I built an app with java Android studio. But my laptop crashes and I lost all data code. The app is still installed and work very well in my cell phone. I haven't been able to locate the APK file in the cell phone.
Is there any way I can recover the app code? How should I proceed?
Recovering source code is partially possible. There are app decompiler available like Jadx which can decompile DEX code to Java code. However the decompilation is not 100% accurate (the decompiled is some times simply wrong) and also can fail for various reasons. A second problem is that the decompiler can not detect which class belongs to a library and which was written by you, so it decompiles everything.
So in the end you can use the decompiled code to extract important parts of your app or use it to remember how you solved a certain problem. So you will have to invest a lot of work to make it an app again, but decompiling the old may save you some hours.
For extracting the APK file(s) that belong to your app. For doing so you can use adb; see How do I get an apk file from an Android device? for details.
Alternatively you can use an app like Amaze which allows to do the same using the built-in "App Manager". It allows to copy the APK file(s) of an app to the sdcard section so that you can simply copy it via USB from a PC.
