBy:NSLayoutRelationEqual
toItem:view2
attribute:NSLayoutAttributeCenterX
multiplier:1.f constant:0.f],
[NSLayoutConstraint
constraintWithItem:view1
attribute:NSLayoutAttributeCenterY
relatedBy:NSLayoutRelationEqual
toItem:view2
attribute:NSLayoutAttributeCenterY
multiplier:1.f constant:0.f] ];
})];
2. Without autolayout:
I prefer:
UIView *parentView, *childView;
[childView setFrame:({
CGRect frame = childView.frame;
frame.origin.x = (parentView.frame.size.width - frame.size.width) / 2.0;
frame.origin.y = (parentView.frame.size.height - frame.size.height) / 2.0;
CGRectIntegral(frame);
})];
The easiest way:
child.center = parent.center
You can use
yourView.center = CGPointMake(CGRectGetMidX(superview.bounds), CGRectGetMidY(superview.bounds))
And In Swift 3.0
yourView.center = CGPoint(x: superview.bounds.midX, y: superview.bounds.midY)
Set this autoresizing mask to your inner view.
With IOS9 you can use the layout anchor API.
The code would look like this:
childview.centerXAnchor.constraintEqualToAnchor(parentView.centerXAnchor).active = true
childview.centerYAnchor.constraintEqualToAnchor(parentView.centerYAnchor).active = true
The advantage of this over CGPointMake or CGRect is that with those methods you are setting the center of the view to a constant but with this technique you are setting a relationship between the two views that will hold forever, no matter how the parentview changes.
Just be sure before you do this to do:
self.view.addSubview(parentView)
self.view.addSubView(chidview)
and to set the translatesAutoresizingMaskIntoConstraints for each view to false.
This will prevent crashing and AutoLayout from interfering.
Using the same center in the view and subview is the simplest way of doing it. You can do something like this,
UIView *innerView = ....;
innerView.view.center = self.view.center;
[self.view addSubView:innerView];
Another solution with PureLayout using autoCenterInSuperview.
// ...
UIView *innerView = [UIView newAutoLayoutView];
innerView.backgroundColor = [UIColor greenColor];
[innerView autoSetDimensionsToSize:CGSizeMake(100, 30)];
[outerview addSubview:innerView];
[innerView autoCenterInSuperview];
This is it how it looks like:
In c# or Xamarin.ios, we can use like this
imageView.Center = new CGPoint(tempView.Frame.Size.Width / 2,
tempView.Frame.Size.Height / 2);
This worked for me
childView.centerXAnchor.constraint(equalTo: parentView.centerXAnchor).isActive = true
childView.centerYAnchor.constraint(equalTo: parentView.centerYAnchor).isActive = true
I would use:
child.center = CGPointMake(parent.bounds.height / 2, parent.bounds.width / 2)
This is simple, short, and sweet. If you use #Hejazi's answer above and parent.center is set to anything other than (0,0) your subview will not be centered!
func callAlertView() {
UIView.animate(withDuration: 0, animations: {
let H = self.view.frame.height * 0.4
let W = self.view.frame.width * 0.9
let X = self.view.bounds.midX - (W/2)
let Y = self.view.bounds.midY - (H/2)
self.alertView.frame = CGRect(x:X, y: Y, width: W, height: H)
self.alertView.layer.borderWidth = 1
self.alertView.layer.borderColor = UIColor.red.cgColor
self.alertView.layer.cornerRadius = 16
self.alertView.layer.masksToBounds = true
self.view.addSubview(self.alertView)
})
}// calculation works adjust H and W according to your requirement
I have UITextView where user types a text. When the keyboard is shown, I add inputView with UIlabel on it. I want this UIlabel to hold character length of the text. It seems very easy task, but unfortunatelly it does not update this word counter UILabel when user change text..
this is how I load the inputView
_textView.inputView = [self inputAccessoryView];
in inputAccessoryView I simply add UILabel as a subview. When keyboard is show, UILabel is also show with inputView. I track changes on
- (void)textViewDidChange:(UITextView *)textView
unfortunatelly the UILabel is never updated (redrawn). When I log in to console its value, the value is correct, so its updating, but the UIlabel is never redrawn and holds the default value.
Can anyone help me with this?
did you
_textView.delegate = self;
?
I know it was 5 years ago, but it might help others, who like me stumble upon your question.
I use a UIToolbar as my inputAccessoryView (in my case it has a label, a flexible separator and a button).
On textFieldEditingChanged event I rebuild part of the toolbar like this
#IBAction func textFieldEditingChanged(_ sender: UITextField) {
//get a reference to the toolbar
let toolBar = sender.inputAccessoryView as! UIToolbar
//create a new label and set size + other properties
toolbarLabel = UILabel(frame: CGRect(x: 0, y: 0, width: 40, height: 22))
toolbarLabel.text = mySpecificCalculatedString(sender.text!)
toolbarLabel.font = defaultFont(17)
toolbarLabel.adjustsFontSizeToFitWidth = true
let width = toolbarLabel.textRect(forBounds: CGRect(x: 0, y: 0, width: maxWidthForLabel, height: 0), limitedToNumberOfLines: 1).size.width
toolbarLabel.frame = CGRect(x: 0, y: 0, width: width, height: 22)
toolbarLabel.textColor = .black
toolbarLabel.tag = 666
//rebuild the specific tolbar item
let customView = UIBarButtonItem(customView: toolbarLabel)
toolBar.items![0] = customView
}
Note: simply changing the text of the label did not work for me either, I had to reinitialize it.
Hope it helps.
How do I enable zooming in a UIScrollView?
Answer is here:
A scroll view also handles zooming and panning of content. As the user makes a pinch-in or pinch-out gesture, the scroll view adjusts the offset and the scale of the content. When the gesture ends, the object managing the content view should update subviews of the content as necessary. (Note that the gesture can end and a finger could still be down.) While the gesture is in progress, the scroll view does not send any tracking calls to the subview.
The UIScrollView class can have a delegate that must adopt the UIScrollViewDelegate protocol. For zooming and panning to work, the delegate must implement both viewForZoomingInScrollView: and scrollViewDidEndZooming:withView:atScale:; in addition, the maximum (maximumZoomScale) and minimum (minimumZoomScale) zoom scale must be different.
So:
You need a delegate that implements UIScrollViewDelegate and is set to delegate on your UIScrollView instance
On your delegate you have to implement one method: viewForZoomingInScrollView: (which must return the content view you're interested in zooming). You can also implement scrollViewDidEndZooming:withView:atScale: optionally.
On your UIScrollView instance, you have to set the minimumZoomScale and the maximumZoomScale to be different (they are 1.0 by default).
Note: The interesting thing about this is what if you want to break zooming. Is it enough to return nil in the viewForZooming... method? It does break zooming, but some of the gestures will be messed up (for two fingers). Therefore, to break zooming you should set the min and max zoom scale to 1.0.
Have a read through this Ray Wenderlich tutorial:
http://www.raywenderlich.com/76436/use-uiscrollview-scroll-zoom-content-swift
If you follow through the section 'Scrolling and Zooming a Larger Image' it will get a image up and enable you to pinch and zoom.
In case the link gets altered, here's the main info:
Put this code in your view controller (this sets the main functionality):
override func viewDidLoad() {
super.viewDidLoad()
// 1
let image = UIImage(named: "photo1.png")!
imageView = UIImageView(image: image)
imageView.frame = CGRect(origin: CGPoint(x: 0, y: 0), size:image.size)
scrollView.addSubview(imageView)
// 2
scrollView.contentSize = image.size
// 3
var doubleTapRecognizer = UITapGestureRecognizer(target: self, action: "scrollViewDoubleTapped:")
doubleTapRecognizer.numberOfTapsRequired = 2
doubleTapRecognizer.numberOfTouchesRequired = 1
scrollView.addGestureRecognizer(doubleTapRecognizer)
// 4
let scrollViewFrame = scrollView.frame
let scaleWidth = scrollViewFrame.size.width / scrollView.contentSize.width
let scaleHeight = scrollViewFrame.size.height / scrollView.contentSize.height
let minScale = min(scaleWidth, scaleHeight);
scrollView.minimumZoomScale = minScale;
// 5
scrollView.maximumZoomScale = 1.0
scrollView.zoomScale = minScale;
// 6
centerScrollViewContents()
}
Add this to the class:
func centerScrollViewContents() {
let boundsSize = scrollView.bounds.size
var contentsFrame = imageView.frame
if contentsFrame.size.width < boundsSize.width {
contentsFrame.origin.x = (boundsSize.width - contentsFrame.size.width) / 2.0
} else {
contentsFrame.origin.x = 0.0
}
if contentsFrame.size.height < boundsSize.height {
contentsFrame.origin.y = (boundsSize.height - contentsFrame.size.height) / 2.0
} else {
contentsFrame.origin.y = 0.0
}
imageView.frame = contentsFrame
}
And then this if you want the double tap gesture to be recognised:
func scrollViewDoubleTapped(recognizer: UITapGestureRecognizer) {
// 1
let pointInView = recognizer.locationInView(imageView)
// 2
var newZoomScale = scrollView.zoomScale * 1.5
newZoomScale = min(newZoomScale, scrollView.maximumZoomScale)
// 3
let scrollViewSize = scrollView.bounds.size
let w = scrollViewSize.width / newZoomScale
let h = scrollViewSize.height / newZoomScale
let x = pointInView.x - (w / 2.0)
let y = pointInView.y - (h / 2.0)
let rectToZoomTo = CGRectMake(x, y, w, h);
// 4
scrollView.zoomToRect(rectToZoomTo, animated: true)
}
If you want more detail read the tutorial, but that pretty much covers it.
Make sure you set your viewController as the scrollViews delegate and implement:
func viewForZooming(in scrollView: UIScrollView) -> UIView? {
return imageView
}
I don't think this is working for iOS 5.0 and Xcode 4.3+
Im looking for the same here, I found this its for images but it may help you.
http://www.youtube.com/watch?v=Ptm4St6ySEI