问题描述

动态设置UILabel的文本颜色

创建label：

.H 文件：

@interface ViewController : UIViewController
{
    NSArray * phraseAry ;
    UIView * containerView;
    UILabel * oldLabel;
    NSMutableArray *dataArray;
}
@property (strong, nonatomic) IBOutlet UIScrollView *myScrollView;

.M 文件

- (void)viewDidLoad
{
    [super viewDidLoad];
    heightValue = 20;
    widthValue = 0;
    xValue = 5;
    yValue = 10;
containerView = [[UIView alloc] init];
    for (int i=0; i<phraseAry.count; i++) {
        widthValue = [self returnWidth:[phraseAry objectAtIndex:i]];
        int newXValue = xValue+widthValue+5;
        //NSLog(@"newXValue : %i",newXValue);
        if (newXValue > 310) {
            yValue +=20;
            xValue = 5;
            newXValue = xValue+widthValue+5;
            UILabel *lbl = [[UILabel alloc] initWithFrame:CGRectMake(xValue, yValue, widthValue, heightValue)];
            lbl.text = [phraseAry objectAtIndex:i];
            [lbl setFont:[UIFont fontWithName:@"Helvetica" size:14.0]];
            lbl.tag = i;
            lbl.textColor = [UIColor colorWithRed:(92/255.0) green:(109/255.0) blue:(43/255.0) alpha:1];
            [containerView addSubview:lbl];
            xValue = newXValue;
        } else {
            UILabel *lbl = [[UILabel alloc] initWithFrame:CGRectMake(xValue, yValue, widthValue, heightValue)];
            lbl.text = [phraseAry objectAtIndex:i];
            [lbl setFont:[UIFont fontWithName:@"Helvetica" size:14.0]];
            lbl.tag = i;
            lbl.textColor = [UIColor colorWithRed:(92/255.0) green:(109/255.0) blue:(43/255.0) alpha:1];
            [containerView addSubview:lbl];
            xValue = newXValue;
        }
    }

    containerView.frame = CGRectMake(0, 0, 320, yValue);
    //add code to customize, e.g. polygonView.backgroundColor = [UIColor blackColor];
    [self.myScrollView addSubview:containerView];
    self.myScrollView.contentSize = containerView.frame.size;
}

设置背景颜色和文本颜色：

- (void)updateLabelMethod
 {
            oldLabel.backgroundColor = [UIColor clearColor];
            UILabel *label = (UILabel *)[containerView viewWithTag:2];
            oldLabel = label;
            label.backgroundColor = [UIColor colorWithRed:(98/255.0) green:(147/255.0) blue:(216/255.0) alpha:1];
            label.textColor = [UIColor whiteColor];
            containerView.backgroundColor = [UIColor clearColor];
}

背景颜色实现更新，但是文本颜色更新会报错：

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[UIView setTextColor:]: unrecognized selector sent to instance 0xbaa3b30'

不知道怎么设置？谢谢

解决方案

异常提示信息很清楚的说明了出错的原因。
主要的问题出在：你使用viewWithTag拿到的 UI并非是UILabel对象，而是UIView。这个从报错的信息中可以看出

 [UIView setTextColor:]: unrecognized selector sent to instance

所以根据上面的分析，问题的关键在于，在你的updateLabelMethod中

UILabel *label = (UILabel *)[containerView viewWithTag:2];

你所拿到实际上并非UIlabel对象。出现这个的原因很有可能是某个UIView 和 UILabel同时设置了tag的值为2, 在使用viewWithTag查找时，首先找到的是那个UIView 就返回给了你，当你给UIview 发送setTextColor消息时肯定会报错的。