42de305b7c
The reasoning for calling showSystemUi() in the onCreate method before was to make the transitions for immersive mode more smooth. However, it's only needed when the PDF has actually loaded, i.e. when the immersive mode makes sense to use. Before, Snackbars were partially covered by the navigation UI due to the showSystemUi() setting the View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION flag. Moving it so that the function is only called when a PDF is loaded fixes this issue.
Simple Android PDF viewer based on pdf.js and content providers. The app doesn't require any permissions. The PDF stream is fed into the sandboxed WebView without giving it access to content or files. Content-Security-Policy is used to enforce that the JavaScript and styling properties within the WebView are entirely static content from the apk assets. It reuses the hardened Chromium rendering stack while only exposing a tiny subset of the attack surface compared to actual web content. The PDF rendering code itself is memory safe with dynamic code evaluation disabled, and even if an attacker did gain code execution by exploiting the underlying web rendering engine, they're within the Chromium renderer sandbox with no access to the network (unlike a browser), files, or other content.