UIButton的使用

使用UIButton时需要注意的是：

1.UIButton的创建有专门的类方法（buttonWithType:，UILabel没有）；

2.UIButton常用的属性包括：frame、titile、tag等；

3.UIButton使用addTarget方法关联处理方法，一个UIButton可以有多个不同的按钮响应方法，多个UIButton也可以共享一个处理方法（用tag做区分）；

// 创建文件按钮
- (void) createRectUI {
    // 穿件圆角矩形按钮
    UIButton *btn1 = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    btn1.frame = CGRectMake(100, 100, 100, 50);
    [btn1 setTitle:@"按钮1" forState:UIControlStateNormal];
    btn1.titleLabel.font = [UIFont systemFontOfSize:18];
    [self.view addSubview:btn1];
    
    UIButton *btn2 = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    btn2.frame = CGRectMake(100, 200, 100, 50);
    [btn2 setTitle:@"按钮2" forState:UIControlStateNormal];
    btn2.titleLabel.font = [UIFont systemFontOfSize:18];
    [self.view addSubview:btn2];
    
    btn1.tag = 101;
    [btn1 addTarget:self action:@selector(btnPressed:) forControlEvents:UIControlEventTouchUpInside];
    btn2.tag = 102;
    [btn2 addTarget:self action:@selector(btnPressed:) forControlEvents:UIControlEventTouchUpInside];
}

- (void) btnPressed : (UIButton*) btn {
    NSInteger tag = btn.tag;
    if(tag == 101){
        NSLog(@"btn1 pressed!");
    }else{
        NSLog(@"btn2 pressed!");
    }
}