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

{

获取刚开始触摸屏幕时的两个点

NSArray * allTouches = [touches allObjects];

UITouch * firstTouch = [allTouches firstObject];

UITouch * secondTouch = [allTouches lastObject];

_firstPreviousLocation = [firstTouch locationInView:self];

_secondPreviousLocation = [secondTouch locationInView:self];

}

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

{

只有一个手指触摸屏幕,则不处理捏合操作.

if (1 == [touches count]) {

return;

}

获得两个手指移动之后的位置.

NSArray  * allTouches = [touches allObjects];

UITouch * firstTouch = [allTouches firstObject];

UITouch * secoundTouch = [allTouches lastObject];

获取两个手指之前的位置

CGPoint _firstPreviousLocation = [firstTouch previousLocationInView:self];

CGPoint _secondPreviousLocation = [secoundTouch previousLocationInView:self];

获取两个手指当前的位置

CGPoint firstCurrentLocation = [firstTouch locationInView:self];

CGPoint sencondCurrentLocation = [secoundTouch locationInView:self];

获取之前两个点距离

CGFloat previousDistance = [self distanceOfPoint1:_firstPreviousLocation point2:_secondPreviousLocation];

获取当前两个点距离

CGFloat currentDistance = [self distanceOfPoint1:firstCurrentLocation point2:sencondCurrentLocation];

求变化的比例  处理previousDistance 可能为0 的情况 . 为0 就初一1

CGFloat scale = currentDistance / previousDistance ? previousDistance : 1;

CGFloat scale = currentDistance / previousDistance;

修改视图的大小按比例缩放

self.bounds = CGRectMake(0, 0, self.bounds.size.width * scale , self.bounds.size.height * scale);

存储当前点

_firstPreviousLocation = firstCurrentLocation;

_secondPreviousLocation = sencondCurrentLocation;

}

计算两个点的距离

- (CGFloat)distanceOfPoint1:(CGPoint)point1 point2:(CGPoint)point2

{

CGFloat dx = point1.x-point2.x;

CGFloat dy = point1.y-point2.y;

return sqrt(pow(dx, 2) + pow(dy, 2));

}