Android 在SharedReferences中存储和检索目录Uri

我正在尝试使用SharedReferences存储和检索目录Uri，但无法使其正常工作

这是我当前用于在用户选择目录后保留目录路径的代码：

        @Override
        public void onActivityResult(int requestCode, int resultCode, Intent data) {
            switch(requestCode) {
                case ACTIVITY_DOCUMENT_TREE:
                    if(resultCode == RESULT_OK) {
                        Uri treeUri = data.getData();
                        DocumentFile pickedDir = DocumentFile.fromTreeUri(getActivity(), treeUri);

                        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(getActivity());
                        SharedPreferences.Editor editor = prefs.edit();
                        editor.putString("the_file", pickedDir.getUri().toString());
                        editor.apply();
                    }
                    break;
            }
        }

这是我从SharedReferences加载目录的当前代码：

SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(getActivity());
String path = prefs.getString("the_file", null);
// the value is:
// content://com.android.externalstorage.documents/tree/primary%3APictures%2FMyApp/document/primary%3APictures%2FMyApp
Uri uri = Uri.parse(path);
File f = new File(uri.toString());
// to test if it was successful, listFiles() - this leads to a NullPointerException
f.listFiles();
// java.lang.NullPointerException: Attempt to get length of null array

我还尝试了uri.getPath（），而不是uri.toString（），结果相同

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我做错了什么？

我现在让它工作了。我尝试从uri字符串创建常规文件对象，而不是DocumentFile

这是调整后的代码：

SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(getActivity());
String path = prefs.getString("the_file", null);
Uri uri = Uri.parse(path);
DocumentFile dir = DocumentFile.fromTreeUri(getActivity(), uri);
dir.listFiles(); // working fine now

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路径中的值是多少？是否已调试并检查？是，路径的值为：content://com.android.externalstorage.documents/tree/primary%3APictures%2FMyApp/document/primary%3APictures%2FMyAppI 将此信息添加到问题中。