UICollectionViewFlowLayout *flowLayOut = [[UICollectionViewFlowLayout alloc] init];
_collectionView = [[UICollectionView alloc] initWithFrame:CGRectMake(0, 29, DEVICE_SCREEN_WIDTH, DEVICE_SCREEN_HEIGHT-DEVICE_STATUS_BAR_HEIGHT-DEVICE_NAVIGATION_BAR_HEIGHT - 29) collectionViewLayout:flowLayOut];
_collectionView.delegate = self;
_collectionView.dataSource = self;
_collectionView.backgroundColor = COLOR_HEX(0xf7f7f7, 1.0);
[self.view addSubview:_collectionView];
[_collectionView registerNib:[UINib nibWithNibName:@"InstallUnitCollectionViewCell" bundle:[NSBundle mainBundle]] forCellWithReuseIdentifier:@"InstallUnitCollectionViewCell"];

pragma mark ---- UICollectionViewDataSource

• (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
  {
  InstallUnitCollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"InstallUnitCollectionViewCell" forIndexPath:indexPath];
  return cell;
  }

• (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
  {
  return 1;
  }

• (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
  {

  return 5;
  }

• (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
  {

}

pragma mark ---- UICollectionViewDelegateFlowLayout

• (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
  {
  CGSize size = CGSizeMake((DEVICE_SCREEN_WIDTH-40)/3, (DEVICE_SCREEN_WIDTH-40)/3);
  return size;
  }

• (UIEdgeInsets)collectionView:(UICollectionView )collectionView layout:(UICollectionViewLayout)collectionViewLayout insetForSectionAtIndex:(NSInteger)section
  {
  //左右的又兼具
  return UIEdgeInsetsMake(10,10, 0, 0);
  }

//- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section
//{
// //上下距离
// return 10;
//
//}

• (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section
  {
  return 0.0001;
  }