概述

本节课介绍Android中可实现二级可展开收缩列表的ExpandableListView容器，笔者感觉它非常难用并且难理解，很多时候我们可能需要对控件进行扩展和定制，然而它不太方便扩展，它使用难点主要在数据结构上和对控件的事件监听，其他的实现方式类似ListView，下面会提供笔者在实际开发中使用到的案例。

案例

上面实现的效果可展开的二级列表，每个组项都可能有若干个子项，默认的ExpandableListView不太美观，我们需要通过自定义布局类美化它，在使用过程中有一些需要我们去了解的点，会在实现过程提一下。

实现过程

源码已经上传到Git@OSC，各位可以clone参考
http://git.oschina.net/devilwwj/AndroidDevelopCourse/tree/master/code?dir=1&filepath=code&oid=7961fb146029fb10776b101b918c59ff77fbd672&sha=e65897b0a246924292356f2b488d430c081081ff

布局分为：
- Activity布局
- 组项布局（layout_expand_group.xml)
- 子项布局（layout_expand_item.xml)

layout/activity_expandablelistview.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <ExpandableListView
        android:id="@+id/expandablelistview"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:cacheColorHint="@color/transparent"
        android:childDivider="@color/transparent"
        android:fastScrollEnabled="true"
        android:groupIndicator="@color/transparent"
        android:divider="@null"
        android:listSelector="@color/transparent"
        android:choiceMode="singleChoice"
        android:scrollbars="none" >
    </ExpandableListView>
</LinearLayout>

layout/layout_expand_group.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/group_layout"
    android:layout_width="match_parent"
    android:layout_height="57dp"
    android:background="#ffffff"
    android:clickable="true"
    android:minHeight="?android:attr/listPreferredItemHeight" >
    <ImageView
        android:id="@+id/iv_group_icon"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_centerVertical="true"
        android:layout_marginLeft="18dp"
        android:background="@drawable/ic_leftnav_10" />
    <TextView
        android:id="@+id/tv_group_text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerVertical="true"
        android:layout_marginLeft="59dp"
        android:text="时局"
        android:textColor="#333333"
        android:textSize="16sp" />
    <View
        android:id="@+id/item_group_devider"
        android:layout_width="match_parent"
        android:layout_height="0.5dp"
        android:layout_alignLeft="@+id/tv_group_text"
        android:layout_alignParentBottom="true"
        android:background="@color/listview_divider"
        android:layout_marginRight="10dp"
        android:visibility="visible"/>
    <ImageView
        android:id="@+id/iv_expand"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:layout_centerVertical="true"
        android:layout_marginRight="25dp"
        android:clickable="true"
        android:padding="5dp"
        android:src="@drawable/ic_leftnav_down" />
</RelativeLayout>

layout/layout_expand_item.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="40dp"
    android:background="@drawable/slidingmenu_item_selector"
    android:minHeight="?android:attr/listPreferredItemHeight" >
    <!-- android:color="@drawable/item_selected_text_color"/> -->
    <TextView
        android:id="@+id/tv_item_text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerVertical="true"
        android:layout_marginLeft="75dp"
        android:text="时局"
        android:textColor="@drawable/slidingmenu_item_text_selector"
        android:textSize="15sp"
        android:clickable="true"
        />

    <View
        android:id="@+id/item_devider"
        android:layout_width="match_parent"
        android:layout_height="0.5dp"
        android:layout_alignParentBottom="true"
        android:layout_marginLeft="59dp"
        android:layout_marginRight="10dp"
        android:background="@color/listview_divider"
        android:visibility="visible" />

</RelativeLayout>

自定义Adapter
- 继承BaseExpandableListAdapter并实现以下方法
- getGroupCount（获取组项的个数）
- getChildrenCount（获取子项个数）
- getGroup（获取组对象）
- getChild（获取子对象）
- getGroupId（获取组项id）
- getChildId（获取子项id）
- hasStableIds（组和子元素是否持有稳定的ID）
- getGroupView（获取显示指定组的视图对象）
- getChildView（获取显示指定项的视图对象）
- isChildSelectable（子项是否可选中）
- 传入组项列表（如：List<GroupItem>)
- 传入子项列表（如：List<List<Category>> ）

适配器代码：
com.devilwwj.androiddevelopcourse.adapters.ExpandableListViewAdapter

package com.devilwwj.androiddevelopcourse.adapters;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.BaseExpandableListAdapter;
import android.widget.ExpandableListView;
import android.widget.ImageView;
import android.widget.RelativeLayout;
import android.widget.TextView;

import com.devilwwj.androiddevelopcourse.R;
import com.devilwwj.androiddevelopcourse.domain.Category;
import com.devilwwj.androiddevelopcourse.domain.GroupItem;

import java.util.HashMap;
import java.util.List;

/**
 * 自定义可展开列表的适配器
 */
public class ExpandableListViewAdapter extends BaseExpandableListAdapter {

    private Context mContext;// 上下文
    private ExpandableListView expandableListView; // 可展开列表对象
    private List<GroupItem> groupList; // 组列表
    private List<List<Category>> childList; // 子项列表
    private LayoutInflater inflater;

    // 自定义接口回调监听器
    private OnGroupExpandListener OnGroupExpandListener;
    private OnGroupClickListener onGroupClickListener;
    private OnChildItemClickListener onChildClickListener;
    private HashMap<Integer, Boolean> maps = new HashMap<Integer, Boolean>();

    private boolean expandStateAtPosition = false;

    public OnGroupClickListener getOnGroupClickListener() {
        return onGroupClickListener;
    }

    public void setOnGroupClickListener(
            OnGroupClickListener onGroupClickListener) {
        this.onGroupClickListener = onGroupClickListener;
    }

    public OnGroupExpandListener getOnGroupExpandListener() {
        return OnGroupExpandListener;
    }

    public void setOnGroupExpandListener(
            OnGroupExpandListener onGroupExpandListener) {
        OnGroupExpandListener = onGroupExpandListener;
    }

    public OnChildItemClickListener getOnChildClickListener() {
        return onChildClickListener;
    }

    public void setOnChildClickListener(
            OnChildItemClickListener onChildClickListener) {
        this.onChildClickListener = onChildClickListener;
    }

    private int mExpandedGroupPosition;

    public int getExpandedGroupPosition() {
        return mExpandedGroupPosition;
    }

    public void setExpandedGroupPosition(int mExpandedGroupPosition) {
        this.mExpandedGroupPosition = mExpandedGroupPosition;

    }

    public ExpandableListViewAdapter(Context context,
                                     ExpandableListView expandableListView, List<GroupItem> groupList,
                                     List<List<Category>> childList) {
        super();
        this.mContext = context;
        this.expandableListView = expandableListView;
        this.groupList = groupList;
        this.childList = childList;

        inflater = LayoutInflater.from(context);

        // 初始化列表展开状态
        for (int i = 0; i < groupList.size(); i++) {
            maps.put(i, false);
        }
    }

    private int mGroupPosition = 0;
    private int mChildPosition = 0;

    /**
     * 设置子项被选中方法
     *
     * @param groupPosition
     * @param childPosition
     */
    public void setItemChecked(int groupPosition, int childPosition) {
        if (expandableListView == null) {
            return;
        }
        this.mGroupPosition = groupPosition;
        this.mChildPosition = childPosition;

        int numberOfGroupThatIsOpened = 0;

        for (int i = 0; i < groupPosition; i++) {
            if (expandableListView.isGroupExpanded(i)) {
                numberOfGroupThatIsOpened += this.getChildrenCount(i);
            }
        }

        int position = numberOfGroupThatIsOpened + groupPosition
                + childPosition + 1;

        if (!expandableListView.isItemChecked(position)) {
            expandableListView.setItemChecked(position, true);
        }
    }

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

    @Override
    public int getChildrenCount(int groupPosition) {
        return childList.get(groupPosition).size();
    }

    /*
     * 获得组项 (non-Javadoc)
     *
     * @see android.widget.ExpandableListAdapter#getGroup(int)
     */
    @Override
    public GroupItem getGroup(int groupPosition) {
        return groupList.get(groupPosition);
    }

    @Override
    public Category getChild(int groupPosition, int childPosition) {
        return childList.get(groupPosition).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(final int groupPosition, boolean isExpanded,
                             View convertView, ViewGroup parent) {
        final GroupViewHolder groupViewHolder;

        if (convertView == null) {
            convertView = inflater.inflate(R.layout.layout_expand_group, parent,
                    false);
            groupViewHolder = new GroupViewHolder(convertView);
            convertView.setTag(groupViewHolder);
        } else {
            groupViewHolder = (GroupViewHolder) convertView.getTag();
        }

        GroupItem groupItem = groupList.get(groupPosition);
        groupViewHolder.itemGroupIcon.setBackgroundResource(groupItem
                .getDrawableId());
        groupViewHolder.itemGroupText.setText(groupItem.getText());

        // 如果该组没有子项，则不显示箭头
        if (childList.get(groupPosition).size() == 0) {
            groupViewHolder.itemArrow.setVisibility(View.GONE);
            groupViewHolder.itemGroupLayout
                    .setOnClickListener(new OnClickListener() {

                        @Override
                        public void onClick(View v) {
                            onGroupClickListener.onGroupClick(groupPosition);
                        }
                    });
        } else {
            groupViewHolder.itemArrow.setVisibility(View.VISIBLE);
            groupViewHolder.itemGroupLayout
                    .setOnClickListener(new OnClickListener() {

                        @Override
                        public void onClick(View v) {
                            OnGroupExpandListener.onGroupExpand(groupPosition);
                        }
                    });
        }

        groupViewHolder.itemGroupText.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                onGroupClickListener.onGroupClick(groupPosition);
            }
        });

        groupViewHolder.itemArrow.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {

                OnGroupExpandListener.onGroupExpand(groupPosition);
            }
        });

        // 判断isExpanded就可以控制按下还是关闭，同时更换图片,这里使用属性动画来控制旋转
        if (isExpanded) {
            groupViewHolder.itemArrow
                    .setImageResource(R.drawable.ic_leftnav_up);

            // 没有孩子项就不隐藏分割线
            if (childList.get(groupPosition).size() > 0) {
                groupViewHolder.itemDivider.setVisibility(View.INVISIBLE);
            } else {
                groupViewHolder.itemDivider.setVisibility(View.VISIBLE);
            }
        } else {
            groupViewHolder.itemArrow
                    .setImageResource(R.drawable.ic_leftnav_down);
            groupViewHolder.itemDivider.setVisibility(View.VISIBLE);
        }

        return convertView;
    }

    @Override
    public View getChildView(final int groupPosition, final int childPosition,
                             boolean isLastChild, View convertView, ViewGroup parent) {
        final ChildViewHolder childViewHolder;
        if (convertView == null) {
            convertView = inflater.inflate(R.layout.layout_expand_item,
                    parent, false);
            childViewHolder = new ChildViewHolder(convertView);
            convertView.setTag(childViewHolder);
        } else {
            childViewHolder = (ChildViewHolder) convertView.getTag();
        }

        String content = childList.get(groupPosition).get(childPosition)
                .getTitle();

        // 设置内容
        childViewHolder.itemChildText.setText(content);

        // 设置文本点击事件
        childViewHolder.itemChildText.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                onChildClickListener.onChildItemClick(groupPosition,
                        childPosition);
            }
        });

        if (childPosition == childList.get(groupPosition).size() - 1) {
            childViewHolder.itemDivider.setVisibility(View.VISIBLE);
        } else {
            childViewHolder.itemDivider.setVisibility(View.GONE);
        }

        // 设置子项被选中的状态


        return convertView;
    }

    @Override
    public boolean isChildSelectable(int groupPosition, int childPosition) {
        // 设置孩子项可选中
        return true;
    }

    private static class GroupViewHolder {
        RelativeLayout itemGroupLayout;
        ImageView itemGroupIcon;
        TextView itemGroupText;
        ImageView itemArrow;
        View itemDivider;

        public GroupViewHolder(View convertView) {
            itemGroupLayout = (RelativeLayout) convertView
                    .findViewById(R.id.group_layout);
            itemGroupIcon = (ImageView) convertView
                    .findViewById(R.id.iv_group_icon);
            itemGroupText = (TextView) convertView
                    .findViewById(R.id.tv_group_text);
            itemArrow = (ImageView) convertView.findViewById(R.id.iv_expand);
            itemDivider = (View) convertView
                    .findViewById(R.id.item_group_devider);

        }

    }

    private static class ChildViewHolder {
        TextView itemChildText;
        View itemDivider;

        public ChildViewHolder(View convertView) {
            itemChildText = (TextView) convertView
                    .findViewById(R.id.tv_item_text);
            itemDivider = (View) convertView.findViewById(R.id.item_devider);

        }
    }

    public interface OnGroupExpandListener {
        void onGroupExpand(int position);
    }

    public interface OnGroupClickListener {
        void onGroupClick(int position);
    }

    public interface OnChildItemClickListener {
        void onChildItemClick(int groupPosition, int childPosition);
    }

    public boolean getExpandStateAtPosition(int groupPosition) {
        // 获得当前位置的展开状态
        expandStateAtPosition = maps.get(groupPosition).booleanValue();
        return expandStateAtPosition;
    }

    public void setExpandStateAtPosition(int groupPosition,
                                         boolean expandStateAtPosition) {
        this.expandStateAtPosition = expandStateAtPosition;
        maps.put(groupPosition, expandStateAtPosition);
    }
}

解析一下上面的代码，我们可以看到ExpandableListView除了一个组项，每个组项下面有若干个子项，我们在使用的时候首先要确定要展示的数据结构，组项有groupPosition来标识位置，然而子项需要根据groupPosition和ChildPosition来标识位置，我们设置数据的时候分别在getGroupView和getChildView方法来设置组视图和子项视图数据，最后返回填充数据的视图对象，一些逻辑控制的代码也是在这两个方法中进行，比如控制组项的展开、组项的点击、子项的点击、子项被选中效果等等，这里笔者是自定义了回调接口来满足业务的需求，Android API也提供的类似的方法，大家可以查看官方文档。

Activity代码
com.devilwwj.androiddevelopcourse.activities.ExpandableListViewTestActivity

package com.devilwwj.androiddevelopcourse.activities;

import android.content.Context;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.View;
import android.widget.ExpandableListView;

import com.devilwwj.androiddevelopcourse.R;
import com.devilwwj.androiddevelopcourse.adapters.ExpandableListViewAdapter;
import com.devilwwj.androiddevelopcourse.domain.Category;
import com.devilwwj.androiddevelopcourse.domain.GroupItem;
import com.devilwwj.androiddevelopcourse.utils.ResourceUtil;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.util.ArrayList;
import java.util.List;

/**
 * A022-列表容器之ExpandableListView
 *
 * @author devilwwj
 */
public class ExpandableListViewTestActivity extends ActionBarActivity implements ExpandableListViewAdapter.OnGroupClickListener, ExpandableListViewAdapter.OnGroupExpandListener
        , ExpandableListViewAdapter.OnChildItemClickListener {
    private ExpandableListView expandableListView;
    private Context mContext;
    private ExpandableListViewAdapter expandAdapter;
    private List<GroupItem> groupList;
    private List<List<Category>> childList;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_expandablelistview);
        mContext = ExpandableListViewTestActivity.this;


        expandableListView = (ExpandableListView) this.findViewById(R.id.expandablelistview);
        expandableListView.setGroupIndicator(null); // 去掉默认指示器

        // 设置展开列表数据
        setExpandableListView();

    }


    private void setExpandableListView() {
        try {
            // 这里分别模拟组项和子项数据
            groupList = new ArrayList<GroupItem>();
            childList = new ArrayList<List<Category>>();

            ResourceUtil resourceUtil = new ResourceUtil(this);
            // 从本地获取目录
            String str = getString(R.string.categories);
            JSONObject jsonObject = new JSONObject(str);
            JSONObject categoryObj = jsonObject.optJSONObject("categories");
            // 左边侧边栏
            JSONArray jsonArray = categoryObj.optJSONArray("left");

            for (int i = 0; i < jsonArray.length(); i++) {
                JSONArray groupArray = jsonArray.getJSONArray(i);
                GroupItem groupItem = new GroupItem();

                groupItem.setDrawableId(resourceUtil.getResId("ic_leftnav_"
                        + (i + 1), "drawable"));
                JSONObject groupObj = groupArray.optJSONObject(0);
                groupItem.setGroupId(groupObj.optString("cat_id")); // 设置组别的分类id
                groupItem.setText(groupObj.optString("title"));
                groupList.add(groupItem);
                List<Category> categories = new ArrayList<Category>();
                if (groupArray.length() > 0) { // 如果多于一项分类
                    for (int index = 1; index < groupArray.length(); index++) {
                        JSONObject itemObj = groupArray.optJSONObject(index);
                        Category categorie = new Category();
                        categorie.setTitle(itemObj.optString("title"));
                        categorie.setCat_id(itemObj.optString("cat_id"));
                        categories.add(categorie);
                    }
                }

                childList.add(categories);
            }

            // 实例化适配器
            expandAdapter = new ExpandableListViewAdapter(this, expandableListView, groupList, childList);
            expandableListView.setAdapter(expandAdapter);


            // 设置ExpandableListView的相关事件监听
            // 子项选中、子项被点击、组项展开、组项被点击
            // expandableListView.setOnItemSelectedListener(itemSelectedListener);
            expandableListView.setOnChildClickListener(mOnChildClickListener);
//            expandableListView.setOnGroupExpandListener(mOnGroupExpandListener);
            // expandableListView.setOnGroupClickListener(mOnGroupClickListener);
            expandAdapter.setOnGroupClickListener(this);
            expandAdapter.setOnGroupExpandListener(this);
            expandAdapter.setOnChildClickListener(this);
        } catch (JSONException e) {
            e.printStackTrace();
        }

    }

    final private ExpandableListView.OnChildClickListener mOnChildClickListener = new ExpandableListView.OnChildClickListener() {

        @Override
        public boolean onChildClick(ExpandableListView parent, View v,
                                    final int groupPosition, final int childPosition, long id) {

            // 设置子项被选中的背景
            // expandAdapter.setItemChecked(groupPosition, childPosition);

            // 返回true，列表不可展开
            return false;
        }
    };

    final private ExpandableListView.OnGroupExpandListener mOnGroupExpandListener = new ExpandableListView.OnGroupExpandListener() {

        @Override
        public void onGroupExpand(int groupPosition) {
            for (int i = 0, count = expandableListView
                    .getExpandableListAdapter().getGroupCount(); i < count; i++) {
                expandAdapter.setExpandedGroupPosition(groupPosition);
                if (groupPosition != i) { // 关闭其他组
                    expandableListView.collapseGroup(i);
                }
            }
        }
    };

    final private ExpandableListView.OnGroupClickListener mOnGroupClickListener = new ExpandableListView.OnGroupClickListener() {

        @Override
        public boolean onGroupClick(ExpandableListView parent, View v,
                                    final int groupPosition, long id) {

            return true;
        }
    };

    @Override
    public void onGroupExpand(int position) {
        // 组项被展开时会回调这个方法
        if (expandAdapter.getExpandStateAtPosition(position)) {
            // 收起
            expandableListView.collapseGroup(position);
            expandAdapter.setExpandStateAtPosition(position, false);
        } else {
            expandableListView.expandGroup(position, true);
            expandAdapter.setExpandStateAtPosition(position, true);
        }
    }

    @Override
    public void onGroupClick(int position) {
        // 执行选中后的操作
    }

    @Override
    public void onChildItemClick(int groupPosition, int childPosition) {
        // 子项被点击会回调这个方法
    }
}

最后

实际开发中，我们可能会遇到其他UI上的需求，原生的效果是完全不能满足我们的，这里提一点就是，熟练掌握API和解决问题能力很重要，不管UI怎么变我们都有办法去实现，可能只要我们找到对应的API设置一下或者看看有没有大神造好了轮子，终究我们还是可以找到解决方案，在Android开发当中我们经常打交道也最头痛的是UI，多实践和学习才能更好的完成工作，谢谢大家。

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