如何在Xcode中跟蹤多個觸摸

Question

最近我做了一個可以同時拖動多個對象的應用程序。我曾嘗試使用UIPanGestureRecognizer來獲取手指觸摸的座標，但我無法知道哪個觸摸屬於哪個手指。

我需要支持四個手指同時平移而不會相互干擾使用Objective-C。

我已經搜索了一段時間的營養，但他們顯示的答案並不適合我。任何幫助，將不勝感激。

Answer 1

我在相同的問題上奮鬥了很長時間，終於解決了它。以下是我的DrawView.m中的代碼，它是UIView的一個子類，它能夠使用drawRect:支持圖形。

#import "DrawView.h" 

#define MAX_TOUCHES 4 

@interface DrawView() { 

    bool touchInRect[MAX_TOUCHES]; 
    CGRect rects[MAX_TOUCHES]; 
    UITouch *savedTouches[MAX_TOUCHES]; 
} 

@end 

@implementation DrawView 

-(id)initWithCoder:(NSCoder *)aDecoder { 
    self = [super initWithCoder:aDecoder]; 
    if (self) { 
     // Initialization code 
     self.multipleTouchEnabled = YES; 
     for (int i=0; i<MAX_TOUCHES; i++) { 
      rects[i] = CGRectMake(200, 200, 50 ,50); 
      savedTouches[i] = NULL; 
      touchInRect[i] = false; 
     } 
    } 
    return self; 
} 

- (void)drawRect:(CGRect)rect { 
    // Drawing code 
    [[UIColor blueColor] set]; 
    CGContextRef context = UIGraphicsGetCurrentContext(); 

    for (int i=0; i<MAX_TOUCHES; i++) { 
     CGContextFillRect(context, rects[i]); 
     CGContextStrokePath(context); 
    } 
} 

#pragma mark - Handle Touches 

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { 

    NSArray *allTouches = [touches allObjects]; 
    for (int i=0; i<[allTouches count]; i++) { 
     UITouch *touch = allTouches[i]; 
     CGPoint newPoint = [touch locationInView:self]; 

     for (int j=0; j<MAX_TOUCHES; j++) { 
      if (CGRectContainsPoint(rects[j], newPoint) && !touchInRect[j]) { 
       touchInRect[j] = true; 
       savedTouches[j] = touch; 
       break; 
      } 
     } 
    } 
} 

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { 

    NSArray *allTouches = [touches allObjects]; 
    for (int i=0; i<[allTouches count]; i++) { 
     UITouch *touch = allTouches[i]; 
     CGPoint newPoint = [touch locationInView:self]; 

     for (int j=0; j<MAX_TOUCHES; j++) { 
      if (touch == savedTouches[j]) { 
       rects[j] = [self rectWithSize:rects[j].size andCenter:newPoint]; 
       [self setNeedsDisplay]; 
       break; 
      } 
     } 
    } 
} 

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event { 

    NSArray *allTouches = [touches allObjects]; 
    for (int i=0; i<[allTouches count]; i++) { 
     UITouch *touch = allTouches[i]; 

     for (int j=0; j<MAX_TOUCHES; j++) { 
      if (touch == savedTouches[j]) { 
       touchInRect[j] = false; 
       savedTouches[j] = NULL; 
       break; 
      } 
     } 
    } 
} 


- (CGRect)rectWithSize:(CGSize)size andCenter:(CGPoint)point { 
    return CGRectMake(point.x - size.width/2, point.y - size.height/2, size.width, size.height); 
} 

@end 

我將MAX_TOUCHES設置爲4，因此屏幕上會出現四個對象。其基本概念是當調用touchesBegan::時，將每個UITouch ID存儲在savedTouches數組中，並稍後在調用touchesMoved::時將每個ID與屏幕上的觸摸進行比較。

只需將代碼粘貼到您的.m文件中即可使用。抽樣結果如下所示：

希望這有助於:)