如何在SurfaceView上显示相机预览？

Question

我正在尝试在SurfaceView上打开相机硬件。在布局中，我创建了一个SurfaceView，然后打开相机，如下面的代码所示。当我运行代码时，CameraAvailableCB中的toast出现并显示“onCameraAvailable”，但SurfaceView上没有任何内容。

如何在SurfaceView上显示相机显示？

代码

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

    this.mBtnCapture = (Button) findViewById(R.id.actMain_btn_capture);
    this.mSurfaceView = (SurfaceView) findViewById(R.id.actMain_surfaceView);
    this.mSurfaceHolder = this.mSurfaceView.getHolder();
    this.mSurfaceHolder.addCallback(this);
    this.mCameraManager = (CameraManager) this.getSystemService(Context.CAMERA_SERVICE);

    try {
        cameraIDsList = this.mCameraManager.getCameraIdList();

        for (String id : cameraIDsList) {
            Log.v(TAG, "CameraID: " + id);
        }

    } catch (CameraAccessException e) {
        e.printStackTrace();
    }

    cameraStateCB = new CameraDevice.StateCallback() {
        @Override
        public void onOpened(CameraDevice camera) {
            Toast.makeText(getApplicationContext(), "onOpened", Toast.LENGTH_SHORT).show();

            //requesting permission
            int permissionCheck = ContextCompat.checkSelfPermission(activity, Manifest.permission.CAMERA);
            if (permissionCheck != PackageManager.PERMISSION_GRANTED) {

                if (ActivityCompat.shouldShowRequestPermissionRationale(activity, Manifest.permission.CAMERA)) {

                } else {
                    ActivityCompat.requestPermissions(activity, new String[]{Manifest.permission.CAMERA}, MY_PERMISSIONS_REQUEST_CAMERA);
                    Toast.makeText(getApplicationContext(), "request permission", Toast.LENGTH_SHORT).show();
                }

            } else {
                Toast.makeText(getApplicationContext(), "PERMISSION_ALREADY_GRANTED", Toast.LENGTH_SHORT).show();
            }

            //opening the camera
            try {
                mCameraManager.openCamera(cameraIDsList[1], cameraStateCB, new Handler());

            } catch (CameraAccessException e) {
                e.printStackTrace();
            }
        }

        @Override
        public void onDisconnected(CameraDevice camera) {
            Toast.makeText(getApplicationContext(), "onDisconnected", Toast.LENGTH_SHORT).show();
        }

        @Override
        public void onError(CameraDevice camera, int error) {
            Toast.makeText(getApplicationContext(), "onError", Toast.LENGTH_SHORT).show();
        }
    };

    CameraManager.AvailabilityCallback cameraAvailableCB = new CameraManager.AvailabilityCallback() {
        @Override
        public void onCameraAvailable(String cameraId) {
            super.onCameraAvailable(cameraId);

            Toast.makeText(getApplicationContext(), "onCameraAvailable", Toast.LENGTH_SHORT).show();
        }

        @Override
        public void onCameraUnavailable(String cameraId) {
            super.onCameraUnavailable(cameraId);

            Toast.makeText(getApplicationContext(), "onCameraUnavailable", Toast.LENGTH_SHORT).show();
        }
    };
    this.mCameraManager.registerAvailabilityCallback(cameraAvailableCB, new Handler());
}



@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
    super.onRequestPermissionsResult(requestCode, permissions, grantResults);

    switch (requestCode) {
        case MY_PERMISSIONS_REQUEST_CAMERA:
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED)
                // Open Camera
                break;
    }
}

@Override
public void surfaceCreated(SurfaceHolder holder) {
    Log.w(TAG, "surfaceCreated");
}

@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
    Log.w(TAG, "surfaceChanged");
}

@Override
public void surfaceDestroyed(SurfaceHolder holder) {
    Log.w(TAG, "surfaceDestroyed");
}

Answer 1

要使用Camera2 API显示来自相机的预览，您应该执行以下步骤：

1. 获得使用相机设备的许可
2. 使用CameraManager打开与相机的连接
3. 准备好Surface预览
4. 使用打开的相机设备和所需的表面（它不仅可以包括预览表面）创建CaptureSession
5. 创建CaptureSession后，您需要创建并配置CaptureRequest并将其提交给CaptureSession

需要注意的是，准备曲面和打开与相机的连接是独立的过程，因此您需要确保在创建CaptureSession之前它们都已完成。

以下是在屏幕上显示相机预览的活动示例：

public class MainActivity extends AppCompatActivity implements SurfaceHolder.Callback, Handler.Callback {
    static final String TAG = "CamTest";
    static final int MY_PERMISSIONS_REQUEST_CAMERA = 1242;
    private static final int MSG_CAMERA_OPENED = 1;
    private static final int MSG_SURFACE_READY = 2;
    private final Handler mHandler = new Handler(this);
    SurfaceView mSurfaceView;
    SurfaceHolder mSurfaceHolder;
    CameraManager mCameraManager;
    String[] mCameraIDsList;
    CameraDevice.StateCallback mCameraStateCB;
    CameraDevice mCameraDevice;
    CameraCaptureSession mCaptureSession;
    boolean mSurfaceCreated = true;
    boolean mIsCameraConfigured = false;
    private Surface mCameraSurface = null;

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

        this.mSurfaceView = (SurfaceView) findViewById(R.id.SurfaceViewPreview);
        this.mSurfaceHolder = this.mSurfaceView.getHolder();
        this.mSurfaceHolder.addCallback(this);
        this.mCameraManager = (CameraManager) this.getSystemService(Context.CAMERA_SERVICE);

        try {
            mCameraIDsList = this.mCameraManager.getCameraIdList();
            for (String id : mCameraIDsList) {
                Log.v(TAG, "CameraID: " + id);
            }
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }

        mCameraStateCB = new CameraDevice.StateCallback() {
            @Override
            public void onOpened(CameraDevice camera) {
                Toast.makeText(getApplicationContext(), "onOpened", Toast.LENGTH_SHORT).show();

                mCameraDevice = camera;
                mHandler.sendEmptyMessage(MSG_CAMERA_OPENED);
            }

            @Override
            public void onDisconnected(CameraDevice camera) {
                Toast.makeText(getApplicationContext(), "onDisconnected", Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onError(CameraDevice camera, int error) {
                Toast.makeText(getApplicationContext(), "onError", Toast.LENGTH_SHORT).show();
            }
        };
    }

    @Override
    protected void onStart() {
        super.onStart();

        //requesting permission
        int permissionCheck = ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA);
        if (permissionCheck != PackageManager.PERMISSION_GRANTED) {
            if (ActivityCompat.shouldShowRequestPermissionRationale(this, Manifest.permission.CAMERA)) {

            } else {
                ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.CAMERA}, MY_PERMISSIONS_REQUEST_CAMERA);
                Toast.makeText(getApplicationContext(), "request permission", Toast.LENGTH_SHORT).show();
            }
        } else {
            Toast.makeText(getApplicationContext(), "PERMISSION_ALREADY_GRANTED", Toast.LENGTH_SHORT).show();
            try {
                mCameraManager.openCamera(mCameraIDsList[1], mCameraStateCB, new Handler());
            } catch (CameraAccessException e) {
                e.printStackTrace();
            }
        }
    }

    @Override
    protected void onStop() {
        super.onStop();
        try {
            if (mCaptureSession != null) {
                mCaptureSession.stopRepeating();
                mCaptureSession.close();
                mCaptureSession = null;
            }

            mIsCameraConfigured = false;
        } catch (final CameraAccessException e) {
            // Doesn't matter, cloising device anyway
            e.printStackTrace();
        } catch (final IllegalStateException e2) {
            // Doesn't matter, cloising device anyway
            e2.printStackTrace();
        } finally {
            if (mCameraDevice != null) {
                mCameraDevice.close();
                mCameraDevice = null;
                mCaptureSession = null;
            }
        }
    }

    @Override
    public boolean handleMessage(Message msg) {
        switch (msg.what) {
            case MSG_CAMERA_OPENED:
            case MSG_SURFACE_READY:
                // if both surface is created and camera device is opened
                // - ready to set up preview and other things
                if (mSurfaceCreated && (mCameraDevice != null)
                        && !mIsCameraConfigured) {
                    configureCamera();
                }
                break;
        }

        return true;
    }

    private void configureCamera() {
        // prepare list of surfaces to be used in capture requests
        List<Surface> sfl = new ArrayList<Surface>();

        sfl.add(mCameraSurface); // surface for viewfinder preview

        // configure camera with all the surfaces to be ever used
        try {
            mCameraDevice.createCaptureSession(sfl,
                    new CaptureSessionListener(), null);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }

        mIsCameraConfigured = true;
    }


    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);

        switch (requestCode) {
            case MY_PERMISSIONS_REQUEST_CAMERA:
                if (ActivityCompat.checkSelfPermission(this, Manifest.permission.CAMERA) == PackageManager.PERMISSION_GRANTED)
                    try {
                        mCameraManager.openCamera(mCameraIDsList[1], mCameraStateCB, new Handler());
                    } catch (CameraAccessException e) {
                        e.printStackTrace();
                    }
                break;
        }
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        mCameraSurface = holder.getSurface();
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
        mCameraSurface = holder.getSurface();
        mSurfaceCreated = true;
        mHandler.sendEmptyMessage(MSG_SURFACE_READY);
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        mSurfaceCreated = false;
    }

    private class CaptureSessionListener extends
            CameraCaptureSession.StateCallback {
        @Override
        public void onConfigureFailed(final CameraCaptureSession session) {
            Log.d(TAG, "CaptureSessionConfigure failed");
        }

        @Override
        public void onConfigured(final CameraCaptureSession session) {
            Log.d(TAG, "CaptureSessionConfigure onConfigured");
            mCaptureSession = session;

            try {
                CaptureRequest.Builder previewRequestBuilder = mCameraDevice
                        .createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
                previewRequestBuilder.addTarget(mCameraSurface);
                mCaptureSession.setRepeatingRequest(previewRequestBuilder.build(),
                        null, null);
            } catch (CameraAccessException e) {
                Log.d(TAG, "setting up preview failed");
                e.printStackTrace();
            }
        }
    }
}

Answer 2

有了 CameraX ，现在很容易。

    // Create a preview use case instance
val preview = Preview.Builder().build()

// Bind the preview use case and other needed user cases to a lifecycle
val camera = cameraProvider.bindToLifecycle(lifecycleOwner, cameraSelector, preview, imageAnalysis, imageCapture)

// Create a surfaceProvider using the bound camera's cameraInfo
val surfaceProvider = previewView.createSurfaceProvider(camera.cameraInfo)

// Attach the surfaceProvider to the preview use case to start preview
preview.setSurfaceProvider(surfaceProvider)


<androidx.camera.view.PreviewView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:scaleType="fitEnd" />

https://medium.com/androiddevelopers/display-a-camera-preview-with-previewview-86562433d86c