This chapter discusses methods for creating apps with simple animations—objects that move. You’ll learn the basics of creating two-dimensional games with App Inventor and become comfortable with image sprites and handling events like two objects colliding.
When you see an object moving smoothly along the computer screen, what you’re really seeing is a quick succession of images with the object in a slightly different place each time. It’s an illusion not much different from “flipbooks,” in which you see a moving picture by flipping quickly through the pages (and it’s also how far more sophisticated animated films are made!).
With App Inventor, you’ll define animation by placing
objects within a
Canvas component and
moving those objects around the
Canvas over time. In this chapter, you’ll
learn how the
system works, how the Clock.Timer event can be
used to trigger movement, how to control the speed of objects, and how
to respond to events such as two objects colliding.
You can drag a
component into your app from the Basic palette. After dragging it out,
Height. Often, you’ll want the
Canvas to span the width of the device
screen. To do this, choose “Fill parent” when specifying the
Width, as shown in Figure 17-1.