android 高級之旅 （六）ExpandableListView 使用詳解

ExpandableListView和ListView有很多相似之處，E可以實現qq那樣的下拉列表。如效果圖

佈局代碼：

    <ExpandableListView
        android:layout_width="match_parent"
        android:id="@+id/expandable_lv"
        android:listSelector="#ffbaaa"
        android:background="#ffffff"
        android:cacheColorHint="#c92c2c"
        android:layout_height="match_parent">
    </ExpandableListView>

group.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:orientation="vertical"
              android:layout_width="match_parent"
              android:layout_height="match_parent">

    <TextView
        android:layout_width="match_parent"
        android:id="@+id/group_tv"
        android:gravity="center"
        android:text="1122"
        android:layout_height="48dp"/>
</LinearLayout>

child.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="match_parent"
              android:layout_height="match_parent"
              android:orientation="horizontal">

    <ImageView
        android:id="@+id/child_iv"
        android:layout_width="60dp"
        android:layout_height="60dp"
        android:src="@mipmap/ic_launcher"/>

    <LinearLayout
        android:padding="6dp"
        android:layout_width="match_parent"
        android:layout_height="60dp"
        android:orientation="vertical">

        <TextView
            android:id="@+id/tv1"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1"
            android:text="111111111"/>

        <TextView
            android:id="@+id/tv2"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1"
            android:text="111111111"/>

        <TextView
            android:id="@+id/tv3"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1"
            android:text="111111111"/>


    </LinearLayout>

</LinearLayout>

MianActivity

public class MainActivity extends AppCompatActivity {

    private LayoutInflater inflater;
    private ExpandableListView exLv;
    private List<StrBean> groupList;
    private List<ChildBean> childList;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        exLv = (ExpandableListView) findViewById(R.id.expandable_lv);
        inflater = LayoutInflater.from(MainActivity.this);
        groupList = new ArrayList<>();
        childList = new ArrayList<>();
        initData();
//        exLv.setBottom(10);

        exLv.setAdapter(new MyAdapter(groupList,MainActivity.this));

    }

    private void initData() {
        for (int i = 0; i < 5; i++) {
            StrBean strBean = new StrBean();
            strBean.setChildSize(8);
            strBean.setStrName("深航"+i);
            for (int j = 0; j < 8; j++) {
                ChildBean childBean = new ChildBean();
                childBean.setPrice(1+j+"萬");
                childBean.setSecondPrice(1+"萬");
                childBean.setTitle("商務卡");
                childList.add(childBean);
            }
            strBean.setList(childList);
            groupList.add(strBean);
        }

    }
}

最重要的 adpter

public class MyAdapter extends BaseExpandableListAdapter {
    private List<StrBean> groupList;
    Context context;
    private Object childHolder;

    public MyAdapter(List<StrBean> groupList, Context context) {
        this.groupList = groupList;
        this.context = context;
    }

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

    @Override
    public int getChildrenCount(int groupPosition) {
        return groupList.get(groupPosition).getChildSize();
    }

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

    @Override
    public Object getChild(int groupPosition, int childPosition) {
        return groupList.get(groupPosition);
    }

    @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) {

        View view = null;
        GroupHolder groupHolder = null;
        if (convertView != null) {
            view = convertView;
            groupHolder = (GroupHolder) view.getTag();
        } else {
            view = View.inflate(context, R.layout.group, null);
            groupHolder = new GroupHolder();
            groupHolder.exTv = (TextView) view.findViewById(R.id.group_tv);
            view.setTag(groupHolder);
        }
        groupHolder.exTv.setText(groupList.get(groupPosition).getStrName());
        return view;
    }

    @Override
    public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
        View view = null;
        ChildHolder childHolder = null;
        if (convertView != null) {
            view = convertView;
            childHolder = (ChildHolder) view.getTag();
        } else {
            view = View.inflate(context, R.layout.child, null);
            childHolder = new ChildHolder();
            childHolder.iv = (ImageView) view.findViewById(R.id.child_iv);
            childHolder.priceTv = (TextView) view.findViewById(R.id.tv1);
            childHolder.scPriceTv = (TextView) view.findViewById(R.id.tv2);
            childHolder.titleTv = (TextView) view.findViewById(R.id.tv3);
            view.setTag(childHolder);

        }
        childHolder.scPriceTv.setText(groupList.get(groupPosition).getList().get(childPosition).getSecondPrice());
        childHolder.titleTv.setText(groupList.get(groupPosition).getList().get(childPosition).getTitle());
        childHolder.priceTv.setText(groupList.get(groupPosition).getList().get(childPosition).getPrice());
        return view;
    }

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

    class GroupHolder{
        TextView exTv;
    }
    class ChildHolder{
        ImageView iv;
        TextView priceTv;
        TextView scPriceTv;
        TextView titleTv;
    }
}

前面介紹過ExpandableListView與ListView類似，所以ListView Adapter中存在的方法，ExpandableListView Adapter必定存在，只是Group和Child分別重寫了ListView Adapter中的方法，同時新增加了兩個方法，分別是hasStableIds() 和isChildSelectable(int groupPosition, int childPosition)，所以，ExpandableListView Adapter中總共重寫了10個方法。
其中要注意hasStableIds() 和isChildSelectable(int groupPosition, int childPosition)這兩個方法。hasStableIds() 主要是用來判斷ExpandableListView內容id是否有效的(返回true or false)，系統會跟據id來確定當前顯示哪條內容，也就是firstVisibleChild的位置。而isChildSelectable(int groupPosition, int childPosition)用來判斷某Group某個child是否可可選。我們可以添加條件控制某Group某個child可點或不可點擊。當不加任何條件直接返回false,所有的組的child均不可點擊。

關於expandablelistview的點擊事件，直接添加點擊事件即可。需要注意的是：

1. 當設置setOnGroupClickListener監聽並讓其返回true時,所有Group消費點擊事件，事件均不能分發傳遞給child(換言之，設置setOnChildClickListener不起任何作用)。

2.默認設置完Group以及child，Group左邊會默認有以上下切換的圖標，假如你有強迫症可以通過mListView.setGroupIndicator(null)去除。

3.前面已經簡單說明了isChildSelectable(int groupPosition, int childPosition)方法的作用，所以當我們需要child可點擊時，必須將setOnGroupClickListener和isChildSelectable對應設置爲false和true。

4.說到這裏也許讀者會問，到底還是沒有說出圖一的做法。現在對圖一進行詳細的介紹。圖一主要是將Group設置爲不能收縮並且使其默認展開(即設置setOnGroupClickListener返回true，並且添加源碼中setAdapter後三行代碼)。