Android How to Program, 3/e

6.12 Cannonball Subclass of GameElement

The Cannonball subclass of GameElement (Sections 6.12.1–6.12.4) represents a cannonball fired from the cannon.

6.12.1 Instance Variables and Constructor

The Cannonball constructor (Fig. 6.15) receives the cannonball’s radius rather than width and height in the GameElement constructor. Lines 15–16 call super with width and height values calculated from the radius. The constructor also receives the horizontal velocity of the Cannonball, velocityX, in addition to its vertical velocity, velocityY. Line 18 initializes onScreen to true because the Cannonball is initially on the screen.

Fig. 6.15 Cannonball instance variables and constructor

Figure 6.15 Full Alternative Text

6.12.2 Methods getRadius, collidesWith ...