java - 尝试使用 CameraX 和 MLKit 构建条形码扫描仪，但在 BarcodeScanning.getClient() 出现“MlKitContext 尚未初始化”异常

Question

我目前正在尝试使用 CameraX 和 MLKit 构建条形码扫描仪，但在我的 BarcodeAnalyzer 应用程序中调用 BarcodeScanning.getClient() 时，我不断收到“MlKitContext 尚未初始化”异常。我曾尝试在 SO 和其他网站上进行搜索，但我发现的所有其他示例和解决方案要么看起来像我的代码，要么是用 Kotlin 编写的。我不知道这是哪里出错了！仅使用没有任何图像分析的相机预览就可以了，但由于某种原因，上下文似乎没有正确地传输到条形码分析器或其他东西。我错过了什么？

这是错误消息：

E/PreviewUseCase: Binding failed in startCameraPreview: 
    java.lang.IllegalStateException: MlKitContext has not been initialized
        at com.google.android.gms.common.internal.Preconditions.checkState(com.google.android.gms:play-services-basement@@17.4.0:29)
        at com.google.mlkit.common.sdkinternal.MlKitContext.getInstance(com.google.mlkit:common@@17.1.1:2)
        at com.google.mlkit.vision.barcode.BarcodeScanning.getClient(com.google.android.gms:play-services-mlkit-barcode-scanning@@16.1.4:1)
        at com.myscannerapp.ap.barcode.BarcodeAnalyzerX.<init>(BarcodeAnalyzerX.java:29)
        at com.myscannerapp.ap.camera.ScanningCameraX$1.<init>(ScanningCameraX.java:66)
        at com.myscannerapp.ap.camera.ScanningCameraX.lambda$startCameraPreview$0(ScanningCameraX.java:66)
        at com.myscannerapp.ap.camera.-$$Lambda$ScanningCameraX$WAwB0W8s9LNCXGHteEApbFdwKUk.run(Unknown Source:8)
        at android.os.Handler.handleCallback(Handler.java:883)
        at android.os.Handler.dispatchMessage(Handler.java:100)
        at android.os.Looper.loop(Looper.java:237)
        at android.app.ActivityThread.main(ActivityThread.java:8167)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:496)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1100)

以下是我的扫描片段、扫描相机类和条形码分析器类的代码。我试图删除不相关的代码以使其更易于阅读，希望这会有所帮助。哦，“BarcodeCallback”类只是我用来向我的活动发送数据的接口。

这是我的 ScanningFragment 的代码：

public class ScanningFragment extends Fragment implements FragmentCommunicationInterface {
    private BarcodeCallback mBarcodeCallback;
    private ScanningCameraX mScanningCameraX;
    private Context mContext;

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_barcode_scanner,container,false);

        mScanningCameraX = new ScanningCameraX(mContext,view.findViewById(R.id.rt_scan_camera), mBarcodeCallback);

        return view;
    }

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        mContext = context;
        mBarcodeCallback = (BarcodeCallback)getActivity();
    }

    @Override
    public void onResume() {
        super.onResume();
        mScanningCameraX.startCameraPreview();
    }
}

这是我的 ScanningCameraX 类的代码：

public class ScanningCameraX {
    private Context mContext;
    private PreviewView mPreviewView;
    private BarcodeCallback mBarcodeCallback;
    private ListenableFuture<ProcessCameraProvider> cameraProviderFuture;

    public ScanningCameraX (Context context, PreviewView previewView, BarcodeCallback barcodeCallback){
        mContext = context;
        mPreviewView = previewView;
        mBarcodeCallback = barcodeCallback;
    }

    public void startCameraPreview() {
        cameraProviderFuture = ProcessCameraProvider.getInstance(mContext);

        final Context CONTEXT = mContext;
        final PreviewView PREVIEW_VIEW = mPreviewView;
        final BarcodeCallback BARCODE_CALLBACK = mBarcodeCallback;

        cameraProviderFuture.addListener(() -> {
            try {
                ProcessCameraProvider cameraProvider = cameraProviderFuture.get();
                Preview preview = new Preview.Builder()
                        .build();

                preview.setSurfaceProvider(PREVIEW_VIEW.getSurfaceProvider());

                ImageAnalysis imageAnalysis =
                        new ImageAnalysis.Builder()
                                .setTargetResolution(new Size(1280, 720))
                                .setBackpressureStrategy(ImageAnalysis.STRATEGY_KEEP_ONLY_LATEST)
                                .build();


                imageAnalysis.setAnalyzer(ContextCompat.getMainExecutor(CONTEXT), new BarcodeAnalyzerX(BARCODE_CALLBACK) {
                    @Override
                    public void analyze(@NonNull ImageProxy image) {
                        int rotationDegrees = image.getImageInfo().getRotationDegrees();
                        // insert future code here.
                    }
                });

                CameraSelector cameraSelector = new CameraSelector.Builder().requireLensFacing(CameraSelector.LENS_FACING_BACK).build();
                cameraProvider.unbindAll();
                cameraProvider.bindToLifecycle((LifecycleOwner) CONTEXT, cameraSelector, preview, imageAnalysis);
            } catch (Exception e) {
                Log.e("PreviewUseCase", "Binding failed in startCameraPreview: ", e);
            }
        }, ContextCompat.getMainExecutor(mContext));
    }
}

最后是我的 BarcodeAnalyzerX 的代码，在“scanner = BarcodeScanning.getClient();”中一切都出错了 部分：

 public class BarcodeAnalyzerX implements ImageAnalysis.Analyzer {
    private BarcodeScanner scanner;
    private BarcodeCallback mBarcodeCallback;

    public BarcodeAnalyzerX(BarcodeCallback barcodeCallback) {
        scanner = BarcodeScanning.getClient();
        mBarcodeCallback = barcodeCallback;
    }

    @Override
    public void analyze(ImageProxy imageProxy) {
        Image mediaImage = imageProxy.getImage();
        final BarcodeCallback BARCODE_CALLBACK = mBarcodeCallback;
        if (mediaImage != null) {
            InputImage image = InputImage.fromMediaImage(mediaImage, imageProxy.getImageInfo().getRotationDegrees());
            Task<List<Barcode>> result = scanner.process(image)
                    .addOnSuccessListener(new OnSuccessListener<List<Barcode>>() {
                        @Override
                        public void onSuccess(List<Barcode> barcodes) {
                            for (Barcode barcode:barcodes){
                                BARCODE_CALLBACK.UpdateBarcode(barcode);
                            }
                        }
                    })
                    .addOnFailureListener(new OnFailureListener() {
                        @Override
                        public void onFailure(Exception e) {
                            Log.d("BarcodeAnalyzer","Analyzer failed with exception: " + e);
                        }
                    })
                    .addOnCompleteListener(new OnCompleteListener<List<Barcode>>() {
                        @Override
                        public void onComplete(@NonNull Task<List<Barcode>> task) {
                            imageProxy.close();
                        }
                    });
        }
    }
}

标签： javaandroidandroid-contextandroid-cameraxgoogle-mlkit

Answer 1

TRoque a linha mScanningCameraX = new ScanningCameraX(mContext,view.findViewById(R.id.rt_scan_camera), mBarcodeCallback);

PARA mScanningCameraX = new ScanningCameraX(this.getActivity().getApplicationContext(),view.findViewById(R.id.rt_scan_camera), mBarcodeCallback);