ViewfinderView.java

/*
 * Copyright (C) 2008 ZXing authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.xiaomi.xms.sales.zxing;

import android.content.Context;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.view.View;

import com.google.zxing.ResultPoint;
import com.xiaomi.xms.sales.R;
import com.xiaomi.xms.sales.zxing.camera.CameraManager;

import java.util.ArrayList;
import java.util.List;

/**
 * This view is overlaid on top of the camera preview. It adds the viewfinder
 * rectangle and partial transparency outside it, as well as the laser scanner
 * animation and result points.
 * 
 * @author dswitkin@google.com (Daniel Switkin)
 */
public final class ViewfinderView extends View {

    private static final int[] SCANNER_ALPHA = {
            0, 64, 128, 192, 255, 192, 128, 64
    };
    private static final long ANIMATION_DELAY = 80L;
    private static final int CURRENT_POINT_OPACITY = 0xA0;
    private static final int MAX_RESULT_POINTS = 20;
    private static final int POINT_SIZE = 6;

    private CameraManager cameraManager;
    private final Paint paint;
    private final Paint paintCorner;
    private Bitmap resultBitmap;
    private final int maskColor;
    private final int resultColor;
    private final int laserColor;
    private final int frameColor;
    private int scannerAlpha;
    private List<ResultPoint> possibleResultPoints;
    private int i = 0;
    private Rect mRect;
    private Drawable lineDrawable;

    // This constructor is used when the class is built from an XML resource.
    public ViewfinderView(Context context, AttributeSet attrs) {
        super(context, attrs);

        // Initialize these once for performance rather than calling them every
        // time in onDraw().
        paint = new Paint(Paint.ANTI_ALIAS_FLAG);
        paintCorner = new Paint(Paint.DITHER_FLAG);
        Resources resources = getResources();
        maskColor = resources.getColor(R.color.viewfinder_mask);
        resultColor = resources.getColor(R.color.result_view);
        laserColor = resources.getColor(R.color.viewfinder_laser);
        frameColor = resources.getColor(R.color.scan_frame);
        scannerAlpha = 0;
        possibleResultPoints = new ArrayList<ResultPoint>(5);
        mRect = new Rect();
        lineDrawable = getResources().getDrawable(R.drawable.zx_code_line);
    }

    public void setCameraManager(CameraManager cameraManager) {
        this.cameraManager = cameraManager;
    }

    @Override
    public void onDraw(Canvas canvas) {
        if (cameraManager == null) {
            return; // not ready yet, early draw before done configuring
        }
        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);

        paintCorner.setColor(frameColor);
        paintCorner.setAntiAlias(true);
        paintCorner.setStrokeWidth(10);
        canvas.drawLine(frame.left - 5, frame.top, frame.left + 16, frame.top, paintCorner);
        canvas.drawLine(frame.left, frame.top, frame.left, frame.top + 16, paintCorner);
        canvas.drawLine(frame.right - 16, frame.top, frame.right + 5, frame.top, paintCorner);
        canvas.drawLine(frame.right, frame.top, frame.right, frame.top + 16, paintCorner);
        canvas.drawLine(frame.left - 5, frame.bottom, frame.left + 16, frame.bottom, paintCorner);
        canvas.drawLine(frame.left, frame.bottom - 16, frame.left, frame.bottom, paintCorner);
        canvas.drawLine(frame.right - 16, frame.bottom, frame.right + 5, frame.bottom, paintCorner);
        canvas.drawLine(frame.right, frame.bottom - 16, frame.right, frame.bottom, paintCorner);
        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 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;

            if ((i += 5) < frame.bottom - frame.top) {
                mRect.set(frame.left - 6, frame.top + i - 6, frame.right + 6,
                        frame.top + 6 + i);
                lineDrawable.setBounds(mRect);
                lineDrawable.draw(canvas);
                invalidate();
            } else {
                i = 0;
            }

            // 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);
        }
    }

    public void drawViewfinder() {
        Bitmap resultBitmap = this.resultBitmap;
        this.resultBitmap = null;
        if (resultBitmap != null) {
            resultBitmap.recycle();
        }
        invalidate();
    }

    /**
     * Draw a bitmap with the result points highlighted instead of the live
     * scanning display.
     * 
     * @param barcode An image of the decoded barcode.
     */
    public void drawResultBitmap(Bitmap barcode) {
        resultBitmap = barcode;
        invalidate();
    }

    public void addPossibleResultPoint(ResultPoint point) {
        List<ResultPoint> points = possibleResultPoints;
        synchronized (points) {
            points.add(point);
            int size = points.size();
            if (size > MAX_RESULT_POINTS) {
                // trim it
                points.subList(0, size - MAX_RESULT_POINTS / 2).clear();
            }
        }
    }

}