Monthly Archives: July 2010

Welcome to the fourth and final part of the Android tutorial on how to make your own zoom control like the one used in Sony Ericsson X10 Mini in the Camera and Album applications. Click here to go to the prevoius part of this tutorial. As usual the source code is included, see below. Don’t forgett to download ‘Sony Ericsson Tutorials’ from Android market to see demos of this and other tutorials in action.

[Download] One Finger Zoom sample project – Part 4 (220kb)

In this part we’ll focus on introducing dynamic behavior to our zoom such as fling and bounce by animating the zoom state. Dynamic behavior adds a lot in terms of looks, feedback and usability.

Dynamics

To implement dynamic behavior we’re going to subclass the Dynamics class introduced in the final part of the list tutorial. Make sure to read through that tutorial if you want to know more about the Dynamics base class.

The Dynamics class is useful for applying dynamic behavior to a value, the class itself holds a position and a velocity and functionality for setting min and max positions. When subclassing Dynamics we must implement the onUpdate(int) method that is responsible for updating the state. This gives us control over the dynamic behavior and in our Dynamics sub-class we’ll implement basic friction and spring physics to handle fling and edge bounce. If you want to know more about spring physics then this is a nice place to start.

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