Android 二级列表控件ExpandableListView 的简单使用

先上图：

页面布局

布局很简单，就一个ExpandableListView ，直接上布局截图，相信各位能看懂

 由于其控件会默认自带箭头，我们可以通过XML中在ExpandableListView控件加上

     android:groupIndicator="@null"

取消掉其自带的指示器箭头，当然除了在xml上，也可通过在代码中，当绑定完控件后调用代码也可实现取消效果

 expandableListView.setGroupIndicator(null);

接下来是我们重点要研究的适配器FoodinfoExpandableAdapter，继承并重写了BaseExpandableListAdapter这个类的相关函数，其中注释我已经详细写在代码中，若是不懂或者写错，希望各位可以交流或指出，大家一起加深对其认识。

public class FoodinfoExpandableAdapter extends BaseExpandableListAdapter {private final Context context;private List<Foodinfo> data;public FoodinfoExpandableAdapter(Context context, List<Foodinfo> data) {this.context = context;this.data = data;}/*** 获取组的数目** @return 返回一级列表组的数量*/@Overridepublic int getGroupCount() {return data == null ? 0 : data.size();}/*** 获取指定组中的子节点数量** @param groupPosition 子元素组所在的位置* @return 返回指定组中的子数量*/@Overridepublic int getChildrenCount(int groupPosition) {return data.get(groupPosition).getFoodinfoChildrenList().size();}/*** 获取与给定组相关联的对象** @param groupPosition 子元素组所在的位置* @return 返回指定组的子数据*/@Overridepublic Object getGroup(int groupPosition) {return data.get(groupPosition).getFoodType();}/*** 获取与给定组中的给定子元素关联的数据** @param groupPosition 子元素组所在的位置* @param childPosition 子元素的位置* @return 返回子元素的对象*/@Overridepublic Object getChild(int groupPosition, int childPosition) {return data.get(groupPosition).getFoodinfoChildrenList().get(childPosition);}/*** 获取组在给定位置的ID（唯一的）** @param groupPosition 子元素组所在的位置* @return 返回关联组ID*/@Overridepublic long getGroupId(int groupPosition) {return groupPosition;}/*** 获取给定组中给定子元素的ID(唯一的)** @param groupPosition 子元素组所在的位置* @param childPosition 子元素的位置* @return 返回子元素关联的ID*/@Overridepublic long getChildId(int groupPosition, int childPosition) {return childPosition;}/*** @return 确定id 是否总是指向同一个对象*/@Overridepublic boolean hasStableIds() {return true;}/*** @return 返回指定组的对应的视图 （一级列表样式）*/@Overridepublic View getGroupView(final int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {ParentHolder parentHolder;if (convertView == null) {convertView = LayoutInflater.from(context).inflate(R.layout.level_item, null);parentHolder = new ParentHolder();parentHolder.tvParent = convertView.findViewById(R.id.tv_parent);parentHolder.img_left = convertView.findViewById(R.id.img_left);parentHolder.img_right = convertView.findViewById(R.id.img_right);convertView.setTag(parentHolder);} else {parentHolder = (ParentHolder) convertView.getTag();}parentHolder.tvParent.setText(data.get(groupPosition).getFoodType());parentHolder.img_left.setImageResource(data.get(groupPosition).getFoodTypeImg());//共用一个右箭头，如果展开则顺时针旋转90°选择，否则不旋转if (isExpanded) parentHolder.img_right.setRotation(90F);else parentHolder.img_right.setRotation(0F);return convertView;}/*** @return 返回指定位置对应子视图的视图*/@Overridepublic View getChildView(final int groupPosition, final int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {final ChildrenHolder childrenHolder;if (convertView == null) {convertView = LayoutInflater.from(context).inflate(R.layout.level2_item, null);childrenHolder = new ChildrenHolder();childrenHolder.tvChild = convertView.findViewById(R.id.tv_child);childrenHolder.imageView = convertView.findViewById(R.id.child_img);convertView.setTag(childrenHolder);} else {childrenHolder = (ChildrenHolder) convertView.getTag();}childrenHolder.tvChild.setText(data.get(groupPosition).getFoodinfoChildrenList().get(childPosition).getName());childrenHolder.imageView.setImageResource(data.get(groupPosition).getFoodinfoChildrenList().get(childPosition).getFoodinfoChildrenImg());return convertView;}/*** 指定位置的子元素是否可选** @param groupPosition 子元素组所在的位置* @param childPosition 子元素的位置* @return 返回是否可选*/@Overridepublic boolean isChildSelectable(int groupPosition, int childPosition) {return true;}class ParentHolder {TextView tvParent;ImageView img_left, img_right;}class ChildrenHolder {TextView tvChild;ImageView imageView;}}

父布局使用的xml:

子布局使用的xml:

注意在getGroupView中getGroupView的控件不能设置一些抢占焦点的事件或属性，如点击事件或者在代码布局里设置了focusable属性为true，都会导致无法展开子列表。

实体类Foodinfo代码如下：

public class Foodinfo {private String foodType;private int foodTypeImg;private List<FoodinfoChildren> foodinfoChildrenList;public Foodinfo(String foodType, int foodTypeImg, List<FoodinfoChildren> foodinfoChildrenList) {this.foodType = foodType;this.foodTypeImg = foodTypeImg;this.foodinfoChildrenList = foodinfoChildrenList;}public String getFoodType() {return foodType;}public void setFoodType(String foodType) {this.foodType = foodType;}public int getFoodTypeImg() {return foodTypeImg;}public void setFoodTypeImg(int foodTypeImg) {this.foodTypeImg = foodTypeImg;}public List<FoodinfoChildren> getFoodinfoChildrenList() {return foodinfoChildrenList;}public void setFoodinfoChildrenList(List<FoodinfoChildren> foodinfoChildrenList) {this.foodinfoChildrenList = foodinfoChildrenList;}
}

最后是在我们的主界面中实现代码

public class Food_information_Activity extends AppCompatActivity {private static List<Foodinfo> foodinfoList;private static FoodinfoExpandableAdapter foodinfoExpandableAdapter;private ExpandableListView listView;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_food_information);getSupportActionBar().hide();TextView title = findViewById(R.id.title_layout);title.setText("食物分类");listView = findViewById(R.id.food_info_list);initData();initAdapter();}private final String[] foodTypes = {"鱼肉海鲜", "肉类", "蔬菜豆类", "水果"};private final int[] foodTypeImg = {R.drawable.type1, R.drawable.type2, R.drawable.type3, R.drawable.type4};private final String[] yl = {"草鱼", "鲤鱼", "鲫鱼", "鱿鱼"};private final int[] ylImg = {R.drawable.yl1, R.drawable.yl2, R.drawable.yl3, R.drawable.yl4};private final String[] rl = {"牛肉", "猪肉", "羊肉", "鸡肉"};private final int[] rlImg = {R.drawable.rl1, R.drawable.rl2, R.drawable.rl3, R.drawable.rl4};private final String[] sd = {"豌豆", "胡萝卜", "生菜", "空心菜"};private final int[] sdImg = {R.drawable.sd1, R.drawable.sd2, R.drawable.sd3, R.drawable.sd4};private final String[] sg = {"橘子", "哈密瓜", "苹果", "黄桃"};private final int[] sgImg = {R.drawable.sg1, R.drawable.sg2, R.drawable.sg3, R.drawable.sg4};private void initData() {foodinfoList = new ArrayList<>();List<FoodinfoChildren> ylFood = new ArrayList<>();for (int j = 0; j < 4; j++) {ylFood.add(new FoodinfoChildren(yl[j], ylImg[j]));}List<FoodinfoChildren> rlFood = new ArrayList<>();for (int j = 0; j < 4; j++) {rlFood.add(new FoodinfoChildren(rl[j], rlImg[j]));}List<FoodinfoChildren> sdFood = new ArrayList<>();for (int j = 0; j < 4; j++) {sdFood.add(new FoodinfoChildren(sd[j], sdImg[j]));}List<FoodinfoChildren> sgFood = new ArrayList<>();for (int j = 0; j < 4; j++) {sgFood.add(new FoodinfoChildren(sg[j], sgImg[j]));}foodinfoList.add(new Foodinfo(foodTypes[0], foodTypeImg[0], ylFood));foodinfoList.add(new Foodinfo(foodTypes[1], foodTypeImg[1], rlFood));foodinfoList.add(new Foodinfo(foodTypes[2], foodTypeImg[2], sdFood));foodinfoList.add(new Foodinfo(foodTypes[3], foodTypeImg[3], sgFood));}private void initAdapter() {foodinfoExpandableAdapter = new FoodinfoExpandableAdapter(this, foodinfoList);listView.setAdapter(foodinfoExpandableAdapter);/*** 默认展开某个item* *///expandableListView.expandGroup(1);}
}