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

每个View需要分配有效的触摸以避免第三方触摸的干扰。实现方法如下

.h文件，接口定义两个变量

#import <UIKit/UIKit.h>@interface BBSViewController : UIViewController{    UITouch *touch1;    UITouch *touch2;}@end

.m文件，在touchesBegan里为view分配一个特定触摸对象（仅当它还未分配时）。

-(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);        }    }}

在touchesMoved方法里，忽略所有未绑定View的触摸

//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);        }    }}

及时释放已绑定了View的触摸，避免手指一离开屏幕就永久失去对View的控制。

-(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];}

这样多余的触摸将不会影响现有的View的位置。

转载请注明原著：http://blog.csdn.net/marvindev

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