iOS 显示界面的顺序

[[viewController  all]init];//在创建界面的时候调用​

[ viewController loadView]; //这是在创建界面，但是须注意在有XIB文件时不需要写这个方法，否则它会调用这个方法而忽略XIB文件​

[ViewController viewDidLoad]；//视图加载完毕

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[ViewController viewWillAppear:]//视图将要呈现

[MyView drawRect:]//渲染最底层的视图

[SubView drawRect:]//渲染子视图

[ViewController viewDidAppear:]//视图已经呈现

​- （void）viewdidUnload{}//内存不足时调用​

​- (void)didReceiveMemoryWarning {   

​ // Releases the view if it doesn't have a superview.    [super didReceiveMemoryWarning];    // Relinquish ownership any cached data, images, etc that aren't in use.//此方法是收到内存已经满时调用

​}

[ViewController viewWillAppear:]//视图将要消失

[ViewController viewDidAppear:]//视图已经消失

[ ViewController dealloc];//释放​

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