public CaptureActivityHandler(
      CaptureActivity activity,
      Collection<BarcodeFormat> decodeFormats,
      String characterSet,
      CameraManager cameraManager) {
    this.activity = activity;

    // 启动扫描线程
    decodeThread =
        new DecodeThread(
            activity,
            decodeFormats,
            characterSet,
            new ViewfinderResultPointCallback(activity.getViewfinderView()));
    decodeThread.start();

    state = State.SUCCESS;

    // Start ourselves capturing previews and decoding.
    this.cameraManager = cameraManager;

    // 开启相机预览界面
    cameraManager.startPreview();

    restartPreviewAndDecode();
  }
  /** 完成一次扫描后,只需要再调用此方法即可 */
  private void restartPreviewAndDecode() {
    if (state == State.SUCCESS) {
      state = State.PREVIEW;

      // 向decodeThread绑定的handler(DecodeHandler)发送解码消息
      cameraManager.requestPreviewFrame(decodeThread.getHandler(), R.id.decode);
      activity.drawViewfinder();
    }
  }
  @SuppressWarnings("deprecation")
  @Override
  public void handleMessage(Message message) {
    switch (message.what) {
      case R.id.restart_preview: // 准备进行下一次扫描
        Log.d(TAG, "Got restart preview message");
        restartPreviewAndDecode();
        break;
      case R.id.decode_succeeded:
        Log.d(TAG, "Got decode succeeded message");
        state = State.SUCCESS;
        Bundle bundle = message.getData();
        Bitmap barcode = null;
        float scaleFactor = 1.0f;
        if (bundle != null) {
          byte[] compressedBitmap = bundle.getByteArray(DecodeThread.BARCODE_BITMAP);
          if (compressedBitmap != null) {
            barcode =
                BitmapFactory.decodeByteArray(compressedBitmap, 0, compressedBitmap.length, null);
            // Mutable copy:
            barcode = barcode.copy(Bitmap.Config.ARGB_8888, true);
          }
          scaleFactor = bundle.getFloat(DecodeThread.BARCODE_SCALED_FACTOR);
        }
        activity.handleDecode((Result) message.obj, barcode, scaleFactor);
        break;
      case R.id.decode_failed:
        // We're decoding as fast as possible, so when one decode fails,
        // start another.
        state = State.PREVIEW;
        cameraManager.requestPreviewFrame(decodeThread.getHandler(), R.id.decode);
        break;
      case R.id.return_scan_result:
        Log.d(TAG, "Got return scan result message");
        activity.setResult(Activity.RESULT_OK, (Intent) message.obj);
        activity.finish();
        break;
      case R.id.launch_product_query:
        Log.d(TAG, "Got product query message");
        String url = (String) message.obj;

        Intent intent = new Intent(Intent.ACTION_VIEW);
        intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_WHEN_TASK_RESET);
        intent.setData(Uri.parse(url));

        /** 这段代码是zxing项目组想要用chrome打开浏览器浏览url */
        ResolveInfo resolveInfo =
            activity.getPackageManager().resolveActivity(intent, PackageManager.MATCH_DEFAULT_ONLY);
        String browserPackageName = null;
        if (resolveInfo != null && resolveInfo.activityInfo != null) {
          browserPackageName = resolveInfo.activityInfo.packageName;
          Log.d(TAG, "Using browser in package " + browserPackageName);
        }

        // Needed for default Android browser / Chrome only apparently
        if ("com.android.browser".equals(browserPackageName)
            || "com.android.chrome".equals(browserPackageName)) {
          intent.setPackage(browserPackageName);
          intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
          intent.putExtra(Browser.EXTRA_APPLICATION_ID, browserPackageName);
        }

        try {
          activity.startActivity(intent);
        } catch (ActivityNotFoundException ignored) {
          Log.w(TAG, "Can't find anything to handle VIEW of URI " + url);
        }
        break;
    }
  }