java - ObjectInputStream 无法正确转换对象

Question

我有两个类。在第一个类中，我从List中写入数据，在第二堂课中，我想读取这些数据并将其放入listview中。它正确保存数据，但是当我尝试获取它时，logcat 给出错误:

java.lang.ClassCastException: pl.pawelfrydrych.CHAPS.AdapterPlanuProbOnline$podzialPlanu cannot be cast to pl.pawelfrydrych.CHAPS.AdapterPlanuProbOffline$podzialPlanu
            at pl.pawelfrydrych.CHAPS.AdapterPlanuProbOffline$AdapterDlaPlanu.getView(AdapterPlanuProbOffline.java:115)

我不明白为什么，因为我总是得到相同类型的数据。

一流的写入方法:

public void SaveAsFile(List<podzialPlanu> lista){
// lista - List<podzialPlanu> podzialPlanuList2 = new ArrayList<podzialPlanu>();

        try {
            FileOutputStream saveFile = new FileOutputStream(Environment.getExternalStorageDirectory().getPath() + "/" + "planProby.sav");
            ObjectOutputStream save = new ObjectOutputStream(saveFile);

            save.writeObject(lista);

            save.close();


        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

还有主类，当我尝试从该文件获取数据并将其放入我的 ListView 时

public class AdapterPlanuProbOffline extends Activity implements Serializable {

    List<String> DzienDataList;
    List<String> GodzinaList;
    List<String> RodzajList;
    List<String> ProgramList;
    List<String> UwagiList;
    List<String> listaDni;
    List<String> listaMiesiecy;
    File plik;


    public class podzialPlanu implements Serializable{
        String DzienData;
        String Godzina;
        String Rodzaj;
        String Program;
        String Uwagi;
    }

    AdapterDlaPlanu nowyAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.listviewy);



        nowyAdapter = new AdapterDlaPlanu();

        ListView listView1 = (ListView) findViewById(R.id.listView1);
        listView1.setAdapter(nowyAdapter);

    }



    public class AdapterDlaPlanu extends BaseAdapter implements Serializable{

        List<podzialPlanu> podzialPlanuList = getData();

        @Override
        public int getCount() {
            return podzialPlanuList.size();
        }

        @Override
        public Object getItem(int position) {
            return podzialPlanuList.get(position);
        }

        @Override
        public long getItemId(int position) {
            return position;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {

            if(convertView == null){
               LayoutInflater inflater = (LayoutInflater) AdapterPlanuProbOffline.this.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
               convertView = inflater.inflate(R.layout.planproby,parent,false);
            }



            TextView DzienDataTextView = (TextView) convertView.findViewById(R.id.dzienDataTextView);
            TextView GodzinaTextView = (TextView) convertView.findViewById(R.id.godzinaTextView);
            TextView RodzajZajecTextView = (TextView) convertView.findViewById(R.id.rodzajzajecTextView);
            TextView ProgramTextView = (TextView) convertView.findViewById(R.id.programTextView);
            TextView UwagiTextView = (TextView) convertView.findViewById(R.id.uwagiTextView);




/// here is a problem with getData() method
    DzienDataTextView.setText(getData().get(position).DzienData);
    GodzinaTextView.setText(getData().get(position).Godzina);
    RodzajZajecTextView.setText(getData().get(position).Rodzaj);
    ProgramTextView.setText(getData().get(position).Program);
    UwagiTextView.setText(getData().get(position).Uwagi);



            return convertView;
        }

        public podzialPlanu getPodzialPlanu(int position){
            return podzialPlanuList.get(position);
        }
    }




    public List<podzialPlanu> getData()  {

        List<podzialPlanu> podzialPlanuList2 = new ArrayList<podzialPlanu>();
        List< List<String> > listaGlowna = new ArrayList<List<String>>();


        for( int i = 0; i < 5; i++ ) {
            listaGlowna.add(new ArrayList<String>());
        }

        DzienDataList = new ArrayList<String>();
        GodzinaList = new ArrayList<String>();
        RodzajList = new ArrayList<String>();
        ProgramList = new ArrayList<String>();
        UwagiList = new ArrayList<String>();
        listaDni = new ArrayList<String>();
        listaMiesiecy = new ArrayList<String>();

        try {

            FileInputStream file = new FileInputStream(Environment.getExternalStorageDirectory().getPath() + "/" + "planProby.sav");
            ObjectInputStream restore = new ObjectInputStream(file);

            podzialPlanuList2 = (List<podzialPlanu>) restore.readObject();

            restore.close();

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (StreamCorruptedException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        return podzialPlanuList2;
    }

Answer 1

好吧，让我们看看异常消息:

java.lang.ClassCastException: 
          pl.pawelfrydrych.CHAPS.AdapterPlanuProbOnline$podzialPlanu 
cannot be cast to 
          pl.pawelfrydrych.CHAPS.AdapterPlanuProbOffline$podzialPlanu

你看出区别了吗？请注意，有两个不同的 podzialPlanu类。

现在如果SaveAsFile您的问题中的方法是创建序列化的方法，那么List<podzialPlanu>参数类型实际上指的是:

   pl.pawelfrydrych.CHAPS.AdapterPlanuProbOnline.podzialPlanu

而不是

   pl.pawelfrydrych.CHAPS.AdapterPlanuProbOffline.podzialPlanu

<小时/>

Yes, so what should I do? If is there serialization, then I can't get this data in another class?

好的，所以真正的问题不是序列化。如果您跳过序列化/反序列化步骤，您也会遇到同样的问题。

事实上，这两个嵌套类不相关。您不能在不相关的类之间进行转换。所以你要么需要:

• 仅使用一个内部类
• 强制转换为正确的内部类，或者
• 使内部类相关(例如使用公共(public)接口(interface)或父类(super class))并强制转换为公共(public)父类(super class)型。

假设内部类是public ，您不应该遇到“访问”问题。