ios - 标签边框未出现(iOS)

Question

我已经在Interface Builder中创建了一个文本标签(title_label)，已经在FirstViewController.h文件中声明了它，现在我想为其添加边框。我已经添加了执行此操作的代码，但是当我运行应用程序时，边框根本不会出现。

这是代码:

#import "FirstViewController.h"
#import <QuartzCore/QuartzCore.h>

@interface FirstViewController ()

@end

@implementation FirstViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    title_label.layer.borderColor = [UIColor greenColor].CGColor;
    title_label.layer.borderWidth = 4.0;
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

这是 FirstViewController.h的内容:

#import <UIKit/UIKit.h>

@interface FirstViewController : UIViewController {

IBOutlet UILabel *title_label;

}

@end

Answer 1

#import <QuartzCore/QuartzCore.h>

- (void)viewDidLoad
{
    [super viewDidLoad];
    UILabel *title_label = [[UILabel alloc]initWithFrame:CGRectMake(20, 30, 150, 40)];
    title_label.text = @"Text Which Comes";
    title_label.layer.borderColor = [UIColor greenColor].CGColor;
    title_label.layer.borderWidth = 4.0;
    title_label.layer.cornerRadius = 5.0;
    [self.view addSubview:title_label];
}

导入的 QuartzCore 框架