把UIButton包装成UIBarButtonItem.就导致按钮点击区域扩大
UIButton *btn = [UIButton buttonWithType:UIButtonTypeCustom];
[btn setImage:[UIImage imageNamed:@"nav_item_game_icon"] forState:UIControlStateNormal];
[btn setImage:[UIImage imageNamed:@"nav_item_game_click_icon"] forState:UIControlStateHighlighted];
[btn sizeToFit];
[btn addTarget:self action:@selector(game) forControlEvents:UIControlEventTouchUpInside];
UIView *containView = [[UIView alloc]initWithFrame:btn.bounds];
[containView addSubview:btn];
self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc]initWithCustomView:containView];