iOS代码实现：创建按钮，绑定按钮事件，读取控件值

//
//  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");
    }
}