Day2

-(void)viewDidLoad
{
    [super viewDidLoad];
    
    UIButton *btn = [[UIButton alloc]init];
    btn.frame = CGRectMake(0, 100, 100, 100);
    [btn setTitle:@"click" forState:UIControlStateNormal];
    [btn setTitleColor:[UIColor redColor] forState:UIControlStateNormal];
    
    UIImage *image = [UIImage imageNamed:@"btn_01"];
    [btn setBackgroundImage:image forState:UIControlStateNormal];
    
    [btn setBackgroundImage:[UIImage imageNamed:@"btn_02"] forState:UIControlStateHighlighted];
    
    [self.view addSubview:btn];
    
}

//添加button点击事件  self.click方法
[btn addTarget:self action:@selector(click:) forControlEvents:UIControlEventTouchUpInside];

self.headImageView = btn;//相当于连线 监听方法连线