JFrame、JPanel、KeyListener问题

Question

import javax.swing.JFrame;

public class Main extends JFrame {

public Board board = new Board();

public Main() {
    add(board);
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    pack();
    setVisible(true);
}

public static void main(String args[]) {
    new Main();
}

import javax.swing.JPanel;

public class Board extends JPanel {

public TextLabel textLabel1 = new TextLabel("Hi", "Hello", "Bye");
public TextLabel textLabel2 = new TextLabel("Bye", "GoodBye", "Farewell");

public Board() {

    addKeyListener(textLabel1); //this could be a ball in my game
    addKeyListener(textLabel2); //this could be something else...
    add(textLabel1);
    add(textLabel2);
    setFocusable(true);
}

import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.JLabel;

public class TextLabel extends JLabel implements KeyListener {

private String txt1, txt2;

public TextLabel(String text, String txt1, String txt2) {
    setText(text);
    this.txt1 = txt1;
    this.txt2 = txt2;
}
public void keyPressed(KeyEvent e) {
    int key = e.getKeyCode();

    if (key == KeyEvent.VK_A) {
        setText(txt1);
    }

    if (key == KeyEvent.VK_L) {
        setText(txt2);
    }

}
@Override
public void keyReleased(KeyEvent e) {
    // TODO Auto-generated method stub

}
@Override
public void keyTyped(KeyEvent e) {
    // TODO Auto-generated method stub

}
}

Answer 1

如果你希望你的简单游戏是内存/CPU高效的，我建议采取一个完全不同的路线。

1. 使用Gameloop。似乎您没有使用任何类型的操作监听器或循环来处理更新。你需要一些东西来处理更新，比如当玩家从a点移动到B点时，你需要一种方法来不断增加实体的坐标，直到它到达目的地。ActionListener和使用Swing计时器将适用于简单的游戏，但如果您想在将来认真对待游戏开发，请从正确的方式开始。

public类Main{public static void Main(String[]args){Game Game=new Game（）；//init JFrame并将Game添加到其中

        game.start();
        while(game.isRunning()) {
            game.update();
            game.repaint();
        }
    }
}

class Game extends Canvas {
    private boolean running = true;
    private Ball ball = new Ball(0, 0, 50, 50);

    public void start() {   
        running = true;
    }

    public void stop() {
        //clean-up
        running = false;
    }

    public void update() { //update game logic
        ball.update();
    }

    @Override
    public void paint(Graphics g) { //render game
        super.paint(g); //clears previous graphics

        ball.render(g); //passes graphics down to entity
    }
}

这将给你一个清晰的设计你的游戏，以及分离渲染与游戏逻辑。这是球课的样子

class Ball {
    private int currentX, currentY, width, height;

    public Ball(int x, int y, int w, int h) {
        currentX = x; currentY = y;
        width = w; height = h;
    }

    public void update() {
        currentX++; //moves ball to right
    }

    public void render(Graphics g) {
        g.setColor(Color.BLUE);
        g.fillRect(currentX, currentY, width, height);
    }
}

您会注意到，当运行这样的东西时，CPU使用率会相当高。这是因为控制游戏的while循环以极快的速度循环。有许多方法可以精确定时地减缓这一速度。我将向您展示一个非常简单的方法：

int fps = 30;
int oneNanoSec = 1000000000;
int secondsPerLoop = oneNanoSecond/fps; //divide a second into 30 slices
while(game.isRunning()) {
    long start = System.nanoTime(); //see what time it is when we start

    game.update();
    game.render();

    long end = System.nanoTime(); //see what time it is when the game is finished updating/rendering
    long sleepTime = secondsPerLoop - (end-start);

    if(sleepTime > 0) {
        try {
            Thread.sleep(sleepTime);
        }catch(InterruptedException e) {
            e.printStackTrace();
        }
    } else
        Thread.yield();
}

这个计时器会看到更新和渲染花了多长时间，然后根据你想要更新/渲染的速度，运行游戏的线程会Hibernate（暂停）。