ios – UICollectionView委托方法cellForItemAtIndexPath：未从sizeForItemAtIndexPath调用indexPath

[collectionView cellForItemATindexPath:indexPath:]

从内部

[collectionView:layout:sizeForItemATindexPath:]

然后不会触发委托方法.知道为什么不呢？

你可以看到它here.

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemATindexPath:(NSIndexPath *)indexPath {

    Customcatell *cell = [self.collectionView dequeueReusableCellWithReusEIDentifier:@"Customcatell" forIndexPath:indexPath];

    [cell configureWithData:self.data[indexPath.row]];

    return cell;
}


- (CGSizE)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemATindexPath:(NSIndexPath *)indexPath {

    Customcatell * cell = (Customcatell *)[collectionView cellForItemATindexPath:indexPath];

    return [cell preferredSize];
}

我想要做的是询问电池的首选尺寸.

我可以

Customcatell * cell = (Customcatell *)[self collectionView:collectionView cellForItemATindexPath:indexPath];

但随后会触发一个永无止境的循环周期

为什么它的委托方法不应该被调用呢？

解决方法

- (CGSizE)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemATindexPath:(NSIndexPath *)indexPath {

    return [Customcatell preferredSizeWithData:self.data[indexPath.row]; 

}

Customcatell * cell = (Customcatell *)[collectionView cellForItemATindexPath:indexPath];

- (CGSizE)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemATindexPath:(NSIndexPath *)indexPath

Customcatell * cell = (Customcatell *)[self collectionView:collectionView cellForItemATindexPath:indexPath];