ExpandableListView（可展开的列表组件）的说明以及其用法

ExpandableListView的用法和ListView非常像，只是其所显示的列表项应该由ExpandableListAdapter提供，下面是它的xml属性及说明：

然而，接下来是用事实说话了：

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1、该项目的布局文件非常简单，和ListView差不多，此处就不贴出代码了。

2、ExpandableListViewActivity.java关键代码如下：

（要定义一个全局的私有的listView变量）

listView = (ExpandableListView) findViewById(R.id.list);
MyExpandableListAdapter adapter = new MyExpandableListAdapter();
listView.setAdapter(adapter);

3、MyExpandableListAdapter代码如下：

public class MyExpandableListAdapter implements ExpandableListAdapter {
    int[] logos = new int[]{
            R.drawable.word,
            R.drawable.excel,
            R.drawable.email,
            R.drawable.ppt
    };
    private String[] armTypes = new String[]{
            "WORD", "EXCEL", "EMAIL", "PPT"
    };
    private String[][] arms = new String[][]{
            {"文档编辑", "文档排版", "文档处理", "文档打印"},
            {"表格编辑", "表格排版", "表格处理", "表格打印"},
            {"收发邮件", "管理邮箱", "登录登出", "注册绑定"},
            {"演示编辑", "演示排版", "演示处理", "演示打印"},
    };

    @Override
    public void registerDataSetObserver(DataSetObserver observer) {

    }

    @Override
    public void unregisterDataSetObserver(DataSetObserver observer) {

    }

    @Override
    public int getGroupCount() {
        return armTypes.length;
    }

    @Override
    public int getChildrenCount(int groupPosition) {
        return arms[groupPosition].length;
    }

    @Override
    public Object getGroup(int groupPosition) {
        return armTypes[groupPosition];
    }

    @Override
    public Object getChild(int groupPosition, int childPosition) {
        return arms[groupPosition][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) {
        LinearLayout ll = new LinearLayout(ExpandableListViewActivity.this);
        ll.setOrientation(LinearLayout.HORIZONTAL);
        ImageView logo = new ImageView(ExpandableListViewActivity.this);
        logo.setImageResource(logos[groupPosition]);
        logo.setPadding(36, 15, 0, 0);
        ll.addView(logo);
        TextView textView = getTextView();
        textView.setText(getGroup(groupPosition).toString());
        textView.setPadding(10, 0, 0, 0);
        ll.addView(textView);
        return ll;
    }

    @Override
    public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
        TextView textView = getTextView();
        textView.setText(getChild(groupPosition, childPosition).toString());
        return textView;
    }

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

    @Override
    public boolean areAllItemsEnabled() {
        return false;
    }

    @Override
    public boolean isEmpty() {
        return false;
    }

    @Override
    public void onGroupExpanded(int groupPosition) {

    }

    @Override
    public void onGroupCollapsed(int groupPosition) {

    }

    @Override
    public long getCombinedChildId(long groupId, long childId) {
        return 0;
    }

    @Override
    public long getCombinedGroupId(long groupId) {
        return 0;
    }

    private TextView getTextView() {
        AbsListView.LayoutParams lp = new AbsListView.LayoutParams(ViewGroup.LayoutParams.FILL_PARENT, 64);
        TextView textView = new TextView(ExpandableListViewActivity.this);
        textView.setLayoutParams(lp);
        textView.setGravity(Gravity.CENTER_VERTICAL | Gravity.LEFT);
        textView.setPadding(36, 0, 0, 0);
        textView.setTextSize(20);
        return textView;
    }
}

代码上面没有做多少注释，在这里说明一下吧：

该adapter有两个关键方法：getChildView（）和getGroupView（）；

        ----------前者返回的view对象作为子列表项，后者返回的view作为组列表项。

4、下面是该程序的运行界面了：