新建RootViewController 继承于 UIViewController

新建RootView 继承于 UIView

AppDelegate.m 中引入 #import "RootViewController.h"

#pragma mark - 重写#pragma mark dealloc- (void)dealloc{    [_window release];    [super dealloc];}    //设置window    self.window = [[[UIWindow alloc] init] autorelease];    self.window.frame = [UIScreen mainScreen].bounds;    self.window.backgroundColor = [UIColor whiteColor];    [self.window makeKeyAndVisible];    // 设置根视图控制器    RootViewController *rootVC = [[RootViewController alloc] init];    self.window.rootViewController = rootVC;    [rootVC release];

RootViewController.m 中引入 #import "RootView.h"

@interface RootViewController ()@property (nonatomic, retain) RootView *rootView;@end

#pragma mark - 重写#pragma mark dealloc- (void)dealloc{    [_rootView release];    [super dealloc];}

编写 loadView 函数，函数中永远仅仅写三句话

- (void)loadView{    // 设置当前视图为根视图    self.rootView = [[RootView alloc] initWithFrame:[UIScreen mainScreen].bounds];    self.view = self.rootView;    [_rootView release];}

能够在 RootView.m 中编写视图了。