iOS触摸事件UITouch应用详解

/*
  定义属性
 */
@interface ViewController ()
{
  CGPoint _startPoint; //开始点击的点
  CGPoint _endPoint; //结束点击的点
  
  UILabel *_label1; //显示当前触摸的状态的标签
  UILabel *_label2;
  UILabel *_label3;
  UILabel *_label4;
  UIImageView *_imageView; //笑脸图片
}

/*
  触摸事件UITouch的系列方法如下所示 <一>到<四>
 */

#pragma mark <一> 当一个或多个手指触碰屏幕时，发送touchesBegan:withEvent:消息
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
  _label1.text = @"触摸 开始 ";
  
  //1. 首先获取触摸屏幕的手指
  UITouch * touch = [touches anyObject];
  
  //2. 点击的当前点的坐标
  CGPoint point = [touch locationInView:self.view];
  _label2.text = [NSString stringWithFormat:@"当前点得坐标:x=%.1f, y=%.1f",point.x,point.y];
  
  //4. 获取触摸屏幕的次数
  int tapCount = touch.tapCount;
  //5. 获取触摸屏幕的手指根数
  int fingerCount = touches.count;
  
  _label3.text = [NSString stringWithFormat:@"触摸屏幕次数为%i, 触摸的手指数为%i",tapCount,fingerCount];
  
  //6. 当前视图默认只支持单点触摸 如果想添加多点触摸 必须开启多点触摸模式
  self.view.multipleTouchEnabled = YES;
  
  //7.1. 得到开始点击的点,得到最后点击的点，计算一下，看看做了什么操作
  _startPoint = [touch locationInView:self.view];
  _label4.text = @"";
}

#pragma mark <二> 当一个或多个手指在屏幕上移动时，发送touchesMoved:withEvent:消息
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
  _label1.text = @"触摸 move...";
  CGPoint point = [[touches anyObject] locationInView:self.view];
  _label2.text = [NSString stringWithFormat:@"当前点得坐标:x=%.1f, y=%.1f",point.x,point.y];
}

#pragma mark <三> 当一个或多个手指离开屏幕时，发送touchesEnded:withEvent:消息
-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
  _label1.text = @"触摸 结束";
  CGPoint point = [[touches anyObject] locationInView:self.view];
  
  //3. 判断是否进入了图片范围内
  if (CGRectContainsPoint(_imageView.frame, point)) {
    _label2.text = @"停留在笑脸图片范围内";
  }
  else
  {
    _label2.text = @"停留在笑脸图片外面";
  }
  
  //7.2 计算开始到结束偏移量
  float distanceX = fabsf(point.x - _startPoint.x);
  //获取手指纵向移动的偏移量
  float distanceY = fabsf(point.y - _startPoint.y);
  
  _label4.text = [NSString stringWithFormat:@"x偏移了%.1f，y方向偏移了%.1f",distanceX,distanceY];
  
  _startPoint = CGPointZero;
}

#pragma mark <四> 当触摸序列被诸如电话呼入这样的系统事件打断所意外取消时，发送touchesCancelled:withEvent:消息-(void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
{
  _label1.text = @"触摸 取消";
}