ios控制器生存週期

• iOS中控制器的生命週期

　　通常咱們在建立控制器的時候，有三種方法。

　　1.  直接經過代碼建立

　　2.  經過storyboard建立

　　3.  經過Xib，在建立控制器的時候傳入一個Xib文件做爲這個控制器的view。

 

• 直接經過代碼建立

　　經過代碼建立這種凡是，咱們打印調用順序能夠發現

　　

　　對應的代碼調用順序就是  loadView -> viewDidLoad -> viewWillAppear -> viewWillLayoutSubviews -> viewDidLayoutSubviews -> viewDidAppear

　　

// 1. 
- (void)loadView; // This is where subclasses should create their custom view 
hierarchy if they aren't using a nib. Should never be called directly.

// 2.
- (void)viewDidLoad; // Called after the view has been loaded. For view controllers created in code, this is after -loadView. For view controllers unarchived from a nib, this is after the view is set.

// 3.
- (void)viewWillAppear:(BOOL)animated;    // Called when the view is about to made visible. Default does nothing

// 4.
- (void)viewWillLayoutSubviews NS_AVAILABLE_IOS(5_0);
// Called just after the view controller's view's layoutSubviews method is invoked. Subclasses can implement as necessary. The default is a nop.

// 5.
- (void)viewDidLayoutSubviews NS_AVAILABLE_IOS(5_0);

　　控制器建立以後，彈出另外一個控制器(當前控制器消失)，執行的代碼順序 viewWillDisappear -> viewWillLayoutSubviews -> viewDidLayoutSubviews -> viewDidDisappear

　　

　　

// 1.
- (void)viewWillDisappear:(BOOL)animated; // Called when the view is dismissed, covered or otherwise hidden. Default does nothing

// 2.
- (void)viewWillLayoutSubviews NS_AVAILABLE_IOS(5_0);
// Called just after the view controller's view's layoutSubviews method is invoked. Subclasses can implement as necessary. The default is a nop.

// 3.
- (void)viewDidLayoutSubviews NS_AVAILABLE_IOS(5_0);

// 4.
- (void)viewDidDisappear:(BOOL)animated;  // Called after the view was dismissed, covered or otherwise hidden. Default does nothing

 

• 經過storyboard建立控制器

　　

UIStoryboard *storyBoard = [UIStoryboard storyboardWithName:NSStringFromClass([CViewController class]) bundle:nil];
CViewController *touch = [storyBoard instantiateViewControllerWithIdentifier:NSStringFromClass([CViewController class])];
[self presentViewController:touch animated:YES completion:nil];

　　爲了方便，同時減小手誤，這裏重用ID咱們使用類名

　　 

　　經過打印來觀察

　　

　　能夠看到代碼的調用順序就是 awakeFromNib -> loadView -> viewWillAppear -> viewWillLayoutSubviews -> viewDidLayoutSubviews -> viewDidAppear

// 1.
- (void)awakeFromNib NS_REQUIRES_SUPER;

// 2.
- (void)loadView; // This is where subclasses should create their custom view hierarchy if they aren't using a nib. Should never be called directly.

// 3.
- (void)viewDidLoad; // Called after the view has been loaded. For view controllers created in code, this is after -loadView. For view controllers unarchived from a nib, this is after the view is set.

// 4.
- (void)viewWillAppear:(BOOL)animated;    // Called when the view is about to made visible. Default does nothing

// 5.
- (void)viewWillLayoutSubviews NS_AVAILABLE_IOS(5_0);
// Called just after the view controller's view's layoutSubviews method is invoked. Subclasses can implement as necessary. The default is a nop.
- (void)viewDidLayoutSubviews NS_AVAILABLE_IOS(5_0);

// 6.
- (void)viewDidAppear:(BOOL)animated;     // Called when the view has been fully transitioned onto the screen. Default does nothing

　　這裏須要注意的是，咱們是控制器經過storyboard來加載，那麼是根據storyboard的描述建立view。

　　

• 經過XIB來建立加載控制器

　　首先建立一個XIB，快捷鍵 command + N 來建立。

　　

　　

　　建立後XIB以後咱們還須要設置文件

　　

這裏設置爲咱們建立的控制器

　　

　　全部須要的已經設置好，這時候咱們能夠來碼代碼了。

DViewController *touch = [[DViewController alloc] initWithNibName:NSStringFromClass([DViewController class]) bundle:nil];
[self presentViewController:touch animated:YES completion:nil];

　　下面咱們來觀察控制器的生命週期

　　代碼層面上就是

// 1.
- (void)loadView; // This is where subclasses should create their custom view hierarchy if they aren't using a nib. Should never be called directly.

// 2.
- (void)viewDidLoad; // Called after the view has been loaded. For view controllers created in code, this is after -loadView. For view controllers unarchived from a nib, this is after the view is set.

// 3.
- (void)viewWillAppear:(BOOL)animated;    // Called when the view is about to made visible. Default does nothing

// 4.可能會屢次調用
- (void)viewWillLayoutSubviews NS_AVAILABLE_IOS(5_0);
// Called just after the view controller's view's layoutSubviews method is invoked. Subclasses can implement as necessary. The default is a nop.
- (void)viewDidLayoutSubviews NS_AVAILABLE_IOS(5_0);

// 5.
- (void)viewDidAppear:(BOOL)animated;     // Called when the view has been fully transitioned onto the screen. Default does nothing

　　說明：

　　加載XIB的時候，咱們一樣能夠不指定XIB名稱，這樣loadView 就會最終加載與控制器同名的 XIB （命名規範很重要啊）

DViewController *touch = [[DViewController alloc] init];
[self presentViewController:touch animated:YES completion:nil];

　　同時，若是咱們刪掉 DViewController.xib ,同時建立一個 DView.xib 當咱們用以上不指定xib名稱，一樣是能夠加載出來的（命名規範很重要）。

　　咱們能夠知道，加載xib的過程是，若是指定名稱，那麼加載指定名稱的xib，若是沒有指定名稱就會加載和控制器同名的xib，若是沒有就會找去控制器名相同可是沒有 controller 的xib來加載。

 

• A present B控制器再返回，兩個控制器的生命週期

　　1. 建立A控制器

　　

　　流程：

A:loadView
A:viewDidLoad
A:viewWillAppear
A:viewWillLayout...
A:viewDidAppear

　　2. A present 到B控制器

　　

　　流程：

A:loadView
A:viewDidLoad
A:viewWillAppear
A:viewWillLayout...    // 可能屢次調用
A:viewDidAppear

-------------- Present B控制器 --------------

B:loadView
B:viewDidLoad

A:viewWillDisappear

B:viewWillAppear
B:viewLayout....   // 可能屢次調用

A;viewLayout...   // 可能屢次調用

B:viewDidAppear   // 屢次調用，會跟下面的調用順序可能會有些調換

A:viewDidDisappear