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
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