最近iphone需求要做到一些动画，想让一个图片围绕frame外的一个中心点进行旋转，但无论用center还是用anchorPoint，都要不到我想要的效果，只能采用此“小手段”来实现。如果有人有更好的实现方式，欢迎留言、评论、拍砖！

@begin

    UIView *bgVw = [[UIView alloc] initWithFrame:CGRectMake(0, 30, 300, 300)];
    bgVw.backgroundColor = [UIColor clearColor];
    
    UIView *centerVw = [[UIView alloc] initWithFrame:CGRectMake(100, 130, 100, 100)];
    centerVw.backgroundColor = [UIColor blueColor];
    [self.view addSubview:centerVw];
    
    UIView *vw = [[UIView alloc] initWithFrame:CGRectMake(0, 125, 50, 50)];
    vw.backgroundColor = [UIColor brownColor];
    
    UIView *vw2 = [[UIView alloc] initWithFrame:CGRectMake(250, 125, 50, 50)];
    vw2.backgroundColor = [UIColor redColor];
    
    UIView *vw3 = [[UIView alloc] initWithFrame:CGRectMake(125, 0, 50, 50)];
    vw3.backgroundColor = [UIColor orangeColor];
    
    UIView *vw4 = [[UIView alloc] initWithFrame:CGRectMake(125, 250, 50, 50)];
    vw4.backgroundColor = [UIColor greenColor];
    
    [bgVw addSubview:vw];
    [bgVw addSubview:vw2];
    [bgVw addSubview:vw3];
    [bgVw addSubview:vw4];
    [self.view addSubview:bgVw];
    
    
    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationDuration:1.0f];
    [UIView setAnimationRepeatAutoreverses:YES];
    [UIView setAnimationRepeatCount:10];
    bgVw.layer.anchorPoint = CGPointMake(0.5, 0.5);
    bgVw.transform = CGAffineTransformMakeRotation([self radians:-180]);
    
    [UIView commitAnimations];

@end

  昨天看了sina微博,看到cell右下角的图片,就想到思路应该是clip+rotate,今天随手测试,确实如此,果断上code:

UIView *containView=[[UIView alloc] initWithFrame:CGRectMake(50, 50, 200, 80)];

containView.backgroundColor=[UIColor redColor];

containView.layer.cornerRadius=10;

containView.clipsToBounds=YES;

[window addSubview:containView];

UIButton *btn=[UIButton buttonWithType:UIButtonTypeCustom];

btn.frame=CGRectMake((200-80), (80-40), 100, 60);

[btn setBackgroundImage:[UIImage imageNamed:@"touxiang.jpg"] forState:UIControlStateNormal];

[btn addTarget:self action:@selector(buttonPressed) forControlEvents:UIControlEventTouchUpInside];

btn.layer.transform=CATransform3DMakeRotation(30.0*M_PI/180.0, 0, 0, 1);

[containView addSubview:btn];

还是很简单的,就两个地方:

1.containView.clipsToBounds=YES;当subviews的size超出superview的范围时,就把超出的那部分剪切掉;另外,在NO的情况下,超出的那部分是不能响应touchUpInside,不知为何...

2.btn.layer.transform=CATransform3DMakeRotation(30.0*M_PI/180.0, 0, 0, 1);这个简单地在Z上变换一下而已,细节参考文档

效果如下:

对于java的参数传递到底是值传递还是引用传递，一直是一个很疑惑的概念，到现在为止还是不怎么清楚，不过对于StringBuffer 和String类的参数传递也是一知半解。现在就做一个简单的例子测试

public class testBuffer {
	public static void main(String[] args) {
		StringBuffer a = new StringBuffer("A");   
        StringBuffer b = new StringBuffer("B");   
        operate(a,b);   
        String s1="A";
        String s2="B";
        operate(s1,s2);
        System.out.println(a + " " + b);//1  
        
        System.out.println(s1 + " " + s2);//1  
	}

	 private static void operate(StringBuffer a, StringBuffer b) {   
	        a.append(b);   
	        b = a;//2   
	    } 
	 
	 private static void operate(String a, String b) {   
	        a=a+b;   
	        b = a;//2   
	    } 
	 
}

运行结果为：

AB B
A B

也就是说当参数为StringBuffer时，当两个参数为A B时，得到的结果为AB B

党参数为String，两个参数为A B时，得到的结果为A B。

我也不知道这个到底是什么原因，只能死记