Subscribe in a readerTouch screens are a great way to interact with applications on mobile devices. With a touch screen, users can easily tap, drag, fling, or slide to quickly perform actions in their favorite applications. But it's not always that easy for developers. With Android, it's easy to recognize simple actions, like a swipe, but it's much more difficult to handle complicated gestures, which also require developers to write a lot of code. That's why we have decided to introduce a new gestures API in Android 1.6. This API, located in the new package android.gesture, lets you store, load, draw and recognize gestures. In this post I will show you how you can use the android.gesture API in your applications. Before going any further, you should download the source code of the examples.
Creating a gestures library
The Android 1.6 SDK comes with a new application pre-installed on the emulator, called Gestures Builder. You can use this application to create a set of pre-defined gestures for your own application. It also serves as an example of how to let the user define his own gestures in your applications. You can find the source code of Gestures Builders in the samples directory of Android 1.6. In our example we will use Gestures Builder to generate a set of gestures for us (make sure to create an AVD with an SD card image to use Gestures Builder.) The screenshot below shows what the application looks like after adding a few gestures:
As you can see, a gesture is always associated with a name. That name is very important because it identifies each gesture within your application. The names do not have to be unique. Actually it can be very useful to have several gestures with the same name to increase the precision of the recognition. Every time you add or edit a gesture in the Gestures Builder, a file is generated on the emulator's SD card, /sdcard/gestures. This file contains the description of all the gestures, and you will need to package it inside your application inside the resources directory, in /res/raw.
