public class UpdateManger {
 // 應用程序Context
 private Context mContext;
 // 提示消息
 private String updateMsg = "有最新的軟件包，請下載！";
 // 下載安裝包的網絡路徑
 private String apkUrl = "http://softfile.3g.qq.com:8080/msoft/179/24659/43549/qq_hd_mini_1.4.apk";
 private Dialog noticeDialog;// 提示有軟件更新的對話框
 private Dialog downloadDialog;// 下載對話框
 private static final String savePath = "/sdcard/updatedemo/";// 保存apk的文件夾
 private static final String saveFileName = savePath + "UpdateDemoRelease.apk";
 // 進度條與通知UI刷新的handler和msg常量
 private ProgressBar mProgress;
 private static final int DOWN_UPDATE = 1;
 private static final int DOWN_OVER = 2;

 private int progress;// 當前進度
 private Thread downLoadThread; // 下載線程
 private boolean interceptFlag = false;// 用戶取消下載
 // 通知處理刷新界面的handler
 private Handler mHandler = new Handler() {
  @SuppressLint("HandlerLeak")
  @Override
  public void handleMessage(Message msg) {
   switch (msg.what) {
   case DOWN_UPDATE:
    mProgress.setProgress(progress);
    break;
   case DOWN_OVER:
    installApk();
    break;
   }
   super.handleMessage(msg);
  }
 };
 public UpdateManger(Context context) {
  this.mContext = context;
 }
 // 顯示更新程序對話框，供主程序調用
 public void checkUpdateInfo() {
  showNoticeDialog();
 }
 private void showNoticeDialog() {
  android.app.AlertDialog.Builder builder = new android.app.AlertDialog.Builder(
    mContext);// Builder，可以通過此builder設置改變AleartDialog的默認的主題樣式及屬性相關信息
  builder.setTitle("軟件版本更新");
  builder.setMessage(updateMsg);
  builder.setPositiveButton("下載", new OnClickListener() {
   @Override
   public void onClick(DialogInterface dialog, int which) {
    dialog.dismiss();// 當取消對話框后進行操作一定的代碼？取消對話框
    showDownloadDialog();
   }
  });
  builder.setNegativeButton("以后再說", new OnClickListener() {
   @Override
   public void onClick(DialogInterface dialog, int which) {
    dialog.dismiss();
   }
  });
  noticeDialog = builder.create();
  noticeDialog.show();
 }
 protected void showDownloadDialog() {
  android.app.AlertDialog.Builder builder = new android.app.AlertDialog.Builder(mContext);
  builder.setTitle("軟件版本更新");
  final LayoutInflater inflater = LayoutInflater.from(mContext);
  View v = inflater.inflate(R.layout.progress, null);
  mProgress = (ProgressBar) v.findViewById(R.id.progress);
  builder.setView(v);// 設置對話框的內容為一個View
  builder.setNegativeButton("取消", new OnClickListener() {
   @Override
   public void onClick(DialogInterface dialog, int which) {
    dialog.dismiss();
    interceptFlag = true;
   }
  });
  downloadDialog = builder.create();
  downloadDialog.show();
  downloadApk();
 }
 private void downloadApk() {
  downLoadThread = new Thread(mdownApkRunnable);
  downLoadThread.start();
 }
 protected void installApk() {
  File apkfile = new File(saveFileName);
  if (!apkfile.exists()) {
   return;
  }
  Intent i = new Intent(Intent.ACTION_VIEW);
  i.setDataAndType(Uri.parse("file://" + apkfile.toString()),
    "application/vnd.android.package-archive");// File.toString()會返回路徑信息
  mContext.startActivity(i);
 }
 private Runnable mdownApkRunnable = new Runnable() {
  @Override
  public void run() {
   URL url;
   try {
    url = new URL(apkUrl);
    HttpURLConnection conn = (HttpURLConnection) url.openConnection();
    conn.connect();
    int length = conn.getContentLength();
    InputStream ins = conn.getInputStream();
    File file = new File(savePath);
    if (!file.exists()) {
     file.mkdir();
    }
    String apkFile = saveFileName;
    File ApkFile = new File(apkFile);
    FileOutputStream outStream = new FileOutputStream(ApkFile);
    int count = 0;
    byte buf[] = new byte[1024];
    do {
     int numread = ins.read(buf);
     count += numread;
     progress = (int) (((float) count / length) * 100);
     // 下載進度
     mHandler.sendEmptyMessage(DOWN_UPDATE);
     if (numread <= 0) {
      // 下載完成通知安裝
      mHandler.sendEmptyMessage(DOWN_OVER);
      break;
     }
     outStream.write(buf, 0, numread);
    } while (!interceptFlag);// 點擊取消停止下載
    outStream.close();
    ins.close();
   } catch (Exception e) {
    e.printStackTrace();
   }
  }
 };
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content" >

<ProgressBar
android:id="@+id/progress"
style="?android:attr/progressBarStyleHorizontal"
android:layout_width="fill_parent"
android:layout_height="wrap_content" />

</LinearLayout>