Originally Posted by WietsedeVries
The biggest problem is that I don't only want a replacement for the application launcher but also the notification drawer and everything else. Is it possible to replace them also? I don't think so, so I think I'll work on a custom rom.
These changes you are talking about can be done. They are system changes so not supported by the android app installer.
Eg: Your notification drawer, status bar are part of SystemUI.apk. The source for this is can be found in the AOSP source code under android/frameworks/base/...
You can make your modifications, compile it into an apk and then make a flashable zip to replace the current one (or push it via a rooted adb console).
or you can compile the entire source code into a flashable zip (eg CM7,9 etc..) and use it a replacement ROM with your modifications.
This is the line between an application under the android runtime and the android runtime itself.
these files, under framework are part of the OS. so to provide a customized version of the operating itself is what people like to call ROMs.
Now ROMs (like any OS) are device dependant. Windows has the code to run in a lot of different hardware configs, but android aims to be small. It should have only the minimum required code to efficiently run itself on a device.
Thats the kernel. The kernel communicates with the hardware and so the rest of the hardware can happily talk to a working kernel and expect the hardware to function as advertised. Kernel is a simple program which goes into the RAM on system start and sits there directing the operation of the phone.
Kernel devs work on making sure the hardware and the android runtime work perfectly together. Now, in this imperfect world, not all sources are open, even though they should be. and therein the issue lies.
If you want to compile android from source and make sure it works on your phone, first you need to make sure you have the kernel with all the changes(patches) to it made by the vendor (chap who made the phone and bullied you into buying it) to get it working on your hardware.
If you dont have that, you have to do it yourself. Or wait for someone else to do it.
once you can compile android and get it working on your phone with all the itty bitty hardware working A-OK.. then you can browse through the source, make changes as per your individual requirements and compile it into a ROM.
see the changes to the OS are separate from the changes to the kernel. The kernel changes are for hardware-software interaction so they are phone SPECIFIC.
but changes to your custom android OS (ROM) can be "cherry-picked" from other ROM/gerrit/AOSP/CM/AOKP sources and put inside your own source tree to get included in your build.
so if you have all the device / kernel stuff from a working android distribution, you can take the source of another android distribution and swap the device stuff into it and see if it works.
hope this helps.