android listview局部刷新和模拟应用下载

在android开发中，listview是比较常用的一个组件，在listview的数据需要更新的时候，一般会用notifyDataSetChanged()这个函数，但是它会更新listview中所有可视范围内的item，这样对性能肯定会有影响。比较常见的情景是android应用商店中的下载列表，当我们下载一款游戏的时候，只需要更新这款游戏对应的进度就可以了。本文就来模拟android应用商店的游戏下载，实现对listview的局部刷新，只实现一个简单的demo，不去真的下载文件。
1. 首先来创建代表应用商店中的app文件的类：AppFile.java，包含了一些基本的属性，源码：

package com.alexzhou.downloadfile; /** * author:alexzhou  * email :zhoujiangbohai@163.com  * date :2013-1-27 *  * 游戏列表中的app文件 **/ public class AppFile {     public int id;    public String name;    // app的大小    public int size;    // 已下载大小    public int downloadSize;    // 下载状态:正常,正在下载，暂停，等待，已下载    public int downloadState;}

2. 由于实际开发时，AppFile的属性比较多，这里创建一个辅助类：DownloadFile.java，代表下载中的文件，源码：

package com.alexzhou.downloadfile; /** * author:alexzhou  * email :zhoujiangbohai@163.com  * date :2013-1-27 *  * 下载的文件 **/ public class DownloadFile {     public int downloadID;    public int downloadSize;    public int totalSize;    public int downloadState;}

3. 接下来需要一个下载管理类：DownloadManager.java，它管理所有下载任务。当同时下载很多任务的时候，界面会卡，所以指定只能同时下载3个任务，每个任务会启动一个线程，这里使用了ExecutorService线程池。当提交了超过三个下载任务时，只执行前3个任务，第四个任务会等到前面有一个下载完成后再下载，以此类推。这里还用到了android提供的一个工具类SparseArray，它是用来替代HashMap的，性能比HashMap要好。下面看源码：

package com.alexzhou.downloadfile;import java.util.ArrayList;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import android.os.Handler;import android.os.Message;import android.util.Log;import android.util.SparseArray;/**author:alexzhou email :zhoujiangbohai@163.comdate  :2013-1-27下载管理 **/public class DownloadManager {// 下载状态：正常，暂停，下载中，已下载，排队中public static final int DOWNLOAD_STATE_NORMAL = 0x00;public static final int DOWNLOAD_STATE_PAUSE = 0x01;public static final int DOWNLOAD_STATE_DOWNLOADING = 0x02;public static final int DOWNLOAD_STATE_FINISH = 0x03;public static final int DOWNLOAD_STATE_WAITING = 0x04;// SparseArray是android中替代Hashmap的类,可以提高效率private SparseArray<DownloadFile> downloadFiles = new SparseArray<DownloadFile>();// 用来管理所有下载任务private ArrayList<DownloadTask> taskList = new ArrayList<DownloadTask>();private Handler mHandler;private final static Object syncObj = new Object();private static DownloadManager instance;private ExecutorService executorService;private DownloadManager(){// 最多只能同时下载3个任务，其余的任务排队等待executorService = Executors.newFixedThreadPool(3);}public static DownloadManager getInstance(){if(null == instance){synchronized(syncObj) {instance = new DownloadManager();}return instance;}return instance;}public void setHandler(Handler handler) {this.mHandler =  handler;}// 开始下载，创建一个下载线程public void startDownload(DownloadFile file) {downloadFiles.put(file.downloadID, file);DownloadTask task = new DownloadTask(file.downloadID);taskList.add(task);executorService.submit(task);}public void stopAllDownloadTask() {while(taskList.size() != 0){DownloadTask task = taskList.remove(0);// 可以在这里做其他的处理task.stopTask();}// 会停止正在进行的任务和拒绝接受新的任务executorService.shutdownNow();}// 下载任务class DownloadTask implements Runnable {private boolean isWorking = false;private int downloadId;public DownloadTask(int id){this.isWorking = true;this.downloadId = id;}public void stopTask(){this.isWorking = false;}// 更新listview中对应的itempublic void update(DownloadFile downloadFile){Message msg = mHandler.obtainMessage();if(downloadFile.totalSize == downloadFile.downloadSize)downloadFile.downloadState = DOWNLOAD_STATE_FINISH;msg.obj = downloadFile;msg.sendToTarget();}public void run() {// 更新下载文件的状态DownloadFile downloadFile = downloadFiles.get(downloadId);downloadFile.downloadState = DOWNLOAD_STATE_DOWNLOADING;while(isWorking){// 检测是否下载完成if(downloadFile.downloadState != DOWNLOAD_STATE_DOWNLOADING){downloadFiles.remove(downloadFile.downloadID);taskList.remove(this);isWorking = false;break;}//Log.e("", "downloadSize="+downloadFile.downloadSize+"; size="+downloadFile.totalSize);// 这里只是模拟了下载，每一秒更新一次item的下载状态if(downloadFile.downloadSize <= downloadFile.totalSize){this.update(downloadFile);}if(downloadFile.downloadSize < downloadFile.totalSize){try {Thread.sleep(100);} catch (InterruptedException e) {e.printStackTrace();downloadFile.downloadState = DOWNLOAD_STATE_PAUSE;this.update(downloadFile);downloadFiles.remove(downloadId);isWorking = false;break;}++ downloadFile.downloadSize;}}}}}

4. 接下来就需要实现listview的adapter了，这里比较重要的一个函数是updateView，这是实现listview局部刷新的关键，通过索引index得到listview中对应位置的子view，然后再更新该view的数据。源码：

package com.alexzhou.downloadfile;import android.content.Context;import android.graphics.drawable.Drawable;import android.os.Handler;import android.os.Message;import android.util.Log;import android.util.SparseArray;import android.view.LayoutInflater;import android.view.View;import android.view.View.OnClickListener;import android.view.ViewGroup;import android.widget.BaseAdapter;import android.widget.Button;import android.widget.ImageView;import android.widget.LinearLayout;import android.widget.ListView;import android.widget.TextView;/**author:alexzhou email :zhoujiangbohai@163.comdate  :2013-1-27app列表的数据适配器 **/public class AppListAdapter extends BaseAdapter {private SparseArray<AppFile> dataList = null;private LayoutInflater inflater = null;private Context mContext;private DownloadManager downloadManager;private ListView listView;public AppListAdapter(Context context, SparseArray<AppFile> dataList) {this.inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);this.dataList = dataList;this.mContext = context;this.downloadManager = DownloadManager.getInstance();this.downloadManager.setHandler(mHandler);}public void setListView(ListView view){this.listView = view;}@Overridepublic int getCount() {return dataList.size();}@Overridepublic Object getItem(int position) {return dataList.get(position);}@Overridepublic long getItemId(int position) {return position;}// 改变下载按钮的样式private void changeBtnStyle(Button btn, boolean enable){if(enable){btn.setBackgroundResource(R.drawable.btn_download_norm);}else{btn.setBackgroundResource(R.drawable.btn_download_disable);}btn.setEnabled(enable);}@Overridepublic View getView(int position, View convertView, ViewGroup parent) {final ViewHolder holder;if (null == convertView) {holder = new ViewHolder();convertView = inflater.inflate(R.layout.listitem_app, null);holder.layout = (LinearLayout) convertView.findViewById(R.id.gamelist_item_layout);holder.icon = (ImageView) convertView.findViewById(R.id.app_icon);holder.name = (TextView) convertView.findViewById(R.id.app_name);holder.size = (TextView) convertView.findViewById(R.id.app_size);holder.btn = (Button) convertView.findViewById(R.id.download_btn);convertView.setTag(holder);} else {holder = (ViewHolder) convertView.getTag();}// 这里position和app.id的值是相等的final AppFile app = dataList.get(position);//Log.e("", "id="+app.id+", name="+app.name);holder.name.setText(app.name);holder.size.setText((app.downloadSize * 100.0f / app.size) + "%");Drawable drawable = mContext.getResources().getDrawable(R.drawable.app_icon);holder.icon.setImageDrawable(drawable);switch(app.downloadState){case DownloadManager.DOWNLOAD_STATE_NORMAL:holder.btn.setText("下载");this.changeBtnStyle(holder.btn, true);break;case DownloadManager.DOWNLOAD_STATE_DOWNLOADING:holder.btn.setText("下载中");this.changeBtnStyle(holder.btn, false);break;case DownloadManager.DOWNLOAD_STATE_FINISH:holder.btn.setText("已下载");this.changeBtnStyle(holder.btn, false);break;case DownloadManager.DOWNLOAD_STATE_WAITING:holder.btn.setText("排队中");this.changeBtnStyle(holder.btn, false);break;}holder.btn.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View v) {DownloadFile downloadFile = new DownloadFile();downloadFile.downloadID = app.id;downloadFile.downloadState = DownloadManager.DOWNLOAD_STATE_WAITING;app.downloadState = DownloadManager.DOWNLOAD_STATE_WAITING;downloadFile.downloadSize = app.downloadSize;downloadFile.totalSize = app.size;holder.btn.setText("排队中");    changeBtnStyle(holder.btn, false);downloadManager.startDownload(downloadFile);}});return convertView;}static class ViewHolder {LinearLayout layout;ImageView icon;TextView name;TextView size;Button btn;}private Handler mHandler = new Handler() {public void handleMessage(Message msg){DownloadFile downloadFile = (DownloadFile)msg.obj;AppFile appFile = dataList.get(downloadFile.downloadID);appFile.downloadSize = downloadFile.downloadSize;appFile.downloadState = downloadFile.downloadState;// notifyDataSetChanged会执行getView函数，更新所有可视item的数据//notifyDataSetChanged();// 只更新指定item的数据，提高了性能updateView(appFile.id);}};// 更新指定item的数据private void updateView(int index){int visiblePos = listView.getFirstVisiblePosition();int offset = index - visiblePos;//Log.e("", "index="+index+"visiblePos="+visiblePos+"offset="+offset);// 只有在可见区域才更新if(offset < 0) return;View view = listView.getChildAt(offset);final AppFile app = dataList.get(index);ViewHolder holder = (ViewHolder)view.getTag();//Log.e("", "id="+app.id+", name="+app.name);holder.name.setText(app.name);holder.size.setText((app.downloadSize * 100.0f / app.size) + "%");Drawable drawable = mContext.getResources().getDrawable(R.drawable.app_icon);holder.icon.setImageDrawable(drawable);switch(app.downloadState){case DownloadManager.DOWNLOAD_STATE_DOWNLOADING:holder.btn.setText("下载中");this.changeBtnStyle(holder.btn, false);break;case DownloadManager.DOWNLOAD_STATE_FINISH:holder.btn.setText("已下载");this.changeBtnStyle(holder.btn, false);break;}}}

布局文件listitem_app.xml：

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:id="@+id/gamelist_item_layout"    android:layout_width="fill_parent"    android:layout_height="wrap_content"    android:gravity="center_vertical"    android:background="@drawable/style_listitem_background"    android:paddingBottom="5dp"    android:paddingTop="5dp" >     <ImageView        android:id="@+id/app_icon"        android:layout_width="53dip"        android:layout_height="53dip"        android:layout_marginLeft="5dip"        android:adjustViewBounds="false"        android:padding="5dp" />     <LinearLayout        android:layout_width="match_parent"        android:layout_height="60dp"        android:layout_marginLeft="5dp"        android:layout_weight="1"        android:gravity="center_vertical"        android:orientation="vertical" >         <TextView            android:id="@+id/app_name"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:singleLine="true"            android:text=""            android:textColor="#000000"            android:textSize="13sp" />         <TextView            android:id="@+id/app_size"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:textColor="#000000"            android:textSize="10sp" />     </LinearLayout>     <Button        android:id="@+id/download_btn"        android:layout_width="55dip"        android:layout_height="30dip"        android:layout_marginRight="10dip"        android:background="@drawable/style_btn_download"        android:focusable="false"        android:text="@string/download"        android:textColor="#ffffffff"        android:textSize="12sp" /> </LinearLayout>

listview中item样式文件style_listitem_background.xml：

<?xml version="1.0" encoding="utf-8"?><selector xmlns:android="http://schemas.android.com/apk/res/android">   <!-- 没有焦点时的背景颜色 -->  <item android:state_window_focused="false"  >      <shape>          <gradient             android:startColor="#ffffff"             android:endColor="#E3E3E3"             android:angle="-90" />        </shape>   </item>    <!-- 非触摸模式下获得焦点并单击时的背景颜色 -->      <item android:state_focused="true" android:state_pressed="true"        android:drawable="@drawable/bg_listview_item_selected" />   <!--触摸模式下单击时的背景颜色  -->  <item android:state_focused="false" android:state_pressed="true"        android:drawable="@drawable/bg_listview_item_selected" />    <!--选中时的背景颜色  -->  <item android:state_selected="true"  android:drawable="@drawable/bg_listview_item_selected" />   <!--获得焦点时的背景  颜色-->  <item android:state_focused="true" android:drawable="@drawable/bg_listview_item_selected" /> </selector>

item中的button样式文件style_btn_download.xml：

<?xml version="1.0" encoding="utf-8"?><selector xmlns:android="http://schemas.android.com/apk/res/android">    <item android:state_pressed="true"        android:drawable="@drawable/btn_download_pressed" />    <item android:drawable="@drawable/btn_download_norm" /></selector>

字符文件strings.xml：

<?xml version="1.0" encoding="utf-8"?><resources>    <string name="app_name">AndroidDownloadFile</string>    <string name="download">下载</string></resources>

5. 最后创建MainActivity.java，源码：

package com.alexzhou.downloadfile; import android.app.Activity;import android.os.Bundle;import android.util.SparseArray;import android.widget.ListView; public class MainActivity extends Activity {    private SparseArray<AppFile> appList = new SparseArray<AppFile>();     private ListView listView;     @Override    public void onCreate(Bundle savedInstanceState)    {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        initData();        initUI();    }     private void initData()    {        for(int i =0; i<20; i++)        {            AppFile app = new AppFile();            app.name = "快玩游戏--" + (i+1);            app.size = 100;            app.id = i;            app.downloadState = DownloadManager.DOWNLOAD_STATE_NORMAL;            app.downloadSize = 0;            appList.put(app.id, app);        }    }     private void initUI()    {        listView = (ListView)this.findViewById(R.id.listview);        AppListAdapter adapter = new AppListAdapter(this, appList);        adapter.setListView(listView);        listView.setAdapter(adapter);    }     @Override    protected void onDestroy() {        super.onDestroy();        DownloadManager.getInstance().stopAllDownloadTask();    } }

布局文件activity_main.xml：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:orientation="vertical"android:layout_width="fill_parent"android:layout_height="fill_parent"><ListViewandroid:id="@+id/listview"android:layout_width="fill_parent"android:layout_height="fill_parent"android:fastScrollEnabled="true"/></LinearLayout>

到此为止，代码部分已经全部完成了，下面来看看最终效果图：

android listview局部刷新和模拟应用下载_第1张图片

android listview局部刷新和模拟应用下载_第2张图片

这里对比一下分别使用updateView和notifyDataSetChanged时，有什么不一样，看看打印日志：
(1)使用notifyDataSetChanged时，listview可视范围内的所有子项都更新了。

android listview局部刷新和模拟应用下载_第3张图片

(2)使用updateView时，只更新了指定的子项。

android listview局部刷新和模拟应用下载_第4张图片

实例源码地址 :http://pan.baidu.com/share/link?shareid=229182&uk=167811495

转载请注明来自：Alex Zhou的程序世界，本文链接：http://codingnow.cn/android/1059.html

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