UITouch

• 触摸事件基本都是发生在 viewController 中，首先触摸的对象是视图，而视图的类 UIView 继承了 UIRespnder 类，但是要对事件作出处理，还需要重写 UIResponder 类中定义的事件处理函数。根据不同的触摸状态，程序会调用相应的处理函数。

1、touch 的创建

// 获取任意一个触摸对象
UITouch *touch = [touches anyObject];
// 获取任意一个触摸对象
UITouch *touch = [[event allTouches] anyObject];
// 获取指定的 view 触摸对象
UITouch *touch = [[event touchesForView:myView] anyObject];
// 获取指定的 window 触摸对象
UITouch *touch = [[event touchesForWindow:self.view.window] anyObject];

2、touch 的设置

• 在系统触摸事件处理方法中实现

// 设置接收多点触摸
/*
默认为 NO，即视图默认不接收多点触摸
*/
self.view.multipleTouchEnabled = YES;

3、touch 的获取

• 在系统触摸事件处理方法中实现

// 获取触摸窗口
UIWindow *touchWindow = touch.window;
// 获取触摸视图
UIView *touchView = touch.view;
// 获取触摸手势
NSArray *touchGesture = touch.gestureRecognizers;
// 获取触摸次数
NSUInteger tapCount = touch.tapCount;
// 获取触摸时间
NSTimeInterval timestamp = touch.timestamp;
// 获取触摸状态
/*
UITouchPhaseBegan,         // whenever a finger touches the surface.     触摸开始
UITouchPhaseMoved,         // whenever a finger moves on the surface.    接触点移动
UITouchPhaseStationary,    // whenever a finger is touching the surface but hasn't moved
// since the previous event.                  接触点无移动
UITouchPhaseEnded,         // whenever a finger leaves the surface.      触摸结束
UITouchPhaseCancelled,     // whenever a touch doesn't end but we need to stop tracking
// (e.g. putting device to face)              触摸取消
*/
UITouchPhase touchPhase = touch.phase;
// 获取触摸位置
// 上次触摸点的位置
CGPoint lastPoint = [touch previousLocationInView:self.view];
// 当前触摸点的位置
CGPoint currentPoint = [touch locationInView:self.view];
// 获取触摸半径
CGFloat majorRadius = touch.majorRadius;
CGFloat majorRadiusTolerance = touch.majorRadiusTolerance;

4、系统触摸事件处理方法

• 不用手动调用

// 触摸开始，重写 UIResponder 中定义的方法
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
}
// 触摸移动，重写 UIResponder 中定义的方法
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
}
// 触摸结束，重写 UIResponder 中定义的方法
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
}
// 触摸取消，重写 UIResponder 中定义的方法
- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event {
}

5、视图随触摸移动

// 触摸移动
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
	// 获取触摸对象
	UITouch *touch = [touches anyObject];
	UIView *tapView = touch.view;
	// 获取触摸点位置
	CGPoint lastPoint = [touch previousLocationInView:self.view];
	CGPoint currentPoint = [touch locationInView:self.view];
	// 改变视图中心坐标
	CGPoint tapViewCenter = tapView.center;
	tapViewCenter.x += currentPoint.x - lastPoint.x;
	tapViewCenter.y += currentPoint.y - lastPoint.y;
	tapView.center = tapViewCenter;
}

6、单击／双击触摸

// 触摸结束
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
	UITouch *touch = [touches anyObject];
	// 单击
	if (touch.tapCount == 1) {
		// 响应单击触摸事件
		[self performSelector:@selector(singleTapClick) withObject:nil afterDelay:0];
	}
	// 双击
	else if (touch.tapCount == 2) {
		// 取消单击触摸响应事件
		[NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(singleTapClick) object:nil];
		// 响应双击触摸事件
		[self performSelector:@selector(doubleTapClick) withObject:nil afterDelay:0];
	}
}
// 单击触摸响应事件处理
- (void)singleTapClick {
	self.view.backgroundColor = [UIColor greenColor];
}
// 双击触摸响应事件处理
- (void)doubleTapClick {
	self.view.backgroundColor = [UIColor orangeColor];
}