Tony/153 refactor file browsing code

[tonypioneer]

Pull Request Details

What issue does this PR address

• Fixed the issue that uploaded files will appear in unexpected directories.
• Refactored file-browsing code built upon basePath.

Associated Issue

• This PR relates to issue
  • SOLID UI: refactor file-browsing code built upon basePath #153
  • SOLID UI: Uploaded file appears in unexpected directory #193

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Build and run the app.

Checklist

Complete the check-list below to ensure your branch is ready for PR.

• Screenshots included in linked issue #
• Changes adhere to the style and coding guidelines
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• Any dependent changes have been merged and published in downstream modules
• The update contains no confidential information
• The update has no duplicated content
• No lint check errors are related to these changes (make prep or flutter analyze lib)
• Integration test dart test output or screenshot included in issue #
• I tested the PR on these devices:
  • Android
  • iOS
  • Linux
  • MacOS
  • Windows
  • Web
• I have identified reviewers
• The PR has been approved by reviewers

Finalising

Once PR discussion is complete and reviewers have approved:

• Merge dev into the this branch
• Resolve any conflicts
• Add a one line summary into the CHANGELOG.md
• Push to the git repository and review
• Merge the PR into dev