public void onStartCrop(Activity activity, Fragment fragment, @NonNull BoxingCropOption cropConfig,
                            @NonNull String path, int requestCode) {
        if (ensureLoader()) {
            throw new IllegalStateException("init method should be called first");
        }
        if (cropConfig == null) {
            throw new IllegalArgumentException("crop config is null.");
        }
        mCrop.onStartCrop(activity, fragment, cropConfig, path, requestCode);
    }
A loader holding {@link IBoxingCrop} to crop images.

@author ChenSL
boxing/src/main/java/com/bilibili/boxing/BoxingCrop.java