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.google.zxing.client.android;

import idv.Zero.KerKerInput.R;
import android.content.Context;
import android.content.res.Resources;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.View;

/**
 * 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 = 100L;

  private final Paint paint;
  private final Rect box;
  private final int maskColor;
  private final int frameColor;
  private final int laserColor;
  private int scannerAlpha;

  // 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();
    box = new Rect();
    Resources resources = getResources();
    maskColor = resources.getColor(R.color.viewfinder_mask);
    frameColor = resources.getColor(R.color.viewfinder_frame);
    laserColor = resources.getColor(R.color.viewfinder_laser);
    scannerAlpha = 0;
  }

  @Override
  public void onDraw(Canvas canvas) {
    Rect frame = CameraManager.get().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(maskColor);
    box.set(0, 0, width, frame.top);
    canvas.drawRect(box, paint);
    box.set(0, frame.top, frame.left, frame.bottom + 1);
    canvas.drawRect(box, paint);
    box.set(frame.right + 1, frame.top, width, frame.bottom + 1);
    canvas.drawRect(box, paint);
    box.set(0, frame.bottom + 1, width, height);
    canvas.drawRect(box, paint);

    // Draw a two pixel solid black border inside the framing rect
    paint.setColor(frameColor);
    box.set(frame.left, frame.top, frame.right + 1, frame.top + 2);
    canvas.drawRect(box, paint);
    box.set(frame.left, frame.top + 2, frame.left + 2, frame.bottom - 1);
    canvas.drawRect(box, paint);
    box.set(frame.right - 1, frame.top, frame.right + 1, frame.bottom - 1);
    canvas.drawRect(box, paint);
    box.set(frame.left, frame.bottom - 1, frame.right + 1, frame.bottom + 1);
    canvas.drawRect(box, 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;
    box.set(frame.left + 2, middle - 1, frame.right - 1, middle + 2);
    canvas.drawRect(box, paint);
    
    // Request another update at the animation interval, but only repaint the laser line,
    // not the entire viewfinder mask.
    postInvalidateDelayed(ANIMATION_DELAY, box.left, box.top, box.right, box.bottom);
  }

  public void drawViewfinder() {
    invalidate();
  }
}