iOS Development Tutorial: Gesture Recognition Method

I feel it is necessary to make a brief summary of gesture recognition in iOS development. In the previous blog post on iOS development of custom emoji keyboard (component encapsulation and automatic layout), a tap gesture was used, which is to return from the emoji keyboard to the system keyboard when tapping the TextView. The hand in the TextView was added using storyboard. The following will first show how to add gestures to the corresponding controls using storyboard, and then add gestures to our controls in a pure code way. The usage of gestures is relatively simple. Similar to the usage of buttons, it is also a target action callback. Without further ado, let's get to the point of today. There are a total of six gesture recognitions: tap gesture (TapGestureRecognizer), swipe gesture (SwipeGestureRecognizer), long press gesture (LongPressGestureRecognizer), drag gesture (PanGestureRecognizer), pinch gesture (PinchGestureRecognizer), rotation gesture (RotationGestureRecognizer);

In fact, these gestures can be fully realized with touch events. Apple encapsulates common touch events into gestures to provide them to users. Readers can use TouchesMoved to write drag gestures, etc.

First, use storyboard to add gesture recognition to the control. Of course, you need to take a screenshot when using storyboard.

1. Use storyboard to add gesture recognition. The steps are the same as adding a Button. First, we have to find the corresponding gesture and drag the gesture recognition control to the control where we want to add the gesture. The screenshot is as follows

2. Adding a callback event to the gesture we dragged out is no different from adding a callback event to the Button. Just add the business logic to be implemented in the callback method. The screenshot is as follows:

2. Add gesture recognition with pure code

Using storyboard can greatly simplify our operation, but we still need to know how to use pure code, just like editing a web page with Dreamwear (of course, the drag and drop function of storyboard is much more powerful than that of Dreamwear). Using pure code is more flexible and easier to maintain. However, using storyboard can reduce our workload. The two must be used together to greatly improve our development efficiency. Personally, I feel that it is better to use pure code to build the framework (the relationship between controllers) and small things with storyboard. The following shows how to add gesture recognition to our controls using pure code.

1. Adding TapGestureRecognizer

The code for initializing TapGestureRecongnizer is as follows:

 1       //Create a new tap gesture  
 2 UITapGestureRecognizer *tapGesture = [[UITapGestureRecognizer alloc] initWithTarget:self action: @selector (tapGesture:)];
 3       //Set the number of clicks and click finger index  
 4 tapGesture.numberOfTapsRequired = 1 ; //Number of clicks  
 5 tapGesture.numberOfTouchesRequired = 1 ; //Number of click fingers  
 6 [self.view addGestureRecognizer:tapGesture];

Add the corresponding business logic in the callback method:

 1   //Tap gesture trigger method  
 2 -( void )tapGesture:(id)sender
 3 {
 4       //What to do after tapping  
 5 }

2. Long Press Gesture (LongPressGestureRecognizer)

Initialization code:

 //Add long press gesture  
 2 UILongPressGestureRecognizer *longPressGesture = [[UILongPressGestureRecognizer alloc] initWithTarget:self action: @selector (longPressGesture:)];
 3       //Set the long press time  
 4 longPressGesture.minimumPressDuration = 0.5 ; //(2 seconds)  
 5 [self.view addGestureRecognizer:longPressGesture];

Add the corresponding method in the corresponding callback method (executed when the gesture starts):

 1   //Long press gesture trigger method  
 2 -( void )longPressGesture:(id)sender
 3 {
 4 UILongPressGestureRecognizer *longPress = sender;
 5       if (longPress.state == UIGestureRecognizerStateBegan)
 6 {
 7 UIAlertView *alter = [[UIAlertView alloc] initWithTitle:@ "Prompt" message:@ "Long press to trigger" delegate:nil cancelButtonTitle:@ "Cancel" otherButtonTitles: nil];
 8 [alter show];
 9 }
 0 }

Code description: The common states of gestures are as follows

Start: UIGestureRecognizerStateBegan

Changed: UIGestureRecognizerStateChanged

End: UIGestureRecognizerStateEnded

Cancellation: UIGestureRecognizerStateCancelled

Failure: UIGestureRecognizerStateFailed

3. Swipe Gesture (SwipeGestureRecognizer)

When initializing the swipe gesture, you need to specify the swipe direction, up, down, left, and right. If you want to add multiple swipe directions, you have to add multiple swipe gestures, but the callback method is the same.

Add swipe gestures, one to the left and one to the right. The code is as follows:

 1       //Add swipe gesture  
 2 UISwipeGestureRecognizer *swipeGesture = [[UISwipeGestureRecognizer alloc] initWithTarget:self action: @selector (swipeGesture:)];
 3       //Set the swipe direction  
 4 swipeGesture.direction = UISwipeGestureRecognizerDirectionRight; //Default is right  
 5 [self.view addGestureRecognizer:swipeGesture];
 6       
 7       //Add swipe gesture  
 8 UISwipeGestureRecognizer *swipeGestureLeft = [[UISwipeGestureRecognizer alloc] initWithTarget:self action: @selector (swipeGesture:)];
 9       //Set the swipe direction  
 10 swipeGestureLeft.direction = UISwipeGestureRecognizerDirectionLeft; //Default is right  
 11 [self.view addGestureRecognizer:swipeGestureLeft];

The callback method is as follows:

 1   //Swipe gesture trigger method  
 2 -( void )swipeGesture:(id)sender
 3 {
 4 UISwipeGestureRecognizer *swipe = sender;
 5       if (swipe.direction == UISwipeGestureRecognizerDirectionLeft)
 6 {
 7           //Swipe left to do something  
 8 }
 9       if (swipe.direction == UISwipeGestureRecognizerDirectionRight)
 10 {
 11           //Swipe right to do something  
 12 }
 13 }
 14       

4. Pinch Gesture Recognizer

Pinch gesture initialization

    //Add pinch gesture  
 2 UIPinchGestureRecognizer *pinchGesture = [[UIPinchGestureRecognizer alloc] initWithTarget:self action: @selector (pinchGesture:)];
 3 [self.view addGestureRecognizer:pinchGesture];

Method to trigger pinch gesture (zoom in or out):

   1   ////Pinch gesture trigger method  
 2 -( void ) pinchGesture:(id)sender
 3 {
 4 UIPinchGestureRecognizer *gesture = sender;
 5       
 6       //When the gesture changes  
 7       if (gesture.state == UIGestureRecognizerStateChanged)
 8 {
 9           //The scaling ratio recorded by the scale attribute in the pinch gesture  
 10 _imageView.transform = CGAffineTransformMakeScale(gesture.scale, gesture.scale);
 11 }
 12       
 13       //Resume after finishing  
 14       if (gesture.state==UIGestureRecognizerStateEnded)
 15 {
 16 [UIView animateWithDuration: 0.5 animations:^{
 17 _imageView.transform = CGAffineTransformIdentity; //Cancel all deformations  
 18 }];
 19 }
 20 }

5. Drag gesture (PanGestureRecognizer)

Initialization of drag gesture

 //Add drag gesture  
 2 UIPanGestureRecognizer *panGesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action: @selector (panGesture:)];
 3 [self.view addGestureRecognizer:panGesture];

The method to be used for drag gestures (getting the moving point through translationInView, similar to the TouchesMoved method)

 1   //Drag gesture  
 2 -( void )panGesture:(id)sender
 3 {
 4 UIPanGestureRecognizer *panGesture = sender;
 5       
 6 CGPoint movePoint = [panGesture translationInView:self.view];
 7       
 8       //Do what you want to do  
 9 }

6. Rotation Gesture (RotationGestureRecognizer)

Initialization of the rotation gesture

   //Add rotation gesture  
 2 UIRotationGestureRecognizer *rotationGesture = [[UIRotationGestureRecognizer alloc] initWithTarget:self action: @selector (rotationGesture:)];
 3 [self.view addGestureRecognizer:rotationGesture];

The method called by the rotation gesture:

 Copy code 
 
 1   //Rotation gesture  
 2 -( void )rotationGesture:(id)sender
 3 {
 4       
 5 UIRotationGestureRecognizer *gesture = sender;
 6       
 7       if (gesture.state==UIGestureRecognizerStateChanged)
 8 {
 9 _imageView.transform=CGAffineTransformMakeRotation(gesture.rotation);
 10 }
 11       
 12       if (gesture.state==UIGestureRecognizerStateEnded)
 13 {
 14           
 15 [UIView animateWithDuration: 1 animations:^{
 16 _imageView.transform=CGAffineTransformIdentity; //Cancel deformation  
 17 }];
 18 }
 19       
 20 }

Link to this article: http://www.cnblogs.com/ludashi/p/3983008.html