Android开发进阶系列（五） 连接服务器下载文件或资源

对于简单的应用程序，很少会需要连接服务器，单机运行就行了。但是当你需要不断更新软件版本，或者你的APP需要用到大量的资源而直接打包进APK文件太大，这时你就需要连接到服务器去下载文件。下面这个项目就提供了如何连接服务器更新APK和如何下载资源的方法。

连接服务器更新APK

1. 服务器上放置一个记录版本号的txt文件，比如version.txt。放置一个用于更新的APK，比如new.apk

   final static String strurl = "http://www.xxx.com/my/version.txt";final static String strurl_apk = "http://www.xxx.com/my/new.apk";

2. MainActivity的onCreate()方法中调用CheckUpdate()方法

   @Overridepublic void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    requestWindowFeature(Window.FEATURE_NO_TITLE);    setContentView(R.layout.main);    ......    CheckUpdate(); // 检查更新}

3. 连接服务器前当然要先判断网络连接，如果是要下载到SD卡的，还要判断是否有SD卡，判断的代码很简单就不贴上了。

   // 检查更新private void CheckUpdate(boolean isAuto) {    // 判断版本号，然后下载       downloader = new HttpDownLoader();    int serverVersion = 1;    serverVersion = Integer.parseInt(FusionField.downloader.downLoadText(strurl));    if(serverVersion > localVersion) {        AlertDialog.Builder builder = new Builder(this);         builder.setTitle("软件升级")                .setMessage("发现新版本，是否升级！")                .setPositiveButton("升级",new DialogInterface.OnClickListener() {                     @Override                    public void onClick(DialogInterface dialog, int which) {                         //开启更新服务UpdateService                        //这里为了把update更好模块化，可以传一些updateService依赖的值                        //如布局ID，资源ID，动态获取的标题,这里以app_name为例                        Intent updateIntent =new Intent(MainActivity.this, UpdateService.class);                        startService(updateIntent);                    }                })                .setNegativeButton("取消", new android.content.DialogInterface.OnClickListener() {                     @Override                    public void onClick(DialogInterface dialog, int which) {                         dialog.dismiss();                     }                 });        builder.create().show();     }}

4. UpdateService.class执行后台下载和通知栏下载进度条的更新

   public class UpdateService extends Service{//文件存储private File updateDir = null;private File updateFile = null; public static String downloadDir = "/download/";//通知栏private NotificationManager updateNotificationManager = null;private Notification updateNotification = null;//通知栏跳转Intentprivate Intent updateIntent = null;private PendingIntent updatePendingIntent = null;//下载状态private final static int DOWNLOAD_COMPLETE = 0;private final static int DOWNLOAD_FAIL = 1;@Override  public void onCreate() {      super.onCreate();  } @Overridepublic int onStartCommand(Intent intent, int flags, int startId) {          //创建文件          if(android.os.Environment.MEDIA_MOUNTED.equals(android.os.Environment.getExternalStorageState())){        updateDir = new File(Environment.getExternalStorageDirectory(),downloadDir);        updateFile = new File(updateDir.getPath(),strurl_apk_name);    }    this.updateNotificationManager = (NotificationManager)getSystemService(NOTIFICATION_SERVICE);    this.updateNotification = new Notification();    //设置下载过程中，点击通知栏，回到主界面    updateIntent = new Intent(this, MainActivity.class);    updatePendingIntent = PendingIntent.getActivity(this,0,updateIntent,0);    //设置通知栏显示内容    updateNotification.icon = android.R.drawable.stat_sys_download;    updateNotification.tickerText = "开始下载";    updateNotification.setLatestEventInfo(this,apk_title,"0%",updatePendingIntent);    //发出通知    updateNotificationManager.notify(0,updateNotification);    //开启一个新的线程下载，如果使用Service同步下载，会导致ANR问题，Service本身也会阻塞    new Thread(new updateRunnable()).start();//这个是下载的重点，是下载的过程    return super.onStartCommand(intent, flags, startId);}private Handler updateHandler = new  Handler(){    @Override    public void handleMessage(Message msg) {        switch(msg.what){            case DOWNLOAD_COMPLETE:                //点击安装PendingIntent                Uri uri = Uri.fromFile(updateFile);                Intent installIntent = new Intent(Intent.ACTION_VIEW);                installIntent.setDataAndType(uri, "application/vnd.android.package-archive");                updatePendingIntent = PendingIntent.getActivity(UpdateService.this, 0, installIntent, 0);                updateNotification.defaults = Notification.DEFAULT_SOUND;//铃声提醒                 updateNotification.setLatestEventInfo(UpdateService.this, FusionField.update_apk_title, "下载完成,点击安装。", updatePendingIntent);                updateNotificationManager.notify(0, updateNotification);                                    //停止服务                stopSelf();                break;            case DOWNLOAD_FAIL:                //下载失败                updateNotification.setLatestEventInfo(UpdateService.this, FusionField.update_apk_title, "下载失败。", updatePendingIntent);                updateNotificationManager.notify(0, updateNotification);                break;            default:                stopSelf();        }    }};class updateRunnable implements Runnable {    Message message = updateHandler.obtainMessage();    public void run() {        message.what = DOWNLOAD_COMPLETE;        try{            //增加权限;            if(!updateDir.exists()){                updateDir.mkdirs();            }            if(!updateFile.exists()){                updateFile.createNewFile();            }            //下载函数            //增加权限;            String strurl = strurl_apk;            long downloadSize = downloadUpdateFile(strurl,updateFile);            if(downloadSize>0){                //下载成功                updateHandler.sendMessage(message);            }        }catch(Exception ex){            ex.printStackTrace();            message.what = DOWNLOAD_FAIL;            //下载失败            updateHandler.sendMessage(message);        }    }}public long downloadUpdateFile(String downloadUrl, File saveFile) throws Exception {    int downloadCount = 0;    int currentSize = 0;    long totalSize = 0;    int updateTotalSize = 0;    HttpURLConnection httpConnection = null;    InputStream is = null;    FileOutputStream fos = null;    try {        URL url = new URL(downloadUrl);        httpConnection = (HttpURLConnection)url.openConnection();        httpConnection.setRequestProperty("User-Agent", "PacificHttpClient");        if(currentSize > 0) {            httpConnection.setRequestProperty("RANGE", "bytes=" + currentSize + "-");        }        httpConnection.setConnectTimeout(10000);        httpConnection.setReadTimeout(20000);        updateTotalSize = httpConnection.getContentLength();        if (httpConnection.getResponseCode() == 404) {            throw new Exception("fail!");        }        is = httpConnection.getInputStream();                           fos = new FileOutputStream(saveFile, false);        byte buffer[] = new byte[4096];        int readsize = 0;        while((readsize = is.read(buffer)) > 0){            fos.write(buffer, 0, readsize);            totalSize += readsize;            //为了防止频繁的通知导致应用吃紧，百分比增加10才通知一次，可自行调整            if((downloadCount == 0)||(int) (totalSize*100/updateTotalSize)-10>downloadCount){                 downloadCount += 10;                updateNotification.setLatestEventInfo(UpdateService.this, "正在下载", (int)totalSize*100/updateTotalSize+"%", updatePendingIntent);                updateNotificationManager.notify(0, updateNotification);            }                                }    } finally {        if(httpConnection != null) {            httpConnection.disconnect();        }        if(is != null) {            is.close();        }        if(fos != null) {            fos.close();        }    }    return totalSize;}@Overridepublic IBinder onBind(Intent arg0) {    // TODO Auto-generated method stub    return null;}}

下载资源文件

和下载APK文件相同的是，都使用HttpDownLoader()方法，不同的是，下载资源文件一般是需要弹出等待进度条阻塞用户操作的。

1. 弹出等待框，开始下载

private ProgressDialog pd; //等待下载滚动圈myRingtoneListView.setOnItemClickListener(new OnItemClickListener() {            @Override               public void onItemClick(AdapterView<?> parent, View view, int position, long id) {                currentSelected = position+1;                // 下载更多                if(position >= ringtoneNum) {                    if(!isNetworkAvaiable()) {                        Toast.makeText(RingtoneActivity.this, "请确认网络连接正常！", Toast.LENGTH_SHORT).show();                        return;                    }                    if(!FusionField.sdState.equals(Environment.MEDIA_MOUNTED)) {                        Toast.makeText(RingtoneActivity.this, "请插入SD卡！", Toast.LENGTH_SHORT).show();                        return;                    }                    final int idToDownload = ringtoneNum+1;                    FusionField.downloader = new HttpDownLoader();                    pd = ProgressDialog.show(RingtoneActivity.this, "正在下载", "请等待。。。",true, true);                    pd.setCanceledOnTouchOutside(false);                    pd.setOnCancelListener(new ProgressDialog.OnCancelListener() {                        @Override                        public void onCancel(DialogInterface dialog) {                            // 终止下载                            pd.dismiss();                        }                    });                     new Thread(){                        public void run(){                            //在这里执行长耗时方法                            int res = downloader.downLoadFile(ringtone_path+"/ringtone"+ idToDownload + ".mp3", "download/ringtone", "/ringtone" + idToDownload + ".mp3");                            //执行完毕后给handler发送一个消息                                                         if(res == 0) {                                          handler.sendEmptyMessage(0);                                MainActivity main = MainActivity.getInstance();                            }                            else if(res == 1)                                handler.sendEmptyMessage(1);                            else                                handler.sendEmptyMessage(3);                            }                    }.start();                    return;                }

1. 下载成功或失败的消息处理

//定义Handler对象        private Handler handler =new Handler(){            @Override            //当有消息发送出来的时候就执行Handler的这个方法            public void handleMessage(Message msg){                switch(msg.what)                {                case 0: // 下载成功                    Toast.makeText(RingtoneActivity.this, "下载完成！", Toast.LENGTH_SHORT).show();                    finish();                    break;                case 1: // 文件已存在                    Toast.makeText(RingtoneActivity.this, "文件已存在！" , Toast.LENGTH_LONG).show();                    break;                case 2: // 下载被取消                    Toast.makeText(RingtoneActivity.this, "已终止下载！", Toast.LENGTH_SHORT).show();                    break;                case 3: // 下载出错                    Toast.makeText(RingtoneActivity.this, "下载中断，请检查网络设置", Toast.LENGTH_SHORT).show();                                                   break;                case 4: // 服务器地址出错                    Toast.makeText(RingtoneActivity.this, "服务器地址解析错误，请检查网络设置", Toast.LENGTH_SHORT).show();                    break;                }                super.handleMessage(msg);                //只要执行到这里就关闭对话框                pd.dismiss();             }        };

• * Android开发进阶系列（一） 序言 *
• * Android开发进阶系列（二） Tab页界面布局 *
• * Android开发进阶系列（三） 系统参数的获取和Broadcast *
• * Android开发进阶系列（四） 左移拉出Menu菜单界面布局 *
• * Android开发进阶系列（五） 连接服务器更新APK或下载资源文件 *
• * Android开发进阶系列（六） ListView的基本用法 *
• * Android开发进阶系列（七） 使用数据库 *
• * Android开发进阶系列（八） 界面美化之自定义弹出框 *
• * Android开发进阶系列（九） AChartEngine专题 *