爲什麼我的平移手勢只會推動它的視線並停止？

Question

這裏是UIPanGesture子類：

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { 
    NSLog(@"touches began"); 
    self ->origLoc = [[touches anyObject] locationInView:self.view.superview]; 
    [super touchesBegan:touches withEvent:event]; 
} 


- (void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { 
if (self.state == UIGestureRecognizerStatePossible) { 
    CGPoint loc = [[touches anyObject] locationInView:self.view.superview]; 
    CGFloat deltaX = fabsf(loc.x - origLoc.x); 
    CGFloat deltaY = fabsf(loc.y - origLoc.y); 
    if (deltaY >= deltaX) { 
     self.state = UIGestureRecognizerStateFailed; 
    } else { 
    [super touchesMoved:touches withEvent:event]; 
    } 
} 
} 

- (CGPoint) translationInView:(UIView *)v { 

CGPoint proposedTranslation = [super translationInView:v]; 
proposedTranslation.y = 0; 
return proposedTranslation; 

} 

這裏是被我的子類UIPanGesture調用的方法：

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

UIView *vv = p.view; 

if (p.state == UIGestureRecognizerStateBegan || p.state == UIGestureRecognizerStateChanged) { 
    CGPoint delta = [p translationInView:vv.superview]; 
    CGPoint c = vv.center; 
    c.x += delta.x; 
    c.y += delta.y; 
    vv.center = c; 
    [p setTranslation:CGPointZero inView:vv.superview]; 
}  
} 

當我試圖拖動我看來，它只是移動一個非常小的量然後停下來。我需要不斷推動它才能讓它移動。有任何想法嗎？

在此先感謝，

Michael。

Answer 1

在我之前的評論，我不清楚爲什麼被繼承，但是你澄清，這是因爲你有多個手勢處理程序正在進行。很好。

所以這裏是一個自定義的平移手勢一些示例代碼，Horizo​​ntalPanGestureRecognizer，這也是引發只有當第一個運動是水平：

// HorizontalPanGestureRecognizer.h 

#import <UIKit/UIKit.h> 

@interface HorizontalPanGestureRecognizer : UIPanGestureRecognizer 
@end 

而且

// HorizontalPanGestureRecognizer.m 

#import "HorizontalPanGestureRecognizer.h" 
#import <UIKit/UIGestureRecognizerSubclass.h> 

@interface HorizontalPanGestureRecognizer() 
{ 
    BOOL _hasConfirmedDirection; 
    BOOL _wasHorizontal; 
    CGPoint _origLoc; 
} 
@end 

@implementation HorizontalPanGestureRecognizer 

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event 
{ 
    [super touchesBegan:touches withEvent:event]; 

    UITouch *touch = [touches anyObject]; 

    _hasConfirmedDirection = NO; 

    _origLoc = [touch locationInView:self.view]; 
} 

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event 
{ 
    [super touchesMoved:touches withEvent:event]; 
    if (self.state == UIGestureRecognizerStateFailed) return; 

    if (!_hasConfirmedDirection) 
    { 
     CGPoint translation = [self translationInView:self.view]; 

     _hasConfirmedDirection = YES; 
     _wasHorizontal = (fabs(translation.x) > fabs(translation.y)); 
    } 
    if (!_wasHorizontal) 
     self.state = UIGestureRecognizerStateFailed; 
} 

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event 
{ 
    [super touchesEnded:touches withEvent:event]; 

    if (!_wasHorizontal) 
     self.state = UIGestureRecognizerStateFailed; 
} 

- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event 
{ 
    [super touchesCancelled:touches withEvent:event]; 

    if (!_wasHorizontal) 
     self.state = UIGestureRecognizerStateFailed; 
} 

- (CGPoint)locationInView:(UIView *)view 
{ 
    CGPoint superLocation = [super locationInView:view]; 

    if (_hasConfirmedDirection) 
     superLocation.y = _origLoc.y; 

    return superLocation; 
} 

- (CGPoint)translationInView:(UIView *)view 
{ 
    CGPoint superTranslation = [super translationInView:view]; 

    if (_hasConfirmedDirection) 
     superTranslation.y = 0.0f; 

    return superTranslation; 
} 

@end 

然後你可以有你處理程序在你的主視圖控制器中使用它（在這個例子中，只是拖動一個UILabel）。在viewDidLoad中，創建手勢：

HorizontalPanGestureRecognizer *recognizer = [[HorizontalPanGestureRecognizer alloc] initWithTarget:self action:@selector(handleCustomPan:)]; 
[self.view addGestureRecognizer:recognizer]; 

然後處理程序看起來像：

- (void)handleCustomPan:(UIPanGestureRecognizer *)sender 
{  
    switch (sender.state) { 
     case UIGestureRecognizerStateChanged: 
      if (!_panLabel) 
      { 
       // In my case I'm creating a UILabel to drag around, whereas you might just drag 
       // whatever countrol you want to drag. 
       // 
       // But, regardless, I'm keeping track of the original center in _panLabelOrigCenter 

       [self makePanLabel:sender]; 
      } 

      CGPoint translate = [sender translationInView:self.view]; 
      _panLabel.center = CGPointMake(_panLabelOrigCenter.x + translate.x, _panLabelOrigCenter.y + translate.y); 

      break; 

     case UIGestureRecognizerStateEnded: 
      [self removePanLabel]; 
      break; 

     default: 
      break; 
    } 
} 

（很顯然，這是ARC代碼如果非ARC，添加必要的附加線。用於例行內存管理的代碼）。

Answer 2

接觸移動的失敗情況看起來像對早期運動會非常敏感。

考慮將它不太敏感...

- (BOOL)movementIsHorizontalX:(CGFloat)x andY:(CGFloat) y { 

    CGFloat absX = fabs(x); 
    CGFloat absY = fabs(y); 

    // if x is small, then accept small y values but not large ones 
    if (absX < 4) return absY < 4; 

    // now we can express horizontal-ness as a slope. we've ruled out small x, so this is a stable calculation 
    CGFloat slope = absY/absX; 
    return slope < 0.10; 

    // you could generalize by passing in the x threshold and percentage slope constants 
} 

Answer 3

我意識到自己的錯誤。我移動了

[super touchesMoved: touches withEvent:event]; 

以外的if語句，現在它似乎工作正常。不是100％確定它爲什麼現在可行，但我很高興。

我們弄清楚如何防止UIScrollView的自受理平移手勢，直到這一次取消/失敗...