前面写了UIWindow、UIViewController，那些都是一些框架，框架需要填充上具体的view才能组成我们的应用，移动应用开发中UI占了很大一部分，最基础的UI实现是使用系统提供的各种控件，其他的就是自定义实现了，作者目前是入门状态，只能写写基础控件了。
iOS中提供了UIButton、UILable、UITextField、UIImageView等基础UI控件，继承于UIView。这里先拿UIButton练练手，为什么拿UIButton呢，因为UIbutton继承自UIControl，UIControl派生自UIView类，每个控件都有很多视图的特性，包括附着于其他视图的能力，所有控件都拥有一套共同的属性和方法，包含显示内容，点击事件等等，UIControl的子类都有事件处理能力。
图、UIControl
UIButton的定义：
UIButton可使用 initWithFrame、buttonWithType两种方式创建：
1）initWithFrame
UIButton *btn=[[UIButton alloc]initWithFrame:CGRectMake(60, 60, 200, 60)]; btn.backgroundColor=[UIColor greenColor]; [btn setTitle:@"btn1" forState:UIControlStateNormal]; [self.view addSubview:btn];
2）buttonWithType
UIButton *btn2=[UIButton buttonWithType:UIButtonTypeRoundedRect]; CGRect rect=CGRectMake(60, 160, 200, 60); btn2.frame=rect; btn2.tag=1001; btn2.backgroundColor=[UIColor colorWithRed:30/255.0 green:200/255.0 blue:125/255.0 alpha:1.0]; [btn2 setTitle:@"btn2" forState:UIControlStateNormal]; [btn2 addTarget:self action:@selector(btn2Pressed) forControlEvents:UIControlEventTouchDown]; [self.view addSubview:btn2];btn2Pressed方法：
-(void)btn2Pressed{ NSLog(@"button pressed"); }
UIButtonType:
typedef enum { UIButtonTypeCustom = 0, // no button type 自定义，无风格 UIButtonTypeRoundedRect, // rounded rect, flat white button, like in address card 白色圆角矩形，类似偏好设置表格单元或者地址簿卡片 UIButtonTypeDetailDisclosure,//蓝色的披露按钮，可放在任何文字旁 UIButtonTypeInfoLight,//微件(widget)使用的小圆圈信息按钮，可以放在任何文字旁 UIButtonTypeInfoDark,//白色背景下使用的深色圆圈信息按钮 UIButtonTypeContactAdd,//蓝色加号(+)按钮，可以放在任何文字旁 } UIButtonType;
UIButton常用属性：
//设置对应状态的标题内容default is nil. title is assumed to be single line
- (void)setTitle:(NSString *)title forState:(UIControlState)state;
//设置对应状态的标题颜色
- (void)setTitleColor:(UIColor *)color forState:(UIControlState)state;
//设置对应状态的标题阴影颜色
- (void)setTitleShadowColor:(UIColor *)color forState:(UIControlState)state;
//设置对应状态的按钮的图片
- (void)setImage:(UIImage *)image forState:(UIControlState)state;
//设置对应状态的按钮背景图片
- (void)setBackgroundImage:(UIImage *)image forState:(UIControlState)state;
UIButton的UIControlState ：
typedef NS_OPTIONS(NSUInteger, UIControlState) { UIControlStateNormal = 0, UIControlStateHighlighted = 1 << 0, // used when UIControl isHighlighted is set UIControlStateDisabled = 1 << 1, UIControlStateSelected = 1 << 2, // flag usable by app (see below) UIControlStateApplication = 0x00FF0000, // additional flags available for application use UIControlStateReserved = 0xFF000000 // flags reserved for internal framework use };
更多属性可参考官方文档。
UIButton添加事件：
[btn addTarget:<#(id)#> action:<#(SEL)#> forControlEvents:<#(UIControlEvents)#>]
这些事件都是基于触摸、基于值、基于编辑。可相应如下事件。
typedef NS_OPTIONS(NSUInteger, UIControlEvents) { UIControlEventTouchDown = 1 << 0, // on all touch downs UIControlEventTouchDownRepeat = 1 << 1, // on multiple touchdowns (tap count > 1) UIControlEventTouchDragInside = 1 << 2, UIControlEventTouchDragOutside = 1 << 3, UIControlEventTouchDragEnter = 1 << 4, UIControlEventTouchDragExit = 1 << 5, UIControlEventTouchUpInside = 1 << 6, UIControlEventTouchUpOutside = 1 << 7, UIControlEventTouchCancel = 1 << 8, UIControlEventValueChanged = 1 << 12, // sliders, etc. UIControlEventEditingDidBegin = 1 << 16, // UITextField UIControlEventEditingChanged = 1 << 17, UIControlEventEditingDidEnd = 1 << 18, UIControlEventEditingDidEndOnExit = 1 << 19, // 'return key' ending editing UIControlEventAllTouchEvents = 0x00000FFF, // for touch events UIControlEventAllEditingEvents = 0x000F0000, // for UITextField UIControlEventApplicationReserved = 0x0F000000, // range available for application use UIControlEventSystemReserved = 0xF0000000, // range reserved for internal framework use UIControlEventAllEvents = 0xFFFFFFFF };
参考：
http://developer.apple.com/library/ios/#documentation/UIKit/Reference/UIButton_Class/UIButton/UIButton.html
一、UIKit结构图