Android zxing

二维码一般在项目都会用到，今天分享下我开发二维码的一些心得。

zxing介绍

github地址：https://github.com/zxing/zxing


代码很多，官方演示的例子在文件android，一个较为完整的app，导入Android studio，发现少了CameraConfigurationUtils，这个类在文件android-core下。官方效果图：

但是实际开发只需要扫码和生成二维码两个功能就夠了，因此我做了抽离删减，最终我的效果图：

zxing使用

添加依赖

compile 'com.google.zxing:core:3.2.1'

扫描二维码

case R.id.qrcode_dencode: //扫描
intent = new Intent(MainActivity.this, CaptureActivity.class);
startActivityForResult(intent, REQUEST_CODE);
break;

回调：

@Override
   protected void onActivityResult(int requestCode, int resultCode, Intent data) {
       super.onActivityResult(requestCode, resultCode, data);
       if (resultCode == RESULT_OK) { //RESULT_OK = -1
           Bundle bundle = data.getExtras();
           String scanResult = bundle.getString("result");
           Toast.makeText(MainActivity.this, scanResult, Toast.LENGTH_LONG).show();
       }
   }

生成二维码

case R.id.qrcode_encode: //生成
try {
       Bitmap mBitmap = QRCodeEncoder.encodeAsBitmap("http://wuxiaolong.me/", 300);
       qrcodeImg.setImageBitmap(mBitmap);

     } catch (Exception e) {
       e.printStackTrace();
     }
    break;

识别二维码

//长按图片识别二维码
       qrcodeImg.setOnLongClickListener(new View.OnLongClickListener() {
           @Override
           public boolean onLongClick(View v) {
               qrcodeImg.setDrawingCacheEnabled(true);
               Bitmap bitmap = Bitmap.createBitmap(qrcodeImg.getDrawingCache());
               qrcodeImg.setDrawingCacheEnabled(false);
               decodeQRCode(bitmap);
               return true;
           }
       });

/**
   * 解析二维码图片
   *
   * @param bitmap   要解析的二维码图片
   */
  public final Map<DecodeHintType, Object> HINTS = new EnumMap<>(DecodeHintType.class);

  public void decodeQRCode(final Bitmap bitmap) {
      new AsyncTask<Void, Void, String>() {
          @Override
          protected String doInBackground(Void... params) {
              try {
                  int width = bitmap.getWidth();
                  int height = bitmap.getHeight();
                  int[] pixels = new int[width * height];
                  bitmap.getPixels(pixels, 0, width, 0, 0, width, height);
                  RGBLuminanceSource source = new RGBLuminanceSource(width, height, pixels);
                  Result result = new MultiFormatReader().decode(new BinaryBitmap(new HybridBinarizer(source)), HINTS);
                  return result.getText();
              } catch (Exception e) {
                  return null;
              }
          }

          @Override
          protected void onPostExecute(String result) {
              Log.d("wxl", "result=" + result);
              Toast.makeText(MainActivity.this, result, Toast.LENGTH_LONG).show();
          }
      }.execute();

  }

由于时间仓促，抽离的代码可能或多或少有些问题，细节待优化。
另外，ViewfinderView自定义属性参考了http://my.oschina.net/smuswc/blog/609413?fromerr=RgSd7WKf

官方zxing例子学习

如果代码涉及core-3.2.1，就不在研究，有兴趣可自行深入去学习。

扫描二维码

代码调用顺序CaptureActivity —–> CaptureActivityHandler —–> CameraManager —–> PreviewCallback —–> DecodeHandler —–> CaptureActivityHandler —–> CaptureActivity。下面一一分析。

CaptureActivity

CaptureActivity入口类，主要做了Camera，Beep，AmbientLight等初始化。CaptureActivityHandler初始化是在initCamera方法里：

private void initCamera(SurfaceHolder surfaceHolder) {
       ……
           // Creating the handler starts the preview, which can also throw a RuntimeException.
           if (handler == null) {
               handler = new CaptureActivityHandler(this, decodeFormats, decodeHints, characterSet, cameraManager);
      ……
   }

CaptureActivityHandler

CaptureActivityHandler构造方法做了DecodeThread初始化，DecodeThread run方法做了DecodeHandler初始化，然后Camera开始扫码工作。

 public CaptureActivityHandler(CaptureActivity activity,
                                 Collection<BarcodeFormat> decodeFormats,
                                 Map<DecodeHintType, ?> baseHints,
                                 String characterSet,
                                 CameraManager cameraManager) {
       this.activity = activity;
       decodeThread = new DecodeThread(activity, decodeFormats, baseHints, characterSet,
               new ViewfinderResultPointCallback(activity.getViewfinderView()));
       decodeThread.start();
       state = State.SUCCESS;

       // Start ourselves capturing previews and decoding.
       this.cameraManager = cameraManager;
       cameraManager.startPreview();
       restartPreviewAndDecode();
   }
private void restartPreviewAndDecode() {
       if (state == State.SUCCESS) {
           state = State.PREVIEW;
           //decodeThread.getHandler()拿到DecodeHandler
           cameraManager.requestPreviewFrame(decodeThread.getHandler(), R.id.decode);
           activity.drawViewfinder();
       }
   }

CameraManager

public synchronized void requestPreviewFrame(Handler handler, int message) {
        OpenCamera theCamera = camera;
        if (theCamera != null && previewing) {
            previewCallback.setHandler(handler, message);
            theCamera.getCamera().setOneShotPreviewCallback(previewCallback);
        }
    }

PreviewCallback

void setHandler(Handler previewHandler, int previewMessage) {
   this.previewHandler = previewHandler;
   this.previewMessage = previewMessage;
 }

 @Override
 public void onPreviewFrame(byte[] data, Camera camera) {
   Point cameraResolution = configManager.getCameraResolution();
   Handler thePreviewHandler = previewHandler;
   if (cameraResolution != null && thePreviewHandler != null) {
     //给DecodeHandler发消息
     Message message = thePreviewHandler.obtainMessage(previewMessage, cameraResolution.x,
         cameraResolution.y, data);
     message.sendToTarget();
     previewHandler = null;
   } else {
     Log.d(TAG, "Got preview callback, but no handler or resolution available");
   }
 }

DecodeHandler

扫码结果，反馈给CaptureActivityHandler

@Override
    public void handleMessage(Message message) {
        if (!running) {
            return;
        }
        int what = message.what;
        if (what == R.id.decode) {
            decode((byte[]) message.obj, message.arg1, message.arg2);
        } else if (what == R.id.quit) {
            running = false;
            Looper.myLooper().quit();
        }
}
 private void decode(byte[] data, int width, int height) {
        long start = System.currentTimeMillis();
        Result rawResult = null;
        PlanarYUVLuminanceSource source = activity.getCameraManager().buildLuminanceSource(data, width, height);
        if (source != null) {
            BinaryBitmap bitmap = new BinaryBitmap(new HybridBinarizer(source));
            try {
                rawResult = multiFormatReader.decodeWithState(bitmap);
            } catch (ReaderException re) {
                // continue
            } finally {
                multiFormatReader.reset();
            }
        }

        Handler handler = activity.getHandler();//拿到CaptureActivityHandler
        if (rawResult != null) {
            // Don't log the barcode contents for security.
            long end = System.currentTimeMillis();
            Log.d(TAG, "Found barcode in " + (end - start) + " ms");
            if (handler != null) {
                //给CaptureActivityHandler发消息
                Message message = Message.obtain(handler, R.id.decode_succeeded, rawResult);
                Bundle bundle = new Bundle();
                bundleThumbnail(source, bundle);
                message.setData(bundle);
                message.sendToTarget();
            }
        } else {
            if (handler != null) {
                Message message = Message.obtain(handler, R.id.decode_failed);
                message.sendToTarget();
            }
        }
    }

CaptureActivityHandler

扫码结果，再反馈给CaptureActivity，这样就走完了扫码过程。

@Override
   public void handleMessage(Message message) {
       int what = message.what;
       if (what == R.id.restart_preview) {
           restartPreviewAndDecode();
       } else if (what == R.id.decode_succeeded) {
           state = State.SUCCESS;
           Bundle bundle = message.getData();
           Bitmap barcode = null;
           float scaleFactor = 1.0f;
           if (bundle != null) {
               byte[] compressedBitmap = bundle.getByteArray(DecodeThread.BARCODE_BITMAP);
               if (compressedBitmap != null) {
                   barcode = BitmapFactory.decodeByteArray(compressedBitmap, 0, compressedBitmap.length, null);
                   // Mutable copy:
                   barcode = barcode.copy(Bitmap.Config.ARGB_8888, true);
               }
               scaleFactor = bundle.getFloat(DecodeThread.BARCODE_SCALED_FACTOR);
           }
           activity.handleDecode((Result) message.obj, barcode, scaleFactor);
       }
}

生成二维码

只需要以下核心代码：

public static Bitmap encodeAsBitmap(String contents, int dimension) throws WriterException {

        String contentsToEncode = contents;
        if (contentsToEncode == null) {
            return null;
        }
        Map<EncodeHintType, Object> hints = null;
        String encoding = guessAppropriateEncoding(contentsToEncode);
        if (encoding != null) {
            hints = new EnumMap<>(EncodeHintType.class);
            hints.put(EncodeHintType.CHARACTER_SET, encoding);
        }
        BitMatrix result;
        try {
            result = new MultiFormatWriter().encode(contentsToEncode, BarcodeFormat.QR_CODE, dimension, dimension, hints);
        } catch (IllegalArgumentException iae) {
            // Unsupported format
            return null;
        }
        int width = result.getWidth();
        int height = result.getHeight();
        int[] pixels = new int[width * height];
        for (int y = 0; y < height; y++) {
            int offset = y * width;
            for (int x = 0; x < width; x++) {
                pixels[offset + x] = result.get(x, y) ? BLACK : WHITE;
            }
        }

        Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
        bitmap.setPixels(pixels, 0, width, 0, 0, width, height);
        return bitmap;
    }

    private static String guessAppropriateEncoding(CharSequence contents) {
        // Very crude at the moment
        for (int i = 0; i < contents.length(); i++) {
            if (contents.charAt(i) > 0xFF) {
                return "UTF-8";
            }
        }
        return null;
    }

源码

官方的例子和我自己的抽离出的代码都上传github了，地址：https://github.com/WuXiaolong/zxingSample



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