UIGestureRecognizer on UIImageView

Question

I have a UIImageView  which I want to be able to resize and rotate etc   Can a UIGestureRecognizer be added to the UIImageView   I would want to add a rotate and pinch recognizer to a UIImageView which would be created at runtime   How does one add these recognizers

User · Answer

I just done this with swift4 by adding 3 gestures together in single view

UIPinchGestureRecognizer : Zoom in and zoom out view.
UIRotationGestureRecognizer : Rotate the view.
UIPanGestureRecognizer : Dragging the view.

Here my sample code

class ViewController: UIViewController: UIGestureRecognizerDelegate{
      //your image view that outlet from storyboard or xibs file.
     @IBOutlet weak var imgView: UIImageView!
     // declare gesture recognizer
     var panRecognizer: UIPanGestureRecognizer?
     var pinchRecognizer: UIPinchGestureRecognizer?
     var rotateRecognizer: UIRotationGestureRecognizer?

     override func viewDidLoad() {
          super.viewDidLoad()
          // Create gesture with target self(viewcontroller) and handler function.  
          self.panRecognizer = UIPanGestureRecognizer(target: self, action: #selector(self.handlePan(recognizer:)))
          self.pinchRecognizer = UIPinchGestureRecognizer(target: self, action: #selector(self.handlePinch(recognizer:)))
          self.rotateRecognizer = UIRotationGestureRecognizer(target: self, action: #selector(self.handleRotate(recognizer:)))
          //delegate gesture with UIGestureRecognizerDelegate
          pinchRecognizer?.delegate = self
          rotateRecognizer?.delegate = self
          panRecognizer?.delegate = self
          // than add gesture to imgView
          self.imgView.addGestureRecognizer(panRecognizer!)
          self.imgView.addGestureRecognizer(pinchRecognizer!)
          self.imgView.addGestureRecognizer(rotateRecognizer!)
     }

     // handle UIPanGestureRecognizer 
     @objc func handlePan(recognizer: UIPanGestureRecognizer) {    
          let gview = recognizer.view
          if recognizer.state == .began || recognizer.state == .changed {
               let translation = recognizer.translation(in: gview?.superview)
               gview?.center = CGPoint(x: (gview?.center.x)! + translation.x, y: (gview?.center.y)! + translation.y)
               recognizer.setTranslation(CGPoint.zero, in: gview?.superview)
          }
     }

     // handle UIPinchGestureRecognizer 
     @objc func handlePinch(recognizer: UIPinchGestureRecognizer) {
          if recognizer.state == .began || recognizer.state == .changed {
               recognizer.view?.transform = (recognizer.view?.transform.scaledBy(x: recognizer.scale, y: recognizer.scale))!
               recognizer.scale = 1.0
         }
     }   

     // handle UIRotationGestureRecognizer 
     @objc func handleRotate(recognizer: UIRotationGestureRecognizer) {
          if recognizer.state == .began || recognizer.state == .changed {
               recognizer.view?.transform = (recognizer.view?.transform.rotated(by: recognizer.rotation))!
               recognizer.rotation = 0.0
           }
     }

     // mark sure you override this function to make gestures work together 
     func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
         return true
     }

}

Any question, just type to comment. thank you

User · Answer

Yes  a UIGestureRecognizer can be added to a UIImageView  As stated in the other answer  it is very important to remember to enable user interaction on the image view by setting its userInteractionEnabled property to YES  UIImageView inherits from UIView  whose user interaction property is set to YES by default  however  UIImageView s user interaction property is set to NO by default   From the UIImageView docs      New image view objects are configured to disregard user events by   default  If you want to handle events in a custom subclass of   UIImageView  you must explicitly change the value of the   userInteractionEnabled property to YES after initializing the object    Anyway  on the the bulk of the answer  Here s an example of how to create a UIImageView with a UIPinchGestureRecognizer  a UIRotationGestureRecognizer  and a UIPanGestureRecognizer   First  in viewDidLoad  or another method of your choice  create an image view  give it an image  a frame  and enable its user interaction  Then create the three gestures as follows  Be sure to utilize their delegate property  most likely set to self   This will be required to use multiple gestures at the same time   -  void viewDidLoad        super viewDidLoad           set up the image view     UIImageView  imageView     UIImageView alloc  initWithImage  UIImage imageNamed   someImage          imageView setBounds CGRectMake 0 0  0 0  120 0  120 0         imageView setCenter self view center        imageView setUserInteractionEnabled YES       lt --- This is very important         create and configure the pinch gesture     UIPinchGestureRecognizer  pinchGestureRecognizer     UIPinchGestureRecognizer alloc  initWithTarget self action  selector pinchGestureDetected          pinchGestureRecognizer setDelegate self        imageView addGestureRecognizer pinchGestureRecognizer           create and configure the rotation gesture     UIRotationGestureRecognizer  rotationGestureRecognizer     UIRotationGestureRecognizer alloc  initWithTarget self action  selector rotationGestureDetected          rotationGestureRecognizer setDelegate self        imageView addGestureRecognizer rotationGestureRecognizer           creat and configure the pan gesture     UIPanGestureRecognizer  panGestureRecognizer     UIPanGestureRecognizer alloc  initWithTarget self action  selector panGestureDetected          panGestureRecognizer setDelegate self        imageView addGestureRecognizer panGestureRecognizer          self view addSubview imageView      add the image view as a subview of the view controllers view     Here are the three methods that will be called when the gestures on your view are detected  Inside them  we will check the current state of the gesture  and if it is in either the began or changed UIGestureRecognizerState we will read the gesture s scale rotation translation property  apply that data to an affine transform  apply the affine transform to the image view  and then reset the gestures scale rotation translation       -  void pinchGestureDetected  UIPinchGestureRecognizer   recognizer       UIGestureRecognizerState state    recognizer state        if  state    UIGestureRecognizerStateBegan    state    UIGestureRecognizerStateChanged                CGFloat scale    recognizer scale            recognizer view setTransform CGAffineTransformScale recognizer view transform  scale  scale             recognizer setScale 1 0            -  void rotationGestureDetected  UIRotationGestureRecognizer   recognizer       UIGestureRecognizerState state    recognizer state        if  state    UIGestureRecognizerStateBegan    state    UIGestureRecognizerStateChanged                CGFloat rotation    recognizer rotation            recognizer view setTransform CGAffineTransformRotate recognizer view transform  rotation             recognizer setRotation 0            -  void panGestureDetected  UIPanGestureRecognizer   recognizer       UIGestureRecognizerState state    recognizer state        if  state    UIGestureRecognizerStateBegan    state    UIGestureRecognizerStateChanged                CGPoint translation    recognizer translationInView recognizer view            recognizer view setTransform CGAffineTransformTranslate recognizer view transform  translation x  translation y             recognizer setTranslation CGPointZero inView recognizer view             Finally and very importantly  you ll need to utilize the UIGestureRecognizerDelegate method gestureRecognizer  shouldRecognizeSimultaneouslyWithGestureRecognizer to allow the gestures to work at the same time  If these three gestures are the only three gestures that have this class assigned as their delegate  then you can simply return YES as shown below  However  if you have additional gestures that have this class assigned as their delegate  you may need to add logic to this method to determine which gesture is which before allowing them to all work together   -  BOOL gestureRecognizer  UIGestureRecognizer   gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer  UIGestureRecognizer   otherGestureRecognizer       return YES      Don t forget to make sure that your class conforms to the UIGestureRecognizerDelegate protocol  To do so  make sure that your interface looks something like this    interface MyClass   MySuperClass  lt UIGestureRecognizerDelegate gt    If you prefer to play with the code in a working sample project yourself  the sample project I ve created containing this code can be found here

User · Answer

SWIFT 3 Example  override func viewDidLoad          self backgroundImageView addGestureRecognizer          UITapGestureRecognizer init target  self  action  selector didTapImageview                  self backgroundImageView isUserInteractionEnabled   true    func didTapImageview   sender  Any           do something     No gesture recongnizer delegates or other implementations where necessary

User · Answer

Swift 2 0 Solution  You create a tap  pinch or swipe gesture recognizer in the same manor  Below I ll walk you through 4 steps to getting your recognizer up and running   4 Steps  1   Inherit from UIGestureRecognizerDelegate by adding it to your class signature   class ViewController  UIViewController  UIGestureRecognizerDelegate         2   Control drag from your image to your viewController to create an IBOutlet    IBOutlet weak var tapView  UIImageView    3   In your viewDidLoad add the following code      create an instance of UITapGestureRecognizer and tell it to run     an action we ll call  handleTap   let tap   UITapGestureRecognizer target  self  action  Selector  handleTap        we use our delegate tap delegate   self    allow for user interaction tapView userInteractionEnabled   true    add tap as a gestureRecognizer to tapView tapView addGestureRecognizer tap    4   Create the function that will be called when your gesture recognizer is tapped   You can exclude the   nil if you choose    func handleTap sender  UITapGestureRecognizer    nil           just creating an alert to prove our tap worked      let tapAlert   UIAlertController title   hmmm      message   this actually worked    preferredStyle  UIAlertControllerStyle Alert      tapAlert addAction UIAlertAction title   OK   style   Destructive  handler  nil       self presentViewController tapAlert  animated  true  completion  nil        Your final code should look something like this   class ViewController  UIViewController  UIGestureRecognizerDelegate         IBOutlet weak var tapView  UIImageView       override func viewDidLoad             super viewDidLoad            let tap   UITapGestureRecognizer target  self  action  Selector  handleTap             tap delegate   self         tapView userInteractionEnabled   true         tapView addGestureRecognizer tap             func handleTap sender  UITapGestureRecognizer    nil            let tapAlert   UIAlertController title   hmmm      message   this actually worked    preferredStyle  UIAlertControllerStyle Alert          tapAlert addAction UIAlertAction title   OK   style   Destructive  handler  nil           self presentViewController tapAlert  animated  true  completion  nil

User · Answer

For Blocks lover you can use ALActionBlocks to add action of gestures in block    weak ALViewController  wSelf   self  imageView userInteractionEnabled   YES  UITapGestureRecognizer  gr     UITapGestureRecognizer alloc  initWithBlock   UITapGestureRecognizer  weakGR        NSLog   pan      NSStringFromCGPoint  weakGR locationInView wSelf view          self imageView addGestureRecognizer gr

User · Answer

You can also drag a tap gesture recogniser to the image view in Storyboard  Then create an action by ctrl   drag to the code

User · Answer

Check that userInteractionEnabled is YES on the UIImageView   Then you can add a gesture recognizer   imageView userInteractionEnabled   YES  UIPinchGestureRecognizer  pgr     UIPinchGestureRecognizer alloc       initWithTarget self action  selector handlePinch     pgr delegate   self   imageView addGestureRecognizer pgr    pgr release       -  void handlePinch  UIPinchGestureRecognizer   pinchGestureRecognizer       handle pinch

User · Answer

Swift 4 2  myImageView isUserInteractionEnabled   true let tapGestureRecognizer   UITapGestureRecognizer target  self  action   selector imageTapped   tapGestureRecognizer numberOfTapsRequired   1 myImageView addGestureRecognizer tapGestureRecognizer    and when tapped    objc func imageTapped   sender  UITapGestureRecognizer          do something when image tapped    print  image tapped

[ios] UIGestureRecognizer on UIImageView

Examples related to ios

Examples related to objective-c

Examples related to uiimageview

Examples related to uigesturerecognizer