ios - 更改 UIPickerView pickerView :viewForRow: attributes based on a certain condition

Question

我正在尝试根据特定条件更改 viewForRow 中的文本颜色。当我按下按钮时， View 会更改为不同的颜色，但我也想更改选择器中文本的颜色。我使用“viewForRow”是因为我有自定义 View 。

//adds subcategories to the wheel
-(UIView *)pickerView:(UIPickerView *)pickerView viewForRow:(NSInteger)row forComponent:(NSInteger)component reusingView:(UIView *)view
{
    UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, pickerView.frame.size.width, 44)];
    label.backgroundColor = [UIColor clearColor];


    if (!self.isBackgroundWhite)//Boolean that changes when the background changes
    {
        NSLog(@"Set white text");
        label.textColor = [UIColor whiteColor];

    }else{

        label.textColor = [UIColor blackColor];
    }



    if (row == 1) {
        label.text = [NSString stringWithFormat:@"  %@",[self.servicesArray objectAtIndex:row]];
        label.font = [UIFont fontWithName:@"HelveticaNeue-Bold" size:18];
    }else{
        label.text = [NSString stringWithFormat:@"     -%@",[self.servicesArray objectAtIndex:row] ];
        label.font = [UIFont fontWithName:kAppFont size:16];
    }
        return label;
}

编辑:感谢@Rich，我能够发现我的问题，我只需要调用[self.pickerView reloadAllComponents];

Answer 1

如果您只想更改文本颜色，只需使用其他委托(delegate)方法 pickerView:attributedTitleForRow:forComponent:

- (NSAttributedString *)pickerView:(UIPickerView *)pickerView attributedTitleForRow:(NSInteger)row forComponent:(NSInteger)component
{

    NSString *title;
    UIFont *font;
    if (row == 1) {
        title = [NSString stringWithFormat:@"  %@",[self.servicesArray objectAtIndex:row]];
        font = [UIFont fontWithName:@"HelveticaNeue-Bold" size:18];
    } else{
        title = [NSString stringWithFormat:@"     -%@",[self.servicesArray objectAtIndex:row] ];
        font = [UIFont fontWithName:kAppFont size:16];
    }

    UIColor *textColor;
    if (self.isBackgroundWhite) {
        textColor = [UIColor blackColor];
    } else {
        NSLog(@"Set white text");
        textColor = [UIColor whiteColor];
    }

    NSMutableParagraphStyle *paragraphStyle = [[NSParagraphStyle defaultParagraphStyle] mutableCopy];
    paragraphStyle.alignment = NSTextAlignmentLeft;

    NSDictionary *attributes = @{NSForegroundColorAttributeName : textColor, 
                                            NSFontAttributeName : font,
                                  NSParagraphStyleAttributeName : paragraphStyle};

    return [[NSAttributedString alloc] initWithString:title attributes:attributes];
}

另请注意，当更改 isBackgroundWhite 时，您应该调用 [self.pickerView reloadAllComponents];。我会通过重写 backgroundWhite 的 setter 并在 bool 值更改时重新加载选择器 View 来做到这一点。

编辑:
在 iOS 7(在 iOS 6 上工作正常)中似乎存在一个“错误”(有意或无意)，在 返回的 NSAttributedString 上设置了 UIFont pickerView:attributedTitleForRow:forComponent: 方法。因此，虽然以上适用于文本颜色，但字体不会改变。幸运的是，您可以使用问题中的代码来解决这个问题。参见 this answer了解更多信息。