Develop Reference

Android Modifying in-call screen via AOSP

I've read elsewhere that
“Developers cant customize the in-call screen because of security concerns”
So, I am trying to understand the functionality of the in-call screen at the source level.
Can any Android devs, especially those that have created their own custom ROMs, tell me which specific classes in the AOSP are responsible for both display and functionality of this screen?

Take a look at the source:(from the horse's mouth):
https://code.google.com/p/incomingcallplus/source/checkout
Esp. the BETA Version 0.8.0
By the way, if you are interested in some R&D, I have worked towards this so i know we can access PhoneStateListener and get the status of a call for off the hook, idle and ringing.
http://www.tutorialforandroid.com/2009/01/get-phone-state-when-someone-is-calling_22.html
Also,
Android: How to customize income call screen

This may be a bit late but right now Android support for custom in-call screen by implementing InCallService. The application needs to be set as the default dialer to make it work. For more info https://developer.android.com/reference/android/telecom/InCallService.html

Can I make Pattern Password Screen Locker android app

Has anyone got experience with developing an application to replace the default lock screen? I've been told it is not possible, however this application manages it.
Any tutorials or guidance you know of would be appreciated.

100% possible. Here are some links to get you started.
Android App and Pattern Lock Screen
Android Lock Screen Widget
Developing a custom lock screen

Try this one:
lockscreenswitchwidget

You can implement deviceAdminReciever to use device locks and all please have a look at this it explains everything about locks setting passwords.....
Update:
Use this library Link
and Source Here..

Having a problen to develop lockscreen for android

I want to develop an android application that will be an alternative lockscreen.
I searched a lot and i couldn't found an explanation about how to make an app to work like a lockscreen. I understand that there is no official android API for lockscreens, but there must be way, because there are a lot of alternative lockscreens applications in the market.
Does someone know how could i make my app work like a lockscreen? Or if there is a basic code out there of lockscreen app that i can learn from it how to do it?
Thanks a lot (:

The way this is usually accomplished is creating an app that becomes the home application and then when the screen is turned on display your custom lockscreen and hide it when the user successfully unlocks it so they can use the device.
Make sure to take a look at the numerous questions on SO that are very similar to this.

How can I develop an app able to actually replace lockscreen? [duplicate]

I know that there is already some apps can do this, such as:
WidgetLocker Lockscreen
Flyscreen
I want to know how to do this in my app? What classes I can use? Or what articles I should read? I don't want to change the Android's source code.
And I wonder if it will be different to deal with when the screen is locked by draw pattern?

Have a look at this answer. You need to write your own home screen app which will implement the lockscreen behaviour that you require. There is sample code for writing your own home screen app in the Android SDK.

Pattern Unlock Screen (new activity, not using the system one)

I'm trying to make a screen with a pattern like Android Pattern Screen but not using it (I don't want lock my phone, only put a "private" section with a "door").
I need a screen to control the access a special section of my app so I have thought to use a pattern screen.
How can I do this? Where can I found a piece of code or and example?
Thanks :)
PD. The Screen I need is similar to this: http://www.actualidadgoogle.com/wp-content/uploads/2011/11/patron-desbloq-android.png

You can get the code from the android source. You can find the source here