Android SDK
The Android Software Development Kit (SDK) contains the necessary tools to create, compile and package Android application. Most of these tools are command line based.The Android SDK also provides an Android device emulator, so that Android applications can be tested without a real Android phone. You can create Android virtual devices (AVD) via the Android SDK, which run in this emulator.
The Android SDK contains the Android debug bridge (adb) tool which allows to connect to an virtual or real Android device.
Google provides the
Android
Development Tools
(ADT) to develop
Android applications with Eclipse. ADT is a set of
components
(plug-ins) which
extend the Eclipse IDE with Android
development
capabilities.
ADT contains all required functionalities to create, compile, debug and deploy Android applications from the Eclipse IDE. ADT also allows to create and start AVDs.
ADT contains all required functionalities to create, compile, debug and deploy Android applications from the Eclipse IDE. ADT also allows to create and start AVDs.
The Android system uses a special virtual machine, i.e. the
Dalvik
Virtual
Machine
to run Java based applications. Dalvik uses an
own
bytecode format
which is different from Java bytecode.
Therefore you cannot directly run Java class files on Android, they need to get converted in the Dalvik bytecode format.
Therefore you cannot directly run Java class files on Android, they need to get converted in the Dalvik bytecode format.
Android applications are primarily written in the Java
programming
language. The Java source files are converted to Java
class files by
the Java compiler.
The Android SDK contains a tool called dx which converts Java class files into a
These dex files are therefore much smaller in size than the corresponding class files.
The
The resulting
The Android Development Tools (ADT) performs these steps transparently to the user.
If you use the ADT tooling you press a button the whole Android application (
The Android SDK contains a tool called dx which converts Java class files into a
.dex
(Dalvik Executable)
file. All class files of one application are
placed in one compressed
.dex
file. During this conversion process
redundant
information in the class
files are optimized in the .dex
file. For example if the same String
is found in different class
files,
the
.dex
file
contains only once reference of this String.
These dex files are therefore much smaller in size than the corresponding class files.
The
.dex
file and the resources of an Android project, e.g. the
images and
XML
files, are packed into an
.apk
(Android Package)
file. The program
aapt
(Android Asset Packaging Tool) performs this packaging.
The resulting
.apk
file contains all necessary data to run the
Android application and
can be deployed to an Android device via the
adb
tool.
The Android Development Tools (ADT) performs these steps transparently to the user.
If you use the ADT tooling you press a button the whole Android application (
.apk
file) will be
created and
deployed.
The ADT allows the developer to define certain
artifacts, e.g.
Strings and layout files, in two ways: via a rich
editor, and
directly
via XML. This is done via multi-page editors in Eclipse. In these
editors you can
switch
between both
representations by
clicking on the
tab
on the lower
part of the
screen.
For example if you open the
For example if you open the
res/layout/main.xml
file in the
Package Explorer
View of Eclipse, you can switch between the two
representations as
depicted in the
following
screenshot.
(vogella.com)
