似乎无法弄清楚 ExpandableListAdapter

Question

我正在尝试编写一个简单的示例，该示例通过网络提取外部数据并通过ExpandableListAdapter 填充ExpandableListView。我已经尝试了几个例子并且几乎迷失了。我熟悉使用 ArrayAdapter 类，但似乎 ExpandableListAdapter 有很大不同。这是我当前不显示任何内容的应用程序代码：

MyExpandableListAdapter：

public class MyExpandableListAdapter extends BaseExpandableListAdapter {

    public static class GroupHolder {
        TextView title;
    }

    public static class ChildHolder {
        TextView title;
        ImageView icon;
    }


    // groups.getChildren() returns the children
    private List<Group> groups;

    private Context context;

    private LayoutInflater inflater;

    public MyExpandableListAdapter(Context context, List<Group> groups) {
        this.context = context;
        this.groups = groups;
        this.inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    }

    public boolean hasStableIds() {
        return true;
    }

    public Object getGroup(int groupPosition) {
        return groups.get(groupPosition);
    }

    public int getGroupCount() {
        return groups.size();
    }

    public long getGroupId(int groupPosition) {
        return groupPosition;
    }

    public View getGroupView(int groupPosition, boolean isExpanded,
            View convertView, ViewGroup parent) {
        GroupHolder holder;

        if (convertView != null) {
            holder = (GroupHolder)convertView.getTag();
        } else {
            convertView = inflater.inflate(R.layout.group_item, parent, false);

            holder = new GroupHolder();
            holder.title = (TextView) convertView.findViewById(R.id.group_item_title);

            convertView.setTag(holder);
        }

        holder.title.setText(this.groups.get(groupPosition).getName());

        return convertView;
    }

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

    public Object getChild(int groupPosition, int childPosition) {
        return groups.get(groupPosition).getChildren().get(childPosition);
    }

    public long getChildId(int groupPosition, int childPosition) {
        return childPosition;
    }

    public int getChildrenCount(int groupPosition) {
        return groups.get(groupPosition).getChildren().size();
    }

    public View getChildView(int groupPosition, int childPosition,
            boolean isLastChild, View convertView, ViewGroup parent) {
        ChildHolder holder;

        if (convertView != null) {
            holder = (ChildHolder) convertView.getTag();
        } else {
            convertView = inflater.inflate(R.layout.child_item, parent, false);

            holder = new ChildHolder();
            holder.title = (TextView) convertView.findViewById(R.id.child_item_title);
            holder.icon = (ImageView) convertView.findViewById(R.id.child_item_icon);

            convertView.setTag(holder);
        }

        holder.title.setText(groups.get(groupPosition).getChildren().get(childPosition).getName());
//      TODO add in image loading.

        return convertView;
    }
}

MyExpandableListActivity：

public class MyExpandableListActivity extends ExpandableListActivity {

    private List<Group> groups;

    private ExpandableListAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.group_list);

        this.groups = new ArrayList<Group>();
        Group group = new Group("$1", "Colors");
        Child child = new Child("$2", "Red");
        groups.getChildren().add(child);

        this.adapter = new MyExpandableListAdapter(this, groups);

        setListAdapter(this.adapter);
    }
}

R.layout.group_list：

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

    <ExpandableListView android:id="@+id/android:list"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"/>

    <TextView android:id="@+id/android:empty"
            android:text="EMPTY! DOOM!"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"/>
</LinearLayout>

R.layout.group_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/group_item_title"/>
</LinearLayout>

R.layout.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"
        android:orientation="horizontal">

    <ImageView android:id="@+id/child_item_icon"
            android:layout_width="48px" android:layout_height="48px"/>

    <TextView android:id="@+id/child_item_title"/>
</LinearLayout>

当然，我看到的是“EMPTY！DOOM！”而不是我在活动中添加的列表项。我究竟做错了什么？

另外，SimpleExpandableListAdapter 似乎应该让事情变得简单，但我完全不知道它是如何工作的或如何使用它。谁能帮我解决这个问题？

Answer 1

这周我对两个项目在同一时间和同一空间中尝试使用“fill_parent”有所了解。您的列表可能被推到后面或屏幕外。我看到你的 group_list 布局中有一个类似的设置。希望对隐形列表有帮助。

Answer 2

如何在 group_list.xml 中将 LinearLayout 更改为垂直方向？

它与ExpandableListActivity 文档中给出的布局不太匹配。

您还可以在 getView() 方法等位置设置断点，并查看它是否被调用。