MarteEngine: Rotate and scale

Alarms and Tweens是唯一的改变你的entity的行为的方式：你可以改变位置（和许多其他属性），但是MarteEngine帮助你操作你的entity的角度和缩放。

Rotate

旋转一个entity仅仅是一个角度上的改变，所以MarteEngine可以旋转与entity关联的图像或动画，我们通过定义一个entity上的alarm实现：

public class RotateEntity extends Entity {

    private static final String ROTATE_ME = "rotate_me";

    public RotateEntity(float x, float y, Image image) {
        super(x, y, image);

        // we set that image or animation must be rotate with Entity
        setCentered(true);
        // we define and alarm so we can rotate entity every 2 seconds
        setAlarm(ROTATE_ME, 2, false, true);
    }

    @Override
    public void alarmTriggered(String name) {
        if (name.equalsIgnoreCase(ROTATE_ME)) {
            // let's rotate a bit
            int angle = this.getAngle();
            angle += 2;
            if (angle >= 360)
                angle -= 360;
            this.setAngle(angle);
        }
    }

}

We can mark on setCentered(true) in entity constructor: you must let know to MarteEngine that image or animation associated to entity rotate with it.. in some cases you simply don't want this behaviour.

Scale

Scale entity image or animation is not so different: just change scale properties on Entity:

public class ScaleEntity extends Entity {

    private static final String SCALE_ME = "scale_me";
    private float scaleDir = -0.1f;

    public ScaleEntity(float x, float y, Image image) {
        super(x, y, image);

        // we define and alarm so we can scale entity every 2 seconds
        setAlarm(SCALE_ME, 2, false, true);
    }

    @Override
    public void alarmTriggered(String name) {
        if (name.equalsIgnoreCase(SCALE_ME)) {
            // let's scale entity
            this.scale += scaleDir;
            if (this.scale <= 0.1f || this.scale >= 2.0f){
                scaleDir *= -1;
            }
        }
    }
}

In this example we are scaling entity image from a minimum of 0.1 to 2.0 of his original width and height!