UIPickerView去掉背景上的黑线

- (UIView *)pickerView:(UIPickerView *)pickerView viewForRow:(NSInteger)row forComponent:(NSInteger)component reusingView:(nullable UIView *)view;
{
    UILabel* pickerLabel = (UILabel*)view;
    if (!pickerLabel){
        pickerLabel = [[UILabel alloc] init];
        pickerLabel.font=[UIFont systemFontOfSize: weight:];
        pickerLabel.textColor=[UIColor whiteColor];
        pickerLabel.textAlignment=;
        [pickerLabel setBackgroundColor:[UIColor clearColor]];
    }
    pickerLabel.text=[self pickerView:pickerView titleForRow:row forComponent:component];
    //在该代理方法里添加以下两行代码删掉上下的黑线
    [[pickerView.subviews objectAtIndex:] setHidden:TRUE];
    [[pickerView.subviews objectAtIndex:] setHidden:TRUE];
    return pickerLabel;
}