给视图添加阴影

UIImageView *imageview = [[UIImageView alloc] initWithFrame:CGRectMake(1, 1, 66.0f, 76.0f)];

imageview.tag=1;
[imageview setImage:img];
imageview.layer.shadowColor=[UIColor blackColor].CGColor;
imageview.userInteractionEnabled=YES;
imageview.layer.shadowOpacity=0.5;
imageview.layer.shadowOffset = CGSizeMake(5,3);

imageview.layer.shadowColor = [UIColor blueColor].CGColor;

此代码再3.1.3下运行失败。