Is there a way to get a list of all classes from a .dex file?

You can use the dexlib2 library as a standalone library (available in maven), to read the dex file and get a list of classes.

DexFile dexFile = DexFileFactory.loadDexFile("classes.dex", 19 /*api level*/);
for (ClassDef classDef: dexFile.getClasses()) {
    System.out.println(classDef.getType());
}

Note that the class names will be of the form "Ljava/lang/String;", which is how they are stored in the dex file (and in a java class file). To convert, just remove the first and last letter, and replace / with .

Use the command line tool dexdump from the Android-SDK. It's in $ANDROID_HOME/build-tools/<some_version>/dexdump. It prints a lot more info than you probably want. I didn't find a way to make dexdump less verbose, but

dexdump classes.dex | grep 'Class descriptor'

should work.