Store image from camera into private app cache directory

I would like to capture an image from the camera and save it to the private app cache directory. I realize that I have to give the camera app permission to write to my private directory, so I added the FLAG_GRANT_WRITE_URI_PERMISSION flag.

What's happening is, that the camera app opens, I can take the picture, but when i click on the OK button, nothing happens. The camera app stays open. No log output. I guess it's because of a permission problem.

private void getCameraImage() {
    try {
        mTmpFile = File.createTempFile("tmp", ".jpg", getCacheDir());
        Uri imgUri = Uri.fromFile(mTmpFile);
        Intent i = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
        i.putExtra(MediaStore.EXTRA_OUTPUT, imgUri);
        i.addFlags(Intent.FLAG_GRANT_WRITE_URI_PERMISSION);
        // i.setData(imgUri); // if uncommented, i get an ActivityNotFound Exception
        startActivityForResult(i, REQUEST_CAMERA);
    } catch (IOException e) {
        Log.e(TAG, "getCameraImage()", e);
        Toast.makeText(this, "Something went wrong", Toast.LENGTH_SHORT).show();
    }
}

Any insights, on how I could correct that?

Edit:

When I change the directory to the public SD card, then it works fine.

mTmpFile = File.createTempFile("tmp", ".jpg", Environment.getExternalStorageDirectory());

Thanks Simon