我正在尝试用cameraX制作简单的相机应用程序，但我不能保存照片

// 导入所需的类
import androidx.camera.core.Camera;
import androidx.camera.core.CameraSelector;
import androidx.camera.core.ImageCapture;
import androidx.camera.core.ImageCaptureException;
import androidx.camera.core.Preview;
import androidx.camera.lifecycle.ProcessCameraProvider;
import androidx.camera.view.PreviewView;

// 在您的Activity或Fragment中的成员变量中声明所需的变量
private PreviewView previewView;
private ImageCapture imageCapture;

// 在您的onCreate方法中初始化相机和预览
previewView = findViewById(R.id.preview_view);
ListenableFuture<ProcessCameraProvider> cameraProviderFuture = ProcessCameraProvider.getInstance(this);
cameraProviderFuture.addListener(() -> {
    try {
        ProcessCameraProvider cameraProvider = cameraProviderFuture.get();
        bindPreview(cameraProvider);
    } catch (ExecutionException | InterruptedException e) {
        e.printStackTrace();
    }
}, ContextCompat.getMainExecutor(this));

// 创建预览并绑定到相机
private void bindPreview(ProcessCameraProvider cameraProvider) {
    Preview preview = new Preview.Builder().build();
    CameraSelector cameraSelector = new CameraSelector.Builder()
            .requireLensFacing(CameraSelector.LENS_FACING_BACK)
            .build();
    preview.setSurfaceProvider(previewView.getSurfaceProvider());

    // 创建图像捕获用例
    imageCapture = new ImageCapture.Builder().build();

    // 绑定相机和生命周期
    Camera camera = cameraProvider.bindToLifecycle(this, cameraSelector, preview, imageCapture);
}

// 拍照并保存照片
private void takePhoto() {
    File photoFile = new File(getExternalFilesDir(Environment.DIRECTORY_PICTURES), "photo.jpg");
    ImageCapture.OutputFileOptions outputFileOptions = new ImageCapture.OutputFileOptions.Builder(photoFile).build();

    imageCapture.takePicture(outputFileOptions, ContextCompat.getMainExecutor(this), new ImageCapture.OnImageSavedCallback() {
        @Override
        public void onImageSaved(@NonNull ImageCapture.OutputFileResults outputFileResults) {
            // 照片保存成功
            Toast.makeText(MainActivity.this, "照片保存成功", Toast.LENGTH_SHORT).show();
        }

        @Override
        public void onError(@NonNull ImageCaptureException exception) {
            // 照片保存失败
            Toast.makeText(MainActivity.this, "照片保存失败", Toast.LENGTH_SHORT).show();
            exception.printStackTrace();
        }
    });
}