触摸事件UITouch的应用

/*
    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";
}