版本記錄

前言

在APP中很多時(shí)候我們都需要用到父子控制器來(lái)達(dá)到我們的需求，這個(gè)用的次數(shù)不是很頻繁，但是在大的項(xiàng)目中搭建架構(gòu)的時(shí)候還是會(huì)用到的，接下來(lái)我們就詳細(xì)的解析一下父子控制器。相關(guān)代碼已發(fā)到 Github - 刀客傳奇

幾個(gè)基本概念

1. 定義

父子控制器，指的是一個(gè)控制器通過addChildViewController:方法添加多個(gè)控制器，被添加的控制器稱為子控制器，添加多個(gè)子控制器的控制器稱為父控制器。

2. 父子控制器關(guān)系

• 父控制器處理的事件會(huì)自動(dòng)傳遞給子控制器。
• 子控制器處理的事件會(huì)自動(dòng)傳給父控制器。
• 子控制器可以通過屬性parentViewController獲取父控制器 。
• 父控制器可以通過屬性childViewControllers獲取所有子控制器。
• A控制器添加到B控制器上后，A控制器就會(huì)被強(qiáng)引用，即使A控制器的view不正在顯示，A控制器和A控制器的view都不會(huì)被銷毀。

3. 什么時(shí)候使用父子控制器？

當(dāng)Apple提供的框架不能滿足開發(fā)者的時(shí)候，考慮重新搭建框架。比如UITabBarController的tabBar默認(rèn)是在底部，想要把它放到頂部或者左邊，實(shí)現(xiàn)起來(lái)會(huì)很困難，這時(shí)考慮到模仿UITabBarController的功能，搭建新的框架可能會(huì)更簡(jiǎn)單。

4. 創(chuàng)建父子控制器方法

一個(gè)控制器使用addChildViewController:方法添加子控制器。

如果兩個(gè)控制器的視圖View是父子關(guān)系，那么這兩個(gè)控制器也應(yīng)該是父子關(guān)系，也就是說應(yīng)該利用代碼創(chuàng)建父子關(guān)系。

5. 父子控制器優(yōu)點(diǎn)和注意事項(xiàng)

• 當(dāng)父控制器發(fā)生一些重大的事件，可以通知到子控制器，比如說屏幕旋轉(zhuǎn)。

• 不要自己創(chuàng)建數(shù)組來(lái)管理子控制器，用 UIViewController 自帶的 childViewControllers 數(shù)組可以避免掉很多不必要的麻煩。

• 可以在整體布局中嵌套一個(gè)scrollview，使子控制器可以進(jìn)行滑動(dòng)切換，實(shí)現(xiàn)類似網(wǎng)易新聞和今日頭條不同頻道加載的效果。

6. 父子控制器的接口及幾個(gè)重要方法

下面我們要看一下父子控制器需要的幾個(gè)重要方法。

• addChildViewController添加子控制器，建立父子關(guān)系
  • 如果重寫此方法，必須在實(shí)現(xiàn)中調(diào)用父類實(shí)現(xiàn)
  • 調(diào)用addChildViewController:會(huì)自動(dòng)調(diào)用child的willMoveToParentViewController:方法，不會(huì)自動(dòng)調(diào)用didMoveToParentViewController方法；
  • 如果childController已經(jīng)有一個(gè)不同的父控制器，那么它將首先通過調(diào)用removeFromParentViewController從當(dāng)前的父控制器移除。
  • 如果一個(gè)父控制器的內(nèi)容中包含了另一個(gè)控制器的view，那么父子控制器的關(guān)系是必要的.

/*
  If the child controller has a different parent controller, it will first be removed from its current parent
  by calling removeFromParentViewController. If this method is overridden then the super implementation must
  be called.
*/
- (void)addChildViewController:(UIViewController *)childController NS_AVAILABLE_IOS(5_0);

• removeFromParentViewController從父控制器中移除子控制器
  • 將控制器從父控制器的子控制器數(shù)組中移除；如果重寫此方法，必須在實(shí)現(xiàn)中調(diào)用父類實(shí)現(xiàn)。

/*
  Removes the the receiver from its parent's children controllers array. If this method is overridden then
  the super implementation must be called.
*/
- (void)removeFromParentViewController NS_AVAILABLE_IOS5_0);

• willMoveToParentViewController將要添加到父控制器。

  • 此方法會(huì)在視圖控制器被添加或移除之前調(diào)用。
  • 自定義容器類控制器在調(diào)用child的removeFromParentViewController方法前，必須先調(diào)用child的willMoveToParentViewController:nil方法；
  • 如果重寫此方法，必須在實(shí)現(xiàn)中調(diào)用父類實(shí)現(xiàn)；
  • 將要從parent移除時(shí)，參數(shù)傳遞nil，將要添加到parent時(shí)，參數(shù)傳父控制器；調(diào)用addChildViewController:會(huì)自動(dòng)調(diào)用child的willMoveToParentViewController:方法，但不會(huì)自動(dòng)調(diào)用didMoveToParentViewController方法，可以在子控制器過渡完成時(shí)手動(dòng)調(diào)用didMoveToParentViewController，或者在沒有過渡效果時(shí)直接手動(dòng)調(diào)用didMoveToParentViewController；同樣的，removeFromParentViewController方法不會(huì)自動(dòng)調(diào)用[self willMoveToParentViewController:nil]而需要我們手動(dòng)進(jìn)行調(diào)用，但會(huì)自動(dòng)調(diào)用didMoveToParentViewController方法。

• didMoveToParentViewController添加到父控制器

  • 此方法會(huì)在視圖控制器被添加或移除之后調(diào)用；
  • 自定義容器類控制器在調(diào)用addChildViewController方法之后，必須調(diào)用child的didMoveToParentViewController:parent方法，如果有過渡過程，需要在過渡完成之后調(diào)用，否則直接調(diào)用；
  • 如果重寫此方法，必須在實(shí)現(xiàn)中調(diào)用父類實(shí)現(xiàn);

/*
  These two methods are public for container subclasses to call when transitioning between child
  controllers. If they are overridden, the overrides should ensure to call the super. The parent argument in
  both of these methods is nil when a child is being removed from its parent; otherwise it is equal to the new
  parent view controller.

  addChildViewController: will call [child willMoveToParentViewController:self] before adding the
  child. However, it will not call didMoveToParentViewController:. It is expected that a container view
  controller subclass will make this call after a transition to the new child has completed or, in the
  case of no transition, immediately after the call to addChildViewController:. Similarly,
  removeFromParentViewController does not call [self willMoveToParentViewController:nil] before removing the
  child. This is also the responsibilty of the container subclass. Container subclasses will typically define
  a method that transitions to a new child by first calling addChildViewController:, then executing a
  transition which will add the new child's view into the view hierarchy of its parent, and finally will call
  didMoveToParentViewController:. Similarly, subclasses will typically define a method that removes a child in
  the reverse manner by first calling [child willMoveToParentViewController:nil].
*/
- (void)willMoveToParentViewController:(nullable UIViewController *)parent NS_AVAILABLE_IOS(5_0);
- (void)didMoveToParentViewController:(nullable UIViewController *)parent NS_AVAILABLE_IOS(5_0);

• transitionFromViewController控制器轉(zhuǎn)場(chǎng)
  • 此方法用于在不同的子控制器之間過渡。
  • 過渡完成時(shí)，toViewController的view將被添加到fromViewController的view的父視圖上，fromViewController的view將被從父視圖上移除；
  • 對(duì)于iOS本來(lái)的容器類控制器例如導(dǎo)航控制器與TabbarController，請(qǐng)不要調(diào)用此方法；
    也可以直接用UIView的API，但是要確保，在fromViewController的view移除時(shí)toViewController的view已經(jīng)被添加到了視圖層級(jí)中；
  • 此方法底層中實(shí)現(xiàn)的順序是：添加toViewController的view，執(zhí)行動(dòng)畫，動(dòng)畫完成時(shí)移除fromViewController的view；
  • 如果重寫此方法，必須在實(shí)現(xiàn)中調(diào)用父類實(shí)現(xiàn)。

/*
  This method can be used to transition between sibling child view controllers. The receiver of this method is
  their common parent view controller. (Use [UIViewController addChildViewController:] to create the
  parent/child relationship.) This method will add the toViewController's view to the superview of the
  fromViewController's view and the fromViewController's view will be removed from its superview after the
  transition completes. It is important to allow this method to add and remove the views. The arguments to
  this method are the same as those defined by UIView's block animation API. This method will fail with an
  NSInvalidArgumentException if the parent view controllers are not the same as the receiver, or if the
  receiver explicitly forwards its appearance and rotation callbacks to its children. Finally, the receiver
  should not be a subclass of an iOS container view controller. Note also that it is possible to use the
  UIView APIs directly. If they are used it is important to ensure that the toViewController's view is added
  to the visible view hierarchy while the fromViewController's view is removed.
*/
- (void)transitionFromViewController:(UIViewController *)fromViewController toViewController:(UIViewController *)toViewController duration:(NSTimeInterval)duration options:(UIViewAnimationOptions)options animations:(void (^ __nullable)(void))animations completion:(void (^ __nullable)(BOOL finished))completion NS_AVAILABLE_IOS(5_0);

一個(gè)簡(jiǎn)單實(shí)例

下面我們就看一個(gè)簡(jiǎn)單實(shí)例，三個(gè)按鈕點(diǎn)擊后選擇對(duì)應(yīng)的子控制器，看一下代碼。

#import "ViewController.h"
#import "JJChildVCOne.h"
#import "JJChildVCTwo.h"
#import "JJChildVCThree.h"

#define kViewControllerScreenWidth     [UIScreen mainScreen].bounds.size.width
#define kViewControllerScreenHeight    [UIScreen mainScreen].bounds.size.height

@interface ViewController ()

@property (nonatomic, strong) UIViewController *currentVC;

@end

@implementation ViewController

#pragma mark -  Override Base Function

- (void)viewDidLoad
{
    [super viewDidLoad];
    
    self.view.backgroundColor = [UIColor whiteColor];
    
    //設(shè)置UI
    [self setupUI];
    
    //加子控制器
    [self setupChildVC];
}

#pragma mark -  Object Private Function

- (void)setupChildVC
{
    JJChildVCOne *childOneVC = [[JJChildVCOne alloc] init];
    childOneVC.view.backgroundColor = [UIColor redColor];
    
    JJChildVCTwo *childTwoVC = [[JJChildVCTwo alloc] init];
    childTwoVC.view.backgroundColor = [UIColor blueColor];
    
    JJChildVCThree *childThreeVC = [[JJChildVCThree alloc] init];
    childThreeVC.view.backgroundColor = [UIColor greenColor];
    
    [self addChildViewController:childOneVC];
    [self addChildViewController:childTwoVC];
    [self addChildViewController:childThreeVC];
}

- (void)setupUI
{
    for (NSInteger i = 0; i < 3; i ++) {
        UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
        NSString *title = [NSString stringWithFormat:@"切換%d", i];
        [button setTitle:title forState:UIControlStateNormal];
        button.tag = i;
        [button addTarget:self action:@selector(buttonDidClick:) forControlEvents:UIControlEventTouchUpInside];
        button.titleLabel.font = [UIFont boldSystemFontOfSize:20.0];
        
        //不同標(biāo)簽的差異化設(shè)置
        if (i == 0) {
            button.backgroundColor = [UIColor redColor];
        }
        else if (i == 1){
            button.backgroundColor = [UIColor blueColor];
        }
        else {
            button.backgroundColor = [UIColor greenColor];
        }
        
        [self.view addSubview:button];
        button.frame = CGRectMake(i * kViewControllerScreenWidth / 3, 0.0, kViewControllerScreenWidth / 3, 40);
    }
}

#pragma mark -  Action && Notification

- (void)buttonDidClick:(UIButton *)button
{
    UIViewController *vc = self.childViewControllers[button.tag];
    vc.view.frame = CGRectMake(0.0, 40.0, kViewControllerScreenWidth, kViewControllerScreenHeight - 40.0);
    //移除掉當(dāng)前顯示的控制器的view
    [self.currentVC.view removeFromSuperview];
    self.currentVC = vc;
    //把選中的控制器view顯示到界面上
    [self.view addSubview:self.currentVC.view];
}

@end

下面看一下效果圖

后記

未完，待續(xù)~~~