Motorola J2ME Specifications download pdf (Page 56)

Animation Frames

An animated sprite is created from an image divided into sections as described in the

constructor Sprite(Image, int, int). The individual sections of the image are considered the

raw frames of the

Sprite. The method getNumRawFrames returns the number of raw

frames.

Sprite Drawing

Sprites can be drawn at anytime using the draw(Graphics) method. The sprite

will be drawn on the

Graphics object, according to the current state information

maintained by the Sprite (i.e. position, frame, visibility). Some potential uses of Sprites

include:

• Arbitrarily draw the Sprite on a

GameScreen.

• A Sprite can be added to a

PlayField. Then PlayField.draw(Graphics, int, int) will

automatically draw all the Sprites associated with the

PlayField.

• draw(Graphics) could be called from the

paint() method in a subclass of

Canvas.

• draw(Graphics) could be called at any time to draw the

Sprite on a MIDP mutable

image. This is virtually identical to the first bullet, drawing on a

GameScreen.

Only in the case where a set of Sprites are a part of a container object (i.e. where the

Sprite is associated with a PlayField) is the depth information automatically

handled by the system. In other situations, managing the drawing order is the

responsibility of the developer.

Sprite Constructor

The Sprite class defines the following constructors:

• public Sprite(Image img) – Creates a new non-animated

Sprite

from an

Image object. All animation operations on a non-animated Sprite behave as

if there is a single raw frame. At construction time, the

Sprite's position will be set

to (0,0), the depth will be set to 0, and the Sprite will be visible. The Sprite shall

behave as if the image used in creation were cached. If a mutable image is used to

create the Sprite, the Sprite's appearance should not reflect changes to mutable

source image.

• public Sprite(Image img, int fWidth, int fHeight) –

Creates a new animated

Sprite from an Image. The constructor parameters are

the following:

− img - Image to use for Sprite;

− fWidth - width, in pixels, of the individual raw frames;

− fHeight - height, in pixels, of the individual raw frames.

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Motorola J2ME Specifications Page 56

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