The ADT plugin for Eclipse, including the new visual layout editor, was updated and made available today. If you go back about a month or so to Google I/O, one of the most popular developer sessions was given by Tor Norbye and Xavier Ducrohet as they went over all the upcoming improvements to Android development tools, and when they talked about this one, the packed house cheered.
I know most of you aren't Android application developers, and are asking yourself what exactly this is, and what all the fuss is about. ADT (short for Android Development Tools) is a plugin for Eclipse -- an integrated development environment used by many to write and build Android applications. Eclipse is a stand alone program that can be used to write all sorts of applications, and is a very popular tool for Android developers writing apps in Java. Installing the ADT brings the tools needed by Eclipse to make those Android apps, and puts everything together into one happy, geeky program.
In today's update, the visual layout editor is the clear star of the show. In previous versions of the ADT, developers were forced to depend on unofficial (but done well in many cases) layout editors or to hard code the way their application looks by hand. As you can imagine, having a graphical WYSIWYG editor was something everyone wanted, and Google delivered. This does two things -- takes the time needed to hardcode the layout of an application and frees it to be used in better ways, and gives designers a unified set of tools to make beautiful apps. We might not understand all the fuss here, but trust me -- this is something developers have wanted and needed for quite a while, and it's great news for both those who code the apps, and those who use them. After the jump you'll find the ADT developers session video if you're looking for more info.
Source: Android developer website