Android Listview动态加载数据

 

在研究网络数据加载的问题，比如我有几百，甚至上千条数据，这些数据如果一次性全部加载到arraylist，然后再加载到Listview中。我们必然会去单独开线程来做，这样造成的结果就是会出现等待时间很长，用户体验非常不好。我的想法是动态加载数据，第一次加载十条，然后往下面滑动的时候再追加十条，再往下面滑动的时候再去追加，这样大大减少了用户等待的时间，同时给处理数据留下了时间。网上看到了这样一个例子，挺好的，我改动了一下，达到了我想要的结果。

001import android.app.Activity;

002import android.os.Bundle;

003import android.os.Handler;

004import android.os.Message;

005import android.view.Gravity;

006import android.view.View;

007import android.view.ViewGroup;

008import android.widget.AbsListView;

009import android.widget.BaseAdapter;

010import android.widget.LinearLayout;

011import android.widget.ListView;

012import android.widget.ProgressBar;

013import android.widget.TextView;

014import android.widget.Toast;

015import android.widget.AbsListView.OnScrollListener;

016import android.widget.LinearLayout.LayoutParams;

017  

018public class ListViewForLoading extendsActivity implementsOnScrollListener {

019  

020    privatelistViewAdapter adapter = newlistViewAdapter();

021    ListView listView;

022    LinearLayout loadingLayout;

023    privateThread mThread;

024    /**

025     * 设置布局显示属性

026     */

027    privateLayoutParams mLayoutParams = newLinearLayout.LayoutParams(

028            LinearLayout.LayoutParams.WRAP_CONTENT,

029            LinearLayout.LayoutParams.WRAP_CONTENT);

030    /**

031     * 设置布局显示目标最大化属性

032     */

033    privateLayoutParams FFlayoutParams = newLinearLayout.LayoutParams(

034            LinearLayout.LayoutParams.FILL_PARENT,

035            LinearLayout.LayoutParams.FILL_PARENT);

036  

037    privateProgressBar progressBar;

038  

039    /** Called when the activity is first created. */

040    @Override

041    publicvoid onCreate(Bundle savedInstanceState) {

042        super.onCreate(savedInstanceState);

043        setContentView(R.layout.main);

044        init();

045    }

046  

047    privatevoid init() {

048        // TODO Auto-generated method stub

049        // 线性布局

050        LinearLayout layout =new LinearLayout(this);

051        // 设置布局 水平方向

052        layout.setOrientation(LinearLayout.HORIZONTAL);

053        // 进度条

054        progressBar =new ProgressBar(this);

055        // 进度条显示位置

056        progressBar.setPadding(0,0, 15,0);

057        // 把进度条加入到layout中

058        layout.addView(progressBar, mLayoutParams);

059        // 文本内容

060        TextView textView =new TextView(this);

061        textView.setText("加载中...");

062        textView.setGravity(Gravity.CENTER_VERTICAL);

063        // 把文本加入到layout中

064        layout.addView(textView, FFlayoutParams);

065        // 设置layout的重力方向，即对齐方式是

066        layout.setGravity(Gravity.CENTER);

067  

068        // 设置ListView的页脚layout

069        loadingLayout =new LinearLayout(this);

070        loadingLayout.addView(layout, mLayoutParams);

071        loadingLayout.setGravity(Gravity.CENTER);

072  

073        // 得到一个ListView用来显示条目

074        listView = (ListView) findViewById(R.id.tv);

075        // 添加到脚页显示

076        listView.addFooterView(loadingLayout);

077        // 给ListView添加适配器

078        listView.setAdapter(adapter);

079        // 给ListView注册滚动监听

080        listView.setOnScrollListener(this);

081    }

082  

083    /**

084     * 要用用于生成显示数据

085     * 

086     * @author huangbq

087     * 

088     */

089    classlistViewAdapter extendsBaseAdapter {

090        intcount = 10;

091  

092        publicint getCount() {

093            returncount;

094        }

095  

096        publicObject getItem(intpos) {

097            returnpos;

098        }

099  

100        publiclong getItemId(intpos) {

101            returnpos;

102        }

103  

104        publicView getView(intpos, View v, ViewGroup p) {

105            TextView view;

106            if(v == null) {

107                view =new TextView(ListViewForLoading.this);

108            }else {

109                view = (TextView) v;

110            }

111            view.setText("ListItem "+ pos);

112            view.setTextSize(20f);

113            view.setGravity(Gravity.CENTER);

114            view.setHeight(60);

115            returnview;

116        }

117    }

118  

119    @Override

120    publicvoid onScroll(AbsListView view,int firstVisibleItem,

121            intvisibleItemCount, inttotalItemCount) {

122        // TODO Auto-generated method stub

123        if(firstVisibleItem+visibleItemCount==totalItemCount)

124        {

125            //开线程去下载网络数据

126            if(mThread == null|| !mThread.isAlive()) {

127                mThread =new Thread() {

128                    @Override

129                    publicvoid run() {

130                        try{

131                            //这里放你网络数据请求的方法，我在这里用线程休眠5秒方法来处理

132                            Thread.sleep(5000);

133                        }catch (InterruptedException e) {

134                            e.printStackTrace();

135                        }

136                        Message message =new Message();

137                        message.what =1;

138                        handler.sendMessage(message);

139                    }

140                };

141                mThread.start();                

142            }

143        }

144    }

145  

146    @Override

147    publicvoid onScrollStateChanged(AbsListView view,int scrollState) {

148        // TODO Auto-generated method stub        

149    }

150  

151    privateHandler handler = newHandler() {

152        @Override

153        publicvoid handleMessage(Message msg) {

154            // TODO Auto-generated method stub

155            switch(msg.what) {

156            case1:

157                if(adapter.count <= 41) {

158                    adapter.count +=10;

159                    intcurrentPage = adapter.count / 10;

160                    Toast.makeText(getApplicationContext(),"第"+ currentPage + "页", Toast.LENGTH_LONG).show();

161                }else {

162                    listView.removeFooterView(loadingLayout);

163                }

164                //重新刷新Listview的adapter里面数据

165                adapter.notifyDataSetChanged();

166                break;

167            default:

168                break;

169            }

170        }

171  

172    };

173}

运行结果如下图：

转自：http://www.cnblogs.com/tanlon/archive/2011/03/20/1989323.html