/*
 * 獲取當前程序的版本號
 */
private String getVersionName() throws Exception{
  //獲取packagemanager的實例
  PackageManager packageManager = getPackageManager();
  //getPackageName()是你當前類的包名，0代表是獲取版本信息
  PackageInfo packInfo = packageManager.getPackageInfo(getPackageName(), 0);
  return packInfo.versionName;
}

/*
 * 用pull解析器解析服務器返回的xml文件 (xml封裝了版本號)
 */
public static UpdataInfo getUpdataInfo(InputStream is) throws Exception{
  XmlPullParser parser = Xml.newPullParser();
  parser.setInput(is, "utf-8");//設置解析的數(shù)據(jù)源
  int type = parser.getEventType();
  UpdataInfo info = new UpdataInfo();//實體
  while(type != XmlPullParser.END_DOCUMENT ){
    switch (type) {
    case XmlPullParser.START_TAG:
      if("version".equals(parser.getName())){
        info.setVersion(parser.nextText()); //獲取版本號
      }else if ("url".equals(parser.getName())){
        info.setUrl(parser.nextText()); //獲取要升級的APK文件
      }else if ("description".equals(parser.getName())){
        info.setDescription(parser.nextText()); //獲取該文件的信息
      }
      break;
    }
    type = parser.next();
  }
  return info;
}

public static File getFileFromServer(String path, ProgressDialog pd) throws Exception{
  //如果相等的話表示當前的sdcard掛載在手機上并且是可用的
  if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
    URL url = new URL(path);
    HttpURLConnection conn = (HttpURLConnection) url.openConnection();
    conn.setConnectTimeout(5000);
    //獲取到文件的大小
    pd.setMax(conn.getContentLength());
    InputStream is = conn.getInputStream();
    File file = new File(Environment.getExternalStorageDirectory(), "updata.apk");
    FileOutputStream fos = new FileOutputStream(file);
    BufferedInputStream bis = new BufferedInputStream(is);
    byte[] buffer = new byte[1024];
    int len ;
    int total=0;
    while((len =bis.read(buffer))!=-1){
      fos.write(buffer, 0, len);
      total+= len;
      //獲取當前下載量
      pd.setProgress(total);
    }
    fos.close();
    bis.close();
    is.close();
    return file;
  }
  else{
    return null;
  }
}

/*
 * 從服務器獲取xml解析并進行比對版本號
 */
public class CheckVersionTask implements Runnable{
  public void run() {
    try {
      //從資源文件獲取服務器 地址
      String path = getResources().getString(R.string.serverurl);
      //包裝成url的對象
      URL url = new URL(path);
      HttpURLConnection conn = (HttpURLConnection) url.openConnection();
      conn.setConnectTimeout(5000);
      InputStream is =conn.getInputStream();
      info = UpdataInfoParser.getUpdataInfo(is);
      if(info.getVersion().equals(versionname)){
        Log.i(TAG,"版本號相同無需升級");
        LoginMain();
      }else{
        Log.i(TAG,"版本號不同 ,提示用戶升級 ");
        Message msg = new Message();
        msg.what = UPDATA_CLIENT;
        handler.sendMessage(msg);
      }
    } catch (Exception e) {
      // 待處理
      Message msg = new Message();
      msg.what = GET_UNDATAINFO_ERROR;
      handler.sendMessage(msg);
      e.printStackTrace();
    }
  }
}
Handler handler = new Handler(){
  @Override
  public void handleMessage(Message msg) {
    // TODO Auto-generated method stub
    super.handleMessage(msg);
    switch (msg.what) {
    case UPDATA_CLIENT:
      //對話框通知用戶升級程序
      showUpdataDialog();
      break;
    case GET_UNDATAINFO_ERROR:
      //服務器超時
      Toast.makeText(getApplicationContext(), "獲取服務器更新信息失敗", 1).show();
      LoginMain();
      break;
    case DOWN_ERROR:
      //下載apk失敗
      Toast.makeText(getApplicationContext(), "下載新版本失敗", 1).show();
      LoginMain();
      break;
    }
  }
};
/*
 *
 * 彈出對話框通知用戶更新程序
 *
 * 彈出對話框的步驟：
 * 1.創(chuàng)建alertDialog的builder.
 * 2.要給builder設置屬性, 對話框的內(nèi)容,樣式,按鈕
 * 3.通過builder 創(chuàng)建一個對話框
 * 4.對話框show()出來
 */
protected void showUpdataDialog() {
  AlertDialog.Builder builer = new Builder(this) ;
  builer.setTitle("版本升級");
  builer.setMessage(info.getDescription());
  //當點確定按鈕時從服務器上下載 新的apk 然后安裝
  builer.setPositiveButton("確定", new OnClickListener() {
  public void onClick(DialogInterface dialog, int which) {
      Log.i(TAG,"下載apk,更新");
      downLoadApk();
    }
  });
  //當點取消按鈕時進行登錄
  builer.setNegativeButton("取消", new OnClickListener() {
    public void onClick(DialogInterface dialog, int which) {
      // TODO Auto-generated method stub
      LoginMain();
    }
  });
  AlertDialog dialog = builer.create();
  dialog.show();
}
/*
 * 從服務器中下載APK
 */
protected void downLoadApk() {
  final ProgressDialog pd;  //進度條對話框
  pd = new ProgressDialog(this);
  pd.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
  pd.setMessage("正在下載更新");
  pd.show();
  new Thread(){
    @Override
    public void run() {
      try {
        File file = DownLoadManager.getFileFromServer(info.getUrl(), pd);
        sleep(3000);
        installApk(file);
        pd.dismiss(); //結(jié)束掉進度條對話框
      } catch (Exception e) {
        Message msg = new Message();
        msg.what = DOWN_ERROR;
        handler.sendMessage(msg);
        e.printStackTrace();
      }
    }}.start();
}
//安裝apk
protected void installApk(File file) {
  Intent intent = new Intent();
  //執(zhí)行動作
  intent.setAction(Intent.ACTION_VIEW);
  //執(zhí)行的數(shù)據(jù)類型
  intent.setDataAndType(Uri.fromFile(file), "application/vnd.android.package-archive");
  startActivity(intent);
}
/*
 * 進入程序的主界面
 */
private void LoginMain(){
  Intent intent = new Intent(this,MainActivity.class);
  startActivity(intent);
  //結(jié)束掉當前的activity
  this.finish();
}

public class UpdataInfo {
  private String version;
  private String url;
  private String description;
  public String getVersion() {
    return version;
  }
  public void setVersion(String version) {
    this.version = version;
  }
  public String getUrl() {
    return url;
  }
  public void setUrl(String url) {
    this.url = url;
  }
  public String getDescription() {
    return description;
  }
  public void setDescription(String description) {
    this.description = description;
  }
}

<?xml version="1.0" encoding="utf-8"?>
<info>
  <version>2.0</version>
  <url>http://192.168.1.187:8080/mobilesafe.apk</url>
  <description>檢測到最新版本，請及時更新！</description>
</info>