最近项目中使用一个三级展示列表，要求第一级和第二季都可以折叠，并有不同的图标变换，第三层展示数据，可点击。经过一盘折腾，算是实现了，效果就在下面：

这里写图片描述
思路：
最外层是ExpandableListView，它的子视图又是一个ExpandableListView,这个子ExpandableListView的子视图是我们的第三级展示界面，也就是GridView。分析清楚了之后，写起来就简单了，下面说说遇到的问题。

1，最外层的ExpandableListView嵌套的子ExpandableListView必须解决显示不全的问题。
2，在解决了上面的问题后，会发现，最里层的GridView如果不做处理也会出现显示不全的问题。
3，当上述两个问题都解决了之后，如果我们把最外层和第二层的ExpandableListView都使用自定义的ExpandableListView时，任然会出现子ExpandableListView显示不全问题，所以，这两个ExpandableListView不能使用同一个。

思路和问题都搞定了，我们现在看看主要的类代码：
这是MainActivity.java初始化方法代码

public class MainActivity extends AppCompatActivity {

    private ExpandableListView expandableListView;
    private List<String> groupList = new ArrayList<>();
    private ParentExpandAdapter parentExpandAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        initData();
        initView();
    }

    private void initData() {
        for (int i = 0; i < 11; i++) {
            groupList.add("Android工程师之版权 " + (1 + i));
        }
    }

    private void initView() {
        setContentView(R.layout.activity_main);
        expandableListView = (ExpandableListView) findViewById(R.id.expand_main);
        parentExpandAdapter = new ParentExpandAdapter(MainActivity.this, groupList);
        expandableListView.setAdapter(parentExpandAdapter);

        // 被展开组的监听
        expandableListView.setOnGroupExpandListener(new ExpandableListView.OnGroupExpandListener() {
            @Override
            public void onGroupExpand(int groupPosition) {
                // 保证每次只有一个组是展开状态
                for (int i = 0; i < parentExpandAdapter.getGroupCount(); i++) {
                    if (i != groupPosition) {
                        expandableListView.collapseGroup(i);
                    }
                }
            }
        });
    }
}

初始化了ExpandableListView，并设置了每次只展开一个组监听。

ParentExpandAdapter.java代码

public class ParentExpandAdapter extends BaseExpandableListAdapter {

    private Context context;
    private List<String> parentList;

    public ParentExpandAdapter(Context context, List<String> parentList) {
        this.context = context;
        this.parentList = parentList;
    }

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

    @Override
    public int getChildrenCount(int groupPosition) {
        return 5;
    }

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

    @Override
    public Object getChild(int groupPosition, int childPosition) {
        return parentList.get(childPosition);
    }

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

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

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

    @Override
    public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {
        ParentViewHolder parentHolder;
        if (null == convertView) {
            parentHolder = new ParentViewHolder();
            convertView = View.inflate(context, R.layout.fire_tab_parent_group_item, null);
            parentHolder.parentTv = (TextView) convertView.findViewById(R.id.parentGroupTV);
            parentHolder.parentIv = (ImageView) convertView.findViewById(R.id.iv_parent_group_indicator);
            convertView.setTag(parentHolder);
        } else {
            parentHolder = (ParentViewHolder) convertView.getTag();
        }
        parentHolder.parentTv.setText(parentList.get(groupPosition));
        if (isExpanded) {
            parentHolder.parentIv.setImageResource(R.drawable.icon_arrow_up);
        } else {
            parentHolder.parentIv.setImageResource(R.drawable.icon_arrow_down);
        }
        return convertView;
    }

    @Override
    public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
        ChildViewHolder childHolder;
        if (null == convertView) {
            childHolder = new ChildViewHolder();
            convertView = View.inflate(context, R.layout.item_expand_group_child, null);
            childHolder.childExpandLv = (ExpandableListView) convertView.findViewById(R.id.expand_group_item);
            convertView.setTag(childHolder);
        } else {
            childHolder = (ChildViewHolder) convertView.getTag();
        }
        childHolder.childExpandLv.setAdapter(new ChildExpandAdapter(context, parentList.subList(3, 7)));
        return convertView;
    }

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

    class ParentViewHolder {
        TextView parentTv;
        ImageView parentIv;
    }

    class ChildViewHolder {
        // 二级视图又是一个ExpandableListView
        ExpandableListView childExpandLv;
    }

}

因为一级只有一个TextView和一个ImageView，比较简单。因为子视图又是一个ExpandableListView，所以这里设置了监听，保证每次只展开一个分组，如果没有这个需求当然可以不设置，另外就是通过判断增加了指示箭头。

二级适配器ChildExpandAdapter.java代码

public class ChildExpandAdapter extends BaseExpandableListAdapter {

    private Context context;
    private List<String> parentList;

    public ChildExpandAdapter(Context context, List<String> parentList) {
        this.context = context;
        this.parentList = parentList;
    }

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

    @Override
    public int getChildrenCount(int groupPosition) {
        return 1;
    }

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

    @Override
    public Object getChild(int groupPosition, int childPosition) {
        return parentList.get(childPosition);
    }

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

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

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

    @Override
    public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {
        ParentViewHolder parentHolder;
        if (null == convertView) {
            parentHolder = new ParentViewHolder();
            convertView = View.inflate(context, R.layout.fire_tab_child_group_item, null);
            parentHolder.parentTv = (TextView) convertView.findViewById(R.id.childGroupTV);
            parentHolder.parentIv = (ImageView) convertView.findViewById(R.id.iv_fire_tab_child_indicator);
            convertView.setTag(parentHolder);
        } else {
            parentHolder = (ParentViewHolder) convertView.getTag();
        }
        parentHolder.parentTv.setText(parentList.get(groupPosition));
        if (isExpanded) {
            parentHolder.parentIv.setImageResource(R.drawable.icon_arrow_up);
        } else {
            parentHolder.parentIv.setImageResource(R.drawable.icon_arrow_down);
        }
        return convertView;
    }

    @Override
    public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
        ChildViewHolder childHolder;
        if (null == convertView) {
            childHolder = new ChildViewHolder();
            convertView = View.inflate(context, R.layout.item_child_child, null);
            childHolder.gridView = (GridView) convertView.findViewById(R.id.gv_child_child_item);
            convertView.setTag(childHolder);
        } else {
            childHolder = (ChildViewHolder) convertView.getTag();
        }
        childHolder.gridView.setAdapter(new GridViewAdapter(context, getList()));
        return convertView;
    }

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

    class ParentViewHolder {
        TextView parentTv;
        ImageView parentIv;
    }

    class ChildViewHolder {
        // 此ExpandableListView的ClildView又是一个GridView
        GridView gridView;
    }

    private List<String> getList() {
        List<String> list = new ArrayList<>();
        for (int i = 0; i < 50; i++) {
            list.add("android " + i);
        }
        return list;
    }
}

根据我们前面的分析，这里的二级ChildView是一个GridView，这里做了初始化，并设置了点击监听。

再来看看最重要的代码——自定义ExpandableListView

public class CustomExpandableListview extends ExpandableListView {

    public CustomExpandableListview(Context context) {
        super(context);
    }

    public CustomExpandableListview(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public CustomExpandableListview(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        int expandSpec = MeasureSpec.makeMeasureSpec(Integer.MAX_VALUE >> 2,
                MeasureSpec.AT_MOST);
        super.onMeasure(widthMeasureSpec, expandSpec);
    }
}

这里通过测量，计算出子ExpandableListView的高度，解决了显示不全问题，GridView也是一样的。

至此，除了GridView的适配器代码外，其它的都贴出来了，完整代码已上传至github，关注公众号“code小生”获取地址以及更多项目地址。