Android應用 開發中,採用ListView組件來展示數據是很常用的功能,當一個應用要展現很多的數據時,一般情況下都不會把所有的數據一次就展示出來,而是通過分頁 的形式來展示數據,個人覺得這樣會有更好的用戶體驗。因此,很多應用都是採用分批次加載的形式來獲取用戶所需的數據。例如:微博客戶端可能會在用戶滑動至 列表底端時自動加載下一頁數據,也可能在底部放置一個"查看更多"按鈕,用戶點擊後,加載下一頁數據。
下面通過一個Demo來展示ListView功能如何實現:該Demo通過在ListView列表的底部添加一個“查看更多...”按鈕來加載新聞(模擬新聞客戶端)分頁數據。同時限定每次加載10條記錄,但完全加載完數據後,就 把ListView列表底部視圖“查看更多...”刪除。假設加載的數據總數爲 38 條記錄。先看下該Demo工程的程序結構圖:
其中包 com.andyidea.bean中News.java類是新聞實體類,包com.andyidea.listview中 paginationListViewActivity.java類是用來展示ListView列表。佈局layout中包含三個佈局文件,分別 爲:list_item.xml , loadmore.xml , main.xml 。下面分別貼下源碼:
layout中的 list_item.xml源碼:
01 |
<? xml
version = "1.0"
encoding = "utf-8" ?> |
03 |
xmlns:android = "http://schemas.android.com/apk/res/android" |
04 |
android:layout_width = "fill_parent" |
05 |
android:layout_height = "fill_parent" |
06 |
android:orientation = "vertical" > |
08 |
android:id = "@+id/newstitle" |
09 |
android:layout_width = "fill_parent" |
10 |
android:layout_height = "wrap_content" /> |
12 |
android:id = "@+id/newscontent" |
13 |
android:layout_width = "fill_parent" |
14 |
android:layout_height = "wrap_content" /> |
layout中loadmore.xml源碼:
01 |
<? xml
version = "1.0"
encoding = "utf-8" ?> |
03 |
xmlns:android = "http://schemas.android.com/apk/res/android" |
04 |
android:layout_width = "fill_parent" |
05 |
android:layout_height = "fill_parent" > |
07 |
android:id = "@+id/loadMoreButton" |
08 |
android:layout_width = "fill_parent" |
09 |
android:layout_height = "wrap_content" |
10 |
android:text = "查看更多..."
/> |
layout中main.xml源碼:
01 |
<? xml
version = "1.0"
encoding = "utf-8" ?> |
02 |
< LinearLayout
xmlns:android = "http://schemas.android.com/apk/res/android" |
03 |
android:orientation = "vertical" |
04 |
android:layout_width = "fill_parent" |
05 |
android:layout_height = "fill_parent" > |
07 |
android:id = "@+id/lvNews" |
08 |
android:layout_width = "fill_parent" |
09 |
android:layout_height = "wrap_content" /> |
包 com.andyidea.bean中News.java類源碼:
01 |
package
com.andyidea.bean; |
12 |
private
String content; |
14 |
public
String getTitle() { |
17 |
public
void setTitle(String title) { |
20 |
public
String getContent() { |
23 |
public
void setContent(String content) { |
24 |
this .content = content; |
包com.andyidea.listview中paginationListViewActivity.java類源碼:
001 |
package
com.andyidea.listview; |
003 |
import
java.util.ArrayList; |
004 |
import
java.util.List; |
006 |
import
com.andyidea.bean.News; |
008 |
import
android.app.Activity; |
009 |
import
android.os.Bundle; |
010 |
import
android.os.Handler; |
011 |
import
android.util.Log; |
012 |
import
android.view.View; |
013 |
import
android.view.ViewGroup; |
014 |
import
android.widget.AbsListView; |
015 |
import
android.widget.AbsListView.OnScrollListener; |
016 |
import
android.widget.BaseAdapter; |
017 |
import
android.widget.Button; |
018 |
import
android.widget.ListView; |
019 |
import
android.widget.TextView; |
020 |
import
android.widget.Toast; |
022 |
public
class PaginationListViewActivity extends
Activity implements
OnScrollListener { |
024 |
private
ListView listView; |
025 |
private
int visibleLastIndex =
0 ; |
026 |
private
int visibleItemCount;
|
027 |
private
int datasize =
38 ; |
028 |
private
PaginationAdapter adapter; |
029 |
private
View loadMoreView; |
030 |
private
Button loadMoreButton; |
031 |
private
Handler handler = new
Handler(); |
033 |
/** Called when the activity is first created. */ |
035 |
public
void onCreate(Bundle savedInstanceState) { |
036 |
super .onCreate(savedInstanceState); |
037 |
setContentView(R.layout.main); |
039 |
loadMoreView = getLayoutInflater().inflate(R.layout.loadmore,
null ); |
040 |
loadMoreButton = (Button)loadMoreView.findViewById(R.id.loadMoreButton); |
041 |
loadMoreButton.setOnClickListener( new
View.OnClickListener() { |
044 |
public
void onClick(View v) { |
045 |
loadMoreButton.setText( "正在加載中..." );
|
046 |
handler.postDelayed( new
Runnable() { |
051 |
adapter.notifyDataSetChanged(); |
052 |
loadMoreButton.setText( "查看更多..." );
|
059 |
listView = (ListView)findViewById(R.id.lvNews); |
060 |
listView.addFooterView(loadMoreView);
|
062 |
listView.setAdapter(adapter); |
063 |
listView.setOnScrollListener( this ); |
067 |
public
void onScrollStateChanged(AbsListView view,
int scrollState) { |
068 |
int
itemsLastIndex = adapter.getCount()- 1 ;
|
069 |
int
lastIndex = itemsLastIndex + 1 ; |
070 |
if
(scrollState == OnScrollListener.SCROLL_STATE_IDLE |
071 |
&& visibleLastIndex == lastIndex) { |
078 |
public
void onScroll(AbsListView view,
int firstVisibleItem, |
079 |
int
visibleItemCount, int
totalItemCount) { |
080 |
this .visibleItemCount = visibleItemCount; |
081 |
visibleLastIndex = firstVisibleItem + visibleItemCount -
1 ; |
083 |
Log.e( "========================= " , "========================" ); |
084 |
Log.e( "firstVisibleItem = " ,firstVisibleItem+ "" ); |
085 |
Log.e( "visibleItemCount = " ,visibleItemCount+ "" ); |
086 |
Log.e( "totalItemCount = " ,totalItemCount+ "" ); |
087 |
Log.e( "========================= " , "========================" ); |
090 |
if (totalItemCount == datasize+ 1 ){ |
091 |
listView.removeFooterView(loadMoreView); |
092 |
Toast.makeText( this ,
"數據全部加載完!" , Toast.LENGTH_LONG).show(); |
099 |
private
void initializeAdapter(){ |
100 |
List<News> news =
new ArrayList<News>(); |
101 |
for ( int
i= 1 ;i<= 10 ;i++){ |
102 |
News items =
new News(); |
103 |
items.setTitle( "Title" +i); |
104 |
items.setContent( "This is News Content" +i); |
107 |
adapter =
new PaginationAdapter(news); |
113 |
private
void loadMoreData(){ |
114 |
int
count = adapter.getCount(); |
116 |
if (count+ 10
<= datasize){ |
117 |
for ( int
i=count+ 1 ; i<=count+ 10 ; i++){ |
118 |
News item =
new News(); |
119 |
item.setTitle( "Title" +i); |
120 |
item.setContent( "This is News Content" +i); |
121 |
adapter.addNewsItem(item); |
124 |
for ( int
i=count+ 1 ; i<=datasize; i++){ |
125 |
News item =
new News(); |
126 |
item.setTitle( "Title" +i); |
127 |
item.setContent( "This is News Content" +i); |
128 |
adapter.addNewsItem(item); |
135 |
class
PaginationAdapter extends
BaseAdapter{ |
137 |
List<News> newsItems; |
139 |
public
PaginationAdapter(List<News> newsitems){ |
140 |
this .newsItems = newsitems; |
144 |
public
int getCount() { |
145 |
return
newsItems.size(); |
149 |
public
Object getItem( int
position) { |
150 |
return
newsItems.get(position); |
154 |
public
long getItemId( int
position) { |
159 |
public
View getView( int
position, View view, ViewGroup parent) { |
161 |
view = getLayoutInflater().inflate(R.layout.list_item,
null ); |
165 |
TextView tvTitle = (TextView)view.findViewById(R.id.newstitle); |
166 |
tvTitle.setText(newsItems.get(position).getTitle()); |
168 |
TextView tvContent = (TextView)view.findViewById(R.id.newscontent); |
169 |
tvContent.setText(newsItems.get(position).getContent()); |
178 |
public
void addNewsItem(News newsitem){ |
179 |
newsItems.add(newsitem); |
最後,運行程序的結果截圖如下:
通過上面的截圖,當我們點擊"查看更多..."按鈕時,就會加載下10條記錄,當加載完所有的記錄後,ListView的底部視圖將會移除。