带键盘的Java Slick 2D绘图

我已经在下面粘贴了主状态。每次我移动键盘时，对象都会移动，但它会刷新页面。如何使对象不刷新，看起来像图像轨迹，并最终绘制

package javagame;

import org.lwjgl.input.*;
import org.newdawn.slick.*;
import org.newdawn.slick.state.*;

public class Menu extends BasicGameState{
    public static String mouse = "MOUSE IS NOT ON THE SCREEN";
    public static String keyBoard = "O";
    public static int keyBoardX = 50;
    public static int keyBoardY = 50;
    public static int xPos;
    public static int yPos;

public Menu (int state) {

}

// This method is just to initiate objects
public void init(GameContainer gameContainer, StateBasedGame stateBasedGame)       
throws SlickException {
}

public void render(GameContainer gameContainer, StateBasedGame     
stateBasedGame, Graphics g) throws SlickException {
    g.drawString(mouse, xPos, 500 - yPos);
    g.drawString(keyBoard, keyBoardX, keyBoardY);
}

public void update(GameContainer gameContainer, StateBasedGame 
stateBasedGame, int delta) throws SlickException {
    // keyboard
    Input input = gameContainer.getInput();

    if (input.isKeyDown(input.KEY_UP)) {
        keyBoardY -= 1;
    } else if (input.isKeyDown(input.KEY_DOWN)) {
        keyBoardY += 1;
    } else if (input.isKeyDown(input.KEY_LEFT)) {
        keyBoardX -= 1;
    } else if (input.isKeyDown(input.KEY_RIGHT)) {
        keyBoardX += 1;
    }
}

public int getID() {
    return 0;
}
}

要使其看起来“像图像轨迹并最终绘制”，实际上必须在前一个位置重新绘制图像，直到您希望它消失为止-否则渲染方法将只重新绘制当前状态，并且不会有“尾随”阴影

一种选择是保留有限的x-y坐标历史记录，并在每次render（）调用时重新绘制历史记录中的所有内容。要创建淡入/拖尾效果，请减小alpha。可以通过在渲染之前在

图形

对象上设置字体，使用具有较低alpha值的

颜色

字体来完成此操作