ExpandableListview：要在每個組下添加子列表延遲加載

Question

我已經實現了expandablelistview及其工作正常。 現在，我想在每個子列表的末尾添加“加載更多”按鈕，因此，如果用戶單擊它，它將從服務器獲取更多項。 無論如何，這樣做是因為經過大量搜索后我找不到任何東西。 任何指導是非常感謝。

這是我的自定義適配器：

public class ExpandableListAdapterAssets extends BaseExpandableListAdapter implements Filterable {

List<View> groupViews;
ItemFilter mFilter;
boolean showCheckBox;
ArrayList<Asset> assetsToClaim;
private Context _context;
private List<AssetCategory> _listDataHeader; // header titles
// child data in format of header title, child title
private HashMap<Integer, List<Asset>> _listDataChild;
private RequestBackendHelper requestBackendHelper;

public ExpandableListAdapterAssets(Context context, List<AssetCategory> listDataHeader,
                                   HashMap<Integer, List<Asset>> listChildData, boolean b)
{
    this._context = context;
    this._listDataHeader = listDataHeader;
    this._listDataChild = listChildData;
    groupViews = new ArrayList<>();
    showCheckBox = b;
    assetsToClaim = new ArrayList<>();
}

@Override
public Asset getChild(int groupPosition, int childPosition)
{
    return this._listDataChild.get(this._listDataHeader.get(groupPosition).getId())
            .get(childPosition);
}


public List<Asset> getChildList(int groupPosition)
{
    return this._listDataChild.get(this._listDataHeader.get(groupPosition).getId());
}

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

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

    final Asset assetChild = getChild(groupPosition, childPosition);

    if (convertView == null)
    {
        LayoutInflater infalInflater = (LayoutInflater) this._context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = infalInflater.inflate(R.layout.list_item, null);
    }

    TextView assetName = (TextView) convertView
            .findViewById(R.id.txt_asset_name);

    assetName.setText(assetChild.getName());

    TextView assetValue = (TextView) convertView
            .findViewById(R.id.txt_asset_value);

    assetValue.setText(getFormattedAmount(assetChild.getValue()));

    ((TextView) convertView.findViewById(R.id.txt_asset_category)).setText(assetChild.getAssetCategory());
    ((TextView) convertView.findViewById(R.id.txt_asset_date)).setText(assetChild.getCreationDate());
    if (showCheckBox)
    {
        CheckBox itemSelect = convertView.findViewById(R.id.chkbox_item_select);
        itemSelect.setVisibility(View.VISIBLE);
        itemSelect.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked)
            {
                if (isChecked)
                {
                    assetsToClaim.add(getChild(groupPosition, childPosition));
                    Log.d("checkbox", "checked: ");
                }
                else
                {
                    assetsToClaim.remove(getChild(groupPosition, childPosition));
                }


            }
        });
    }
    else
    {

    }
    return convertView;
}

@Override
public int getChildrenCount(int groupPosition)
{
    if (_listDataChild == null)
        return 0;
    else if (_listDataChild.size() == 0)
        return 0;

    else
    {
        int position = this._listDataHeader.get(groupPosition).getId();
        int count = this._listDataChild.get(position).size();
        return count;
    }

}

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


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

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

@Override
public View getGroupView(final int groupPosition, boolean isExpanded,
                         View convertView, final ViewGroup parent)
{
    if (convertView == null)
    {
        LayoutInflater infalInflater = (LayoutInflater) this._context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = infalInflater.inflate(R.layout.list_group, null);
    }

    TextView lblListHeader = (TextView) convertView
            .findViewById(R.id.lblListHeader);
    lblListHeader.setTypeface(null, Typeface.BOLD);
    lblListHeader.setText(_listDataHeader.get(groupPosition).getName());
groupViews.add(convertView);
    return convertView;
}

private void requestDeleteCategory(final int groupPosition)
{
    requestBackendHelper = new RequestBackendHelper(_context);
    if (getChildrenCount(groupPosition) == 0)
    {

        requestBackendHelper.deleteCategory(_listDataHeader.get(groupPosition).getId(), _context.getSharedPreferences(MY_PREFS_NAME, Context.MODE_PRIVATE).getString("jwt", "")
                , new VolleyCallBack() {
                    @Override
                    public void onSuccess(String result)
                    {
                        try
                        {
                            JSONObject parentObj = new JSONObject(result);
                            if (parentObj.getBoolean("status"))
                            {
                                requestBackendHelper.createErrorDialog("Category Deleted.", "success");
                                _listDataHeader.remove(groupPosition);
                                _listDataChild.remove(_listDataHeader.get(groupPosition));
                                notifyDataSetChanged();
                            }
                            else
                            {
                                requestBackendHelper.createErrorDialog(parentObj.getString("error"), "");
                            }
                        }
                        catch (JSONException e)
                        {
                            e.printStackTrace();
                        }
                    }

                    @Override
                    public void onFailure(VolleyError error)
                    {
                        requestBackendHelper.createErrorDialog(error.toString(), "");
                    }
                });
    }
    else
    {
        requestBackendHelper.createErrorDialog("The category cannot be deleted until all assets are removed.", "");
    }
}

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

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

public List<View> getGroupViewList()
{
    return groupViews;
}

private void loadEditCategoryAlertDialog(final int groupPosition)
{
    View viewInflated = LayoutInflater.from(_context).inflate(R.layout.activity_add_category_dialog, null);
    final EditText nameInput = viewInflated.findViewById(R.id.categoryNameEditText);
    viewInflated.findViewById(R.id.categoryDescriptionEditText).setVisibility(View.GONE);
    final TextView errorLabel = viewInflated.findViewById(R.id.errorTextView);

    final AlertDialog dialog = new AlertDialog.Builder(_context)
            .setView(viewInflated)
            .setTitle("Edit Category")
            .setPositiveButton(android.R.string.ok, null)
            .setNegativeButton(android.R.string.cancel, null)
            .setCancelable(false)
            .create();

    dialog.setOnShowListener(new DialogInterface.OnShowListener() {
        @Override
        public void onShow(DialogInterface dialogInterface)
        {
            Button okButton = (dialog).getButton(AlertDialog.BUTTON_POSITIVE);
            okButton.setOnClickListener(new DebouncedOnClickListener() {

                @Override
                public void onDebouncedClick(View view)
                {
                    final String categoryName = nameInput.getText().toString();
                    requestRenameCategory(categoryName, groupPosition, dialog, errorLabel);

                }
            });
        }
    });
    dialog.show();
}

private void requestRenameCategory(final String categoryName, final int groupPosition, AlertDialog dialog, TextView errorLabel)
{
    if (categoryName.isEmpty())
    {
        errorLabel.setText(R.string.add_category_validation_error);
    }
    else
    {
        if (requestBackendHelper == null)
            requestBackendHelper = new RequestBackendHelper(_context);
        requestBackendHelper.attemptEditAssetCategory(createEditCategoryJson(categoryName), _listDataHeader.get(groupPosition).getId()
                , _context.getSharedPreferences(MY_PREFS_NAME, Context.MODE_PRIVATE).getString("jwt", "")
                , new VolleyCallBack() {
                    @Override
                    public void onSuccess(String result)
                    {
                        _listDataHeader.get(groupPosition).setName(categoryName);
                        int size = _listDataHeader.get(groupPosition).getAssetCout();
                        for (Asset asset : getChildList(groupPosition))
                            asset.setAssetCategory(categoryName);
                        notifyDataSetChanged();
                                       }
                        notifyDataSetChanged();
                    }

                    @Override
                    public void onFailure(VolleyError error)
                    {

                    }
                });
        dialog.dismiss();
    }
}

private JSONObject createEditCategoryJson(String categoryName)
{
    JSONObject messageObj = new JSONObject();
    JSONObject assetCategoryObj = new JSONObject();
    try
    {
        messageObj.put("name", categoryName);
        assetCategoryObj.put("asset_category", messageObj);
        return assetCategoryObj;
        //contactusObj.put(message);
    }
    catch (JSONException e)
    {
        e.printStackTrace();
    }
    return null;

}

/**
 * <p>Returns a filter that can be used to constrain data with a filtering
 * pattern.</p>
 *
 * <p>This method is usually implemented by {@link Adapter}
 * classes.</p>
 *
 * @return a filter used to constrain data
 */
@Override
public Filter getFilter()
{
    if (mFilter == null)
    {
        mFilter = new ItemFilter();
    }
    return mFilter;
}

private class ItemFilter extends Filter {

    protected FilterResults performFiltering(CharSequence constraint)
    {

        FilterResults results = new FilterResults();

        return results;
    }

    /**
     * <p>Invoked in the UI thread to publish the filtering results in the
     * user interface. Subclasses must implement this method to display the
     * results computed in {@link #performFiltering}.</p>
     *
     * @param constraint the constraint used to filter the data
     * @param results    the results of the filtering operation
     * @see #filter(CharSequence, FilterListener)
     * @see #performFiltering(CharSequence)
     * @see FilterResults
     */
    @Override
    protected void publishResults(CharSequence constraint, FilterResults results)
    {

    }
}

}

這是我設置適配器的方式：

explistAdapter = new ExpandableListAdapterAssets(getActivity(), assetCategories, listDataChild, false);
    expListView.setAdapter(explistAdapter);

Answer 1

您需要使用自定義BaseExpandableAdapter插入“加載更多”按鈕。 此答案似乎相關，因為它顯示了如何提供兩種不同類型的子視圖。 棘手的事情是，當單擊“加載更多”按鈕時，必須將其刪除，然后需要將新項目與底部的一個新的“加載更多”按鈕一起附加在一起-然后是子適配器需要通知。 它的行為必須類似於虛擬列表項，其中getChildView()提供當前的childPosition 。

剛剛看到提供的代碼； 使用Volley，您最有可能需要在第一次加載時少獲取一個項目，這樣適配器就不會由於添加了一個額外的虛擬項目而運行不同步-或至少在最后添加了view-type 2網絡請求，然后再將其添加到適配器中。 另一個選擇可能是讓getChildCount()返回少一個； 在分頁時，在任何情況下都必須注意這個額外的項目。