iOS - UITabBarController中的坑

當你創建一個繼承與UITabBarController的子類 並想給其自定義構造方法 傳一些值的時候這時候問題出現了：

 在創建的時候里面的init方法回調用了 viewdidload，導致每次傳值的時候都會在viewdidload加載完了之后傳的值才能傳過去

如下代碼

- (instancetype)initWithURLStrings:(NSArray *)urls{
    self = [super init];//在調用init的時候回調用viewDidLoad 導致參數傳入進來時已經加載完了
    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:@"首頁" image:@"tab_home_n" selectedImage:@"tab_home_s"];
    
    KHVipVC *vipVC = [[KHVipVC alloc] initWithURL:self.urls[1]];
    [self addChildVc:vipVC title:@"會員" image:@"tab_user_n" selectedImage:@"tab_user_s"];
    
    KHMineDetailVC *settingVC = [[KHMineDetailVC alloc] initWithURL:self.urls[2]];
    [self addChildVc:settingVC title:@"設置" image:@"tab_setting_n" selectedImage:@"tab_setting_s"];
}

- (void)addChildVc:(UIViewController *)childVc title:(NSString *)title image:(NSString *)image selectedImage:(NSString *)selectedImage
{
    // 設置子控制器的文字
    childVc.title = title; // 同時設置tabbar和navigationBar的文字
    
    // 設置子控制器的圖片
    childVc.tabBarItem.image = [UIImage imageNamed:image];

    if (iOS7) {
        childVc.tabBarItem.selectedImage = [[UIImage imageNamed:selectedImage] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
    } else {
        childVc.tabBarItem.selectedImage = [UIImage imageNamed:selectedImage];
    }
    
    // 設置文字的樣式
    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];
    
    // 先給外面傳進來的小控制器 包裝 一個導航控制器
    KHNavigationController *nav = [[KHNavigationController alloc] initWithRootViewController:childVc];
    nav.navigationBarHidden = YES;
    // 添加為子控制器
    [self addChildViewController:nav];
}

 

這是怎么回事的 我們知道在一般控制器中我們想要自定義構造方法 會先走完初始化方法然后再走 viewDidLoad 但是這個UITabBarController怎么這么特殊呢呢？

經過一番查找終於知道了原來這是UITabBarController的一個特性

其實UITabBarController在init的時候，會增UITabbar到self.view，這時候必須加載self.view出來，從而就調用了loadview，進而調用viewdidload、viewwillappear等。這個是UITabBarController的特性

UITabBarController在調用【super init】的時候，系統調用了self.view的東西，但是此時view還沒加載出來，於是系統強制先調用viewdidload去加載self.view，最后加載完了，再接着走init方法中的 if(self)條件語句。

 

解決方案：

就是不要在viewdidload 方法里寫加載界面的代碼，可以單獨再寫個方法，直接在init結束的時候調用。所以我的建議就是直接把viewdidload和viewwillappear方法刪了，加載界面全都在init里寫，如下：

- (instancetype)initWithURLStrings:(NSArray *)urls{
    self = [super init];//在調用init的時候回調用viewDidLoad 導致參數傳入進來時已經加載完了
    if (self) {

        self.urls = urls; //初始化數據
         [self setUpChild]; //這是解決的重點

    }
    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:@"首頁" image:@"tab_home_n" selectedImage:@"tab_home_s"];
    
    KHVipVC *vipVC = [[KHVipVC alloc] initWithURL:self.urls[1]];
    [self addChildVc:vipVC title:@"會員" image:@"tab_user_n" selectedImage:@"tab_user_s"];
    
    KHMineDetailVC *settingVC = [[KHMineDetailVC alloc] initWithURL:self.urls[2]];
    [self addChildVc:settingVC title:@"設置" image:@"tab_setting_n" selectedImage:@"tab_setting_s"];
}

- (void)addChildVc:(UIViewController *)childVc title:(NSString *)title image:(NSString *)image selectedImage:(NSString *)selectedImage
{
    // 設置子控制器的文字
    childVc.title = title; // 同時設置tabbar和navigationBar的文字
    
    // 設置子控制器的圖片
    childVc.tabBarItem.image = [UIImage imageNamed:image];

    if (iOS7) {
        childVc.tabBarItem.selectedImage = [[UIImage imageNamed:selectedImage] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
    } else {
        childVc.tabBarItem.selectedImage = [UIImage imageNamed:selectedImage];
    }
    
    // 設置文字的樣式
    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];
    
    // 先給外面傳進來的小控制器 包裝 一個導航控制器
    KHNavigationController *nav = [[KHNavigationController alloc] initWithRootViewController:childVc];
    nav.navigationBarHidden = YES;
    // 添加為子控制器
    [self addChildViewController:nav];
}

 

 

我發現只有繼承自UINavigationController和UITabBarController的類的init函數會產生loadView、viewDidLoad函數在初始化［super init］函數調用后就執行，一般UIViewController沒有這個問題

@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

0
2
3
1

d