Android中动态更新ListView

在使用ListView时，会遇到当ListView列表滑动到最底端时，添加新的列表项的问题，本文通过代码演示如何动态的添加新的列表项到ListView中。
实现步骤：调用ListView的setOnScrollListener()方法设置滑动监听器，实现OnScrollListener接口的方法，判断当列表滑动到最低端时，加载新的列表项。
其中OnScrollListener接口需要实现如下两个方法：
onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount)
view 报告滑动状态的视图
firstVisibleItem 可视的第一个列表项的索引
visibleItemCount 可视的列表项个数
totalItemCount 总共的列表项个数
onScrollStateChanged(AbsListView view, int scrollState)
view 报告滑动状态的视图
scrollState 滑动状态
滑动状态包括
SCROLL_STATE_IDLE : 0 视图没有滑动
SCROLL_STATE_TOUCH_SCROLL : 1 用户正在触摸滑动，手指仍在屏幕上
SCROLL_STATE_FLING : 2 用户之前触摸滑动，现在正在滑行，直到停止
下面通过代码给大家演示效果
main.xml

1	<?xml version="1.0" encoding="utf-8"?>

2	<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

3	android:orientation="vertical"

4	android:layout_width="fill_parent"

5	android:layout_height="fill_parent"

6

>

7

<ListView

8	android:id="@id/android:list"

9	android:layout_width="match_parent"

10	android:layout_height="match_parent"

11	android:layout_weight="1"

12	android:drawSelectorOnTop="false"

13

/>

14	</LinearLayout>

footer.xml

1	<?xml version="1.0" encoding="utf-8"?>

2	<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

3	android:layout_width="fill_parent"

4	android:layout_height="wrap_content"

5	android:gravity="center"

6	android:orientation="horizontal"

7

>

8	<ProgressBar

9	android:id="@+id/progressbar"

10	android:layout_width="wrap_content"

11	android:layout_height="wrap_content"

12	style="\?android:attr/progressBarStyleSmall"

13

/>

14

<TextView

15	android:layout_width="wrap_content"

16	android:layout_height="wrap_content"

17	android:textSize="20.0sp"

18	android:text="正在加载..."

19

/>

20	</LinearLayout>

MainActicity.xml

1	package com.szy.listview;

2

3	import android.app.ListActivity;

4	import android.os.Bundle;

5	import android.os.Handler;

6	import android.os.Message;

7	import android.view.Gravity;

8	import android.view.View;

9	import android.view.ViewGroup;

10	import android.widget.AbsListView;

11	import android.widget.BaseAdapter;

12	import android.widget.ListView;

13	import android.widget.TextView;

14

15

/**

16	*@author coolszy

17	*@date 2012-3-27

18	*@blog http://blog.92coding.com

19

*/

20	public class MainActivity extends ListActivity

21

{

22	private ListView mListView;

23	private CustomAdapter mAdapter;

24	private int mScrollState;

25	private View mFooter;

26

27

@Override

28	public void onCreate(Bundle savedInstanceState)

29

{

30	super.onCreate(savedInstanceState);

31	setContentView(R.layout.main);

32

33	//获取ListView

34	mListView = getListView();

35	//根据footer.xml描述创建View

36	mFooter = getLayoutInflater().inflate(R.layout.footer, null);

37	// 在ListView底部添加正在加载视图

38	//注意：addFooterView方法需要在调用setListAdapter方法前调用！

39	mListView.addFooterView(mFooter);

40	mAdapter = new CustomAdapter();

41	setListAdapter(mAdapter);

42	//给ListView添加滚动监听器

43	mListView.setOnScrollListener(new AbsListView.OnScrollListener()

44

{

45

@Override

46	public void onScrollStateChanged(AbsListView view, int scrollState)

47

{

48

//记录当前状态

49	mScrollState = scrollState;

50

}

51

52

@Override

53	public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount)

54

{

55	// 可视的最后一个列表项的索引

56	int lastVisibleItem = firstVisibleItem + visibleItemCount - 1;

57	//当列表正处于滑动状态且滑动到列表底部时，执行

58	if (mScrollState != AbsListView.OnScrollListener.SCROLL_STATE_IDLE

59	&& lastVisibleItem == totalItemCount - 1)

60

{

61	// 执行线程，模拟睡眠5秒钟后添加10个列表项

62	new Thread()

63

{

64

65	private Handler handler = new Handler()

66

{

67

68

@Override

69	public void handleMessage(Message msg)

70

{

71	super.handleMessage(msg);

72	//增加Item数量

73	mAdapter.count += 10;

74

//通知数据集变化

75	mAdapter.notifyDataSetChanged();

76

}

77

78

};

79

80

@Override

81	public void run()

82

{

83	super.run();

84

try

85

{

86	sleep(5000);

87	handler.sendEmptyMessage(0);

88	} catch (InterruptedException e)

89

{

90	e.printStackTrace();

91

}

92

}

93

94	}.start();

95

}

96

}

97

});

98

}

99

100	private class CustomAdapter extends BaseAdapter

101

{

102	// 初始列表项数量

103	int count = 20;

104

105

@Override

106	public int getCount()

107

{

108	return count;

109

}

110

111

@Override

112	public Object getItem(int position)

113

{

114	return position;

115

}

116

117

@Override

118	public long getItemId(int position)

119

{

120	return position;

121

}

122

123

@Override

124	public View getView(int position, View convertView, ViewGroup parent)

125

{

126	TextView result = (TextView) convertView;

127	//动态创建TextView添加早ListView中

128	if (result == null)

129

{

130	result = new TextView(MainActivity.this);

131	result.setTextAppearance(MainActivity.this, android.R.style.TextAppearance_Large);

132	AbsListView.LayoutParams layoutParams = new AbsListView.LayoutParams

133	(AbsListView.LayoutParams.FILL_PARENT,

134	AbsListView.LayoutParams.WRAP_CONTENT);

135	result.setLayoutParams(layoutParams);

136	result.setGravity(Gravity.CENTER);

137

}

138	result.setText("第 " + (position + 1)+"行");

139	return result;

140

}

141

}

142

}