要在Android 10中显示Camera2效果的预览，您可以按照以下步骤进行操作：

1. 在AndroidManifest.xml文件中添加以下权限：

2. 在Activity中声明以下变量：

private CameraManager cameraManager;
private String cameraId;
private CameraDevice cameraDevice;
private CameraCaptureSession cameraCaptureSession;
private CaptureRequest.Builder captureRequestBuilder;
private Size previewSize;
private ImageReader imageReader;

3. 在onCreate()方法中初始化CameraManager，并获取相机的ID：

cameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
try {
    cameraId = cameraManager.getCameraIdList()[0];
} catch (CameraAccessException e) {
    e.printStackTrace();
}

4. 创建一个CameraDevice.StateCallback来处理相机设备的打开和关闭事件，并在onOpened()方法中创建相机预览会话：

CameraDevice.StateCallback stateCallback = new CameraDevice.StateCallback() {
    @Override
    public void onOpened(@NonNull CameraDevice camera) {
        cameraDevice = camera;
        createCameraPreviewSession();
    }

    @Override
    public void onDisconnected(@NonNull CameraDevice camera) {
        cameraDevice.close();
    }

    @Override
    public void onError(@NonNull CameraDevice camera, int error) {
        cameraDevice.close();
        cameraDevice = null;
    }
};

5. 创建一个createCameraPreviewSession()方法来设置相机的预览会话：

private void createCameraPreviewSession() {
    try {
        SurfaceTexture texture = textureView.getSurfaceTexture();
        texture.setDefaultBufferSize(previewSize.getWidth(), previewSize.getHeight());
        Surface surface = new Surface(texture);

        captureRequestBuilder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
        captureRequestBuilder.addTarget(surface);

        cameraDevice.createCaptureSession(Arrays.asList(surface, imageReader.getSurface()),
            new CameraCaptureSession.StateCallback() {
                @Override
                public void onConfigured(@NonNull CameraCaptureSession session) {
                    if (cameraDevice == null) {
                        return;
                    }

                    cameraCaptureSession = session;
                    try {
                        captureRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
                        cameraCaptureSession.setRepeatingRequest(captureRequestBuilder.build(), null, null);
                    } catch (CameraAccessException e) {
                        e.printStackTrace();
                    }
                }

                @Override
                public void onConfigureFailed(@NonNull CameraCaptureSession session) {
                    Toast.makeText(MainActivity.this, "Failed to create camera preview", Toast.LENGTH_SHORT).show();
                }
            }, null);
    } catch (CameraAccessException e) {
        e.printStackTrace();
    }
}

6. 在onResume()方法中打开相机：

@Override
protected void onResume() {
    super.onResume();
    openCamera();
}

private void openCamera() {
    try {
        cameraManager.openCamera(cameraId, stateCallback, null);
    } catch (CameraAccessException e) {
        e.printStackTrace();
    }
}

7. 在onPause()方法中关闭相机：

@Override
protected void onPause() {
    super.onPause();
    closeCamera();
}

private void closeCamera() {
    if (cameraCaptureSession != null) {
        cameraCaptureSession.close();
        cameraCaptureSession = null;
    }

    if (cameraDevice != null) {
        cameraDevice.close();
        cameraDevice = null;
    }
}

这些步骤将帮助您在Android 10中显示Camera2效果的相机预览。请根据您的需求调整代码，并确保在AndroidManifest.xml文件中添加适当的权限。