What you want to say is,

Case 1) App display directory path as /storage/emulated/0/PDFfiles in the settings and doesn't even create such directory there.
And When it try to save output file there, then it show success message but fail to do so internally.
But when we manually create the directory, then it works as expected.

Case 2) When we change location path from settings then app still trying to save output file in PDFfiles directory.

Right?

I will look into it soon... until then anyone can consider working on this issue :)

@codegsaini @VA1DER Hi, I would like work this, but could you give more examples how this problem happen? Does this error occur in some spefic functions or Is this mistake associated with all of the storage location

@codegsaini Hi, it seems like I have find what the problem is.
First is about the path "/storage/emulated/0/PDFfiles" mentioned in the problem.
The only one place I find in the whole project which is related to that path is this code fragment in PdfToImageFragment.java

    @OnClick(R.id.viewImagesInGallery)
    void onImagesInGalleryClick() {
        Intent intent = new Intent();
        intent.setAction(Intent.ACTION_VIEW);
        Uri imagesUri = Uri.parse("content:///storage/emulated/0/PDFfiles/");
        intent.setDataAndType(imagesUri, "image/*");
        intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
        startActivity(intent);
    }

Although it is named as viewImagesInGallery, it just request some external app to view the image. And the direction is never created.
And I also find two other related problem in the project
One is about it will actually not create the default storage path after installing, the default storage path is created only when after someone execute getDefaultStoragelocation() which is a method in String.utils. And some functions like PdfToImages will not invoke this mehod or they will just create the path arbitrary. So if user first use the PdfToImages, something wrong with path happen. And the storage of different function is ridiculously different.

Second is that I find in the settings the default storage path is fixed. And in English version it is marked as non-changeable. But In Chinese version and or other languages (also find in ja), it is marked as change storage location.

So above all, I considerate that I can first revise the .viewImagesInGallery(). Then encapsulate the method about storage to some storage utils so that everyone will not create some storage path themselves. And I will also create the default storage path immediately after installing. Finally, I will try to allow the storage path to be changed by User.

Is it ok? @codegsaini

create the default storage path immediately after installing

allow the storage path to be changed by User.

@KOISHI-CHEN These two changes may solve the issue. Consider these ....