Android Open Source - ZXingFragment Decoder

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License

The source code is released under:

Apache License

Java Source Code

package de.klimek.zxingfragment;
/*www. j a  va 2 s  . c o m*/
import java.util.Timer;
import java.util.TimerTask;

import android.app.Activity;
import android.graphics.ImageFormat;
import android.hardware.Camera;
import android.hardware.Camera.Parameters;
import android.util.Log;

public class Decoder implements Camera.PreviewCallback {
  public static final String TAG = Decoder.class.getSimpleName();
  private static final Long DECODE_INTERVAL = 500l;
  static final double BOUNDS_FRACTION = 0.6;
  static final double VERTICAL_HEIGHT_FRACTION = 0.3;
  private Activity mActivity;

  private OnDecodedCallback mCallback;
  private DecodeTask mDecodeTask;
  private volatile boolean mDecoding = false;
  private Timer mDelayTimer = new Timer();

  private Camera mCamera;
  private int mCameraDisplayOrientation;
  private byte[] mPreviewBuffer;

  public Decoder(Activity activity) {
    mActivity = activity;
  }

  public void setOnDecodedCallback(OnDecodedCallback callback) {
    mCallback = callback;
  }

  public void startDecoding(Camera camera, int cameraDisplayOrientation) {
    mDecoding = true;

    mCamera = camera;
    mCameraDisplayOrientation = cameraDisplayOrientation;

    // add buffer to camera to prevent garbage collection spam
    mPreviewBuffer = createPreviewBuffer(camera);
    camera.addCallbackBuffer(mPreviewBuffer);
    camera.setPreviewCallbackWithBuffer(this);
  }

  public void stopDecoding() {
    mDecoding = false;
    if (mDecodeTask != null) {
      mDecodeTask.cancel(true);
    }

  }

  private static byte[] createPreviewBuffer(Camera camera) {
    Parameters params = camera.getParameters();
    int width = params.getPreviewSize().width;
    int height = params.getPreviewSize().width;
    int bitsPerPixel = ImageFormat.getBitsPerPixel(params
        .getPreviewFormat());
    int bytesPerPixel = (int) Math.ceil(bitsPerPixel / 8.0);
    int bufferSize = width * height * bytesPerPixel;
    return new byte[bufferSize];
  }

  /*
   * Called when the camera has a buffer, e.g. by calling
   * camera.addCallbackBuffer(buffer). This buffer is automatically removed,
   * but added again after decoding, resulting in a loop until stopDecoding()
   * is called.
   */
  @Override
  public void onPreviewFrame(byte[] data, Camera camera) {
    if (mDecoding) {
      mDecodeTask = new DecodeTask(this, camera, mCameraDisplayOrientation);
      mDecodeTask.execute(data);
    }
  }

  /*
   * called by mDecodeTask
   */
  public void onDecodeSuccess(String string) {
    Log.i(Decoder.TAG, "Decode success.");
    if (mDecoding) {
      mCallback.onDecoded(string);
      // request next frame after delay
      mDelayTimer.schedule(new RequestPreviewFrameTask(), DECODE_INTERVAL);
    }
  }

  /*
   * called by mDecodeTask
   */
  public void onDecodeFail() {
    // Log.i(Decoder.TAG, "Decode fail.");
    if (mDecoding) {
      // request next frame after delay
      mDelayTimer.schedule(new RequestPreviewFrameTask(), DECODE_INTERVAL);
    }
  }

  private class RequestPreviewFrameTask extends TimerTask {

    @Override
    public void run() {
      if (mDecoding) {

        final Runnable addCallBackBufferTask = new Runnable() {
          @Override
          public void run() {
            if (mDecoding) {
              mCamera.addCallbackBuffer(mPreviewBuffer);
            }
          }
        };

        mActivity.runOnUiThread(addCallBackBufferTask);
      }
    }

  }

  public interface OnDecodedCallback {
    void onDecoded(String decodedData);
  }

}

Java Source Code List

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