我正在尝试使用SharedPreferences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;
}
}
这是我当前用于从SharedPreferences中加载目录的代码:
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
我也尝试了uri.getPath(),而不是uri.toString(),结果相同。
我在这里做什么错了?
答案 0 :(得分:0)
我现在开始工作了。我尝试使用uri字符串创建常规File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