xcode5 运行在iphone retain 3.5" 模式下（即对应iphone4, iphone4s）需要开启ARC
//
// main.m
// Hello
//
// Created by lishujun on 14-8-28.
// Copyright (c) 2014年 lishujun. All rights reserved.
// #import <UIKit/UIKit.h> // 视图控制器对象
@interface HelloWorldViewController : UIViewController
@end @implementation HelloWorldViewController -(void) loadView
{
//创建视图对象
UIView *contentView = [[UIView alloc]initWithFrame:[[UIScreen mainScreen] applicationFrame]];
contentView.backgroundColor = [UIColor lightGrayColor];
self.view = contentView; //创建label对象
UILabel *label = [[UILabel alloc]initWithFrame:CGRectMake(0.0, 0.0, 320.0, 30.0)];
label.text = @"Hello World";
label.center = contentView.center; // 垂直居中
label.textAlignment = UITextAlignmentCenter; // 水平居中
label.backgroundColor = [UIColor clearColor];
label.textColor = [UIColor redColor]; //在视图上添加label
[contentView addSubview:label];
} @end // 委托对象
@interface HelloWorldAppDelegate : NSObject <UIApplicationDelegate>
{
IBOutlet UIWindow *window;
} @property (nonatomic, retain) UIWindow *window;
//必须声明为属性,声明为局部变量则无法绘制视图，显示为黑屏
@end @implementation HelloWorldAppDelegate
@synthesize window; -(void) applicationDidFinishLaunching:(UIApplication *)application
{
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen]bounds]];
HelloWorldViewController *viewController = [[HelloWorldViewController alloc]init];
self.window.rootViewController = viewController;
[self.window makeKeyAndVisible];
} @end // 程序入口
int main(int argc, char * argv[])
{
@autoreleasepool {
return UIApplicationMain(argc, argv, nil, @"HelloWorldAppDelegate");
}
}