切换根控制器UIApplication 主屏幕UIScreen 读取文件资源NSBundle

 //主屏幕设为webView
 CGRect frame = [UIScreen mainScreen].applicationFrame;
 UIWebView *webView = [[[UIWebView alloc] initWithFrame:frame] autorelease];
 self.view = webView;

 UIApplication *app = [UIApplication sharedApplication];
 // 显示状态栏
  app.statusBarHidden = NO;
 ChangeController *index = [[ChangeController alloc] init];
 // 设置窗口的根控制器
 app.keyWindow.rootViewController = index;
 [index release];

 //回到根控制器
 popToRootViewControllerAnimationed:YES
3 //返回
 popViewControllerAnimated

  id key = (id)kCFBundleVersionKey;
1 // 检测是否第一次使用这个版本  info.plist
 NSDictionary *info = [NSBundle mainBundle].infoDictionary;
 NSString *currentVersion = [info objectForKey:key];

 // 从沙盒中取出版本号
 NSUserDefaults *defaults =[NSUserDefaults standardUserDefaults];
  NSString *saveVersion = [defaults objectForKey:key];

 //获取图片
  NSString *path = [[NSBuddle mainBuddle] pathForResource:@"resourceName" oftype@"plist"];
 UIImage *image = [[UIImage imageWithContentsOfFile:path];
 UIImage *image = [UIImage imageNamed:@"imageName"];

 //获取plist文件
 NSArray *array =[[NSArrayalloc] initWithContentsOfFile:[[NSBundle mainBundle]  pathForResource:@"name" ofType:@"plist"]];
 NSDictionary *dict=[array objectAtIndex:index];