如果在Android相机预览中遇到了全屏被拉伸的问题，可以通过设置相机预览的四个方向比例来解决。下面是一个代码示例：

import android.content.Context;
import android.content.res.Configuration;
import android.hardware.Camera;
import android.view.SurfaceHolder;
import android.view.SurfaceView;

public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {
    private SurfaceHolder mHolder;
    private Camera mCamera;

    public CameraPreview(Context context, Camera camera) {
        super(context);
        mCamera = camera;
        mHolder = getHolder();
        mHolder.addCallback(this);
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        try {
            mCamera.setPreviewDisplay(holder);
            mCamera.startPreview();
            setCameraDisplayOrientation();
        } catch (Exception e) {
            // 处理异常
        }
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        // 销毁SurfaceView时停止预览并释放相机资源
        mCamera.stopPreview();
        mCamera.release();
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
        // 如果预览正在进行中，则停止预览
        if (mHolder.getSurface() == null) {
            return;
        }
        try {
            mCamera.stopPreview();
        } catch (Exception e) {
            // 处理异常
        }
        // 在此处重新设置相机预览尺寸和方向
        setCameraDisplayOrientation();
        try {
            mCamera.setPreviewDisplay(mHolder);
            mCamera.startPreview();
        } catch (Exception e) {
            // 处理异常
        }
    }

    private void setCameraDisplayOrientation() {
        Camera.CameraInfo info = new Camera.CameraInfo();
        Camera.getCameraInfo(Camera.CameraInfo.CAMERA_FACING_BACK, info);
        int rotation = getWindowManager().getDefaultDisplay().getRotation();
        int degrees = 0;
        switch (rotation) {
            case Surface.ROTATION_0:
                degrees = 0;
                break;
            case Surface.ROTATION_90:
                degrees = 90;
                break;
            case Surface.ROTATION_180:
                degrees = 180;
                break;
            case Surface.ROTATION_270:
                degrees = 270;
                break;
        }
        int result;
        if (info.facing == Camera.CameraInfo.CAMERA_FACING_FRONT) {
            result = (info.orientation + degrees) % 360;
            result = (360 - result) % 360;  // 前置摄像头需要镜像翻转
        } else {
            result = (info.orientation - degrees + 360) % 360;
        }
        mCamera.setDisplayOrientation(result);
    }
}

在上述代码中，setCameraDisplayOrientation() 方法用于设置相机预览的方向。它通过获取设备的旋转角度，并将其与相机的方向进行计算，最终设置相机的显示方向。

此外，还需要在相机预览的布局文件中添加一个SurfaceView用于显示相机预览：

最后，在相机预览的Activity中，实例化Camera对象并将其传递给CameraPreview类：

public class CameraActivity extends AppCompatActivity {
    private Camera mCamera;

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

        mCamera = getCameraInstance();
        CameraPreview mPreview = new CameraPreview(this, mCamera);
        FrameLayout previewLayout = findViewById(R.id.camera_preview);
        previewLayout.addView(mPreview);
    }

    // 获取相机实例
    private Camera getCameraInstance() {
        Camera camera = null;
        try {
            camera = Camera.open();
        } catch (Exception e) {
            // 处理异常
        }
        return camera;
    }
}

通过上述方法，您可以在Android相机预览中解决全屏被拉伸的问题，并保持正确的