关于UIScrollView有些你很难知晓的崩溃情形

关于UIScrollView有些你很难知晓的崩溃情形

为了实现以下的功能(按钮之间的切换效果):

简短的代码如下:

//
//  RootViewController.m
//  BUG
//
//  Copyright (c) 2014年 Y.X. All rights reserved.
//

#import "RootViewController.h"

@interface RootViewController ()

{
    UIView    *_showView;
}

@end

@implementation RootViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    _showView = [[UIView alloc] initWithFrame:self.view.bounds];
    [self.view addSubview:_showView];

    NSArray *title = @[@"YouXianMing",
                       @"XianHui",
                       @"XianMing",
                       @"XianNeng",
                       @"XianRen"];

    [title enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
        // 初始化button
        UIButton *button = [[UIButton alloc] initWithFrame:CGRectMake(50, 50*(idx + 1), 130, 30)];
        button.layer.borderWidth = 1.f;
        [_showView addSubview:button];

        // 设置字体
        button.titleLabel.font = [UIFont fontWithName:@"HelveticaNeue-Thin"
                                                 size:15.f];

        // 设置标题以及标题颜色
        [button setTitle:obj
                forState:UIControlStateNormal];
        [button setTitleColor:[UIColor redColor]
                     forState:UIControlStateNormal];

        // 添加事件
        [button addTarget:self
                   action:@selector(buttonsEvent:)
         forControlEvents:UIControlEventTouchUpInside];
    }];
}

- (void)buttonsEvent:(UIButton *)button
{
    [_showView.subviews enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
        UIButton *tmpButton = obj;

        if ([tmpButton isEqual:button])
        {
            [tmpButton setTitleColor:[UIColor redColor]
                            forState:UIControlStateNormal];
        }
        else
        {
            [tmpButton setTitleColor:[UIColor blackColor]
                            forState:UIControlStateNormal];
        }
    }];
}

@end

之后,将UIView替换成UIScrollView后:

然后就会崩溃-_-!!

崩溃信息:

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[UIImageView setTitleColor:forState:]: unrecognized selector sent to instance 0xa590390'

崩溃原因是_showView.subviews里面有一个UIImageView

我们并没有添加这个东西UIImageView到subviews中呢,其实,这个东西是UIScrollView自己的一个东西......

写上以下保护性语句就没问题了.

话说,UIScrollView跟你偷偷加了点东西让你崩溃了都不知道咋回事-_-!!!