//宏#define kScreenWidth [UIScreen mainScreen].bounds.size.width#define kScreenHeight [UIScreen mainScreen].bounds.size.height#import "MYMainViewController.h"#import "MYFirstViewController.h"#import "MYSecondViewController.h"#import "MYThirdViewController.h"@interface MYMainViewController ()<UIScrollViewDelegate>//控制器名@property (nonatomic, strong) NSArray *VcNames;//選擇欄@property(nonatomic, strong) UIView *clickBar;//底部容器scrollView@property (strong, nonatomic) UIScrollView *containerScrollerView;@end

@implementation MYMainViewController- (UIScrollView *)containerScrollerView{  if (!_containerScrollerView) {    _containerScrollerView = [[UIScrollView alloc]init];    _containerScrollerView.pagingEnabled = YES;    _containerScrollerView.showsVerticalScrollIndicator = NO;    _containerScrollerView.showsHorizontalScrollIndicator = NO;    _containerScrollerView.contentSize = CGSizeMake(kScreenWidth *self.VcNames.count,kScreenHeight);    _containerScrollerView.backgroundColor = [UIColor whiteColor];    _containerScrollerView.delegate = self;  }  return _containerScrollerView;}

//三個子控制器- (NSArray *)VcNames{  if (!_VcNames) {    _VcNames = @[@"控制器一",@"控制器二",@"控制器三"];  }  return _VcNames;}//點擊選擇欄- (UIView *)clickBar{  if (!_clickBar) {    _clickBar = [[UIView alloc]init];    _clickBar.backgroundColor = [UIColor lightGrayColor];    CGFloat width = kScreenWidth / 3;    CGFloat height = 44;    //初始化按鈕    for (NSInteger index = 0; index < 3; index++) {      UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];      [button setTitle:self.VcNames[index] forState:UIControlStateNormal];      [button setTitleColor:[UIColor blueColor] forState:UIControlStateNormal];      button.frame = (CGRect){width *index,0,width,height};      [button addTarget:self action:@selector(buttonClick:) forControlEvents:UIControlEventTouchUpInside];      //綁定tag值      button.tag = index;      [_clickBar addSubview:button];    }  }  return _clickBar;}

- (void)viewDidLoad {  [super viewDidLoad];  self.edgesForExtendedLayout = 0;  //初始化選擇欄  [self initClickBar];  //初始化底部scrollView容器  [self initScrollViewContainer];  //初始化子控制器  [self addChildControllers];}

//按鈕選擇欄- (void)initClickBar{  [self.view addSubview:self.clickBar];  self.clickBar.frame = (CGRect){0,0,[UIScreen mainScreen].bounds.size.width,44};}//初始化滑動容器- (void)initScrollViewContainer{  [self.view addSubview:self.containerScrollerView];  self.containerScrollerView.frame = CGRectMake(0,44,kScreenWidth, kScreenHeight );}//添加子控制器- (void)addChildControllers{  //為了方便直觀 , 在此處設置背景色 (實際開發中,不能在這里設置 , 原因是這里只要調用到了控制器的view屬性 , 該控制器將會執行viewDidLoad方法 , 相當于直接一開始就將三個控制器的所有UI和網絡請求全加載完了 , 負荷會相當重)  MYFirstViewController *firstVc = [[MYFirstViewController alloc]init];  firstVc.view.backgroundColor = [UIColor redColor];  [self addChildViewController:firstVc];  MYSecondViewController *secondVc = [[MYSecondViewController alloc]init];  secondVc.view.backgroundColor = [UIColor blueColor];  [self addChildViewController:secondVc];  MYThirdViewController *thirdVc = [[MYThirdViewController alloc]init];  thirdVc.view.backgroundColor = [UIColor yellowColor];  [self addChildViewController:thirdVc];  //默認展示第一個子控制器  [self scrollViewDidEndDecelerating:self.containerScrollerView];}

//選擇欄按鈕點擊事件- (void)buttonClick:(UIButton *)button{  [self.containerScrollerView setContentOffset:CGPointMake(button.tag *kScreenWidth, 0) animated:YES];}//滑動減速時調用- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{  //獲取contentOffset  CGPoint currentOffset = scrollView.contentOffset;  NSInteger page = currentOffset.x / kScreenWidth;  //取出對應控制器  UIViewController *viewController = self.childViewControllers;  //添加到scrollView容器  //  if (![viewController isViewLoaded]) {  [self.containerScrollerView addSubview:viewController.view];  viewController.view.frame = CGRectMake(page *kScreenWidth, 0,kScreenWidth, kScreenHeight);  //  }}