滾動時的CollectionView抽動/停頓

Question

我有一個UICollectionView ，它顯示播放列表的列表和播放列表中其中一首歌曲的圖像。

- (UICollectionViewCell *)collectionView:(UICollectionView *)cv cellForItemAtIndexPath:(NSIndexPath *)indexPath; {

    playlistCell*    cell = [cv dequeueReusableCellWithReuseIdentifier:@"Cell" forIndexPath:indexPath];

    if(!cell)
    {
        cell = [[playlistCell alloc] init];
    }

    // Configure the cell...

    MPMediaItem *rowItem = [[playlists objectAtIndex:indexPath.row] representativeItem];

    UIImage *cellBG = [self getAlbumArtworkWithSize:CGSizeMake(320, 320) forPlaylist:[playlists objectAtIndex:indexPath.item]];

    cell.image = cellBG;

    return cell;
}

但是，當我滾動時它會抽動/結巴。 它一點都不平滑，滾動時可能會很痛苦。

我如何使它更平滑？

Answer 1

您可以通過使用GCD在后台加載圖像來使UI更具響應性，如下所示：

- (UICollectionViewCell *)collectionView:(UICollectionView *)cv cellForItemAtIndexPath:(NSIndexPath *)indexPath; {

    playlistCell * cell = [cv dequeueReusableCellWithReuseIdentifier:@"Cell" forIndexPath:indexPath];

    if(!cell)
    {
        cell = [[playlistCell alloc] init];
    }

    // Configure the cell...
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
        MPMediaItem *rowItem = [[playlists objectAtIndex:indexPath.row] representativeItem];
        UIImage *cellBG = [self getAlbumArtworkWithSize:CGSizeMake(320, 320) forPlaylist:[playlists objectAtIndex:indexPath.item]];
        dispatch_async(dispatch_get_main_queue(), ^{
            cell.image = cellBG;
        });
    });
    return cell;
}