ExpandableListView

ExpandableListView顧名思義，爲可展開的ListView（相當於ListView的每一行都是一個可以點擊並展開的ListView）

相關知識:

ExpandableListView控件；

ExpandableListView的適配器：BaseExpandableListAdapter（用於繼承）

ExpandableListView未展開時的監聽回調：ExpandableListView.OnGroupCollapseListener,

ExpandableListView展開時的監聽回調ExpandableListView.OnGroupExpandListener

---

Layout

創建一個ExpandableListView的Layout
activity_main

<?xml version="1.0" encoding="utf-8"?>
<ExpandableListView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/expand_list"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content">

</ExpandableListView>

---

再創建兩個Layout，一個是一級目錄的Item佈局，另一個則是二級目錄的Item佈局

item

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

    <TextView
        android:id="@+id/GroupItem"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="TextView"
        android:gravity="center_horizontal"/>

</LinearLayout>

---

child_item

<?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"
    >

    <TextView
        android:id="@+id/ChildItem"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="TextView" />
</LinearLayout>

---

類文件

MainActivity

public class MainActivity extends AppCompatActivity {

    private ExpandableListView expandListView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ArrayList<String> list = new ArrayList<>();

        ExpandAdapter adapter = new ExpandAdapter(list, this);

        expandListView = (ExpandableListView)findViewById(R.id.expand_list);
        expandListView.setAdapter(adapter);
    }

}

---

Item類

public class Item {
    public ArrayList<String> number;
    public String course;

    public Item(String course,ArrayList number){
        this.course = course;
        this.number = number;
    }

}

---

ExpandAdapter類：ExpandableListView的適配器類，大部分需要重寫的方法和BaseAdapter一樣，只不過多了Group及Child的區別，便不再贅敘。

public class ExpandAdapter extends BaseExpandableListAdapter implements ExpandableListView.OnGroupCollapseListener, ExpandableListView.OnGroupExpandListener {

    Context context;
    ArrayList<Item> list;

    Boolean[] isOpen;
    /*創建一個和一級目錄一樣數量元素的數組,用於保存及判斷一級目錄是否被打開，
     *這個數組在該例子中並沒有作用，僅僅是爲了讓繼承的兩個接口所重寫的方法更具體一些
     *即onGroupCollapse(int groupPosition)、onGroupExpand(int groupPosition)
     */

    public ExpandAdapter(ArrayList list,Context context){
        this.list=  list;
        this.context = context;
        initListContext();
    }

    /*爲方便起見，直接添加一些簡單的數據源*/
    public void initListContext() {

        ArrayList<String> number = new ArrayList<>();
        for (int i=0;i<5;i++){
            number.add("課程"+i);
        }

        list.add(new Item("Java",number));
        list.add(new Item("C++",number));
        list.add(new Item("Python",number));
        list.add(new Item("Math",number));
        list.add(new Item("English",number));
    }

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

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

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

    //返回二級標籤的內容
    @Override
    public Object getChild(int groupPosition, int childPosition) {
        return list.get(groupPosition).number.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 true;
    }

    @Override
    public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {
        TextView group_text;

        if (convertView == null) {
            convertView =  LinearLayout.inflate(
                    context, R.layout.item, null);
        }
        group_text = (TextView) convertView.findViewById(R.id.GroupItem);

        group_text.setText(list.get(groupPosition)
                .course);
        return convertView;
    }

    @Override
    public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
       ViewHolder viewHolder;
        if(convertView == null){
            viewHolder = new ViewHolder();
            convertView  = LayoutInflater.from(context).inflate(R.layout.child_item,null);
            viewHolder.itemOfText = (TextView) convertView.findViewById(R.id.ChildItem);
            convertView.setTag(viewHolder);
        }else{
            viewHolder  = (ViewHolder) convertView.getTag();
        }
        viewHolder.itemOfText.setText(list.get(groupPosition).number.get(childPosition));

        return convertView;
    }

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


    //ExpandableListView.OnGroupCollapseListener接口重寫的方法
    //當二級標籤未展開時回調
    @Override
    public void onGroupCollapse(int groupPosition) {
        isOpen[groupPosition] = false;
    }

    //ExpandableListView.OnGroupExpandListener接口重寫的方法
    //當二級標籤展開時回調
    @Override
    public void onGroupExpand(int groupPosition) {
        isOpen[groupPosition] = true;
    }
}

class ViewHolder{
       public  TextView itemOfText;
}