OC, oc Language

OC, oc Language
Effect

• Procedure

  • Draw a rectangle and a alertView is displayed, prompting whether to save the image
  • Click "yes" to save the image to the album.
  • View saved images in the album

Implementation

• Add an imageView to the Controller view to set the image
• Add a pan gesture to the view of the controller.
• Track the pan gesture and draw a rectangular box (Cut area of the image)

• At the end of the pan gesture, alertView prompts "do you want to save the image to the album ?"

  • Click "yes" to save the image.
  • Click "no" and do nothing for now

Steps

• Add an imageView (Set ImagesIn the. m file of the controller.

  @property (weak, nonatomic) IBOutlet UIImageView *imageView;

• Set the cut area of the image drawn by gesture

  • Use the cut area of the image as the member attribute clipView

  @property (nonatomic, weak) UIView *clipView;

  • Create a clipView through lazy loading and initialize it

  -(UIView *) clipView {// if clipView is created, create if (_ clipView = nil) {UIView * view = [[UIView alloc] init]; _ clipView = view; // sets the background color and transparency view of clipView. backgroundColor = [UIColor blackColor]; view. alpha = 0.5; // Add the clipView to the Controller's view. At this time, the clipView is not displayed (its frame is not set) [self. view addSubview: _ clipView];} return _ clipView ;}

• Add a pan gesture to the view of the controller, track the pan gesture, and draw an image cut area.

  • Create and add a gesture

  /** Create gesture **/UIPanGestureRecognizer * pan = [[UIPanGestureRecognizer alloc] initWithTarget: self action: @ selector (pan :)]; /*** when the position of the pan gesture changes, the pan: method is called and the gesture is passed as a parameter * // ** add gesture **/[self. view addGestureRecognizer: pan];

  • Add member attributes to record the starting point of the pan gesture

  @property (nonatomic, assign) CGPoint startPoint;

  • Listen for gesture Movement

  -(Void) pan :( UIPanGestureRecognizer *) pan {CGPoint endPoint = CGPointZero; if (pan. state = UIGestureRecognizerStateBegan) {/** start point of the gesture when you start to click **/self. startPoint = [pan locationInView: self. view];} else if (pan. state = UIGestureRecognizerStateChanged) {/** when the gesture moves, the end point value is dynamically changed and the rectangular area between the start point and the end point is calculated. **/endPoint = [pan locationInView: self. view]; // calculate the width and height of the rectangle area CGFloat w = endPoint. x-self. startPoint. x; CGFloat h = endPoin T. y-self. startPoint. y; // calculate the frame CGRect clipRect = CGRectMake (self. startPoint. x, self. startPoint. y, w, h); // sets the frame self in the cut area. clipView. frame = clipRect;} else if (pan. state = UIGestureRecognizerStateEnded) {/** if the gesture is stopped, the image content in the cut area is drawn to the graphic context ** // enable the bitmap context uigraphicsbeginimagecontextwitexceptions (self. imageView. bounds. size, NO, 0); // create a closed path named UIBezierPath * path = [UIBezierPath bezierPathWithRe Ct: self. clipView. frame]; // set the content that exceeds the limit to not be displayed. [path addClip]; // obtain the drawing context CGContextRef context = UIGraphicsGetCurrentContext (); // set the image rendering context to [self. imageView. layer renderInContext: context]; // obtain the image UIImage * image = UIGraphicsGetImageFromCurrentImageContext (); // disable the bitmap context UIGraphicsEndImageContext (); // remove the cut area view control, and clear [self. clipView removeFromSuperview]; self. clipView = nil; // display the image to imageView self. imageVie W. image = image; // use alertView to indicate whether to save the image to the album UIAlertView * alertView = [[UIAlertView alloc] initWithTitle: @ "Save image" message: @ "do you want to save the image to the album? "Delegate: self cancelButtonTitle: @" no "otherButtonTitles: @" yes ", nil]; [alertView show];}

• Sets the proxy method of alertView to determine whether to save the image.

  -(Void) alertView :( nonnull UIAlertView *) alertView clickedButtonAtIndex :( NSInteger) buttonIndex {// if "yes" is clicked, the image if (buttonIndex = 1) is saved) {UIImageWriteToSavedPhotosAlbum (self. imageView. image, nil);/*** this method can be used to set the method for calling after saving. No setting is made here */}}