Picker 的配置不是有效配置，Swift

Question

我正在开发 Apple 在 WWDC2020 中提供的名为 PHPicker 的新图像选择器 API。当我 select 第二次从选择器中获取图像时出现此错误。代码第一次完美运行。第二次当我点击按钮打开选择器时，应用程序崩溃并出现以下错误。 “由于未捕获的异常而终止应用程序 'NSInternalInconsistencyException'，原因：‘选择器的配置不是有效配置。’”。

 @IBAction func addVideo(_ sender: UIButton) {
        presentPicker(filter: .videos)
  }

 private func presentPicker(filter: PHPickerFilter?) {
        var configuration = PHPickerConfiguration(photoLibrary: .shared())
        
        // Set the filter type according to the user’s selection.
        configuration.filter = filter
        // Set the mode to avoid transcoding, if possible, if your app supports arbitrary image/video encodings.
        configuration.preferredAssetRepresentationMode = .current
        // Set the selection behavior to respect the user’s selection order.
        configuration.selection = .ordered
        // Set the selection limit to enable multiselection.
        configuration.selectionLimit = 1
        // Set the preselected asset identifiers with the identifiers that the app tracks.
        configuration.preselectedAssetIdentifiers = selectedAssetIdentifiers
        
        let picker = PHPickerViewController(configuration: configuration)
        picker.delegate = self
        present(picker, animated: true)
    }


func picker(_ picker: PHPickerViewController, didFinishPicking results: [PHPickerResult]) {
        dismiss(animated: true)
        
        let existingSelection = self.selection
        var newSelection = [String: PHPickerResult]()
        for result in results {
            let identifier = result.assetIdentifier!
            newSelection[identifier] = existingSelection[identifier] ?? result
        }
        
        // Track the selection in case the user deselects it later.
        selection = newSelection
        selectedAssetIdentifiers = results.map(\.assetIdentifier!)
        selectedAssetIdentifierIterator = selectedAssetIdentifiers.makeIterator()
        
        if selection.isEmpty {
            displayEmptyImage()
        } else {
            displayImage()
        }
    }

我使用的代码与 apple 在其网站上提供的代码相同。 https://developer.apple.com/documentation/photokit/phpickerviewcontroller。我刚刚将 selectionLimit 从 0.

更改为 1

Answer 1

你的代码肯定有问题。我有 copy-pasted 你的解决方案，它在模拟器 (iOS 15.0) 上正常工作。

Answer 2

显然有记录（开玩笑，它在头文件中）preselectedAssetIdentifiers 属性仅在 selectionLimit 大于 1 时有效，这是默认值。

这里是苹果开发者论坛的回答，供参考：https://developer.apple.com/forums/thread/705493

Picker 的配置不是有效配置，Swift

Picker's configuration is not a valid configuration, Swift

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