UICollectionView的基本使用

这个控件，看起来与UITableView有点像，而且基本的用法也很相像哦！！！

我们来看看API:

#pragma mark - UICollectionViewDataSource
// 指定Section个数
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
  return 3;
}

// 指定section中的collectionViewCell的个数
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
  return 10;
}

// 配置section中的collectionViewCell的显示
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
  CollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"CellIdentifier" forIndexPath:indexPath];
  cell.backgroundColor = [UIColor redColor];
  cell.textLabel.text = [NSString stringWithFormat:@"(%ld %ld)", indexPath.section, indexPath.row];

  return cell;
}

看看直线布局的API：

#pragma mark - UICollectionViewDelegateFlowLayout
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
  return CGSizeMake(self.view.frame.size.width / 3 - 10, self.view.frame.size.width / 3 - 10);
}

// 设置每个cell上下左右相距
- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout insetForSectionAtIndex:(NSInteger)section {
  return UIEdgeInsetsMake(5, 5, 5, 5);
}

// 设置最小行间距，也就是前一行与后一行的中间最小间隔
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section {
  return 10;
}

// 设置最小列间距，也就是左行与右一行的中间最小间隔
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section {
  return 10;
}

// 设置section头视图的参考大小，与tableheaderview类似
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section {
  return CGSizeMake(self.view.frame.size.width, 40);
}

// 设置section尾视图的参考大小，与tablefooterview类似
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForFooterInSection:(NSInteger)section {
  return CGSizeMake(self.view.frame.size.width, 40);
}

如果是固定的，可以使用全局属性：

NS_CLASS_AVAILABLE_IOS(6_0) @interface UICollectionViewFlowLayout : UICollectionViewLayout

@property (nonatomic) CGFloat minimumLineSpacing;
@property (nonatomic) CGFloat minimumInteritemSpacing;
@property (nonatomic) CGSize itemSize;
@property (nonatomic) CGSize estimatedItemSize NS_AVAILABLE_IOS(8_0); // defaults to CGSizeZero - setting a non-zero size enables cells that self-size via -perferredLayoutAttributesFittingAttributes:
@property (nonatomic) UICollectionViewScrollDirection scrollDirection; // default is UICollectionViewScrollDirectionVertical
@property (nonatomic) CGSize headerReferenceSize;
@property (nonatomic) CGSize footerReferenceSize;
@property (nonatomic) UIEdgeInsets sectionInset;

@end

常用到的代理方法：

#pragma mark - UICollectionViewDelegate
// 允许选中时，高亮
- (BOOL)collectionView:(UICollectionView *)collectionView shouldHighlightItemAtIndexPath:(NSIndexPath *)indexPath {
  NSLog(@"%s", __FUNCTION__);
  return YES;
}

// 高亮完成后回调
- (void)collectionView:(UICollectionView *)collectionView didHighlightItemAtIndexPath:(NSIndexPath *)indexPath {
  NSLog(@"%s", __FUNCTION__);
}

// 由高亮转成非高亮完成时的回调
- (void)collectionView:(UICollectionView *)collectionView didUnhighlightItemAtIndexPath:(NSIndexPath *)indexPath {
  NSLog(@"%s", __FUNCTION__);
}

// 设置是否允许选中
- (BOOL)collectionView:(UICollectionView *)collectionView shouldSelectItemAtIndexPath:(NSIndexPath *)indexPath {
  NSLog(@"%s", __FUNCTION__);
  return YES;
}

// 设置是否允许取消选中
- (BOOL)collectionView:(UICollectionView *)collectionView shouldDeselectItemAtIndexPath:(NSIndexPath *)indexPath {
  NSLog(@"%s", __FUNCTION__);
  return YES;
}

// 选中操作
- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath {
  NSLog(@"%s", __FUNCTION__);
}

// 取消选中操作
- (void)collectionView:(UICollectionView *)collectionView didDeselectItemAtIndexPath:(NSIndexPath *)indexPath {
  NSLog(@"%s", __FUNCTION__);
}

demo:https://github.com/632840804/CollectionViewDemo