iOS

当你创建一个继承与UITabBarController的子类并想给其自定义构造方法传一些值的时候这时候问题出现了：

在创建的时候里面的init方法回调用了 viewdidload，导致每次传值的时候都会在viewdidload加载完了之后传的值才能传过去

如下代码

- (instancetype)initWithURLStrings:(NSArray *)urls{
    self = [super init];//在调用init的时候回调用viewDidLoad 导致参数传入进来时已经加载完了
    if (self) {

        self.urls = urls;
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
     [self setUpChild];
    self.tabBar.backgroundColor = [UIColor whiteColor];

}

- (void)setUpChild{
    // 1.初始化子控制器
    KHHomeVC *home = [[KHHomeVC alloc] initWithURL:self.urls[0]];
    [self addChildVc:home title:@"首页" image:@"tab_home_n" selectedImage:@"tab_home_s"];
    
    KHVipVC *vipVC = [[KHVipVC alloc] initWithURL:self.urls[1]];
    [self addChildVc:vipVC title:@"会员" image:@"tab_user_n" selectedImage:@"tab_user_s"];
    
    KHMineDetailVC *settingVC = [[KHMineDetailVC alloc] initWithURL:self.urls[2]];
    [self addChildVc:settingVC title:@"设置" image:@"tab_setting_n" selectedImage:@"tab_setting_s"];
}

- (void)addChildVc:(UIViewController *)childVc title:(NSString *)title image:(NSString *)image selectedImage:(NSString *)selectedImage
{
    // 设置子控制器的文字
    childVc.title = title; // 同时设置tabbar和navigationBar的文字
    
    // 设置子控制器的图片
    childVc.tabBarItem.image = [UIImage imageNamed:image];

    if (iOS7) {
        childVc.tabBarItem.selectedImage = [[UIImage imageNamed:selectedImage] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
    } else {
        childVc.tabBarItem.selectedImage = [UIImage imageNamed:selectedImage];
    }
    
    // 设置文字的样式
    NSMutableDictionary *textAttrs = [NSMutableDictionary dictionary];
    textAttrs[NSForegroundColorAttributeName] = [UIColor colorWithRed:136/255.0 green:136/255.0 blue:136/255.0 alpha:1];
    NSMutableDictionary *selectTextAttrs = [NSMutableDictionary dictionary];
    selectTextAttrs[NSForegroundColorAttributeName] = [UIColor colorWithRed:0 green:183/255.0 blue:283/255.0 alpha:1];
    [childVc.tabBarItem setTitleTextAttributes:textAttrs forState:UIControlStateNormal];
    [childVc.tabBarItem setTitleTextAttributes:selectTextAttrs forState:UIControlStateSelected];
    
    // 先给外面传进来的小控制器 包装 一个导航控制器
    KHNavigationController *nav = [[KHNavigationController alloc] initWithRootViewController:childVc];
    nav.navigationBarHidden = YES;
    // 添加为子控制器
    [self addChildViewController:nav];
}

这是怎么回事的我们知道在一般控制器中我们想要自定义构造方法会先走完初始化方法然后再走 viewDidLoad 但是这个UITabBarController怎么这么特殊呢呢？

经过一番查找终于知道了原来这是UITabBarController的一个特性

其实UITabBarController在init的时候，会增UITabbar到self.view，这时候必须加载self.view出来，从而就调用了loadview，进而调用viewdidload、viewwillappear等。这个是UITabBarController的特性

UITabBarController在调用【super init】的时候，系统调用了self.view的东西，但是此时view还没加载出来，于是系统强制先调用viewdidload去加载self.view，最后加载完了，再接着走init方法中的 if(self)条件语句。

解决方案：

就是不要在viewdidload 方法里写加载界面的代码，可以单独再写个方法，直接在init结束的时候调用。所以我的建议就是直接把viewdidload和viewwillappear方法删了，加载界面全都在init里写，如下：

- (instancetype)initWithURLStrings:(NSArray *)urls{
    self = [super init];//在调用init的时候回调用viewDidLoad 导致参数传入进来时已经加载完了
    if (self) {

        self.urls = urls; //初始化数据
         [self setUpChild]; //这是解决的重点

    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    self.tabBar.backgroundColor = [UIColor whiteColor];

}


- (void)setUpChild{
    // 1.初始化子控制器
    KHHomeVC *home = [[KHHomeVC alloc] initWithURL:self.urls[0]];
    [self addChildVc:home title:@"首页" image:@"tab_home_n" selectedImage:@"tab_home_s"];
    
    KHVipVC *vipVC = [[KHVipVC alloc] initWithURL:self.urls[1]];
    [self addChildVc:vipVC title:@"会员" image:@"tab_user_n" selectedImage:@"tab_user_s"];
    
    KHMineDetailVC *settingVC = [[KHMineDetailVC alloc] initWithURL:self.urls[2]];
    [self addChildVc:settingVC title:@"设置" image:@"tab_setting_n" selectedImage:@"tab_setting_s"];
}

- (void)addChildVc:(UIViewController *)childVc title:(NSString *)title image:(NSString *)image selectedImage:(NSString *)selectedImage
{
    // 设置子控制器的文字
    childVc.title = title; // 同时设置tabbar和navigationBar的文字
    
    // 设置子控制器的图片
    childVc.tabBarItem.image = [UIImage imageNamed:image];

    if (iOS7) {
        childVc.tabBarItem.selectedImage = [[UIImage imageNamed:selectedImage] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
    } else {
        childVc.tabBarItem.selectedImage = [UIImage imageNamed:selectedImage];
    }
    
    // 设置文字的样式
    NSMutableDictionary *textAttrs = [NSMutableDictionary dictionary];
    textAttrs[NSForegroundColorAttributeName] = [UIColor colorWithRed:136/255.0 green:136/255.0 blue:136/255.0 alpha:1];
    NSMutableDictionary *selectTextAttrs = [NSMutableDictionary dictionary];
    selectTextAttrs[NSForegroundColorAttributeName] = [UIColor colorWithRed:0 green:183/255.0 blue:283/255.0 alpha:1];
    [childVc.tabBarItem setTitleTextAttributes:textAttrs forState:UIControlStateNormal];
    [childVc.tabBarItem setTitleTextAttributes:selectTextAttrs forState:UIControlStateSelected];
    
    // 先给外面传进来的小控制器 包装 一个导航控制器
    KHNavigationController *nav = [[KHNavigationController alloc] initWithRootViewController:childVc];
    nav.navigationBarHidden = YES;
    // 添加为子控制器
    [self addChildViewController:nav];
}

我发现只有继承自UINavigationController和UITabBarController的类的init函数会产生loadView、viewDidLoad函数在初始化［super init］函数调用后就执行，一般UIViewController没有这个问题

@implementation UIViewControllerSubclass

- (id)init {
        NSLog(@"0");
    if (self = [super init]) {
        NSLog(@"1");
    }
    return self;
}

- (void)loadView {
    [super loadView];
    NSLog(@"2");
}

- (void)viewDidLoad {
    [super viewDidLoad];
    NSLog(@"3");
}

@end

console output