这里只three valid heights为UIPickerView (162.0, 180.0 and 216.0)。
您可以使用CGAffineTransformMakeTranslation和CGAffineTransformMakeScale函数来适当地调整选择器以方便您使用。
例子:
CGAffineTransform t0 = CGAffineTransformMakeTranslation (0, pickerview.bounds.size.height/2);
CGAffineTransform s0 = CGAffineTransformMakeScale (1.0, 0.5);
CGAffineTransform t1 = CGAffineTransformMakeTranslation (0, -pickerview.bounds.size.height/2);
pickerview.transform = CGAffineTransformConcat (t0, CGAffineTransformConcat(s0, t1));
change上面的代码height和它picker view to half的re-position确切(Left-x1, Top-y1)位置。
在这里参考更多。