用分类用来扩充button的点击响应区域，一行代码即可设置。
UIButton *testButton = [UIButton buttonWithType:UIButtonTypeCustom];
testButton.frame = CGRectMake(self.view.bounds.size.width * 0.5 - 50, self.view.bounds.size.height * 0.5 - 30, 100, 60);
[testButton setTitle:@"点击测试" forState:UIControlStateNormal];
[testButton setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
[testButton setTitleColor:[UIColor lightGrayColor] forState:UIControlStateHighlighted];
[testButton setBackgroundColor:[UIColor colorWithRed:193/255.0 green:193/255.0 blue:193/255.0 alpha:1.0]];
[testButton addTarget:self action:@selector(testButtonAction) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:testButton];
//设置button的额外响应区域
[testButton setEnlargeEdgeWithTop:100 right:100 bottom:100 left:100];