调整UIPickerView高度

Advantages:

1. Makes setFrame of UIPickerView behave like it should
2. No transform code within your UIViewController
3. Works within viewWillLayoutSubviews to rescale/position the UIPickerView
4. Works on the iPad without UIPopover
5. The superclass always receives a valid height
6. Works with iOS 5

Disadvantages:

1. Requires you to subclass UIPickerView
2. Requires the use of pickerView viewForRow to undo the transformation for the subViews
3. UIAnimations might not work

Solution:

Subclass UIPickerView and overwrite the two methods using the following code. It combines subclassing, fixed height and the transformation approach.

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#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;

}