如何设置Google Vision QR扫描仪只检测一个值？

Question

我使用Google Vision API实现了QR扫描仪（QRScanner类）。一旦检测到值，就会使用Intents将其传递给另一个活动（Info类）。问题是，一旦扫描了QR码，Info类就会多次打开。我想限制QRScanner类只获得一个QR值而Info被分类只打开一次。

QRScanner类

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_qr_scanner);

cameraPreview = (SurfaceView) findViewById(R.id.camera_surface);
qrResult = (TextView) findViewById(R.id.scannerResult);
setupCamera();
}

private void setupCamera() {

BarcodeDetector barcodeDetector = new BarcodeDetector.Builder(this).setBarcodeFormats(Barcode.QR_CODE).build();
final CameraSource cameraSource = new CameraSource.Builder(this, barcodeDetector)
        .setAutoFocusEnabled(true)
        .setRequestedPreviewSize(1600, 1024)
        .build();

cameraPreview.getHolder().addCallback(new SurfaceHolder.Callback() {
    @Override
    public void surfaceCreated(SurfaceHolder holder) {

        if (ActivityCompat.checkSelfPermission(QrScanner.this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {
            // TODO: Consider calling
            //    ActivityCompat#requestPermissions
            // here to request the missing permissions, and then overriding
            //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
            //                                          int[] grantResults)
            // to handle the case where the user grants the permission. See the documentation
            // for ActivityCompat#requestPermissions for more details.
            return;
        }
        try {
            cameraSource.start(cameraPreview.getHolder());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {

    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        cameraSource.stop();
    }
});


barcodeDetector.setProcessor(new Detector.Processor<Barcode>() {
    @Override
    public void release() {

    }

    @Override
    public void receiveDetections(Detector.Detections<Barcode> detections) {

        final SparseArray<Barcode> qrCodes = detections.getDetectedItems();

        if(qrCodes.size()>0)
        {
            qrResult.post(new Runnable() {
                @Override
                public void run() {

                    qrResult.setText(qrCodes.valueAt(0).displayValue);
                    Intent intent = new Intent(QrScanner.this,Info.class);
                    intent.putExtra(QR_CODE,qrCodes.valueAt(0).displayValue);
                    startActivity(intent);
                }
            });
        }
    }
});
}

信息类

Intent intent = getIntent();
QRCODE = (String) intent.getStringExtra(QrScanner.QR_CODE);

DB = FirebaseDatabase.getInstance();
ref = DB.getReference().child("Animals").child(QRCODE);
ref.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {

        String DBAnimalClass = dataSnapshot.child("class").getValue().toString();
        String DBAnimalFamily = dataSnapshot.child("family").getValue().toString();
        String DBAnimalOrder = dataSnapshot.child("order").getValue().toString();

    }

    @Override
    public void onCancelled(@NonNull DatabaseError databaseError) {

    }
});

目前，一旦检测到QR，就会多次调用Info类。我希望QRScanner只获取一个值，而Info类只能调用一次。

Answer 1

您的相机正在连续检测QRCode，您的活动会多次打开。因此，当您成功检测到任何内容时，您需要停止相机。

 if(qrCodes.size()>0)
        {

            cameraSource.stop(); // ADD THIS. THIS WILL STOP CAMERA
            qrResult.post(new Runnable() {
                @Override
                public void run() {

                    qrResult.setText(qrCodes.valueAt(0).displayValue);
                    Intent intent = new Intent(QrScanner.this,Info.class);
                    intent.putExtra(QR_CODE,qrCodes.valueAt(0).displayValue);
                    startActivity(intent);
                }
            });
        }

Answer 2

我认为你需要收集数据并将其传递到内部类之外。

例：

@Override
public void receiveDetections(Detector.Detections<Barcode> detections) {
    final SparseArray<Barcode> qrCodes = detections.getDetectedItems();
    final String qrData = "";
    if(qrCodes.size()>0){
        qrResult.post(new Runnable() {
            @Override
            public void run() {
                qrData = qrCodes.valueAt(0).displayValue;
            }
        });
    }
    qrResult.setText(qrData);
    goToPage(qrData);
}


private void goToPage (String qrData) {
    Intent intent = new Intent(QrScanner.this,IDNA.Info.class);
    intent.putExtra(QR_CODE,qrData);
    startActivity(intent);
}

Answer 3

使用此库MobileVisionBarcodeScanner

您可以启用和禁用多个扫描.setSupportMultipleScan(true/false)

并使用停止扫描

barcodeCapture.stopScanning();

还有更多的功能。

Answer 4

经过一些研究，我发现了如何解决这个问题。但是，通过按下通过intent加载的活动的后退按钮返回此活动后，扫描仪将不再工作，因此应重新加载onCreate（）方法。

工作代码

if(qrCodes.size()>0)
    {

        barcodeDetector.release(); //stops the scanner from reading multiple values
        qrResult.post(new Runnable() {
            @Override
            public void run() {

                qrResult.setText(qrCodes.valueAt(0).displayValue);
                Intent intent = new Intent(QrScanner.this,Info.class);
                intent.putExtra(QR_CODE,qrCodes.valueAt(0).displayValue);
                startActivity(intent);
            }
        });
    }

cameraSource.stop（）无法工作的原因在此链接中说明; https://stackoverflow.com/a/41024780/6737536

希望能帮助到你！！