iOS开发笔记之多点触控（四） 可靠的多点触控，为每个View分配唯一触摸对象

#import <UIKit/UIKit.h>

@interface BBSViewController : UIViewController
{
    UITouch *touch1;
    UITouch *touch2;
}

@end

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event //首次在屏幕上检测到触摸时调用
{
    NSLog(@"touchesBegan");
    for (UITouch *touch in touches)
    {
//        NSLog(@" - %p",touch);
        //获取根视图内触摸点的point
        CGPoint touchPoint = [touch locationInView:self.view];
        //约束两个view的活动范围
        if (touch1 == nil && touchPoint.y < self.view.frame.size.height/2)
        {
            touch1 = touch;
            _view1.center = CGPointMake(touchPoint.x, _view1.center.y);
        }else if (touch2 == nil && touchPoint.y > self.view.frame.size.height/2)
        {
            touch2 = touch;
            _view2.center = CGPointMake(touchPoint.x, _view2.center.y);
        }
    }
}

//以上对触摸进行了初始化，并未处理沿着屏幕移动的触摸。所以，只需要在touchesMoved方法里调用touchesBegan的处理方法来改写移动球拍的逻辑即可。
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event //如果触摸移动到了新的位置则会调用此方法
{
    NSLog(@"touchesMoved");
    for (UITouch *touch in touches)
    {
//        NSLog(@" - %p",touch);
//        [self touchesBegan:touches withEvent:event];
        CGPoint touchPoint = [touch locationInView:self.view];
        
        if (touch == touch1)
        {
            _view1.center = CGPointMake(touchPoint.x, _view1.center.y);
        }
        else if (touch == touch2)
        {
            _view2.center = CGPointMake(touchPoint.x, _view2.center.y);
        }
    }
}

-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event//当触摸离开屏幕调用此方法
{
    NSLog(@"touchesEnded");
    for (UITouch *touchin touches)
    {
        NSLog(@" - %p",touch);
        if (touch == touch1)touch1 = nil;
        else if (touch ==touch2) touch2 = nil;
    }

}

-(void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event//如系统决定取消此次触摸，那可能就不调用touchesEnded方法了，在这种情况下会调用touchesCancelled方法
{
    NSLog(@"touchesCancelled");
//    for (UITouch *touch in touches)
//    {
//        NSLog(@" - %p",touch);
//    }
    [self touchesEnded:toucheswithEvent:event];
}