文件输入 stream 需要从 Object 读取

Question

我正在尝试将数据 onDestroy 方法保存在 bottomsheetDialogFragment 中。 我正在保存有关destroy 方法的信息并获取有关onCreate 方法的保存信息。

但我在这条特定线上遇到错误

listOfItem= new ArrayList<> (Arrays.asList ( split ) );

我正在使用来自 Item class 的 recylerView 添加列表，但我不知道如何将拆分字符串添加到 ArrayList 中。

希望你能理解我的问题。 下面是我的代码非常感谢

public class CustomFragment_1 extends BottomSheetDialogFragment {

private RecyclerView recyclerView;
private CustomAdapter_1 mAdapter;
ArrayList<Item> listOfItem;


String cName;
Button btn;
FlatDialog flatDialog;
EditText editText;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View view = inflater.inflate ( R.layout.fragment_custom_1, container, false );


    recyclerView = (RecyclerView) view.findViewById ( R.id.customRV );
    btn = (Button) view.findViewById ( R.id.button1 );
    editText = (EditText) view.findViewById ( R.id.edt1 );


    LinearLayoutManager linearLayoutManager = new LinearLayoutManager ( getContext () );
    recyclerView.setLayoutManager ( linearLayoutManager );

    listOfItem = new ArrayList<> ();

    mAdapter = new CustomAdapter_1 ( getContext (), listOfItem );
    recyclerView.setAdapter ( mAdapter );

    listOfItem.add ( new Item ( "FreeNow" ) );
    listOfItem.add ( new Item ( "Uber" ) );
    listOfItem.add ( new Item ( "Bolt" ) );


    btn.setOnClickListener ( new View.OnClickListener () {
        @Override
        public void onClick(View view) {


            flatDialog = new FlatDialog ( getActivity () );
            flatDialog.setTitle ( "Company Name" )
                    .setSubtitle ( "Please add the name of the company" )
                    .setFirstTextFieldHint ( "Company Name" )
                    .setFirstButtonText ( "ADD" )
                    .setSecondButtonText ( "CANCEL" )
                    .withFirstButtonListner ( new View.OnClickListener () {
                        @Override
                        public void onClick(View view) {

                            cName = flatDialog.getFirstTextField ();
                            listOfItem.add ( new Item ( cName ) );
                            mAdapter.notifyItemInserted ( listOfItem.size () );

                            flatDialog.dismiss ();

                        }
                    } )
                    .withSecondButtonListner ( new View.OnClickListener () {
                        @Override
                        public void onClick(View view) {
                            flatDialog.dismiss ();
                        }
                    } )
                    .show ();


        }

    } );

    loadContent ();
    return view;
}

public void loadContent() {
    File path = getActivity ().getFilesDir ();
    File readFrom = new File ( path, "list.txt" );
    byte[] content = new byte[(int) readFrom.length ()];

    FileInputStream stream = null;

    try {
        stream = new FileInputStream ( readFrom );
        stream.read ( content );

        String s = new String ( content );
        s = s.substring ( 1, s.length () - 1 );
        String split[] = s.split ( ", " );

        listOfItem = new ArrayList<> ( Arrays.asList ( split ) );

        mAdapter = new CustomAdapter_1 ( getContext (), listOfItem );
        recyclerView.setAdapter ( mAdapter );
    } catch (Exception e) {
        e.printStackTrace ();
    }


}

@Override
public void onDestroy() {
    File path = getContext ().getFilesDir ();
    try {
        FileOutputStream writer = new FileOutputStream ( new File ( path, "list.txt" ) );
        writer.write ( listOfItem.toString ().getBytes () );
        writer.close ();
    } catch (Exception e) {
        e.printStackTrace ();
    }


    super.onDestroy ();
}

}

下面是我得到的错误

error: incompatible types: cannot infer type arguments for ArrayList<>
        listOfItem = new ArrayList<> ( Arrays.asList ( split ) );
                                  ^
reason: inference variable E has incompatible bounds
  equality constraints: Item
  lower bounds: T,String
where E,T are type-variables:
E extends Object declared in class ArrayList
T extends Object declared in method <T>asList(T...)

Answer 1

我将回避您的实际错误，因为您的代码存在多个问题，然后我会建议一种更好的方法来做到这一点。

首先，您应该知道 onDestroy() 并不总是被调用（例如，当应用程序被强制关闭时）。

其次，您尝试在 UI 线程上执行 IO，这将导致您的应用程序在读取和写入数据时都冻结。

您最好使用SharedPreferences之类的东西来存储您的listOfItem数组。 并且您需要在数组更改时将其保存到SharedPreferences ，而不仅仅是 onDestroy()。 这样，即使未调用 onDestroy()，它也将始终是最新的。

最后，如果您坚持自己将对象写入文件存储，最好使用 object 序列化库，例如GSON 。 没有理由重新发明轮子。