教你用两层ExpandableListView嵌套GridView实现三级展示界面

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：

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。