[置顶] android 二维码扫描(zxing使用小结)

主要有三点：

1、界面绘制，包括4个边角、上下滚动的横线、在画布上添加文字

2、调整二维码扫描框的位置。

3、解决图片被压变形的问题。

1、界面绘制

ViewfinderView.java中onDraw()方法

@Override
	public void onDraw(Canvas canvas) {
		// 中间的扫描框，你要修改扫描框的大小，去CameraManager里面修改
		Rect frame = CameraManager.get().getFramingRect();
		int top = frame.top;
		int left = frame.left;
		int right = frame.right;
		int bottom = frame.bottom;
		frame = new Rect(left , top, right , bottom );
		// 初始化中间线滑动的最上边和最下边
		if (!isFirst) {
			isFirst = true;
			slideTop = frame.top;
			slideBottom = frame.bottom;
		}

		// 获取屏幕的宽和高
		int width = canvas.getWidth();
		int height = canvas.getHeight();

		// 画出扫描框外面的阴影部分，共四个部分，扫描框的上面到屏幕上面，扫描框的下面到屏幕下面
		// 扫描框的左边面到屏幕左边，扫描框的右边到屏幕右边
		// 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(OPAQUE);
			canvas.drawBitmap(resultBitmap, frame.left, frame.top, paint);
		} else {
			// 画扫描框边上的角，总共8个部分
			paint.setColor(Color.GREEN);
			canvas.drawRect(frame.left, frame.top, frame.left + ScreenRate,
					frame.top + CORNER_WIDTH, paint);
			canvas.drawRect(frame.left, frame.top, frame.left + CORNER_WIDTH, frame.top
					+ ScreenRate, paint);
			canvas.drawRect(frame.right - ScreenRate, frame.top, frame.right,
					frame.top + CORNER_WIDTH, paint);
			canvas.drawRect(frame.right - CORNER_WIDTH, frame.top, frame.right, frame.top
					+ ScreenRate, paint);
			canvas.drawRect(frame.left, frame.bottom - CORNER_WIDTH, frame.left
					+ ScreenRate, frame.bottom, paint);
			canvas.drawRect(frame.left, frame.bottom - ScreenRate,
					frame.left + CORNER_WIDTH, frame.bottom, paint);
			canvas.drawRect(frame.right - ScreenRate, frame.bottom - CORNER_WIDTH,
					frame.right, frame.bottom, paint);
			canvas.drawRect(frame.right - CORNER_WIDTH, frame.bottom - ScreenRate,
					frame.right, frame.bottom, paint);
			
			//绘制中间的线,每次刷新界面，中间的线往下移动SPEEN_DISTANCE
			
			slideTop += SPEEN_DISTANCE;
			if(slideTop >= frame.bottom){
				slideTop = frame.top;
			}
			Rect lineRect = new Rect();  
            lineRect.left = frame.left;  
            lineRect.right = frame.right;  
            lineRect.top = slideTop;  
            lineRect.bottom = slideTop + 18;  
            canvas.drawBitmap(((BitmapDrawable)(getResources().getDrawable(R.drawable.qrcode_scan_line))).getBitmap(), null, lineRect, paint); 
			
        	//画扫描框下面的字
//            paint.setColor(Color.WHITE);    
//            paint.setTextSize(TEXT_SIZE * density);    
//            paint.setAlpha(0x40);    
//            paint.setTypeface(Typeface.create("System", Typeface.BOLD));   
//            String text = "将二维码放入框内, 即可自动扫描";  
//            float textWidth = paint.measureText(text);  
//              
//            canvas.drawText(text, (width - textWidth)/2, (float) (frame.bottom + (float)TEXT_PADDING_TOP *density), paint); 
			
			

			Collection<ResultPoint> currentPossible = possibleResultPoints;
			Collection<ResultPoint> currentLast = lastPossibleResultPoints;
			if (currentPossible.isEmpty()) {
				lastPossibleResultPoints = null;
			} else {
				possibleResultPoints = new HashSet<ResultPoint>(5);
				lastPossibleResultPoints = currentPossible;
				paint.setAlpha(OPAQUE);
				paint.setColor(resultPointColor);
				for (ResultPoint point : currentPossible) {
					canvas.drawCircle(frame.left + point.getX(), frame.top
							+ point.getY(), 6.0f, paint);
				}
			}
			if (currentLast != null) {
				paint.setAlpha(OPAQUE / 2);
				paint.setColor(resultPointColor);
				for (ResultPoint point : currentLast) {
					canvas.drawCircle(frame.left + point.getX(), frame.top
							+ point.getY(), 3.0f, paint);
				}
			}

			
			//只刷新扫描框的内容，其他地方不刷新
			postInvalidateDelayed(ANIMATION_DELAY, frame.left, frame.top,
					frame.right, frame.bottom);
			
		}
	}

2、调整位置

如果不设置全屏，扫描框的位置和取图的位置高度目测会有50px误差，

不全屏公式：((Y - 标题栏 - 状态栏)/2 - 扫描框高度)/2 = y轴坐标

只要不全屏：就会有误差，导致框中的二维码靠上或者远离二维码才会扫描成功

如果设置为全屏，就不会有误差，请了解内情的大神告知笔者，想知道什么原因造成

CameraManager.java 中 getFramingRect()方法  

public Rect getFramingRect() {
    Point screenResolution = configManager.getScreenResolution();
    if (framingRect == null) {
      if (camera == null) {
        return null;
      }
      /* 确定在固定比例分辨率下二维码扫描框的宽高*/  
      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;
      }
      //计算x轴y轴坐标,可在此调整二维码框的位置
      int leftOffset = (screenResolution.x - width) / 2 ;
      int topOffset = ((screenResolution.y) /2 - height) / 2 ;
      framingRect = new Rect(leftOffset, topOffset, leftOffset + width, topOffset + height);
      Log.d(TAG, "Calculated framing rect: " + framingRect);
    }
    return framingRect;
  }

3、框中图片变形

CameraConfigurationManager.java中void setDesiredCameraParameters(Camera camera)方法

/**
	 * Sets the camera up to take preview images which are used for both preview
	 * and decoding. We detect the preview format here so that
	 * buildLuminanceSource() can build an appropriate LuminanceSource subclass.
	 * In the future we may want to force YUV420SP as it's the smallest, and the
	 * planar Y can be used for barcode scanning without a copy in some cases.
	 */
	void setDesiredCameraParameters(Camera camera) {
		// Camera.Parameters parameters = camera.getParameters();
		// Log.d(TAG, "Setting preview size: " + cameraResolution);
		// parameters.setPreviewSize(cameraResolution.x, cameraResolution.y);
		// setFlash(parameters);
		// setZoom(parameters);
		// //setSharpness(parameters);
		// //modify here
		// camera.setDisplayOrientation(90);
		// camera.setParameters(parameters);
		Camera.Parameters parameters = camera.getParameters();
		List<Size> supportedPreviewSizes = parameters
				.getSupportedPreviewSizes();
		int position = 0;
		if (supportedPreviewSizes.size() > 2) {
			position = supportedPreviewSizes.size() / 2 + 1;// supportedPreviewSizes.get();
		} else {
			position = supportedPreviewSizes.size() / 2;
		}

		int width = supportedPreviewSizes.get(position).width;
		int height = supportedPreviewSizes.get(position).height;
		Log.d(TAG, "Setting preview size: " + cameraResolution);
		camera.setDisplayOrientation(90);
		cameraResolution.x = width;
		cameraResolution.y = height;
		parameters.setPreviewSize(width, height);
		setFlash(parameters);
		setZoom(parameters);
		// setSharpness(parameters);
		camera.setParameters(parameters);
	}

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