Question

标题，我想让你的程序在按下按钮一次后拍摄一个球，然后它继续前进，直到它完成你就无法做任何事情。以下解雇的当前代码。

public void act() 
{
        // Steps for calculating the launch speed and angle
        ProjectileWorld myWorld = (ProjectileWorld) getWorld();
        double shotStrength = myWorld.getSpeedValue();
        double shotAngle = myWorld.getAngleValue();
        // Checks to see if the space key is pressed, if it is, the projectile is fired
        String key = Greenfoot.getKey();  
        if ("space".equals(key))
        { 
            //xSpeed and ySpeed changed as requirements say
            xSpeed = (int)(shotStrength*Math.cos(shotAngle));
            ySpeed = -(int)(shotStrength*Math.sin(shotAngle));
            actualX += xSpeed;
            actualY += ySpeed;
            setLocation ((int) actualX, (int) actualY);
        }

现在，这使得当我拿着空格键时球只会移动，因为就是这样，我可以放开空格键并在球还在空中时改变shotStrength和shotAngle

Answer 1

这里的关键是将“行为”方法的上下文状态更改为“移动球”。

有很多方法可以实现这一点，但基本上取决于如何调用act（）。

我的第一个想法是做这样的事情：

public enum ActionMode{  MovingBall, Shooting, Waiting, Etc }

public void act() 
{
        // Steps for calculating the launch speed and angle
        ProjectileWorld myWorld = (ProjectileWorld) getWorld();
        double shotStrength = myWorld.getSpeedValue();
        double shotAngle = myWorld.getAngleValue();
        // Checks to see if the space key is pressed, if it is, the projectile is fired
        String key = Greenfoot.getKey();  
        if ("space".equals(key)){
            mode = ActionMode.MovingBall;
        }
        while(mode==ActionMode.MovingBall){

            //xSpeed and ySpeed changed as requirements say
            xSpeed = (int)(shotStrength*Math.cos(shotAngle));
            ySpeed = -(int)(shotStrength*Math.sin(shotAngle));
            actualX += xSpeed;
            actualY += ySpeed;
            setLocation ((int) actualX, (int) actualY);
            if( ballHasFinishedMoving(actualX, actualY) ){
                 mode==ActionMode.Waiting;
            }
        }
        ...
}
private boolean ballHasFinishedMoving( int actualX, int actualY ){
       logic to determine if ball has finished.
}

Greenfoot：我如何做到这一点，我按一下按钮，它一直在行动？

1 个答案: