更改UIPickerView選中框顏色

        [pickerView.subviews objectAtIndex:1].layer.borderWidth = 0.5f;

        [pickerView.subviews objectAtIndex:2].layer.borderWidth = 0.5f;

        [pickerView.subviews objectAtIndex:1].layer.borderColor = [UIColor redColor].CGColor;

        [pickerView.subviews objectAtIndex:2].layer.borderColor = [UIColor redColor].CGColor;