Zxing框架进行二维码扫描时候会发现，随着分辨率的增加，扫描框会越来越小，SurfaceView扫描窗口就看不见了，我们可以自己定义扫描窗口的大小，以及适配屏幕问题。

      Zxing包中有个类CameraManager，它是来设置扫描框的大小

      扫描框框初始化数值

  private static  int MIN_FRAME_WIDTH = 240;
  private static  int MIN_FRAME_HEIGHT = 240;
  private static  int MAX_FRAME_WIDTH = 480;
  private static  int MAX_FRAME_HEIGHT = 360;

  public Rect getFramingRect() {
    Point screenResolution = configManager.getScreenResolution();
    if (framingRect == null) {
      if (camera == null) {
        return null;
      }
      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;
  }

      要让扫描框适应不同的分辨率，我们需要根据分辨率将扫描矿的初始值转化就好。

      MIN_FRAME_WIDTH = Dp2Px(context,180);
      MIN_FRAME_HEIGHT =Dp2Px(context,180) ;
      MAX_FRAME_WIDTH = Dp2Px(context,280);
      MAX_FRAME_HEIGHT =Dp2Px(context,240) ;
     dp转为px的方法为

  public static  int Dp2Px( Context context,float dp) { 
	    final float scale = context.getResources().getDisplayMetrics().density; 
	    return (int) (dp * scale + 0.5f); 
	}