Iphone 为什么这只检测CCSprites中心的触摸？

我试图让手指拖动CCSprite，代码如下：

-(BOOL)ccTouchBegan:(UITouch *)touch withEvent:(UIEvent *)event {
    CGPoint location = [touch locationInView: [touch view]];
    CGPoint convertedCoordinate = [[CCDirector sharedDirector] convertToGL:location];

    CGRect redCircleRect = CGRectMake(redCircle.position.x, redCircle.position.y, redCircle.contentSize.width, redCircle.contentSize.height);
    CGRect redCircle2Rect = CGRectMake(redCircle2.position.x, redCircle2.position.y, redCircle2.contentSize.width, redCircle2.contentSize.height);

    if(CGRectContainsPoint(redCircleRect, convertedCoordinate)) {
        //redCircle.position = ccp(convertedCoordinate.x, convertedCoordinate.y);
        NSLog(@"Touched");
        spriteIndex = 1;
    }
    else if(CGRectContainsPoint(redCircle2Rect, convertedCoordinate)) {
        //redCircle2.position = ccp(convertedCoordinate.x, convertedCoordinate.y);
        NSLog(@"Touched2");
        spriteIndex = 2;
    }
    else {
        spriteIndex = 0;
    }
    return YES;
}
-(void)ccTouchMoved:(UITouch *)touch withEvent:(UIEvent *)event {
    CGPoint location = [touch locationInView: [touch view]];
    CGPoint convertedCoordinate = [[CCDirector sharedDirector] convertToGL:location];   

    if (spriteIndex == 1) {
        redCircle.position = ccp(convertedCoordinate.x, convertedCoordinate.y);
    }
    else if (spriteIndex == 2) {
        redCircle2.position = ccp(convertedCoordinate.x, convertedCoordinate.y);
    }

    //CGRect RedCircleRect = CGRectMake(redCircle.position.x, redCircle.position.y, redCircle.contentSize.width, redCircle.contentSize.height);
    //CGRect RedCircle2Rect = CGRectMake(redCircle.position.x, redCircle.position.y, redCircle.contentSize.width, redCircle.contentSize.height);

}

我的逻辑如下：

在cctouches中，我首先获得触摸的位置，将其转换为正确的坐标，然后制作两个CGRect，假设它们与我声明的两个精灵的尺寸和位置相同。然后，我使用CGRectContainsPoint检查手指是否接触到这两个矩形中的一个。在这里，我有一个名为spriteIndex的全局int，我根据所接触的圆分配一个值

接下来，在ccTouchesMoved中，我检查spriteIndex是否已被赋予我尝试移动的两个精灵中的一个的索引，如果是，则将所选精灵的位置设置为触摸位置

问题是：

这段代码只在某种程度上起作用。它允许我拖动ccsprite，但前提是单击中心。精灵是40乘40像素的，所以它绝不是小的。

在下面找到了答案：

应该是：

CGRect redCircleRect = CGRectMake(redCircle.position.x-20.0, redCircle.position.y-20.0, 40.0, 40.0);
CGRect redCircle2Rect = CGRectMake(redCircle2.position.x-20.0, redCircle2.position.y-20.0, 40.0, 40.0);

这是因为，CGRect副本是从中心指针创建的，它应该从左下角创建

CGRect redCircleRect = CGRectMake(redCircle.position.x-20.0, redCircle.position.y-20.0, 40.0, 40.0);
CGRect redCircle2Rect = CGRectMake(redCircle2.position.x-20.0, redCircle2.position.y-20.0, 40.0, 40.0);