Android中ListView分页加载数据.doc

Android中ListView分页加载数据 Android应用开发中，采用ListView组件来展示数据是很常用的功能，当一个应用要展现很多的数据时，一般情况下都不会把所有的数据一次就展示出来，而是通过分页的形式来展示数据，个人觉得这样会有更好的用户体验。因此，很多应用都是采用分批次加载的形式来获取用户所需的数据。例如：微博客户端可能会在用户滑动至列表底端时自动加载下一页数据，也可能在底部放置一个查看更多按钮，用户点击后，加载下一页数据。 下面通过一个Demo来展示ListView功能如何实现：该Demo通过在ListView列表的底部添加一个“查看更多.”按钮来加载新闻(模拟新闻客户端)分页数据。同时限定每次加载10条记录，但完全加载完数据后，就把ListView列表底部视图“查看更多.”删除。假设加载的数据总数为 38 条记录。先看下该Demo工程的程序结构图：其中包 com.andyidea.bean中News.java类是新闻实体类，包com.andyidea.listview中paginationListViewActivity.java类是用来展示ListView列表。布局layout中包含三个布局文件，分别为：list_item.xml ， loadmore.xml ， main.xml 。下面分别贴下源码：layout中的 list_item.xml源码：html view plaincopy1 2 7 11 15 layout中loadmore.xml源码：html view plaincopy16 17 21 26 layout中main.xml源码：html view plaincopy27 28 32 36 /LinearLayou 包 com.andyidea.bean中News.java类源码：html view plaincopy37 package com.andyidea.bean; 38 39 /* 40 * 新闻实体类 41 * author Andy.Chen 42 * mail Chenjunjun.ZJ 43 * 44 */ 45 public class News 46 47 private String title; /标题 48 private String content; /内容 49 50 public String getTitle() 51 return title; 52 53 public void setTitle(String title) 54 this.title = title; 55 56 public String getContent() 57 return content; 58 59 public void setContent(String content) 60 this.content = content; 61 62 63 包com.andyidea.listview中paginationListViewActivity.java类源码：html view plaincopy64 package com.andyidea.listview; 65 66 import java.util.ArrayList; 67 import java.util.List; 68 69 import com.andyidea.bean.News; 70 71 import android.app.Activity; 72 import android.os.Bundle; 73 import android.os.Handler; 74 import android.util.Log; 75 import android.view.View; 76 import android.view.ViewGroup; 77 import android.widget.AbsListView; 78 import android.widget.AbsListView.OnScrollListener; 79 import android.widget.BaseAdapter; 80 import android.widget.Button; 81 import android.widget.ListView; 82 import android.widget.TextView; 83 import android.widget.Toast; 84 85 public class PaginationListViewActivity extends Activity implements OnScrollListener 86 87 private ListView listView; 88 private int visibleLastIndex = 0; /最后的可视项索引 89 private int visibleItemCount; / 当前窗口可见项总数 90 private int datasize = 38; /模拟数据集的条数 91 private PaginationAdapter adapter; 92 private View loadMoreView; 93 private Button loadMoreButton; 94 private Handler handler = new Handler(); 95 96 /* Called when the activity is first created. */ 97 Override 98 public void onCreate(Bundle savedInstanceState) 99 super.onCreate(savedInstanceState); 100 setContentView(R.layout.main); 101 102 loadMoreView = getLayoutInflater().inflate(R.layout.loadmore, null); 103 loadMoreButton = (Button)loadMoreView.findViewById(R.id.loadMoreButton); 104 loadMoreButton.setOnClickListener(new View.OnClickListener() 105 106 Override 107 public void onClick(View v) 108 loadMoreButton.setText(正在加载中.); /设置按钮文字 109 handler.postDelayed(new Runnable() 110 111 Override 112 public void run() 113 loadMoreData(); 114 adapter.notifyDataSetChanged(); 115 loadMoreButton.setText(查看更多.); /恢复按钮文字 116 117 ,2000); 118 119 120 ); 121 122 listView = (ListView)findViewById(R.id.lvNews); 123 listView.addFooterView(loadMoreView); /设置列表底部视图 124 initializeAdapter(); 125 listView.setAdapter(adapter); 126 listView.setOnScrollListener(this); 127 128 129 Override 130 public void onScrollStateChanged(AbsListView view, int scrollState) 131 int itemsLastIndex = adapter.getCount()-1; /数据集最后一项的索引 132 int lastIndex = itemsLastIndex + 1; 133 if (scrollState = OnScrollListener.SCROLL_STATE_IDLE 134 & visibleLastIndex = lastIndex) 135 / 如果是自动加载,可以在这里放置异步加载数据的代码 136 137 138 139 140 Override 141 public void onScroll(AbsListView view, int firstVisibleItem, 142 int visibleItemCount, int totalItemCount) 143 this.visibleItemCount = visibleItemCount; 144 visibleLastIndex = firstVisibleItem + visibleItemCount - 1; 145 146 Log.e(= ,=); 147 Log.e(firstVisibleItem = ,firstVisibleItem+); 148 Log.e(visibleItemCount = ,visibleItemCount+); 149 Log.e(totalItemCount = ,totalItemCount+); 150 Log.e(= ,=); 151 152 /如果所有的记录选项等于数据集的条数，则移除列表底部视图 153 if(totalItemCount = datasize+1) 154 listView.removeFooterView(loadMoreView); 155 Toast.makeText(this, 数据全部加载完!, Toast.LENGTH_LONG).show(); 156 157 158 159 /* 160 * 初始化ListView的适配器 161 */ 162 private void initializeAdapter() 163 List news = new ArrayList(); 164 for(int i=1;i=10;i+) 165 News items = new News(); 166 items.setTitle(Title+i); 167 items.setContent(This is News Content+i); 168 news.add(items); 169 170 adapter = new PaginationAdapter(news); 171 172 173 /* 174 * 加载更多数据 175 */ 176 private void loadMoreData() 177 int count = adapter.getCount(); 178 179 if(count+10 = datasize) 180 for(int i=count+1; i=count+10; i+) 181 News item = new News(); 182 item.setTitle(Title+i); 183 item.setContent(This is News Content+i); 184 adapter.addNewsItem(item); 185 186 else 187 for(int i=count+1; i=datasize; i+) 188 News item = new News(); 189 item.setTitle(Title+i); 190 item.setContent(This is News Content+i); 191 adapter.addNewsItem(item); 192 193 194 195 196 197 198 class PaginationAdapter extends BaseAdapter 199 200 List newsItems; 201 202 public PaginationAdapter(List newsitems) 203 this.newsItems = newsitems; 204 205 206 Override 207 public int getCount() 208 return newsItems.size(); 209 210 211 Override 212 public Object getItem(int position) 213 return newsItems.get(position); 214 215 216 Override 217 public long getItemId(int position) 218 return position; 219 220 221 Override 222 public View getView(int position, View view, ViewGroup parent) 223 if(