A022-列表容器之ExpandableListView

约定不等于承诺〃 2022-08-09 11:44 3阅读 0赞

# 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 #

![ExpandableListView][]

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][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" >
        
        <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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[ExpandableListView]: /images/20220731/f02396df7551417fa4633cf8ccf83dc1.png
[http_git.oschina.net_devilwwj_AndroidDevelopCourse_tree_master_code_dir_1_filepath_code_oid_7961fb146029fb10776b101b918c59ff77fbd672_sha_e65897b0a246924292356f2b488d430c081081ff]: http://git.oschina.net/devilwwj/AndroidDevelopCourse/tree/master/code?dir=1&filepath=code&oid=7961fb146029fb10776b101b918c59ff77fbd672&sha=e65897b0a246924292356f2b488d430c081081ff
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