在iOS Carplay中延迟加载数据 [英] Lazy Loading Data in iOS Carplay
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问题描述
当用户在Carplay中滚动时,如何延迟加载项目?
How to lazy load the items while the user scrolling in Carplay ?
我正在使用MPPlayableContentDataSource中的beginLoadingChildItems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?
I am using beginLoadingChildItems from MPPlayableContentDataSource to load the first set of items but how I can call the next page when a user scrolls to the bottom of the page?
推荐答案
实现此目的的方法是在以下函数中:
The way you can achieve this is inside the following function:
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
}
加载您的惰性数据,然后致电:
Load your lazy data, then call:
completionHandler(nil) // In case of no error has occurred
,但是首先,您需要在以下函数中正确返回项目总数:
,but firstly, you need to return the total items count correctly in the following function:
func numberOfChildItems(at indexPath: IndexPath) -> Int
类似下面的内容,
Something like the below,
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
}
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