CameraX 预览未显示在 PreviewView 中

Question

I've followed the instructions to implement a PreviewView with CameraX here ( https://developer.android.com/training/camerax/preview ). I've also downloaded the example code, which works just fine. But in my code it just wont show the preview. The logs seem fine and it is doing something, because I set the background color of the preview view to green and it gets cleared if I start the preview logic. I'm using this inside a ViewPager with a TabLayout if that makes any difference.

Layout.xml

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">
    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <androidx.camera.view.PreviewView
            android:id="@+id/preview"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />

    </androidx.constraintlayout.widget.ConstraintLayout>
</layout>

Fragment

public class QRFragment extends Fragment {
    public static final String TAG = QRFragment.class.getSimpleName();
    private static final int REQUEST_PERMISSION_CAMERA = 777;

    public static Fragment newInstance() {
        return new QRFragment();
    }

    private GuideQrFragmentBinding binding;
    private ListenableFuture<ProcessCameraProvider> cameraProviderFuture;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        Log.v(TAG, "create view");
        this.binding = GuideQrFragmentBinding.inflate(inflater, container, false);
        // binding.setViewModel(this.mViewModel);
        return binding.getRoot();
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        Log.v(TAG, "view created");
    }

    private void startPreview() {
        Log.v(TAG, "startPreview");
        this.cameraProviderFuture = ProcessCameraProvider.getInstance(this.requireContext());
        this.cameraProviderFuture.addListener(() -> {
            Log.v(TAG, "cameraProviderFuture.Listener");
            try {
                ProcessCameraProvider cameraProvider = cameraProviderFuture.get();

                Preview preview = new Preview.Builder()
                        .build();

                CameraSelector cameraSelector = new CameraSelector.Builder()
                        .requireLensFacing(CameraSelector.LENS_FACING_BACK)
                        .build();

                cameraProvider.unbindAll();
                Camera camera = cameraProvider.bindToLifecycle(this.getViewLifecycleOwner(),
                        cameraSelector,
                        preview);

                preview.setSurfaceProvider(this.binding.preview.getSurfaceProvider());

            } catch (ExecutionException | InterruptedException e) {
                // No errors need to be handled for this Future.
                // This should never be reached.
                Log.e(TAG, "cameraProviderFuture.Listener", e);
            }
        }, ContextCompat.getMainExecutor(this.requireContext()));
    }

    @Override
    public void onResume() {
        super.onResume();

        if( ActivityCompat.checkSelfPermission(this.requireContext(), Manifest.permission.CAMERA) == PackageManager.PERMISSION_GRANTED ) {
            if( this.cameraProviderFuture == null ) {
                this.startPreview();
            }
        } else {
            this.requestPermissions(new String[] { Manifest.permission.CAMERA }, REQUEST_PERMISSION_CAMERA);
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        if( requestCode == REQUEST_PERMISSION_CAMERA ) {
            for( int p = 0; p < permissions.length; p++ ) {
                if( Manifest.permission.CAMERA.equals(permissions[p]) ) {
                    if( grantResults[p] == PackageManager.PERMISSION_GRANTED ) {
                        this.startPreview();
                    } else {

                    }
                }
            }
        } else {
            super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        }
    }
}

Logs

2021-02-01 13:05:18.920 4217-4217/com.myapp.app V/QRFragment: create view
2021-02-01 13:05:18.936 4217-4217/com.myapp.app V/QRFragment: view created
2021-02-01 13:05:18.953 4217-4217/com.myapp.app V/QRFragment: startPreview
2021-02-01 13:05:18.982 4217-4782/com.myapp.app I/CameraManagerGlobal: Connecting to camera service
2021-02-01 13:05:18.985 4217-4782/com.myapp.app D/VendorTagDescriptor: addVendorDescriptor: vendor tag id 3854507339 added
2021-02-01 13:05:18.988 4217-4257/com.myapp.app I/CameraManagerGlobal: Camera 0 facing CAMERA_FACING_BACK state now CAMERA_STATE_CLOSED for client com.myapp.app API Level 2
2021-02-01 13:05:18.989 4217-4257/com.myapp.app I/CameraManagerGlobal: Camera 1 facing CAMERA_FACING_FRONT state now CAMERA_STATE_OPEN for client com.samsung.adaptivebrightnessgo API Level 2
2021-02-01 13:05:18.990 4217-4257/com.myapp.app I/CameraManagerGlobal: Camera 2 facing CAMERA_FACING_FRONT state now CAMERA_STATE_CLOSED for client android.system API Level 2
2021-02-01 13:05:18.990 4217-4257/com.myapp.app I/CameraManagerGlobal: Camera 50 facing CAMERA_FACING_BACK state now CAMERA_STATE_CLOSED for client android.system API Level 2
2021-02-01 13:05:19.046 4217-4782/com.myapp.app D/CameraRepository: Added camera: 0
2021-02-01 13:05:19.099 4217-4782/com.myapp.app I/Camera2CameraInfo: Device Level: INFO_SUPPORTED_HARDWARE_LEVEL_LIMITED
2021-02-01 13:05:19.101 4217-4782/com.myapp.app I/CameraManagerGlobal: postSingleUpdate device: camera id 0 status STATUS_PRESENT
2021-02-01 13:05:19.101 4217-4782/com.myapp.app I/CameraManagerGlobal: postSingleUpdate device: camera id 1 status STATUS_PRESENT
2021-02-01 13:05:19.102 4217-4782/com.myapp.app I/CameraManagerGlobal: postSingleUpdate device: camera id 2 status STATUS_PRESENT
2021-02-01 13:05:19.102 4217-4782/com.myapp.app D/CameraRepository: Added camera: 1
2021-02-01 13:05:19.102 4217-4802/com.myapp.app D/UseCaseAttachState: Active and attached use case: [] for camera: 0
2021-02-01 13:05:19.104 4217-4782/com.myapp.app I/Camera2CameraInfo: Device Level: INFO_SUPPORTED_HARDWARE_LEVEL_LIMITED
2021-02-01 13:05:19.104 4217-4782/com.myapp.app I/CameraManagerGlobal: postSingleUpdate device: camera id 0 status STATUS_PRESENT
2021-02-01 13:05:19.105 4217-4782/com.myapp.app I/CameraManagerGlobal: postSingleUpdate device: camera id 1 status STATUS_PRESENT
2021-02-01 13:05:19.105 4217-4782/com.myapp.app I/CameraManagerGlobal: postSingleUpdate device: camera id 2 status STATUS_PRESENT
2021-02-01 13:05:19.105 4217-4782/com.myapp.app D/CameraRepository: Added camera: 2
2021-02-01 13:05:19.105 4217-4803/com.myapp.app D/UseCaseAttachState: Active and attached use case: [] for camera: 1
2021-02-01 13:05:19.107 4217-4782/com.myapp.app I/Camera2CameraInfo: Device Level: INFO_SUPPORTED_HARDWARE_LEVEL_LIMITED
2021-02-01 13:05:19.108 4217-4782/com.myapp.app I/CameraManagerGlobal: postSingleUpdate device: camera id 0 status STATUS_PRESENT
2021-02-01 13:05:19.108 4217-4782/com.myapp.app I/CameraManagerGlobal: postSingleUpdate device: camera id 1 status STATUS_PRESENT
2021-02-01 13:05:19.108 4217-4802/com.myapp.app D/UseCaseAttachState: Active and attached use case: [] for camera: 2
2021-02-01 13:05:19.108 4217-4782/com.myapp.app I/CameraManagerGlobal: postSingleUpdate device: camera id 2 status STATUS_PRESENT
2021-02-01 13:05:19.110 4217-4217/com.myapp.app V/QRFragment: cameraProviderFuture.Listener
2021-02-01 13:05:19.149 4217-4217/com.myapp.app D/DeferrableSurface: Surface created[total_surfaces=1, used_surfaces=0](androidx.camera.core.SurfaceRequest$2@f584149}
2021-02-01 13:05:19.153 4217-4803/com.myapp.app D/Camera2CameraImpl: {Camera@ea5acee[id=0]} Use case Preview:androidx.camera.core.Preview-ece4a019-fe39-4341-ab30-82f47580d983 INACTIVE
2021-02-01 13:05:19.154 4217-4217/com.myapp.app D/CameraOrientationUtil: getRelativeImageRotation: destRotationDegrees=0, sourceRotationDegrees=90, isOppositeFacing=true, result=90
2021-02-01 13:05:19.154 4217-4803/com.myapp.app D/UseCaseAttachState: Active and attached use case: [] for camera: 0
2021-02-01 13:05:19.155 4217-4217/com.myapp.app D/PreviewView: Surface requested by Preview.
2021-02-01 13:05:19.156 4217-4803/com.myapp.app D/Camera2CameraImpl: {Camera@ea5acee[id=0]} Use cases [Preview:androidx.camera.core.Preview-ece4a019-fe39-4341-ab30-82f47580d983] now ATTACHED
2021-02-01 13:05:19.158 4217-4803/com.myapp.app D/UseCaseAttachState: All use case: [androidx.camera.core.Preview-ece4a019-fe39-4341-ab30-82f47580d983163463287] for camera: 0
2021-02-01 13:05:19.159 4217-4803/com.myapp.app D/UseCaseAttachState: Active and attached use case: [] for camera: 0
2021-02-01 13:05:19.160 4217-4803/com.myapp.app D/Camera2CameraImpl: {Camera@ea5acee[id=0]} Resetting Capture Session
2021-02-01 13:05:19.162 4217-4217/com.myapp.app D/SurfaceView: onWindowVisibilityChanged(0) true android.view.SurfaceView{9f7ad5a V.E...... ......ID 0,0-0,0} of ViewRootImpl@581aad2[MainActivity]
2021-02-01 13:05:19.162 4217-4803/com.myapp.app D/Camera2CameraImpl: {Camera@ea5acee[id=0]} Releasing session in state INITIALIZED
2021-02-01 13:05:19.163 4217-4217/com.myapp.app D/PreviewView: Preview transformation info updated. TransformationInfo{cropRect=Rect(0, 0 - 1440, 1080), rotationDegrees=90, targetRotation=0}
2021-02-01 13:05:19.163 4217-4217/com.myapp.app D/PreviewTransform: Transformation info set: TransformationInfo{cropRect=Rect(0, 0 - 1440, 1080), rotationDegrees=90, targetRotation=0} 1440x1080 false
2021-02-01 13:05:19.165 4217-4803/com.myapp.app D/CameraStateRegistry: tryOpenCamera(Camera@ea5acee[id=0]) [Available Cameras: 1, Already Open: false (Previous state: null)] --> SUCCESS
2021-02-01 13:05:19.169 4217-4803/com.myapp.app D/CameraStateRegistry: Recalculating open cameras:
    Camera                                       State                 
    -------------------------------------------------------------------
    Camera@163f523[id=2]                         UNKNOWN               
    Camera@640eda1[id=1]                         UNKNOWN               
    Camera@ea5acee[id=0]                         OPENING               
    -------------------------------------------------------------------
    Open count: 1 (Max allowed: 1)
2021-02-01 13:05:19.171 4217-4803/com.myapp.app D/Camera2CameraImpl: {Camera@ea5acee[id=0]} Transitioning camera internal state: INITIALIZED --> OPENING
2021-02-01 13:05:19.173 4217-4803/com.myapp.app D/Camera2CameraImpl: {Camera@ea5acee[id=0]} Opening camera.
2021-02-01 13:05:19.175 4217-4803/com.myapp.app D/UseCaseAttachState: All use case: [androidx.camera.core.Preview-ece4a019-fe39-4341-ab30-82f47580d983163463287] for camera: 0
2021-02-01 13:05:19.187 4217-4217/com.myapp.app D/ViewRootImpl@581aad2[MainActivity]: Relayout returned: old=(0,0,1080,2340) new=(0,0,1080,2340) req=(1080,2340)0 dur=9 res=0x1 s={true 498507776000} ch=false
2021-02-01 13:05:19.201 4217-4217/com.myapp.app D/SurfaceView: surfaceCreated 1 #8 android.view.SurfaceView{9f7ad5a V.E...... ......ID 0,0-1440,1080}
2021-02-01 13:05:19.201 4217-4217/com.myapp.app D/SurfaceViewImpl: Surface created.
2021-02-01 13:05:19.201 4217-4217/com.myapp.app D/SurfaceView: surfaceChanged (1440,1080) 1 #8 android.view.SurfaceView{9f7ad5a V.E...... ......ID 0,0-1440,1080}
2021-02-01 13:05:19.202 4217-4217/com.myapp.app D/SurfaceViewImpl: Surface changed. Size: 1440x1080
2021-02-01 13:05:19.207 4217-4217/com.myapp.app D/SurfaceViewImpl: Surface set on Preview.
2021-02-01 13:05:19.411 4217-4257/com.myapp.app I/CameraManagerGlobal: Camera 1 facing CAMERA_FACING_FRONT state now CAMERA_STATE_CLOSED for client com.samsung.adaptivebrightnessgo API Level 2
2021-02-01 13:05:19.422 4217-4257/com.myapp.app I/CameraManagerGlobal: postSingleUpdate device: camera id 0 status STATUS_NOT_AVAILABLE
2021-02-01 13:05:19.423 4217-4257/com.myapp.app I/CameraManagerGlobal: postSingleUpdate device: camera id 0 status STATUS_NOT_AVAILABLE
2021-02-01 13:05:19.425 4217-4257/com.myapp.app I/CameraManagerGlobal: postSingleUpdate device: camera id 0 status STATUS_NOT_AVAILABLE
2021-02-01 13:05:19.428 4217-4257/com.myapp.app I/CameraManagerGlobal: Camera 0 facing CAMERA_FACING_BACK state now CAMERA_STATE_OPEN for client com.myapp.app API Level 2
2021-02-01 13:05:19.452 4217-4803/com.myapp.app D/Camera2CameraImpl: {Camera@ea5acee[id=0]} Use case Preview:androidx.camera.core.Preview-ece4a019-fe39-4341-ab30-82f47580d983 INACTIVE
2021-02-01 13:05:19.455 4217-4803/com.myapp.app D/UseCaseAttachState: Active and attached use case: [] for camera: 0
2021-02-01 13:05:19.458 4217-4803/com.myapp.app D/Camera2CameraImpl: {Camera@ea5acee[id=0]} Use case Preview:androidx.camera.core.Preview-ece4a019-fe39-4341-ab30-82f47580d983 ACTIVE
2021-02-01 13:05:19.460 4217-4803/com.myapp.app D/UseCaseAttachState: Active and attached use case: [androidx.camera.core.Preview-ece4a019-fe39-4341-ab30-82f47580d983163463287] for camera: 0
2021-02-01 13:05:19.470 4217-4803/com.myapp.app D/Camera2CameraImpl: {Camera@ea5acee[id=0]} CameraDevice.onOpened()
2021-02-01 13:05:19.476 4217-4803/com.myapp.app D/Camera2CameraImpl: {Camera@ea5acee[id=0]} Transitioning camera internal state: OPENING --> OPENED
2021-02-01 13:05:19.481 4217-4803/com.myapp.app D/CameraStateRegistry: Recalculating open cameras:
    Camera                                       State                 
    -------------------------------------------------------------------
    Camera@163f523[id=2]                         UNKNOWN               
    Camera@640eda1[id=1]                         UNKNOWN               
    Camera@ea5acee[id=0]                         OPEN                  
    -------------------------------------------------------------------
    Open count: 1 (Max allowed: 1)
2021-02-01 13:05:19.483 4217-4803/com.myapp.app D/UseCaseAttachState: All use case: [androidx.camera.core.Preview-ece4a019-fe39-4341-ab30-82f47580d983163463287] for camera: 0
2021-02-01 13:05:19.497 4217-4803/com.myapp.app D/UseCaseAttachState: Active and attached use case: [androidx.camera.core.Preview-ece4a019-fe39-4341-ab30-82f47580d983163463287] for camera: 0
2021-02-01 13:05:19.505 4217-4803/com.myapp.app D/SyncCaptureSessionBase: [androidx.camera.camera2.internal.SynchronizedCaptureSessionBaseImpl@e53a798] getSurface...done
2021-02-01 13:05:19.506 4217-4803/com.myapp.app D/DeferrableSurface: New surface in use[total_surfaces=1, used_surfaces=1](androidx.camera.core.SurfaceRequest$2@f584149}
2021-02-01 13:05:19.507 4217-4803/com.myapp.app D/DeferrableSurface: use count+1, useCount=1 androidx.camera.core.SurfaceRequest$2@f584149
2021-02-01 13:05:19.507 4217-4803/com.myapp.app D/CaptureSession: Opening capture session.
2021-02-01 13:05:19.646 4217-4803/com.myapp.app D/CaptureSession: Attempting to send capture request onConfigured
2021-02-01 13:05:19.646 4217-4803/com.myapp.app D/CaptureSession: Issuing request for session.
2021-02-01 13:05:19.666 4217-4803/com.myapp.app D/CaptureSession: CameraCaptureSession.onConfigured() mState=OPENED
2021-02-01 13:05:19.667 4217-4803/com.myapp.app D/CaptureSession: CameraCaptureSession.onReady() OPENED
2021-02-01 13:05:20.414 4217-4248/com.myapp.app I/CameraManagerGlobal: Camera 0 facing CAMERA_FACING_BACK state now CAMERA_STATE_ACTIVE for client com.myapp.app API Level 2
2021-02-01 13:05:20.448 4217-4803/com.myapp.app D/StreamStateObserver: Update Preview stream state to STREAMING

Answer 1

I found the problem. I have to set the implementation mode to COMPATIBLE on the preview view.

this.binding.preview.setImplementationMode(PreviewView.ImplementationMode.COMPATIBLE);