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:touches withEvent:event];
}