iOS中左右滑动切换，滑动标签页导航的设计思路
iOS开发中经常（几乎每个APP都含有这样的页面吧，几乎！UI设计师也都是这样抄来抄去…..）
demo见Github：https://github.com/zhengwenming/SliderTab
估计很多人都会说，直接用第三方就可以了，很多人封装过，很好用。而且这样的页面用第三方2分钟搞定，省时省力。 笔者也曾用过第三方，但是屡屡出bug。而且不好修改。所以只能自己写，bug少，代码通俗易懂，童叟无欺。 这里介绍一个第三方DLSlideView，Github地址： https://github.com/agdsdl/DLSlideView，目前达到200多个star。但是中间出了一次bug，说是tableView左滑动删除有问题，后来这个原作者更新了版本，修复了这个bug。但是我使用的过程中又发现一个新bug，就是里面放UIScrollView的时候也有问题。
所以此文章不对代码进行封装，仅提供思路和代码。这样才能真正适配光大开发者（授之以鱼不如授之以渔），因为笔者认为每个页面都有不同，我们需要掌握思路，这样万变不离其宗，任何复杂的UI页面都可以用这个思路去写出来。下面我们来实现这样的一个比较时髦的效果，在导航上面加三个tab（其实就是三个button），支持手势切换，支持点击tab切换。
1.理论分析。 先观察这个效果图，三个UIButton和一个滑动的UILabel，UILabel给一个动画，让他的frame跟随某一个UIButton就可以了。至于跟踪哪个UIButton，当然是点击到的那个UIButton了，那么没点击只是滑动怎么办？UIScrollView的代理里面获取当前获得焦点的UIButton就可以了。三个UIButton分别对应不同的页面，每个页面可能逻辑很多很复杂，这样的话如果写在一个VC里面就显得臃肿了，我们要想办法分离代码，易于维护，并把逻辑分离，这样的话，就要对应3个ViewController。既然支持手势滑动，我们想到的就是UIScrollView，它有分页效果，很6 很87。我们可以把三个vc中的view拿出来，分别贴到UIScrollView上面去（就是addSubView）。理论到此完毕，下面上代码。
2.代码实现。 我们要在HomeViewController里面放一个UIScrollView，然后初始化三个VC，分别拿到三个VC.view,最后把VC.view贴到UIScrollView上面，实现UIScrollView的分页滑动。
#import "HomeViewController.h"#import "NearbyViewController.h"#import "SquareViewController.h"#import "RecommendViewController.h"@interface HomeViewController ()<UIActionSheetDelegate,UIScrollViewDelegate>{UIBarButtonItem *leftButton;NearbyViewController *nearbyVC;SquareViewController *squareVC;RecommendViewController *recommendVC;UIScrollView *mainScrollView;UIView *navView;UILabel *sliderLabel;UIButton *nearbyBtn;UIButton *squareBtn;UIButton *recommendBtn;}@end@implementation HomeViewController//懒加载三个VC-(NearbyViewController *)nearbyVC{if (nearbyVC==nil) { nearbyVC = [[NearbyViewController alloc]init];}return nearbyVC;}-(SquareViewController *)squareVC{if (squareVC==nil) { squareVC = [[SquareViewController alloc]init];}return squareVC;}-(RecommendViewController *)recommendVC{if (recommendVC==nil) { recommendVC = [[RecommendViewController alloc]init];}return recommendVC;}//初始化三个UIBtton和一个滑动的UILabel，命名为sliderLabel，三个btn放倒一个UIView上面navView。-(void)initUI{ navView = [[UIView alloc]initWithFrame:CGRectMake(0, 0, kScreenWidth, 40)];nearbyBtn = [UIButton buttonWithType:UIButtonTypeCustom];nearbyBtn.frame = CGRectMake(0, 0, kScreenWidth/4, navView.frame.size.height);nearbyBtn.titleLabel.font = [UIFont boldSystemFontOfSize:19];[nearbyBtn addTarget:self action:@selector(sliderAction:) forControlEvents:UIControlEventTouchUpInside];[nearbyBtn setTitle:@"附近" forState:UIControlStateNormal];nearbyBtn.tag = 1;[navView addSubview:nearbyBtn];squareBtn = [UIButton buttonWithType:UIButtonTypeCustom];squareBtn.frame = CGRectMake(nearbyBtn.frame.origin.x+nearbyBtn.frame.size.width, nearbyBtn.frame.origin.y, kScreenWidth/4, navView.frame.size.height);squareBtn.titleLabel.font = [UIFont systemFontOfSize:16];[squareBtn addTarget:self action:@selector(sliderAction:) forControlEvents:UIControlEventTouchUpInside];[squareBtn setTitle:@"广场" forState:UIControlStateNormal];squareBtn.tag = 2;[navView addSubview:squareBtn];recommendBtn = [UIButton buttonWithType:UIButtonTypeCustom];recommendBtn.frame = CGRectMake(squareBtn.frame.origin.x+squareBtn.frame.size.width, squareBtn.frame.origin.y, kScreenWidth/4, navView.frame.size.height);recommendBtn.titleLabel.font = [UIFont systemFontOfSize:16];[recommendBtn addTarget:self action:@selector(sliderAction:) forControlEvents:UIControlEventTouchUpInside];[recommendBtn setTitle:@"推荐" forState:UIControlStateNormal];recommendBtn.tag = 3;[navView addSubview:recommendBtn];sliderLabel = [[UILabel alloc]initWithFrame:CGRectMake(0, 40-2, kScreenWidth/4, 4)];sliderLabel.backgroundColor = kBackgroundColor;[navView addSubview:sliderLabel];self.navigationItem.titleView = navView;leftButton = [[UIBarButtonItem alloc]initWithTitle:@"筛选" style:UIBarButtonItemStylePlain target:self action:@selector(leftBarButtonItemPRessed:)];leftButton.tintColor = [UIColor whiteColor];self.navigationItem.leftBarButtonItem = leftButton;}-(UIButton *)theSeletedBtn{if (nearbyBtn.selected) { return nearbyBtn;}else if (squareBtn.selected){ return squareBtn;}else if (recommendBtn.selected){ return recommendBtn;}else{ return nil; }}- (void)viewDidLoad {[super viewDidLoad];[self initUI];[self setMainScrollView];} //初始化UIScrollView-(void)setMainScrollView{mainScrollView = [[UIScrollView alloc]initWithFrame:CGRectMake(0, 0, kScreenWidth, kScreenHeight-kTabBarHeight)];mainScrollView.delegate = self;mainScrollView.backgroundColor = [UIColor whiteColor];mainScrollView.pagingEnabled = YES;mainScrollView.showsHorizontalScrollIndicator = NO;mainScrollView.showsVerticalScrollIndicator = NO;[self.view addSubview:mainScrollView];NSArray *views = @[self.nearbyVC.view, self.squareVC.view,self.recommendVC.view];for (int i = 0; i < views.count; i++){ //添加背景，把三个VC的view贴到mainScrollView上面 UIView *pageView = [[UIView alloc]initWithFrame:CGRectMake(kScreenWidth * i, 0, mainScrollView.frame.size.width, mainScrollView.frame.size.height)]; [pageView addSubview:views[i]]; [mainScrollView addSubview:pageView];}mainScrollView.contentSize = CGSizeMake(kScreenWidth * (views.count), 0);}-(UIButton *)buttonWithTag:(NSInteger)tag{if (tag==1) { return nearbyBtn;}else if (tag==2){ return squareBtn;}else if (tag==3){ return recommendBtn;}else{ return nil;}}-(void)sliderAction:(UIButton *)sender{[self sliderAnimationWithTag:sender.tag];[UIView animateWithDuration:0.3 animations:^{ mainScrollView.contentOffset = CGPointMake(kScreenWidth * (sender.tag - 1), 0);} completion:^(BOOL finished) {}];}-(void)scrollViewDidScroll:(UIScrollView *)scrollView{double index_ = scrollView.contentOffset.x / kScreenWidth;[self sliderAnimationWithTag:(int)(index_+0.5)+1];}#pragma mark - sliderLabel滑动动画- (void)sliderAnimationWithTag:(NSInteger)tag{nearbyBtn.selected = NO;squareBtn.selected = NO;recommendBtn.selected = NO;UIButton *sender = [self buttonWithTag:tag];sender.selected = YES;//动画[UIView animateWithDuration:0.3 animations:^{ sliderLabel.frame = CGRectMake(sender.frame.origin.x, sliderLabel.frame.origin.y, sliderLabel.frame.size.width, sliderLabel.frame.size.height);} completion:^(BOOL finished) { nearbyBtn.titleLabel.font = [UIFont systemFontOfSize:16]; squareBtn.titleLabel.font = [UIFont systemFontOfSize:16]; recommendBtn.titleLabel.font = [UIFont systemFontOfSize:16]; sender.titleLabel.font = [UIFont boldSystemFontOfSize:19];}];}@end好，思路和代码都有了。可以自己去实现了，真的不难，真的不需要用第三方。其实我本可以封装一个给大家用的，但是我没有封装，目的是让每个iOS都能对付UI设计师的这样的页面设计！！
