iOS实现简单的二级菜单效果

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#import "ViewController.h"
#import "CollectionViewCell.h"
#import "CollectionSectionView.h"
@interface ViewController ()<UICollectionViewDelegateFlowLayout,UICollectionViewDataSource>
@property (nonatomic,strong)UICollectionView *collectionView;
@property (nonatomic,copy)NSString *leftOrRight;
@property (nonatomic,strong)NSIndexPath *clickIndexPath;
@end
static NSString *cellIdentifier = @"CollectionViewCell";
static NSString *sectionIdentifier = @"CollectionSectionView";
@implementation ViewController

- (void)viewDidLoad {
 [super viewDidLoad];
 // Do any additional setup after loading the view, typically from a nib.
 UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc] init];
 flowLayout.itemSize = CGSizeMake(50, 25);
 flowLayout.minimumLineSpacing = 0;
 flowLayout.minimumInteritemSpacing = 0;
 flowLayout.headerReferenceSize = CGSizeMake(0, 40);
 flowLayout.sectionInset = UIEdgeInsetsMake(0, 0, 0, 0);
 self.collectionView = [[UICollectionView alloc] initWithFrame:self.view.frame collectionViewLayout:flowLayout];
 _collectionView.backgroundColor = [UIColor whiteColor];
 _collectionView.delegate = self;
 _collectionView.dataSource = self;
 [_collectionView registerClass:[CollectionViewCell class] forCellWithReuseIdentifier:cellIdentifier];
 [_collectionView registerClass:[CollectionSectionView class] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:sectionIdentifier];
 [self.view addSubview:_collectionView];
}
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView{
 return 3;
}
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section{
 if (self.clickIndexPath.section == section) {
  if (self.clickIndexPath.section == 0 && [self.leftOrRight isEqualToString:@"left"]) {
   return 3;
  }
  if (self.clickIndexPath.section == 0 && [self.leftOrRight isEqualToString:@"right"]) {
   return 4;
  }
  if (self.clickIndexPath.section == 1 && [self.leftOrRight isEqualToString:@"left"]) {
   return 10;
  }
  if (self.clickIndexPath.section == 1 && [self.leftOrRight isEqualToString:@"right"]) {
   return 8;
  }
  if (self.clickIndexPath.section == 2 && [self.leftOrRight isEqualToString:@"left"]) {
   return 33;
  }
  if (self.clickIndexPath.section == 2 && [self.leftOrRight isEqualToString:@"right"]) {
   return 6;
  }
 }
 return 0;
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
 CollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:cellIdentifier forIndexPath:indexPath];
 cell.label.text = [NSString stringWithFormat:@"%ld-%ld",indexPath.section,indexPath.row];
 return cell;
}
- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath{
 if ([kind isEqualToString:UICollectionElementKindSectionHeader]) {
  CollectionSectionView *sectionView = [collectionView dequeueReusableSupplementaryViewOfKind:kind withReuseIdentifier:sectionIdentifier forIndexPath:indexPath];
  sectionView.backgroundColor = [UIColor lightGrayColor];
  sectionView.leftStr = @"家具";
  sectionView.rightStr = @"家电";
  [sectionView customBtnHandelAction:^(NSString *leftOrRight) {
   self.clickIndexPath = indexPath;
   self.leftOrRight = leftOrRight;
   [collectionView reloadData];
  }];
  return sectionView;
 }
 return nil;
}
- (void)didReceiveMemoryWarning {
 [super didReceiveMemoryWarning];
 // Dispose of any resources that can be recreated.
}

#import <UIKit/UIKit.h>
typedef void(^BtnHandleAction)(NSString *leftOrRight);
@interface CollectionSectionView : UICollectionReusableView
@property (nonatomic,copy)NSString *leftStr;
@property (nonatomic,copy)NSString *rightStr;
- (void)customBtnHandelAction:(BtnHandleAction)action;
@end

#import "CollectionSectionView.h"
@interface CollectionSectionView ()
@property (nonatomic,strong)UIButton *leftBtn;
@property (nonatomic,strong)UIButton *rightBtn;
@property (nonatomic,copy)BtnHandleAction btnHandelAction;
@end
@implementation CollectionSectionView
- (instancetype)initWithFrame:(CGRect)frame
{
 self = [super initWithFrame:frame];
 if (self) {
  [self setup];
 }
 return self;
}
- (UIButton *)leftBtn{
 if (!_leftBtn) {
  self.leftBtn = [UIButton buttonWithType:(UIButtonTypeCustom)];
  _leftBtn.tag = 2000;
  _leftBtn.frame = CGRectMake(1, 1, self.frame.size.width / 2 - 2, self.frame.size.height - 2);
  _leftBtn.backgroundColor = [UIColor whiteColor];
  [_leftBtn addTarget:self action:@selector(btnAction:) forControlEvents:(UIControlEventTouchUpInside)];
 }
 return _leftBtn;
}
- (UIButton *)rightBtn{
 if (!_rightBtn) {
  self.rightBtn = [UIButton buttonWithType:(UIButtonTypeCustom)];
  _rightBtn.tag = 2001;
  _rightBtn.frame = CGRectMake(self.frame.size.width / 2 + 1, 1, self.frame.size.width / 2 - 2, self.frame.size.height - 2);
  _rightBtn.backgroundColor = [UIColor whiteColor];
  [_rightBtn addTarget:self action:@selector(btnAction:) forControlEvents:(UIControlEventTouchUpInside)];
 }
 return _rightBtn;
}
- (void)btnAction:(UIButton *)sender{
 NSInteger tag = sender.tag;
 if (tag == 2000) {
  self.btnHandelAction(@"left");
 }
 if (tag == 2001) {
  self.btnHandelAction(@"right");
 }
}
- (void)customBtnHandelAction:(BtnHandleAction)action{
 self.btnHandelAction = action;
}
- (void)setup{
 [self addSubview:self.leftBtn];
 [self addSubview:self.rightBtn];
}
- (void)setLeftStr:(NSString *)leftStr{
 [self.leftBtn setTitle:leftStr forState:(UIControlStateNormal)];
 [self.leftBtn setTitleColor:[UIColor blackColor] forState:(UIControlStateNormal)];
}
- (void)setRightStr:(NSString *)rightStr{
 [self.rightBtn setTitle:rightStr forState:(UIControlStateNormal)];
 [self.rightBtn setTitleColor:[UIColor blackColor] forState:(UIControlStateNormal)];
}
@end