可折叠组件（好友列表）小案例

package com.example.demo; import android.content.Context; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.BaseExpandableListAdapter; import android.widget.ImageView; import android.widget.TextView; import java.util.List; import java.util.Map; /** * 自定义的适配器 */ public class CustomExpandListAdapter extends BaseExpandableListAdapter { private final Context context; private final LayoutInflater layoutInflater; // 分组数据 private List<Map<String, String>> groupLists; // 子列表项数据 private List<List<Map<String, String>>> childrenLists; public CustomExpandListAdapter(Context context, List<Map<String, String>> groupLists, List<List<Map<String, String>>> childrenLists) { this.context = context; this.layoutInflater = LayoutInflater.from(context); this.groupLists = groupLists; this.childrenLists = childrenLists; } /** * 列表分组的数量 */ @Override public int getGroupCount() { return groupLists.size(); } /** * 获取每一个分组下，子列表项的数量 * @param groupPosition 分组下标 */ @Override public int getChildrenCount(int groupPosition) { return childrenLists.get(groupPosition).size(); } /** * 获取指定分组下标的对象 * @param groupPosition 分组下标 */ @Override public Object getGroup(int groupPosition) { return groupLists.get(groupPosition); } /** * 获取指定分组下，指定下标的子列表项 * @param groupPosition 分组下标 * @param childPosition 子列表项下标 */ @Override public Object getChild(int groupPosition, int childPosition) { // 这里返回指定分组中的子列表项个数 return childrenLists.get(groupPosition).get(childPosition); } /** * 获取分组ID * @param groupPosition 分组下标 */ @Override public long getGroupId(int groupPosition) { return groupPosition; } /** * 获取子列表项ID * @param groupPosition * @param childPosition */ @Override public long getChildId(int groupPosition, int childPosition) { return childPosition; } @Override public boolean hasStableIds() { return false; } /** * 这是渲染每一个分组的视图 * @param groupPosition 分组下标 * @param isExpanded 是否展开显示 * @param convertView 当前渲染的视图组件 * @param parent 父容器组件 */ @Override public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) { GroupViewHolder groupViewHolder; if (null == convertView) { convertView = layoutInflater.inflate(R.layout.activity_expand_group, null); groupViewHolder = new GroupViewHolder(); groupViewHolder.groupImageView = convertView.findViewById(R.id.group_icon); groupViewHolder.groupTitle = convertView.findViewById(R.id.group_title); groupViewHolder.groupRightText = convertView.findViewById(R.id.group_right_text); convertView.setTag(groupViewHolder); } else { groupViewHolder = (GroupViewHolder) convertView.getTag(); } // 渲染当前分组项 if (isExpanded) { // 展开,显示向下箭头 groupViewHolder.groupImageView.setImageResource(R.drawable.arrow_down); } else { // 不展开,显示向右箭头 groupViewHolder.groupImageView.setImageResource(R.drawable.arrow_right); } Map<String, String> map = groupLists.get(groupPosition); groupViewHolder.groupTitle.setText(map.get("title")); groupViewHolder.groupRightText.setText(map.get("rightText")); return convertView; } /** * 这是渲染某个分组下的子列表项的视图 * @param groupPosition 分组下标 * @param childPosition 子列表项下标 * @param isLastChild 是否最后一个子列表项 * @param convertView 当前渲染的视图组件 * @param parent 父容器组件 */ @Override public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) { ChildrenViewHolder childrenViewHolder; if (null == convertView) { convertView = layoutInflater.inflate(R.layout.activity_expand_group_item, null); childrenViewHolder = new ChildrenViewHolder(); childrenViewHolder.childTitle = convertView.findViewById(R.id.child_title); childrenViewHolder.childStatusText = convertView.findViewById(R.id.child_status_text); convertView.setTag(childrenViewHolder); } else { childrenViewHolder = (ChildrenViewHolder) convertView.getTag(); } List<Map<String, String>> childs = childrenLists.get(groupPosition); Map<String, String> childItemMap = childs.get(childPosition); childrenViewHolder.childTitle.setText(childItemMap.get("title")); childrenViewHolder.childStatusText.setText(childItemMap.get("status")); return convertView; } /** * 子列表项是否可以点击 */ @Override public boolean isChildSelectable(int groupPosition, int childPosition) { // 这里一律返回 true，表示子列表项可以响应事件 return true; } static class GroupViewHolder { ImageView groupImageView; TextView groupTitle; TextView groupRightText; } static class ChildrenViewHolder { TextView childTitle; TextView childStatusText; } }