Modify android internal class(es) / Call Handling

Since the whole Android stuff is open source I was 开发者_开发技巧thinking about to do some minor modifications in a few internal classes from the com.android.internal.telephony package and of course then I would love if somehow my application could use the modified classes. I was thinking about replacing the classes with the original ones at runtime by using reflection or other kind of unknown java tricks :D ...maybe what I'm trying to do is impossible :( I don't know that's why I'm asking.

Note: The changes in the internal classes would not change their functionality in any way, its more about extending their functionality so even if other apps would use the modified versions it would not break them!

Why I want to do it? What I'm trying to achieve ? Well i would like to modify the com.android.internal.telephony.gsm.CallTracker internal class so i could do proper call handling (call blocking etc..) Maybe if you know about another way how to do what I want to I would like to hear about it :)

Note2: I know about the method when you handle the android.intent.action.PHONE_STATE, action , but its simply too late to react when this action is broadcasted. I'm really looking for a better solution even if that solution involve ugly hacks :)

As always thanks for all your replies...

You cannot do this :) I'll let you imagine what would happen if any application was allowed to freely replace core parts of the system. You can download the Android source code and you can modify it and you can upload the modifications to your phone (if your phone is rooted/unlocked) but you cannot apply such modifications with a simple app.

Changing a classes functionality (methods, byte code) after a class ha been loaded is impossible. Reflection/Invocation does not affect classes but static fields and instances only.

Your looking at a way to add additional methods or change existing methods of a running system, because the classes in question probably will be loaded already when your 'hacking' application is executed.

The only technical approach that I see is to change the classes in advance and deploy a modified system. I'm just ignoring possible licensing issues and security at the moment. But even with this way, your software would depend on a custom OS, a branch from some andorid version, disconnected from official updates, and you'd have to ask your customers to install a custom OS with, say, unknown features.

Sidenote - I'm very happy, that this is really impossible, otherwise my mobile would already be full of trojans, viruses, etc...

Romain is correct you can't and shouldn't try to change existing system classes.

That said, implementing call screening as you suggest should be possible by creating a replacement to the dialer application that handles phone calls.

Specifically the intent ACTION_ANSWER should be handled by your application, which could then either implement a dialer-like interface or open the dialer app (or any other call manager) explicitly.

There are actually ways to hack on Android framework classes, it just depends on which ones you want to hack.

1. You must extend the class you intent to hack on.
2. If you want to override package private methods and/or access package private variables you can put your class in the same package.
3. You can use reflection.

I've actually had to do this to work around bugs. Romain is correct, to an extent. It all depends on the structure of the code you are trying to hack on. You definitely can't hack on Android internals, but you can hack on other framework classes like Activity, View, etc.