Android listview局部刷新和模拟应用下载(zhu)

2021-10-04 15:12:42

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：

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.com

date  :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();

    }

    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() != )

        {

            DownloadTask task = taskList.remove();

            // 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item

        public 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();

                    } 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.com

date  :2013-1-27

app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;

    }

    @Override

    public int getCount() {

        return dataList.size();

    }

    @Override

    public Object getItem(int position) {

        return dataList.get(position);

    }

    @Override

    public 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);

    }

    @Override

    public 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() {

            @Override

            public 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 < ) 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;

        }

    }

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.com

date  :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();

    }

    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() != )

        {

            DownloadTask task = taskList.remove();

            // 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item

        public 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();

                    } 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.com

date  :2013-1-27

app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;

    }

    @Override

    public int getCount() {

        return dataList.size();

    }

    @Override

    public Object getItem(int position) {

        return dataList.get(position);

    }

    @Override

    public 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);

    }

    @Override

    public 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() {

            @Override

            public 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 < ) 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=""

        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 =; i<; i++)

        {

            AppFile app = new AppFile();

            app.name = "快玩游戏--" + (i+);

            app.size = ;

            app.id = i;

            app.downloadState = DownloadManager.DOWNLOAD_STATE_NORMAL;

            app.downloadSize = ;

            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"

>

<ListView

android: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(zhu)Android listview局部刷新和模拟应用下载(zhu)

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(zhu)

(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(zhu)

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

上一篇：C# windows服务：C#windows服务中的Timer控件的使用


下一篇：VC 6.0 MFC关闭对话框在win7出现崩溃的情况