修改UIPickView的高度

发现了一个问题，UIPickerView不能改变小于216的高度，利用setframe方法无法修改UIPickerView的高度。

解决方法：

   1、加上pickerView.autoresizingMask = UIViewAutoresizingFlexibleHeight|UIViewAutoresizingFlexibleWidth; 后，能变成超过216的高度，但是依旧不能减小

   2.可以通过创建UIPickerView子类，覆盖- (void) setFrame:(CGRect)frame方法和- (UIView *)pickerView:(UIPickerView *)pickerView viewForRow:(NSInteger)row forComponent:(NSInteger)component reusingView:(UIView *)view方法，通过CGAffineTransformTranslate仿射变换解决。

  代码如下：

        

#define FIXED_PICKER_HEIGHT 216.0f - ( void ) setFrame:(CGRect)frame { CGFloat targetHeight = frame.size.height; CGFloat scaleFactor = targetHeight / FIXED_PICKER_HEIGHT; frame.size.height = FIXED_PICKER_HEIGHT; //fake normal conditions for super self .transform = CGAffineTransformIdentity; //fake normal conditions for super [ super setFrame:frame]; frame.size.height = targetHeight; CGFloat dX= self .bounds.size.width/2, dY= self .bounds.size.height/2; self .transform = CGAffineTransformTranslate(CGAffineTransformScale(CGAffineTransformMakeTranslation(-dX, -dY), 1, scaleFactor), dX, dY); }

- (UIView *)pickerView:(UIPickerView *)pickerView viewForRow:( NSInteger )row forComponent:( NSInteger )component reusingView:(UIView *)view
{
    //Your code goes here

    CGFloat inverseScaleFactor = FIXED_PICKER_HEIGHT/ self .frame.size.height;
    CGAffineTransform scale = CGAffineTransformMakeScale(1, inverseScaleFactor);
    view.transform = scale;
    return   view;
}