java - 在android中的可扩展 ListView 中单击父列表项时加载子项

Question

我正在开发一个包含一个可扩展 ListView 的 Android 应用程序，用于从 Web 服务加载数据，但我不想在启动时加载整个数据，而是先加载父列表，然后在展开 ListView 的特定列表项时加载特定项目的子项目，所以首先是否可能？

我的示例代码:

package adapter;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseExpandableListAdapter;
import android.widget.TextView;

import com.rk.socialsync.R;

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.HashMap;
import java.util.List;

import utils.Global;
import utils.OnlineProperty;

public class ExpandableListAdapter extends BaseExpandableListAdapter {

    private Context _context;
    private List<Date> _listDataHeader;
    private HashMap<Date, List<OnlineProperty>> _listDataChild;

    public ExpandableListAdapter(Context context, List<Date> listDataHeader,
                                 HashMap<Date, List<OnlineProperty>> listChildData) {
        this._context = context;
        this._listDataHeader = listDataHeader;
        this._listDataChild = listChildData;
    }

    @Override
    public OnlineProperty getChild(int groupPosition, int childPosititon) {
        return this._listDataChild.get(this._listDataHeader.get(groupPosition))
                .get(childPosititon);
    }

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

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

        OnlineProperty onlineProperty = getChild(groupPosition, childPosition);

        String child1Text = onlineProperty.getOnlineTime();
        String child2Text = onlineProperty.getOfflineTime();

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

        TextView textOnline = (TextView) convertView.findViewById(R.id.textTimeOnline);
        TextView textOffline = (TextView) convertView.findViewById(R.id.textTimeOffline);
        TextView textView = (TextView) convertView.findViewById(R.id.textTo);

        textView.setTypeface(Global.AppsFont);
        textOnline.setText(child1Text);
        textOffline.setText(child2Text);

        textOffline.setTypeface(Global.AppsFont);
        textOnline.setTypeface(Global.AppsFont);
        return convertView;
    }

    @Override
    public int getChildrenCount(int groupPosition) {
        return this._listDataChild.get(this._listDataHeader.get(groupPosition))
                .size();
    }

    @Override
    public String getGroup(int groupPosition) {
        SimpleDateFormat dateFormat = new SimpleDateFormat("dd/MM/yyyy");
        return dateFormat.format(this._listDataHeader.get(groupPosition));
    }

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

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

    @Override
    public View getGroupView(int groupPosition, boolean isExpanded,
                             View convertView, ViewGroup parent) {
        String headerTitle = (String) getGroup(groupPosition);

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

        TextView textHeader = (TextView) convertView.findViewById(R.id.textExpandable);
        textHeader.setTypeface(Global.AppsFont);
        textHeader.setText(headerTitle);

        return convertView;
    }

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

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

}

其他问题是我想自定义布局更改，例如我在图像中指向的展开按钮，例如 + 和 -

Answer 1

是的，这是可能的，应该通过您的 ExpandableListView 的 OnGroupClickListener 来完成。首先将适配器中的子数组公开并默认初始化:

public HashMap<Date, List<OnlineProperty>> _listDataChild = 
            new HashMap<Date, List<OnlineProperty>>();

下一步覆盖 groupClickListener:

mExpList.setOnGroupClickListener(new ExpandableListView.OnGroupClickListener() {
    @Override
    public boolean onGroupClick(ExpandableListView p, View v, int grpPos, long id) {
        // Check if children not yet fetched
        if (mExpAdapter._listDataChild.get(date) == null) {
            // Fetch list of children for group "grpPos"

            // Add the children to your adapters HashMap
            mExpAdapter._listDataChild.put(date, children);
        }                       
        return false;
    }
});

注释:

• 为避免加载过多，您可以重写适配器中的 onGroupCollapsed 以使其卸载未使用的子项。
• 我提供的代码可能不正确，因为我不知道您的数据结构。你必须适应。