Question

我有一个可扩展的列表视图，我也可以添加。如何保存添加的每个项目。我已经尝试将共享偏好与gson一起使用到json，但这似乎不起作用。这是我的可扩展listview适配器：

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;
    }

以下是使用可扩展列表视图的类，我可以使用AlertDialog添加组，并且还添加名为“Yo”的子项，仅用于测试原因：

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) {}
}

我还有两个名为Group和Child的对象类。如果你需要它我可以展示它们。提前谢谢！

Answer 1

让你的模型类实现Serializable

将最新的arrayList保存到文件中

RegExp

从文件中检索数据

    private void saveDataToFile() {

    FileOutputStream fileOutputStream = null;
    try {
        fileOutputStream = getContext().openFileOutput("fileName", Context.MODE_PRIVATE);
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (NullPointerException e) {

    }
    ObjectOutputStream objectOutputStream = null;
    try {
        objectOutputStream = new ObjectOutputStream(fileOutputStream);
    } catch (IOException e) {
        e.printStackTrace();
    } catch (NullPointerException e) {

    }
    try {
        if (objectOutputStream != null) {
            objectOutputStream.writeObject(yourArrayList); //which data u want to save
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
    try {
        if (objectOutputStream != null) {
            objectOutputStream.close();
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}

如何在android中保存可扩展的列表视图？

1 个答案: