【知识分享】UIButton setTitle 设置为空 失效

时间:2024-07-18 12:33:50

今天开发练习超级猜图,但是碰到了一个奇怪的问题 困扰我一个晚上,低效的夜晚 可恨~

示例说明1


[button setTitle:@"" forState:UIControlStateNormal];
[button setTitle:nil forState:UIControlStateNormal];
//设置失效 因为 当再次获取button的值时,却是在更早的值 (btn.titleLabel.text=在设置为空之前的值)

[view setTitle: @"" forState :UIControlStateNormal ];
[view setTitle: @"" forState :UIControlStateHighlighted ];
[view setTitle: @"" forState :UIControlStateDisabled ];
[view setTitle: @"" forState :UIControlStateSelected ];
[view setTitle: @"" forState :UIControlStateApplication ];
[view setTitle: @"" forState :UIControlStateReserved ];
//
设置失效 (btn.titleLabel.text=在设置为空之前的值)
 

示例说明2:
 -(void)answerClick:(id)answerBtn{

     UIButton *btn=(UIButton*)answerBtn;

      NSString *answerValue=[btn titleForState:UIControlStateNormal];

     //NSString *answerValue=btn.titleLabel.text;

     [btn setTitle:nil forState:UIControlStateNormal];//设置为空

     NSLog(@"title before set nill:%@,title forstate:%@, btn.titleLabel.text:%@",answerValue,[btn titleForState:UIControlStateNormal],btn.titleLabel.text);

 }

输出:2014-09-03 19:59:03.606 05-1超级猜图[895:60b] title before set nill:笑,title forstate:(null), btn.titleLabel.text:笑

原因分析

示例1中   根据UIControlStateNormal设置为空,则必须通过[btn titleForState:UIControlStateNormal] 获取值,如果通过btn.titleLabel.text 会得到设置nil之前的值
因此 通过State赋值 一定要通过State取值,切记