1,UIButton初始化
(1)initWithFrame
UIButton *btn = [ [UIButton alloc] initWithFrame:CGRectMake(10, 20, 30, 10)];
(2)initWithType
UIButton *btn = [UIButton buttonWithType:UIButtonTypeRoundedRect];
能定义的button类型：
typedef enum {
UIButtonTypeCustom = 0, 自定义风格 最常用
UIButtonTypeRoundedRect, 圆角矩形
UIButtonTypeDetailDisclosure, 蓝色小箭头按钮，主要做详细说明用
UIButtonTypeInfoLight, 亮色感叹号
UIButtonTypeInfoDark, 暗色感叹号
UIButtonTypeContactAdd, 十字加号按钮
} UIButtonType;
2,UIButton常用方法
//设置button在view上的位置
btn.frame = CGRectMake(20, 30, 300, 30);
//设置button背景色
btn.backgroundColor = [UIColor redColor];
//设置button填充图片
[btn setImage: [UIImage imageNamed : @“Com.png”] forState: UIControlStateNormal];
//设置button标题
[btn setTitle: @“Title” forState: UIControlStateNormal]; //按钮默认的文本
[btn1 setTitle:@"我被点了！" forState:UIControlStateHighlighted]; //点击时的文本
//添加按钮事件
[btn addTarget: self action: @selector(btnClick) forControlEvents: UIControlEventTouchUpInside]; //事件方法名字是btnClick
//点击时按钮发光，就是在按钮中间发亮光
btn1.showsTouchWhenHighlighted=YES;
3, forState
作用: 定义按钮的文字或图片在何种状态下才会显现
enum {
UIControlStateNormal = 0, 常规状态显现
UIControlStateHighlighted = 1 << 0, 高亮状态显现
UIControlStateDisabled = 1 << 1, 禁用的状态才会显现
UIControlStateSelected = 1 << 2, 选中状态
UIControlStateApplication = 0x00FF0000, 当应用程序标志时
UIControlStateReserved = 0xFF000000 为内部框架预留，可以不管他
};
4,forControlEvents
作用: 设置触发方式
typedef NS_OPTIONS(NSUInteger, UIControlEvents) {
UIControlEventTouchDown = 1 << 0, // 指鼠标左键按下（注：只是“按下”）的动作
UIControlEventTouchDownRepeat = 1 << 1, // 指鼠标左键连续多次重复按下（注：只是“按下”） 的动作，比如，鼠标连续双击、三击、……、多次连击。
说明：多次重复按下时，事件序列是这样的：
UIControlEventTouchDown ->
UIControlEventTouchUpInside ->
UIControlEventTouchDown ->
UIControlEventTouchDownRepeat ->
UIControlEventTouchUpInside ->
UIControlEventTouchDown ->
UIControlEventTouchDownRepeat ->
UIControlEventTouchUpInside ->
......
除了第一次按下外，后面每次摁下都是一个 UIControlEventTouchDown事件，然后紧跟一个 UIControlEventTouchDownRepeat事件。
UIControlEventTouchDragInside = 1 << 2, // 指按下鼠标，然后在控件边界范围内拖动。
UIControlEventTouchDragOutside = 1 << 3, // 与UIControlEventTouchDragInside不同的是，拖动 时，鼠标位于控件边界范围之外。但首先得有个 UIControlEventTouchDown事件，然后接一个 UIControlEventTouchDragInside事件，再接一个 UIControlEventTouchDragExit事件，这时，鼠标已 经位于控件外了，继续拖动就是 UIControlEventTouchDragOutside事件了。
UIControlEventTouchDragEnter = 1 << 4, // 指拖动动作中，从控件边界外到内时产生的事件。
UIControlEventTouchDragExit = 1 << 5, //指拖动动作中，从控件边界内到外时产生的事件。
UIControlEventTouchUpInside = 1 << 6, //指鼠标在控件范围内抬起,前提先得按下,即 UIControlEventTouchDown或 UIControlEventTouchDownRepeat事件。
UIControlEventTouchUpOutside = 1 << 7, //指鼠标在控件边界范围外抬起，前提先得按下，然后拖 动到控件外，即
UIControlEventTouchDown ->
UIControlEventTouchDragInside(n 个) ->
UIControlEventTouchDragExit ->
UIControlEventTouchDragOutside(n 个)
时间序列，再然后就是抬起鼠标，产生 UIControlEventTouchUpOutside事件。
UIControlEventTouchCancel = 1 << 8, //所有触摸取消事件，即一次触摸因为放上了太多手指而被取消，或者被上锁或者电话呼叫打断。
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
};