使用 UIPanGestureRecognizer 的可拖动视图中的动作元素导致视图移动

Question

我想创建一个包含许多动作元素的可拖动视图。为此，我通过 Apple 文档复制了用于从 here.

创建可拖动视图的代码

视图按预期平移，但当单击操作元素时，视图会移动到其他位置。下面是示例代码和 Main.storyboard 的屏幕截图以重现该问题。

ViewController.h 文件

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController

- (IBAction)segmentedAction:(id)sender;
@property (weak, nonatomic) IBOutlet UISegmentedControl *segmentOutlet;
@property (weak, nonatomic) IBOutlet UILabel *label;

@end

这是 ViewController.m 文件中的代码

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}
- (void)adjustAnchorPointForGestureRecognizer:(UIGestureRecognizer *)gestureRecognizer
{
    if (gestureRecognizer.state == UIGestureRecognizerStateBegan) {
        UIView *piece = gestureRecognizer.view;
        CGPoint locationInView = [gestureRecognizer locationInView:piece];
        CGPoint locationInSuperview = [gestureRecognizer locationInView:piece.superview];
        
        piece.layer.anchorPoint = CGPointMake(locationInView.x / piece.bounds.size.width, locationInView.y / piece.bounds.size.height);
        piece.center = locationInSuperview;
    }
}
- (IBAction)panPiece:(UIPanGestureRecognizer *)gestureRecognizer
{
    UIView *piece = [gestureRecognizer view];
    
    [self adjustAnchorPointForGestureRecognizer:gestureRecognizer];
    
    if ([gestureRecognizer state] == UIGestureRecognizerStateBegan || [gestureRecognizer state] == UIGestureRecognizerStateChanged) {
        CGPoint translation = [gestureRecognizer translationInView:self.view];
        
        [piece setCenter:CGPointMake([piece center].x + translation.x, [piece center].y + translation.y)];
        [gestureRecognizer setTranslation:CGPointZero inView:self.view];
    }
}
- (IBAction)segmentedAction:(id)sender {
    self.label.text = [NSString stringWithFormat:@"%ld",self.segmentOutlet.selectedSegmentIndex];
}
@end

任何人都可以指导我这里做错了什么。

提前致谢

Answer 1

好的，终于解决问题了。这是由于自动布局而发生的。当您尝试设置标签的文本时，自动布局会强制视图框架重置为初始值。由于您更改了锚点，它似乎会移动到某个随机位置。

要解决此问题，只需在 viewDidLoad 方法中使用以下行即可；

self.label.translatesAutoresizingMaskIntoConstraints = YES;

或在 adjustAnchorPointForGestureRecognizer:(UIGestureRecognizer *)gestureRecognizer 方法中的 UIView *piece = gestureRecognizer.view; 下面添加以下行：-

piece.translatesAutoresizingMaskIntoConstraints = YES;

干杯！:-)

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