android上画方框

来自zxing开源码

 public Rect getFramingRect() {
    if (framingRect == null) {
      if (camera == null) {
        return null;
      }
      Point screenResolution = configManager.getScreenResolution();
      int width = screenResolution.x * 3 / 4;
     /* if (width < MIN_FRAME_WIDTH) {
        width = MIN_FRAME_WIDTH;
      } else if (width > MAX_FRAME_WIDTH) {
        width = MAX_FRAME_WIDTH;
      }*/
      int height = screenResolution.y * 3 / 4;
     /* if (height < MIN_FRAME_HEIGHT) {
        height = MIN_FRAME_HEIGHT;
      } else if (height > MAX_FRAME_HEIGHT) {
        height = MAX_FRAME_HEIGHT;
      }*/
      int leftOffset = (screenResolution.x - width) / 2;
      int topOffset = (screenResolution.y - height) / 2;
      framingRect = new Rect(leftOffset, topOffset, leftOffset + width, topOffset + height);
      Log.d(TAG, "Calculated framing rect: " + framingRect);
    }
    return framingRect;
  }





 public Rect getFramingRectInPreview() {
    if (framingRectInPreview == null) {
      Rect framingRect = getFramingRect();
      if (framingRect == null) {
        return null;
      }
      Rect rect = new Rect(framingRect);
      Point cameraResolution = configManager.getCameraResolution();
      Point screenResolution = configManager.getScreenResolution();
      rect.left = rect.left * cameraResolution.x / screenResolution.x;
      rect.right = rect.right * cameraResolution.x / screenResolution.x;
      rect.top = rect.top * cameraResolution.y / screenResolution.y;
      rect.bottom = rect.bottom * cameraResolution.y / screenResolution.y;
      framingRectInPreview = rect;
    }
    return framingRectInPreview;
  }




@Override
  public void onDraw(Canvas canvas) {
    Rect frame = cameraManager.getFramingRect();
    if (frame == null) {
      return;
    }
    int width = canvas.getWidth();
    int height = canvas.getHeight();

    // Draw the exterior (i.e. outside the framing rect) darkened
    paint.setColor(resultBitmap != null ? resultColor : maskColor);
    canvas.drawRect(0, 0, width, frame.top, paint);
    canvas.drawRect(0, frame.top, frame.left, frame.bottom + 1, paint);
    canvas.drawRect(frame.right + 1, frame.top, width, frame.bottom + 1, paint);
    canvas.drawRect(0, frame.bottom + 1, width, height, paint);

    if (resultBitmap != null) {
      // Draw the opaque result bitmap over the scanning rectangle
      paint.setAlpha(CURRENT_POINT_OPACITY);
      canvas.drawBitmap(resultBitmap, null, frame, paint);
    } else {

      // Draw a two pixel solid black border inside the framing rect
      paint.setColor(frameColor);
      canvas.drawRect(frame.left, frame.top, frame.right + 1, frame.top + 2, paint);
      canvas.drawRect(frame.left, frame.top + 2, frame.left + 2, frame.bottom - 1, paint);
      canvas.drawRect(frame.right - 1, frame.top, frame.right + 1, frame.bottom - 1, paint);
      canvas.drawRect(frame.left, frame.bottom - 1, frame.right + 1, frame.bottom + 1, paint);

      // Draw a red "laser scanner" line through the middle to show decoding is active
      paint.setColor(laserColor);
      paint.setAlpha(SCANNER_ALPHA[scannerAlpha]);
      scannerAlpha = (scannerAlpha + 1) % SCANNER_ALPHA.length;
      int middle = frame.height() / 2 + frame.top;
      canvas.drawRect(frame.left + 2, middle - 1, frame.right - 1, middle + 2, paint);
      
      Rect previewFrame = cameraManager.getFramingRectInPreview();
      float scaleX = frame.width() / (float) previewFrame.width();
      float scaleY = frame.height() / (float) previewFrame.height();

      List<ResultPoint> currentPossible = possibleResultPoints;
      List<ResultPoint> currentLast = lastPossibleResultPoints;
      int frameLeft = frame.left;
      int frameTop = frame.top;
      if (currentPossible.isEmpty()) {
        lastPossibleResultPoints = null;
      } else {
        possibleResultPoints = new ArrayList<ResultPoint>(5);
        lastPossibleResultPoints = currentPossible;
        paint.setAlpha(CURRENT_POINT_OPACITY);
        paint.setColor(resultPointColor);
        synchronized (currentPossible) {
          for (ResultPoint point : currentPossible) {
            canvas.drawCircle(frameLeft + (int) (point.getX() * scaleX),
                              frameTop + (int) (point.getY() * scaleY),
                              POINT_SIZE, paint);
          }
        }
      }
      if (currentLast != null) {
        paint.setAlpha(CURRENT_POINT_OPACITY / 2);
        paint.setColor(resultPointColor);
        synchronized (currentLast) {
          float radius = POINT_SIZE / 2.0f;
          for (ResultPoint point : currentLast) {
            canvas.drawCircle(frameLeft + (int) (point.getX() * scaleX),
                              frameTop + (int) (point.getY() * scaleY),
                              radius, paint);
          }
        }
      }

      // Request another update at the animation interval, but only repaint the laser line,
      // not the entire viewfinder mask.
      postInvalidateDelayed(ANIMATION_DELAY,
                            frame.left - POINT_SIZE,
                            frame.top - POINT_SIZE,
                            frame.right + POINT_SIZE,
                            frame.bottom + POINT_SIZE);
    }
  }

运行效果图