////  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@property (nonatomic, retain) IBOutlet UITextField *textField;@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;        // 创建文本框    self.textField = [[UITextField alloc]initWithFrame:CGRectMake(100, 100, 97.0, 31.0)];    self.textField.borderStyle = UITextBorderStyleRoundedRect;    self.textField.keyboardType = UIKeyboardTypeNamePhonePad;    self.textField.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter;    [contentView addSubview:self.textField];        // 创建按钮    UIButton *button = [[UIButton alloc]initWithFrame:CGRectMake(0.0, 0.0, 320.0, 30.0)];    [button setTitle:NSLocalizedString(@"Hello", nil) forState:UIControlStateNormal];    button.center = contentView.center;    [contentView addSubview:button];        // 绑定按钮事件    [button addTarget:self action:@selector(buttonClicked:) forControlEvents:UIControlEventTouchUpInside];}-(void) buttonClicked:(UIButton *)button{    // 方法1：从视图层次里获取文本框中文字    NSLog(@"button clicked...");    UITextField *textField = [self.view subviews][0];    NSLog(@"hello, %@", textField.text);        // 方法2：把textField从局部变量变更为类属性    NSLog(@"hello, %@", self.textField.text);        //用对话框弹出信息    UIAlertView *av = [[UIAlertView alloc] initWithTitle:@"Hello"        message:self.textField.text delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];        [av show];}@end// 委托对象@interface HelloWorldAppDelegate : NSObject <UIApplicationDelegate>{    IBOutlet UIWindow *window;}@property (nonatomic, retain) UIWindow *window;@property (nonatomic, retain) HelloWorldViewController *viewController;//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//apple 官方文档把viewController也声明为属性了@end@implementation HelloWorldAppDelegate@synthesize window;@synthesize viewController;-(void) applicationDidFinishLaunching:(UIApplication *)application{    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen]bounds]];    self.viewController = [[HelloWorldViewController alloc]init];    self.window.rootViewController = self.viewController;    [self.window makeKeyAndVisible];}@end// 程序入口int main(int argc, char * argv[]){    @autoreleasepool {        return UIApplicationMain(argc, argv, nil, @"HelloWorldAppDelegate");    }}