ios - 如何在拖动另一个按钮时检测 View 中的 UIButton？

Question

我在 ViewController 中实现了一个可拖动的 UIButton。除了这个可拖动的按钮，我还有两个 UIButton，当我将一个 Button 拖到它们上面并更改静态按钮的标题时，它们应该被检测到。我怎样才能实现这个？

这就是可拖动按钮的实现方式。

@interface ButtonAnimationViewController : UIViewController

@property (weak, nonatomic) IBOutlet UIButton *firstButton; // dragable button
@property (weak, nonatomic) IBOutlet UIButton *oneButton;   //normal button
@property (weak, nonatomic) IBOutlet UIButton *twoButton;   // normal button


@implementation ButtonAnimationViewController

 - (void)viewDidLoad
{
 [super viewDidLoad];
 [self.view addSubview:self.firstButton];
 [self.view addSubview:self.oneButton];
 [self.view addSubview:self.twoButton];

UIPanGestureRecognizer *panGesture 
    = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(dragging:)];
[self.firstButton addGestureRecognizer:panGesture];

UITapGestureRecognizer *tapGesture 
    = [[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(dropping:)];
tapGesture.cancelsTouchesInView = NO;
[self.oneButton addGestureRecognizer:tapGesture];
[self.twoButton addGestureRecognizer:tapGesture];


 -(void)dragging:(UIPanGestureRecognizer*)panGesture {

  if (panGesture.view != self.firstButton)
  {
    return;
  }
   if (panGesture.state == UIGestureRecognizerStateBegan || 
       panGesture.state == UIGestureRecognizerStateChanged)
  {
    CGPoint delta = [panGesture translationInView:self.view];
    CGPoint center = self.firstButton.center;
    center.x += delta.x;
    center.y += delta.y;
    self.firstButton.center = center;
    [panGesture setTranslation:CGPointZero inView:self.view];
  }
    if (panGesture.view == self.oneButton) {
    // I tried this to change the button title.
    NSString *buttonTitle = self.firstButton.titleLabel.text; 
    self.oneButton.titleLabel.text = buttonTitle;
    return;
}
    //if (panGesture.state == UIGestureRecognizerStateEnded) {
   // self.firstButton.center = center;                        
    //[panGesture setTranslation:CGPointZero inView:self.view];
}

Answer 1

诀窍是使用 CGRectIntersectsRect .. 这是了解一个 View 是否与另一个 View 相交的基本构建 block 。看看here有关使用该功能的相关示例。

这里是示例代码:

  if (panGesture.state == UIGestureRecognizerStateBegan || 
       panGesture.state == UIGestureRecognizerStateChanged)
  {
    CGPoint delta = [panGesture translationInView:self.view];
    CGPoint center = self.firstButton.center;
    center.x += delta.x;
    center.y += delta.y;
    self.firstButton.center = center;
    [panGesture setTranslation:CGPointZero inView:self.view];
  }

  // check if there is an overlap
  NSString *draggableButtonTitle = self.firstButton.titleLabel.text;
  if (CGRectIntersectsRect(self.firstButton.frame, self.oneButton.frame)) {
      self.oneButton.titleLabel.text = draggableButtonTitle;
      // i donno if you wanna return here or continue dragging.. up to you
  } else if (CGRectIntersectsRect(self.firstButton.frame, self.twoButton.frame)) {
      self.twoButton.titleLabel.text = draggableButtonTitle;
  }