アンドロイドに展開可能なリストビューを保存するには？

Question

私は追加可能な拡張可能なリストビューを持っています。どのように私は追加されたすべてのアイテムを保存することができます。 gsonとjsonのsharedpreferencesを使ってみましたが、うまくいかないようです。ここで

public class ExpandListAdapter extends BaseExpandableListAdapter { 
    private Context context; 
    private ArrayList<Group> groups; 

    public ExpandListAdapter(Context context, ArrayList<Group> groups) { 
     this.context = context; 
     this.groups = groups; 
    } 

    @Override 
    public Object getChild(int groupPosition, int childPosition) { 
     ArrayList<Child> chList = groups.get(groupPosition).getItems(); 
     return chList.get(childPosition); 
    } 

    @Override 
    public long getChildId(int groupPosition, int childPosition) { 
     return childPosition; 
    } 

    @Override 
    public View getChildView(int groupPosition, int childPosition, 
         boolean isLastChild, View convertView, ViewGroup parent) { 

     Child child = (Child) getChild(groupPosition, 
        childPosition); 
     if (convertView == null) { 
      LayoutInflater infalInflater = (LayoutInflater) context 
        .getSystemService(context.LAYOUT_INFLATER_SERVICE); 
      convertView = infalInflater.inflate(R.layout.child_row, null); 
     } 
     TextView tv = (TextView) convertView.findViewById(R.id.country_name); 
     tv.setText(child.getName().toString()); 

     return convertView; 

    } 

    @Override 
    public int getChildrenCount(int groupPosition) { 
     ArrayList<Child> chList = groups.get(groupPosition) 
       .getItems(); 

     return chList.size(); 
    } 

    @Override 
    public Object getGroup(int groupPosition) { 
     return groups.get(groupPosition); 
    } 

    @Override 
    public int getGroupCount() { 
     return groups.size(); 
    } 

    @Override 
    public long getGroupId(int groupPosition) { 
     return groupPosition; 
    } 

    @Override 
    public View getGroupView(int groupPosition, boolean isExpanded, 
          View convertView, ViewGroup parent) { 
     Group group = (Group) getGroup(groupPosition); 
     if (convertView == null) { 
      LayoutInflater inf = (LayoutInflater) context 
        .getSystemService(context.LAYOUT_INFLATER_SERVICE); 
      convertView = inf.inflate(R.layout.group_header, null); 
     } 
     TextView tv = (TextView) convertView.findViewById(R.id.group_name); 
     tv.setText(group.getName()); 
     return convertView; 
    } 

    @Override 
    public boolean hasStableIds() { 
     return true; 
    } 

    @Override 
    public boolean isChildSelectable(int groupPosition, int childPosition) { 
     return true; 
    } 

拡張可能なリストビューを使用するクラスは、私はAlertDialogとグループを追加することができますされ、それはまた、単にテストの理由から、「ヨ」の名前で子を追加します。ここに私の拡張可能なリストビュー・アダプタは、次のとおりです。

public class classesScreen extends Activity implements AdapterView.OnItemSelectedListener { 
private ExpandListAdapter ExpAdapter; 
private ExpandableListView ExpandList; 
private Button newHeaderBut; 
static ArrayList<Group> group_list; 
ArrayList<Child> child_list; 
String m_text; 

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

    group_list = new ArrayList<Group>(); 

    ExpandList = (ExpandableListView) findViewById(R.id.classesListView); 
    ExpAdapter = new ExpandListAdapter(this, group_list); 
    ExpandList.setAdapter(ExpAdapter); 


    newHeaderBut = (Button) findViewById(R.id.newClassBut); 

    newHeaderBut.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View v) { 

      AlertDialog.Builder builder = new AlertDialog.Builder(classesScreen.this); 
      builder.setTitle("Add a New Class:"); 

      final EditText input = new EditText(classesScreen.this); 

      builder.setView(input); 

      builder.setPositiveButton("OK", new DialogInterface.OnClickListener() { 
       @Override 
       public void onClick(DialogInterface dialog, int which) { 

        m_text = input.getText().toString(); 

        Group gru1 = new Group(); 
        gru1.setName(m_text); 

        child_list = new ArrayList<Child>(); 

        Child ch1 = new Child(); 
        ch1.setName("Yo"); 

        child_list.add(ch1); 

        gru1.setItems(child_list); 

        group_list.add(gru1); 
        ExpAdapter.notifyDataSetChanged(); 
       } 
      }); 

      builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() { 
       @Override 
       public void onClick(DialogInterface dialog, int which) { 
        dialog.cancel(); 
       } 
      }); 
      builder.show(); 
     }); 
    } 

    public void onItemSelected(AdapterView<?> parent, View view, int position, long id){} 

    public void onNothingSelected(AdapterView<?> arg0) {} 
} 

また、グループと子という2つのオブジェクトクラスがあります。私はあなたがそれらを必要とする場合、それらを表示することができます。前もって感謝します！

Answer 1

はファイル

private void getDataFromFile() { 

    FileInputStream fileInputStream = null; 
    try { 
     fileInputStream = getContext().openFileInput("fileName"); 
    } catch (FileNotFoundException e) { 
     e.printStackTrace(); 
     return; 
    } 
    ObjectInputStream objectInputStream = null; 
    try { 
     objectInputStream = new ObjectInputStream(fileInputStream); 
    } catch (IOException |NullPointerException e) { 
     e.printStackTrace(); 
    } 
    try { 
     yourArrayList = (ArrayList<YourClassName>) objectInputStream.readObject(); 
    } catch (IOException e) { 
     e.printStackTrace(); 
    } catch (ClassNotFoundException e) { 
     e.printStackTrace(); 
    } 
    try { 
     objectInputStream.close(); 
    } catch (IOException e) { 
     e.printStackTrace(); 
    } 

}