【Android -- UI 开发】ExpandableListView 的基本使用

前言

• 官方给出的解释是：

A view that shows items in a vertically scrolling two-level list. This differs from the ListView by allowing two levels: groups which can individually be expanded to show its children. The items come from the ExpandableListAdapter associated with this view.

翻译：一种用于垂直滚动展示两级列表的视图，和 ListView 的不同之处就是它可以展示两级列表，分组可以单独展开显示子选项。这些选项的数据是通过 ExpandableListAdapter 关联的。

实例

1. 效果图

2. 布局文件

• main_activity.xml

• 父布局

• 子布局

3. 适配器

public class ExpandableListviewAdapter extends BaseExpandableListAdapter {
    //Model：定义的数据
    private String[] groups;
    //注意，字符数组不要写成{{"A1,A2,A3,A4"}, {"B1,B2,B3,B4，B5"}, {"C1,C2,C3,C4"}}
    private String[][] childs;
    private Context context;
 
    public ExpandableListviewAdapter(Context context,String[] groups,String[][] childs){
        this.context=context;
        this.groups=groups;
        this.childs=childs;
    }
 
    @Override
    public int getGroupCount() {
        return groups.length;
    }
 
    @Override
    public int getChildrenCount(int i) {
        return childs[i].length;
    }
 
    @Override
    public Object getGroup(int i) {
        return groups[i];
    }
 
    @Override
    public Object getChild(int i, int i1) {
        return childs[i][i1];
    }
 
    @Override
    public long getGroupId(int i) {
        return i;
    }
 
    @Override
    public long getChildId(int i, int i1) {
        return i1;
    }
 
    @Override
    //分组和子选项是否持有稳定的ID, 就是说底层数据的改变会不会影响到它们
    public boolean hasStableIds() {
        return true;
    }
 
    @Override
/**
 *
 * 获取显示指定组的视图对象
 *
 * @param groupPosition 组位置
 * @param isExpanded 该组是展开状态还是伸缩状态，true=展开
 * @param convertView 重用已有的视图对象
 * @param parent 返回的视图对象始终依附于的视图组
 */
    public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {
        GroupViewHolder groupViewHolder;
        if (convertView == null){
            convertView = LayoutInflater.from(parent.getContext()).inflate(R.layout.expand_parent_item,parent,false);
            groupViewHolder = new GroupViewHolder();
            groupViewHolder.parent_textview_id = convertView.findViewById(R.id.parent_textview_id);
            groupViewHolder.parent_image = convertView.findViewById(R.id.parent_image);
            convertView.setTag(groupViewHolder);
        }else {
            groupViewHolder = (GroupViewHolder)convertView.getTag();
        }
        groupViewHolder.parent_textview_id.setText(groups[groupPosition]);
        //如果是展开状态，
        if (isExpanded){
            groupViewHolder.parent_image.setImageDrawable(ContextCompat.getDrawable(context,R.drawable.img_arrow_down));
        }else{
            groupViewHolder.parent_image.setImageDrawable(ContextCompat.getDrawable(context,R.drawable.img_arrow_right));
        }
        return convertView;
    }
 
    @Override
    public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
        ChildViewHolder childViewHolder;
        if (convertView==null){
            convertView = LayoutInflater.from(parent.getContext()).inflate(R.layout.expand_chidren_item,parent,false);
            childViewHolder = new ChildViewHolder();
            childViewHolder.chidren_item = (TextView)convertView.findViewById(R.id.chidren_item);
            convertView.setTag(childViewHolder);
 
        }else {
            childViewHolder = (ChildViewHolder) convertView.getTag();
        }
        childViewHolder.chidren_item.setText(childs[groupPosition][childPosition]);
        return convertView;
    }
 
    //指定位置上的子元素是否可选中
    @Override
    public boolean isChildSelectable(int i, int i1) {
        return true;
    }
    static class GroupViewHolder {
        TextView parent_textview_id;
        ImageView parent_image;
    }
 
    static class ChildViewHolder {
        TextView chidren_item;
 
    }
}

4. MainActivity.java

public class ExpandableListviewActivity extends BaseActivity {
    private ExpandableListView expand_list_id;
    //Model：定义的数据
    private String[] groups = {"开发部", "人力资源部", "销售部"};
 
    //注意，字符数组不要写成{{"A1,A2,A3,A4"}, {"B1,B2,B3,B4，B5"}, {"C1,C2,C3,C4"}}
    private String[][] childs = {{"赵珊珊", "钱丹丹", "孙可可", "李冬冬"}, {"周大福", "吴端口", "郑非", "王疯狂"}, {"冯程程", "陈类", "楚哦", "魏王"}};
 
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.expandable_list_view);
        setTitle("ExpandableListView二级下拉",false,"");
        initView();
    }
    private void initView(){
        expand_list_id=findViewById(R.id.expand_list_id);
        ExpandableListviewAdapter adapter=new ExpandableListviewAdapter(this,groups,childs);
        expand_list_id.setAdapter(adapter);
        //默认展开第一个数组
        expand_list_id.expandGroup(0);
        //关闭数组某个数组，可以通过该属性来实现全部展开和只展开一个列表功能
        //expand_list_id.collapseGroup(0);
        expand_list_id.setOnGroupClickListener(new ExpandableListView.OnGroupClickListener() {
            @Override
            public boolean onGroupClick(ExpandableListView expandableListView, View view, int groupPosition, long l) {
                showToastShort(groups[groupPosition]);
                return false;
            }
        });
        //子视图的点击事件
        expand_list_id.setOnChildClickListener(new ExpandableListView.OnChildClickListener() {
            @Override
            public boolean onChildClick(ExpandableListView expandableListView, View view, int groupPosition, int childPosition, long l) {
                showToastShort(childs[groupPosition][childPosition]);
                return true;
            }
        });
        //用于当组项折叠时的通知。
        expand_list_id.setOnGroupCollapseListener(new ExpandableListView.OnGroupCollapseListener() {
            @Override
            public void onGroupCollapse(int groupPosition) {
                showToastShort("折叠了数据___"+groups[groupPosition]);
            }
        });
        //
        //用于当组项折叠时的通知。
        expand_list_id.setOnGroupExpandListener(new ExpandableListView.OnGroupExpandListener() {
            @Override
            public void onGroupExpand(int groupPosition) {
                showToastShort("展开了数据___"+groups[groupPosition]);
            }
        });
    }
}