java - 如何使用 swing 组件向 JLabel 添加刷新计时器

Question

我正在创建一个迷宫游戏，并希望在游戏舞台上显示一个计时器。我尝试过使用 java.util，但它要求我摆脱我的 Swing 计时器。我怎样才能在游戏中添加一个令人耳目一新的计时器

此代码用于制作包含按钮 Pane 和游戏舞台的游戏框架。

import java.awt.CardLayout;
import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.util.HashSet;
import java.util.Set;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.Timer;

/**
 * This class Holds the game pane that has the moving player. It also contains
 * the GamePane
 * 
 * @author 602052004
 *
 */

public class GamePane extends JPanel implements ActionListener, KeyListener {// *change
                                                                                // GamePane
                                                                                // to
                                                                                // GamePane
    // This is were the game screen is made and the player is created.

    static final long serialVersionUID = 1L;
    JLabel player = new JLabel();
    JLabel finish = new JLabel();
    JFrame gameFrame;
    int playerSpeed = 4;
    int FPS = 40;
    // This array holds my JLabels for the walls.I used it so that i can have a
    // for loop with an index for the labels.
    JLabel[] walls = new JLabel[3];
    {

        walls[0] = new JLabel();
        walls[1] = new JLabel();
        walls[2] = new JLabel();

    }
    private final Set<Integer> keys = new HashSet<>();

    // The keys set holds the keys being pressed

    public static void main(String[] args) {
        // Open the GUI window
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                // Create a new object and
                // run its go() method
                new GamePane().go();
            }
        });
    }

    GamePane() {
        // Run the parent class constructor
        super();
        // Allow the panel to get focus
        setFocusable(true);
        // Don't let keys change the focus

    }

    /**
     * This method creates the gameFrame and sets its layout to a cardlayout.It
     * then proceeds the set up the GameFrame.The gameFrame contains the button
     * pane and the gameStage
     * 
     * The walls are an array and are used to create an index which is then used
     * for the collisions.I set up the walls location here
     */
    protected void go() {
        setLayout(new CardLayout());
        // Setup the window
        gameFrame = new JFrame();
        // Add this panel to the window
        gameFrame.setLayout(new CardLayout());
        gameFrame.add(this, "main");
        gameFrame.setContentPane(this);

        // Set's the window properties
        gameFrame.setTitle("main");
        gameFrame.setSize(800, 600);
        gameFrame.setResizable(false);
        gameFrame.setLocationRelativeTo(null);
        gameFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        gameFrame.setVisible(true);
        gameFrame.add(new ButtonPane(gameFrame), "buttons");
        // Creates the new JPanel that will hold the game.
        JPanel gamestage = new JPanel();
        gamestage.setBackground(Color.darkGray);
        gameFrame.add(gamestage, "game");
        gamestage.setLayout(null);
        // *Move the setup of the player and the timer under the walls
        // Get a sample of collisions going so that i can do it over the weekend
        // Setup the movable box
        player.setBounds(25, 25, 20, 20);
        player.setVisible(true);
        player.setBackground(Color.red);
        // Opaque makes the background visible
        player.setOpaque(true);

        // Setup the key listener
        addKeyListener(this);
        // Null layout allows moving objects!!!
        gamestage.add(player);
        // Set the timer
        Timer tm = new Timer(1000 / FPS, this);
        tm.start();

        walls[0].setBounds(10, 15, 10, 480);// left height
        walls[0].setVisible(true);
        walls[0].setBackground(Color.white);
        walls[0].setOpaque(true);
        gamestage.add(walls[0]);

        walls[1].setBounds(10, 10, 490, 10);// top width
        walls[1].setVisible(true);
        walls[1].setBackground(Color.white);
        walls[1].setOpaque(true);
        gamestage.add(walls[1]);

        // wall3.setBounds(x, y, width, height);
        walls[2].setBounds(10, 100, 100, 10);
        walls[2].setVisible(true);
        walls[2].setBackground(Color.white);
        walls[2].setOpaque(true);
        gamestage.add(walls[2]);



        finish.setBounds(30, 455, 20, 20); // *make the game change to the main
                                            // screen when finished
                                            // Add a timer
        finish.setVisible(true);
        finish.setBackground(Color.LIGHT_GRAY);
        finish.setOpaque(true);
        gamestage.add(finish);

    }

    /**
     * Check if two JLabel objects are touching
     * 
     * @param a
     *            The first JLabel
     * @param b
     *            The second JLabel
     * @return true if the JLabels are touching
     */
    public boolean areColliding(JLabel a, JLabel b) {
        return a.getBounds().intersects(b.getBounds());
    }

    /**
     * this method makes the player move. It takes the players speed and
     * subtracts or adds the player speed to the current position of the player.
     * It also figures out were the player is at currently aswell.
     * 
     * @param arg0
     */
    @Override
    public void actionPerformed(ActionEvent arg0) {
        // Move up if W is pressed
        if (keys.contains(KeyEvent.VK_W)) {
            player.setLocation(player.getX(), player.getY() - playerSpeed);
        }
        // Move right if D is pressed
        if (keys.contains(KeyEvent.VK_D)) {
            player.setLocation(player.getX() + playerSpeed, player.getY());
        }
        // Move down if S is pressed
        if (keys.contains(KeyEvent.VK_S)) {
            player.setLocation(player.getX(), player.getY() + playerSpeed);
        }
        // Move left if A is pressed
        if (keys.contains(KeyEvent.VK_A)) {
            player.setLocation(player.getX() - playerSpeed, player.getY());
        }

        for (int i = 0; i < walls.length; i++) {
            // I created a for loop instead
            // of a do loop because the for
            // loop would have been a lot
            // simpler to manage

            if (areColliding(walls[i], player)) { // Reposition the target
                int newX = (int) (25);
                int newY = (int) (25);
                player.setLocation(newX, newY);

            }
        }

        if (areColliding(finish, player)) {
            // Reposition the target
            int newX = 25;
            int newY = 25;
            player.setLocation(newX, newY);
            CardLayout layout = (CardLayout) gameFrame.getContentPane()
                    .getLayout();
            layout.show(gameFrame.getContentPane(), "buttons");
        }
    }

    @Override
    public void keyPressed(KeyEvent e) {
        // Add the key to the list
        // of pressed keys
        if (!keys.contains(e.getKeyCode())) {
            keys.add(e.getKeyCode());
        }
    }

    @Override
    public void keyReleased(KeyEvent e) {
        // Remove the key from the
        // list of pressed keys
        keys.remove((Integer) e.getKeyCode());
    }

    @Override
    public void keyTyped(KeyEvent e) {
    }

}

此代码在按下按钮时显示游戏 Pane

/**
 * This pane contains the button and sets up the button pane
 */
import java.awt.CardLayout;
import java.awt.Color;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class ButtonPane extends JPanel {

    private JButton startBTN;// Calls the JButton
    JFrame game;

    public ButtonPane(JFrame g) {
        game = g;
        setLayout(new GridBagLayout());
        setBackground(Color.gray);// Sets the menu stages color blue
        startBTN = new JButton("Game");// Creates a new button
        add(startBTN);// Adds the button on the startStage

        startBTN.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                if (game.getContentPane().getLayout() instanceof CardLayout) {
                    CardLayout layout = (CardLayout) getParent().getLayout();
                    layout.show(game.getContentPane(), "game");

                }
            }
        });
    }

}

Answer 1

好的，现在您已经有了一个 Timer，它每秒运行 1000/FPS 次，很酷。您真正需要的只是计算两个时间点之间的差异，令人惊讶的是，这非常简单。

首先定义“开始时间”

private Instant startTime;

在您需要它之前，这将是null。当您想启动计时器时，请使用 startTime = Instant.now();

当startTime != null时，你想计算它与现在的差值...

Duration runningTime = Duration.between(startTime, Instant.now());

现在可以告诉您计时器已经运行了多长时间。

接下来，我们需要做出一些决定，例如计时器耗尽时该怎么做，但为此，我们实际上需要知道计时器应该运行多长时间...

private Duration timeOutDuration = Duration.ofSeconds(5);

这只是设置了 5 秒的超时，您可以使用您想要的任何范围。

这样我们就可以计算计时器的剩余时间......

Duration timeRemainig = timeOutDuration.minus(runningTime);

然后决定要做什么......

if (timeRemainig.isNegative() || timeRemainig.isZero()) {
    // Time has run out...
    // startTime = null; // stop the timer
} else {
    // Update the UI
}

Java 8 中引入的日期/时间 API 非常强大且灵活(并且当您了解它时会很有趣)

解决方案可能开始看起来像......

private Duration timeOutDuration = Duration.ofSeconds(5);
private Instant startTime; // Set this when you're ready to start the timer

@Override
public void actionPerformed(ActionEvent arg0) {
    if (startTime != null) {
        Duration runningTime = Duration.between(startTime, Instant.now());
        Duration timeRemainig = timeOutDuration.minus(runningTime);
        if (timeRemainig.isNegative() || timeRemainig.isZero()) {
            // Time has run out...
            // startTime = null; // stop the timer
        } else {
            // Update the UI
        }
    }

格式化输出的Duration通常看起来像......

long hours = timeRemainig.toHours();
long mins = timeRemainig.minusHours(hours).toMinutes();

// Or if you're lucky enough to be using Java 9+
//String formatted = String.format("%dhrs %02dmins", duration.toHours(), duration.toMinutesPart());
String formatted = String.format("%dhrs %02dmins", hours, mins);

或类似，取决于您想要的格式

Why use this approach instead of some "counter"

简单，( super )准确。 Timer 仅保证“至少”间隔，也就是说，它将延迟不少于应用的值，这意味着随着时间的推移可能会引入“拖拽”，从而导致计数器掉落的同步。当然，在短时间内，这可能不是什么大问题，但既然有一种( super 简单)更好的方法来做到这一点，为什么不利用它呢。

该解决方案也非常灵活，适用于广泛的类似问题。我将上述概念用作基于时间的动画的一部分，通常会产生更出色的整体结果。