What language does Android support for application development? and why?

Java was the only officially supported programming language for building distributable third-party Android software.
Android Native Development Kit (Android NDK) which will allow developers to build Android software components with C and C++.

For the native look and feel, we should develop application in JAVA using ADT.
Android has been basically designed and developed in Java.
For easier implementation/cross platform support, one can opt fpr Html5/jQuery ,PhoneGap, etc.

java, because android is it even developed with java

android software was offficially supported by java and it also alows developers to build components or programs with c and c++

Android supports java for apps development.The development kit of android converts the java source code into corresponding byte code(using JIT compiler) and executes the program on android platform.

At launch, Java was the only officially supported programming language for building distributable third-party Android software.
Android Native Development Kit (Android NDK) which will allow developers to build Android software components with C and C++.
In addition to delivering support for native code, Google is also extending Android to support popular dynamic scripting languages.
Earlier this month, Google launched the Android Scripting Environment (ASE) which allows third-party developers to build simple Android applications with perl, JRuby, Python, LUA and BeanShell.
For having idea and usage of ASE, refer this Example link.
Scala is also supported.
For having examples of Scala, refer these Example link-1 , Example link-2 , Example link-3 .
Just now i have referred one Article Here in which i found some useful information as follows: programming language is Java but bridges from other languages exist (C# .net - Mono, etc).
can run script languages like LUA, Perl, Python, BeanShell, etc. 
I have read2nd article at Google Releases 'Simple' Android Programming Language .
For example of this, refer this .
Just now (2 Aug2010) i have read an article which describes regarding "Frink Programming language and Calculating Tool for Android", refer this links Link-1 , Link-2 On4-Aug-2010, i have found Regarding RenderScript.
Basically, It is said to be a C-like language for high performance graphics programming, which helps you easily write efficient Visual effects and animations in your Android Applications.
Its not released yet as it isn't finished.

java.
android is OS not programming language.

Java is one of the official Android app programming languages and turned into the number one language till the emergence of Kotlin.

Java keeps to stay a pinnacle Android app improvement language due to the fact it's miles solid and secure, helps multi-threading, is portable, and is outstanding for complicated architecture – a large asset for plenty of developers today. While that is true, Java does include a few overall performance drawbacks.

xml for design my app and java for write my code

sdk android support java and xml and ndk android is c and c++

java, because android is based on the concepts of Object Oriented Programming(OOP)