Dex Editor Plus Here
Extract APK → decode DEX → edit classes/methods → recompile → install.
You edit Smali, not Java. This has a steep learning curve. You cannot simply "add a line of Java" – you must understand the Dalvik VM’s register machine.
Dex Editor Plus is a lightweight, user-focused hex and binary editor designed for low-friction editing of files, memory dumps, and embedded firmware images. It targets developers, reverse engineers, firmware modders, and power users who need a compact, speedy tool for inspecting and patching binary data without the complexity of larger reverse-engineering suites. dex editor plus