typedef struct UIEdgeInsets {
  CGFloat top, left, bottom, right; // specify amount to inset (positive) for each of the edges. values can be negative to 'outset'
} UIEdgeInsets;

@property(nonatomic)     UIEdgeInsets contentEdgeInsets UI_APPEARANCE_SELECTOR; // default is UIEdgeInsetsZero
@property(nonatomic)     UIEdgeInsets titleEdgeInsets;        // default is UIEdgeInsetsZero
@property(nonatomic)     BOOL     reversesTitleShadowWhenHighlighted; // default is NO. if YES, shadow reverses to shift between engrave and emboss appearance
@property(nonatomic)     UIEdgeInsets imageEdgeInsets;        // default is UIEdgeInsetsZero

UIKIT_STATIC_INLINE UIEdgeInsets UIEdgeInsetsMake(CGFloat top, CGFloat left, CGFloat bottom, CGFloat right) {
  UIEdgeInsets insets = {top, left, bottom, right};
  return insets;
}
 self.view.backgroundColor = [UIColor blackColor];
  UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];//button的类型
  button.frame = CGRectMake(100, 100,90, 90);//button的frame
  button.backgroundColor = [UIColor cyanColor];//button的背景颜色
//  [button setBackgroundImage:[UIImage imageNamed:@"man_64.png"] forState:UIControlStateNormal];
//  在UIButton中有三个对EdgeInsets的设置：ContentEdgeInsets、titleEdgeInsets、imageEdgeInsets
  [button setImage:[UIImage imageNamed:@"IconHome@2x.png"] forState:UIControlStateNormal];//给button添加image
  button.imageEdgeInsets = UIEdgeInsetsMake(5,13,21,button.titleLabel.bounds.size.width);//设置image在button上的位置（上top，左left，下bottom，右right）这里可以写负值，对上写－5，那么image就象上移动5个像素
  [button setTitle:@"首页" forState:UIControlStateNormal];//设置button的title
  button.titleLabel.font = [UIFont systemFontOfSize:16];//title字体大小
  button.titleLabel.textAlignment = NSTextAlignmentCenter;//设置title的字体居中
  [button setTitleColor:[UIColor whiteColor] forState:UIControlStateNormal];//设置title在一般情况下为白色字体
  [button setTitleColor:[UIColor grayColor] forState:UIControlStateHighlighted];//设置title在button被选中情况下为灰色字体
   button.titleEdgeInsets = UIEdgeInsetsMake(71, -button.titleLabel.bounds.size.width-50, 0, 0);//设置title在button上的位置（上top，左left，下bottom，右right）
//  [button setContentEdgeInsets:UIEdgeInsetsMake(70, 0, 0, 0)];//
//  button.contentHorizontalAlignment = UIControlContentHorizontalAlignmentCenter;//设置button的内容横向居中。。设置content是title和image一起变化
  [button addTarget:self action:@selector(tap) forControlEvents:UIControlEventTouchUpInside];
  [self.view addSubview:button];
//button相应的事件
-(void)tap {
  NSLog(@"tap a button");
  UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"hello" message:@"willingseal" delegate:self cancelButtonTitle:@"ok" otherButtonTitles: nil];
  [alertView show];
}