ExpandableListView可擴充的下拉清單簡單的使用

使用ExpandableListView不需要依賴任何架構直接使用即可。      

首先，搭個簡單的布局

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.zzb.expandablelistview.MainActivity">

   <ExpandableListView
       android:id="@+id/edb_lv"
       android:layout_width="match_parent"
       android:layout_height="match_parent"/>

</LinearLayout>      

接下來執行個體化，然後寫個擴充卡，難點：主要是擴充卡比listview的複雜了點，慢慢看看還是很容易弄明白的。

public class MainActivity extends AppCompatActivity {
    private MyExpandableListViewAdapter adapter;
    private ExpandableListView listview;
    private String[] parentList = new String[]{"水果", "蔬菜", "肉類"};
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        listview = (ExpandableListView) findViewById(R.id.edb_lv);
        adapter = new MyExpandableListViewAdapter(this,parentList);
        initialData();
        listview.setAdapter(adapter);
        listview.setOnChildClickListener(new ExpandableListView.OnChildClickListener() {
            @Override
            public boolean onChildClick(ExpandableListView parent, View v, int groupPosition, int childPosition, long id) {
                //groupPosition和childPosition都是從0開始
                Toast.makeText(MainActivity.this, "點選了第"+(groupPosition+1)+"項的第"+(childPosition+1)+"個", Toast.LENGTH_SHORT).show();
                return true;
            }
        });
    }


    private void initialData() {
        adapter.childrenList1.add("蘋果");
        adapter.childrenList1.add("西瓜");
        adapter.childrenList1.add("香蕉");
        adapter.childrenList2.add("青菜");
        adapter.childrenList2.add("黃瓜");
        adapter.childrenList2.add("豆苗");
        adapter.childrenList3.add("雞");
        adapter.childrenList3.add("鴨");
        adapter.childrenList3.add("魚");

    }

}      

然後是擴充卡部分，擴充卡要繼承BaseExpandableListAdapter來寫

public class MyExpandableListViewAdapter extends BaseExpandableListAdapter {
    public Map<String, List<String>> dataset = new HashMap<>();
    public List<String> childrenList1 = new ArrayList<>();
    public List<String> childrenList2 = new ArrayList<>();
    public List<String> childrenList3 = new ArrayList<>();
    private Context context;
    private LayoutInflater inflater;
    private String[] parentList;

    private static final String TAG = "TAG";
    public MyExpandableListViewAdapter(Context context,String[] parentList) {
        this.context = context;
        this.parentList = parentList;
        dataset.put(parentList[0], childrenList1);
        dataset.put(parentList[1], childrenList2);
        dataset.put(parentList[2], childrenList3);
        inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    }

    //  獲得某個父項的某個子項
    @Override
    public Object getChild(int parentPos, int childPos) {
        return dataset.get(parentList[parentPos]).get(childPos);
    }

    //  獲得父項的數量
    @Override
    public int getGroupCount() {
        return dataset.size();
    }

    //  獲得某個父項的子項數目
    @Override
    public int getChildrenCount(int parentPos) {
        return dataset.get(parentList[parentPos]).size();
    }

    //  獲得某個父項
    @Override
    public Object getGroup(int parentPos) {
        return dataset.get(parentList[parentPos]);
    }

    //  獲得某個父項的id
    @Override
    public long getGroupId(int parentPos) {
        return parentPos;
    }

    //  獲得某個父項的某個子項的id
    @Override
    public long getChildId(int parentPos, int childPos) {
        return childPos;
    }

    //  按函數的名字來了解應該是是否具有穩定的id，這個方法目前一直都是傳回false，沒有去改動過
    @Override
    public boolean hasStableIds() {
        return false;
    }

    //  獲得父項顯示的view
    @Override
    public View getGroupView(int parentPos, boolean b, View view, ViewGroup viewGroup) {
        if (view == null) {
            view = inflater.inflate(R.layout.parent_item, null);
        }
        view.setTag(R.layout.parent_item, parentPos);
        view.setTag(R.layout.child_item, -1);
        TextView text = (TextView) view.findViewById(R.id.parent_title);
        text.setText(parentList[parentPos]);
        return view;
    }

    //  獲得子項顯示的view
    @Override
    public View getChildView(int parentPos, int childPos, boolean b, View view, ViewGroup viewGroup) {
        if (view == null) {
            view = inflater.inflate(R.layout.child_item, null);
        }
        view.setTag(R.layout.parent_item, parentPos);
        view.setTag(R.layout.child_item, childPos);
        TextView text = (TextView) view.findViewById(R.id.child_title);
        text.setText(dataset.get(parentList[parentPos]).get(childPos));
        /*text.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Toast.makeText(context, "點到了内置的textview", Toast.LENGTH_SHORT).show();
            }
        });*/
        return view;
    }

    //  子項是否可選中，如果需要設定子項的點選事件，需要傳回true
    @Override
    public boolean isChildSelectable(int groupPosition, int childPosition) {
        return true;
    }
}      

父布局的item布局如下

<?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/parent_title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="20sp"
        android:textColor="@color/black"
        android:text="這是父item"
        android:paddingLeft="30dp"
        android:layout_margin="5dp"/>
</LinearLayout>      

子布局的item也是一個簡單的文字

<?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/child_title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="18sp"
        android:textColor="@color/black"
        android:text="這是子item"
        android:layout_margin="5dp"/>
</LinearLayout>