利用 Button自带的titleLabel和imageView，用来设置label和image的排列方式，eg：上下、左右 UIEdgeInsetsMake
里面的四个参数表示距离上边界、左边界、下边界、右边界的距离，默认都为零，title／image在button的正中央
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]; [objc]
//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 nil];
[alertView show]; }
