更改UIPickerView pickerView：viewForRow：基於一定條件的屬性

Question

我試圖根據一定條件更改viewForRow中的文本顏色。當我按下按鈕時，視圖會變成不同的顏色，但我還想更改選取器中文本的顏色。我使用'viewForRow'是因爲我有一個自定義視圖。

//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; 
} 

編輯：感謝@Rich我能夠發現我的問題，我只需要調用[self.pickerView reloadAllComponents];

Answer 1

如果你只是想更改文本顏色只需使用其他委託方法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]; 
} 

另外一張紙條改變isBackgroundWhite時，你應該叫[self.pickerView reloadAllComponents];。我將通過覆蓋backgroundWhite的setter來完成此操作，並且當布爾值更改時重新加載選取器視圖。

編輯：
似乎有在IOS 7「錯誤」（有意或無意）（在iOS 6正常工作）與設置在從pickerView:attributedTitleForRow:forComponent:方法返回NSAttributedString的UIFont。所以，雖然上面的文字顏色的工作字體不會改變。幸運的是，你可以用問題中的代碼來解決這個問題。有關更多信息，請參閱this answer。