ios - 在 iOS Carplay 中延迟加载数据

Question

用户在 Carplay 中滚动时如何延迟加载项目？

我正在使用 MPPlayableContentDataSource 中的 beginLoadingChildItems 来加载第一组项目，但是当用户滚动到页面底部时如何调用下一页？

标签： iosswiftios13carplay

Answer 1

您可以在以下函数中实现这一点：

func beginLoadingChildItems(at indexPath: IndexPath, completionHandler: @escaping (Error?) -> Void)

例如：

if (indexPath[componentIndex] + 1) % Threshold == 0 { // Threshold is Your Defined Batch Size

    // Load the next corresponding batch 

}

加载你的惰性数据，然后调用：

completionHandler(nil) // In case of no error has occurred

，但首先，您需要在以下函数中正确返回项目总数：

func numberOfChildItems(at indexPath: IndexPath) -> Int

---

像下面这样的东西，

class YourDataSource : MPPlayableContentDataSource {

    private var items = [MPContentItem]()
    private var currentBatch = 0

    func beginLoadingChildItems(at indexPath: IndexPath, completionHandler: @escaping (Error?) -> Void) {

        // indexPath[1]: is current list level, as per CarPlay list indexing (It's an array of the indices as ex: indexPath = [0,1] means Index 0 in the first level and index 1 at the second level).
        // % 8: Means each 8 items, I will perform the corresponding action.
       // currentBatch + 1 == nextBatch, This check in order to ensure that you load the batches in their sequences.

        let currentCount = indexPath[1] + 1

        let nextBatch = (currentCount / 8) + 1

        if currentCount % 8 == 0 && currentBatch + 1 == nextBatch { 

            // Load the next corresponding batch 
            YourAPIHandler.asyncCall { newItems in

                self.currentBatch = self.currentBatch + 1

                items.append(newItems)

                completionHandler(nil)

                MPPlayableContentManager.shared().reloadData()

            }

        } else {

            completionHandler(nil)

        }


    }

}

func numberOfChildItems(at indexPath: IndexPath) -> Int {

    return self.items.count

}