android学习笔记22：可展开的ListView

最新推荐文章于 2024-09-05 10:42:39 发布

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#listview #android #layout #string #object #encoding

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本文将介绍如何在Android应用中利用ExpandableListView组件实现可展开的子类目功能，并通过自定义适配器BaseExpandableListAdapter来提供数据源。演示了一个简单的例子，包括XML布局设计、自定义适配器实现，以及如何将适配器与ExpandableListView关联。

有时在写程序时，我们希望一个listview能展开其下的子类目，在android中可以通过使用ExpandAbleListView来实现，只需要在代码里为ExpandAbleListView设置一个ExpandAbleLIstAdapter的数据源即可。

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
	android:orientation="vertical"
	android:layout_width="fill_parent"
	android:layout_height="fill_parent"
	>
<ExpandableListView 
	android:id="@+id/list" 
	android:layout_width="fill_parent" 
	android:layout_height="wrap_content" 
	android:childIndicator="@drawable/icon" 
	></ExpandableListView>
</LinearLayout>

public class ExpandableListViewTest extends Activity
{
	@Override
	public void onCreate(Bundle savedInstanceState)
	{
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		//创建一个BaseExpandableListAdapter对象
		ExpandableListAdapter adapter = new BaseExpandableListAdapter()
		{
			int[] logos = new int[]
			{
				R.drawable.sunyz_1, 
				R.drawable.sunyz_6,
				R.drawable.sunyz_7
			};
 			private String[] CDs = new String[]
				{ "风筝", "完美的一天", "是时候"};
			private String[][] songs = new String[][]
			{ 
				{ "绿光", "不是真的爱我", "爱情字典", "练习" },
				{ "Honey Honey", "心愿", "明天晴天", "隐形人" },
				{ "愚人的国度", "是时候" , "世说心语" }
			};
			//获取指定组位置、指定子列表项处的子列表项数据
			@Override
			public Object getChild(int groupPosition, int childPosition)
			{
				return songs[groupPosition][childPosition];
			}
			@Override
			public long getChildId(int groupPosition, int childPosition)
			{
				return childPosition;
			}
			@Override
			public int getChildrenCount(int groupPosition)
			{
				return songs[groupPosition].length;
			}
			private TextView getTextView()
			{
				//用于实现条目的虚拟列表的基类. 这里的列表没有空间的定义。 例如，该类的子类可以以网格的形式、走马灯的形式显示，或者作为堆栈等等
				AbsListView.LayoutParams lp = new AbsListView.LayoutParams(
						ViewGroup.LayoutParams.FILL_PARENT, 64);  //设置宽和高 
				TextView textView = new TextView(ExpandableListViewTest.this);
				textView.setLayoutParams(lp);
				textView.setGravity(Gravity.CENTER_VERTICAL | Gravity.LEFT);
				textView.setPadding(36, 0, 0, 0);
				textView.setTextSize(20);
				return textView;
			}
			//该方法决定每个子选项的外观
			@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;
			}
			//获取指定组位置处的组数据
			@Override
			public Object getGroup(int groupPosition)
			{
				return CDs[groupPosition];
			}
			@Override
			public int getGroupCount()
			{
				return CDs.length;
			}
			@Override
			public long getGroupId(int groupPosition)
			{
				return groupPosition;
			}
			//该方法决定每个组选项的外观
			@Override
			public View getGroupView(int groupPosition, boolean isExpanded,
					View convertView, ViewGroup parent)
			{
				LinearLayout ll = new LinearLayout(ExpandableListViewTest.this);
				ll.setOrientation(0);
				ImageView logo = new ImageView(ExpandableListViewTest.this);
				logo.setImageResource(logos[groupPosition]);
				ll.addView(logo);
				TextView textView = getTextView();
				textView.setText(getGroup(groupPosition).toString());				
				ll.addView(textView);			
				return ll;
			}
			@Override
			public boolean isChildSelectable(int groupPosition, int childPosition)
			{
				return true;
			}
			@Override
			public boolean hasStableIds()
			{
				return true;
			}
		};
		ExpandableListView expandListView = (ExpandableListView)
			findViewById(R.id.list);
		expandListView.setAdapter(adapter);
	}
}