在 UIView 动画时重新启动 UIPanGestureRecognizer

Posted 2023-03-16

【中文标题】在 UIView 动画时重新启动 UIPanGestureRecognizer

【英文标题】：Restarting UIPanGestureRecognizer while UIView is animating

【发布时间】：2013-07-22 16:43:22

【问题描述】：

我试图让用户在完成 UIPanGestureRecognizer 方法时获取正在动画的 UIView。我目前能够使用 touchesBegan 和视图的表示层来停止视图并将其居中放置在手指下方。但我希望用户能够重新触发 UIPanGestureRecognizer 方法，而无需抬起手指并在 UIView 上替换它。

我已经为这个挑战工作了一周左右，并且在 SO 和其他地方浏览了各种搜索字符串，阅读了 Ray Wenderlich 的教程等，但仍然没有找到解决方案。看起来我正在尝试做与这个似乎未解决的问题类似的事情：

ios - UIPanGestureRecognizer : drag during animation

我刚刚开始使用 UIView 动画块，还没有深入研究 CABasicAnimation 的工作。是否可以通过某种方式更改下面的代码来做我想做的事？

提前谢谢你。

在 FlingViewController.h 中：

#import <UIKit/UIKit.h>

@interface FlingViewController : UIViewController <UIGestureRecognizerDelegate>

    UIView *myView;


@property (nonatomic, weak) UIView *myView;



@end

在 FlingViewController.m 中：

#import "FlingViewController.h"
#import <QuartzCore/QuartzCore.h>

@interface FlingViewController ()

@end

@implementation FlingViewController

@synthesize myView = _myView;

- (void)viewDidLoad

    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    // Allocate and init view
    myView = [[UIView alloc] initWithFrame:CGRectMake(self.view.center.x - 50,
                                                      self.view.center.y - 50,
                                                      100, 100)];

    // Set view background color
    [myView setBackgroundColor:[UIColor purpleColor]];

    // Create pan gesture recognizer
    UIPanGestureRecognizer *gesture = [[UIPanGestureRecognizer alloc]
                                       initWithTarget:self action:@selector(handleGesture:)];

    // Add gesture recognizer to view
    gesture.delegate = self;
    [myView addGestureRecognizer:gesture];

    // Add myView as subview
    [self.view addSubview:myView];
    NSLog(@"myView added");




- (void)handleGesture:(UIPanGestureRecognizer *)recognizer

    if ((recognizer.state == UIGestureRecognizerStateBegan) ||
        (recognizer.state == UIGestureRecognizerStateChanged))
    
        [recognizer.view.layer removeAllAnimations];

        CGPoint translation = [recognizer translationInView:self.view];
        recognizer.view.center = CGPointMake(recognizer.view.center.x + translation.x,
                                             recognizer.view.center.y + translation.y);
        [recognizer setTranslation:CGPointMake(0, 0) inView:self.view];

    
    else if (recognizer.state == UIGestureRecognizerStateEnded)
    
        CGPoint velocity = [recognizer velocityInView:self.view];
        CGFloat magnitude = sqrtf((velocity.x * velocity.x) + (velocity.y * velocity.y));
        CGFloat slideMult = magnitude / 200;

        float slideFactor = 0.1 * slideMult;
        CGPoint finalPoint = CGPointMake(recognizer.view.center.x + (velocity.x * slideFactor),
                                         recognizer.view.center.y + (velocity.y * slideFactor));
        finalPoint.x = MIN(MAX(finalPoint.x, 0), self.view.bounds.size.width);
        finalPoint.y = MIN(MAX(finalPoint.y, 0), self.view.bounds.size.height);

        [UIView animateWithDuration:slideFactor * 2
                              delay:0
                            options:(UIViewAnimationOptionCurveEaseOut|
                                     UIViewAnimationOptionAllowUserInteraction |
                                     UIViewAnimationOptionBeginFromCurrentState)
                         animations:^
                             recognizer.view.center = finalPoint;
                         
                         completion:^(BOOL finished)
                             NSLog(@"Animation complete");
                         ];
    



// Currently, this method will detect when user touches
// myView's presentationLayer and will center that view under the finger
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event

    UITouch *touch = [touches anyObject];
    CGPoint touchPoint = [touch locationInView:self.view];

    if ([[myView.layer presentationLayer] hitTest:touchPoint])
    
        NSLog(@"Touched!");

        [myView.layer removeAllAnimations];

        myView.center = touchPoint;

        // *** NOTE ***
        // At this point, I want the user to be able to fling
        // the view around again without having to lift the finger
        // and replace  it on the view;  i.e. when myView is moving
        // and the user taps it, it should stop moving and follow
        // user's pan gesture again
        // Similar to unresolved SO question:
        // https://***.com/questions/13234234/ios-uipangesturerecognizer-drag-during-animation

    



- (void)didReceiveMemoryWarning

    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.


@end

【参考方案1】：

如果它对其他人有帮助，根据 Thomas Rued/Jack 对这个 SO 问题的回答，我找到了一个似乎效果很好的解决方案：

CAAnimation - User Input Disabled

我正在使用两个 UIPanGestureRecognizer 来移动 UIView - 一个 (gesture/handleGesture:) 连接到 UIView (myView)，另一个 (bigGesture/superGesture:) 连接到该 UIView 的超级视图 (bigView)。超级视图在动画时检测子视图的表示层的位置。

唯一的问题（到目前为止）是用户仍然可以通过在动画完成之前触摸 myView 动画的结束位置来抓取动画视图。理想情况下，只有表示层位置才是用户可以与视图交互的地方。如果有人对防止过早交互有深入了解，我们将不胜感激。

#import "FlingViewController.h"
#import <QuartzCore/QuartzCore.h>

@interface FlingViewController ()

@end

@implementation FlingViewController

@synthesize myView = _myView;
@synthesize bigView = _bigView;

- (void)viewDidLoad

    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    // *** USING A GESTURE RECOGNIZER ATTACHED TO THE SUPERVIEW APPROACH
    // CAME FROM SO USER THOMAS RUED/JACK AT FOLLOWING LINK:
    // https://***.com/questions/7221688/caanimation-user-input-disabled

    // Set up size for superView (bigView)
    CGRect screenRect = [[UIScreen mainScreen] bounds];

    // Allocate big view
    bigView = [[UIView alloc] initWithFrame:(screenRect)];

    [bigView setBackgroundColor:[UIColor greenColor]];

    [self.view addSubview:bigView];

    // Allocate and init myView
    myView = [[UIView alloc] initWithFrame:CGRectMake(10, 10, 100, 100)];

    // Set view background color
    [myView setBackgroundColor:[UIColor purpleColor]];

    // Create pan gesture recognizer
    UIPanGestureRecognizer *gesture = [[UIPanGestureRecognizer alloc]
                                       initWithTarget:self action:@selector(handleGesture:)];

    UIPanGestureRecognizer *bigGesture = [[UIPanGestureRecognizer alloc]
                                            initWithTarget:self action:@selector(superGesture:)];

    // Add gesture recognizer to view
    gesture.delegate = self;
    bigGesture.delegate = self;
    [myView addGestureRecognizer:gesture];
    [bigView addGestureRecognizer:bigGesture];

    // Add myView as subview of bigView
    [bigView addSubview:myView];
    NSLog(@"myView added");



// This gesture recognizer is attached to the superView,
// and will detect myView's presentation layer while animated
- (void)superGesture:(UIPanGestureRecognizer *)recognizer
    
    CGPoint location = [recognizer locationInView:self.view];

    for (UIView* childView in recognizer.view.subviews)
    
        CGRect frame = [[childView.layer presentationLayer] frame];

        if (CGRectContainsPoint(frame, location))
        // ALTERNATE 'IF' STATEMENT; BOTH SEEM TO WORK:
        //if ([[childView.layer presentationLayer] hitTest:location])
        
            NSLog(@"location = %.2f, %.2f", location.x, location.y);
            [childView.layer removeAllAnimations];
            childView.center = location;
        

        if ((recognizer.state == UIGestureRecognizerStateEnded) &&
            (CGRectContainsPoint(frame, location)))
        
            CGPoint velocity = [recognizer velocityInView:self.view];
            CGFloat magnitude = sqrtf((velocity.x * velocity.x) + (velocity.y * velocity.y));
            CGFloat slideMult = magnitude / 200;

            float slideFactor = 0.1 * slideMult;
            CGPoint finalPoint = CGPointMake(childView.center.x + (velocity.x * slideFactor),
                                             childView.center.y + (velocity.y * slideFactor));
            finalPoint.x = MIN(MAX(finalPoint.x, 0), self.view.bounds.size.width);
            finalPoint.y = MIN(MAX(finalPoint.y, 0), self.view.bounds.size.height);

            [UIView animateWithDuration:slideFactor * 2
                                  delay:0
                                options:(UIViewAnimationOptionCurveEaseOut|
                                         UIViewAnimationOptionAllowUserInteraction |
                                         UIViewAnimationOptionBeginFromCurrentState)
                             animations:^
                                 childView.center = finalPoint;
                             
                             completion:^(BOOL finished)
                                 NSLog(@"Big animation complete");
                             ];
        
    


// This gesture recognizer is attached to myView,
// and will handle movement when myView is not animating
- (void)handleGesture:(UIPanGestureRecognizer *)recognizer


    if ((recognizer.state == UIGestureRecognizerStateBegan) ||
        (recognizer.state == UIGestureRecognizerStateChanged))
    
        [recognizer.view.layer removeAllAnimations];

        CGPoint translation = [recognizer translationInView:self.view];
        recognizer.view.center = CGPointMake(recognizer.view.center.x + translation.x,
                                             recognizer.view.center.y + translation.y);
        [recognizer setTranslation:CGPointMake(0, 0) inView:self.view];

    
    else if (recognizer.state == UIGestureRecognizerStateEnded)
    
        CGPoint velocity = [recognizer velocityInView:self.view];
        CGFloat magnitude = sqrtf((velocity.x * velocity.x) + (velocity.y * velocity.y));
        CGFloat slideMult = magnitude / 200;

        float slideFactor = 0.1 * slideMult;
        CGPoint finalPoint = CGPointMake(recognizer.view.center.x + (velocity.x * slideFactor),
                                         recognizer.view.center.y + (velocity.y * slideFactor));
        finalPoint.x = MIN(MAX(finalPoint.x, 0), self.view.bounds.size.width);
        finalPoint.y = MIN(MAX(finalPoint.y, 0), self.view.bounds.size.height);

        [UIView animateWithDuration:slideFactor * 2
                              delay:0
                            options:(UIViewAnimationOptionCurveEaseOut|
                                     UIViewAnimationOptionAllowUserInteraction |
                                     UIViewAnimationOptionBeginFromCurrentState)
                         animations:^
                             recognizer.view.center = finalPoint;
                         
                         completion:^(BOOL finished)
                             NSLog(@"Animation complete");
                         ];
    



- (void)didReceiveMemoryWarning

    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.


@end