为什么我的屏幕不变红？ [英] Why doesn't my screen turn red?

问题描述

好的，所以我是编程的新手，我正在关注Youtube的教程来构建我自己的游戏。我的问题是我的屏幕没有变红，只是保持灰色。我确定我做错了什么但是日食没有错误。以下是代码：

Ok, so I'm new to programming and I'm following a tutorial on Youtube to build my own game. My problem is that my screen doesn't turn red, it just stays gray. I'm sure I did something wrong but there are no errors on eclipse. Here is the code:

import java.awt.Canvas;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.image.BufferStrategy;

import javax.swing.JFrame;

public class Game extends Canvas implements Runnable {
    private static final long serialVersionUID = 1L;

    public static int width = 300;
    public static int height = width / 16 * 9;
    public static int scale = 3;

    private Thread thread;
    private JFrame frame;
    private boolean running = false;

    public Game() {
       Dimension size = new Dimension(width * scale, height * scale);
       setPreferredSize(size);

       frame = new JFrame();
    }

    public synchronized void start() {
        running = true;
        thread = new Thread("Display");
        thread.start();

    }

    public synchronized void stop() {
        running = false;
        try {
        thread.join();
        } catch(InterruptedException e) {
            e.printStackTrace();
        }
    }

    public void run() {
        while (running) {
            update();
            render();
        }

    }

    public void update() {

    }

    public void render() {
        BufferStrategy bs = getBufferStrategy();
        if (bs == null) {
            createBufferStrategy(3);
            return;
        }

        Graphics g = bs.getDrawGraphics();
        g.setColor(Color.RED);
        g.fillRect(0, 0, getWidth(), getHeight());
        g.dispose();
        bs.show();
    }

    public static void main(String[] args){
        Game game = new Game();
        game.frame.setResizable(false);
        game.frame.setTitle("JJF");
        game.frame.add(game);
        game.frame.pack();
        game.frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        game.frame.setLocationRelativeTo(null);
        game.frame.setVisible(true);

        game.start();


    }

}

推荐答案

您实际上从未提供线程以及要运行的内容......

You never actually provide the Thread with something to run...

public synchronized void start() {
    running = true;
    // Not the reference to this...
    thread = new Thread(this, "Display");
    thread.start();

}

传递此（这是 Game 类的一个实例，它实现 Runnable ），线程将能够调用运行方法

By passing this (which is an instance of your Game class which implements Runnable), the Thread will be able to call your run method

nb：

可视区域的大小应由组件定义，而不是由框架定义。这可以通过覆盖 getPreferredSize 方法并返回您希望组件的首选可视大小来实现。否则，可视区域将是框架的大小减去它的装饰内容，这可能不符合您的期望。

The size of your viewable area should be defined by the component, not the frame. This can be achieved by overriding the getPreferredSize method and returning the preferred viewable size you want the component to be. Otherwise, the viewable area will be the size of the frame minus it's decoration insets, which may not meet your expectations.

在您的游戏循环中，您应该考虑拥有周期之间的小延迟为系统提供实际更新屏幕的时间，这需要一些线程的压力

In your "game-loop" you should consider having a small delay between cycles to give time for the system to actually update the screen, this takes some of the pressure of the Thread

可运行示例

import java.awt.Canvas;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.image.BufferStrategy;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JFrame;

public class Game extends Canvas implements Runnable {

    private static final long serialVersionUID = 1L;

    public static int width = 300;
    public static int height = width / 16 * 9;
    public static int scale = 3;

    private Thread thread;
    private JFrame frame;
    private boolean running = false;

    public Game() {
        Dimension size = new Dimension(width * scale, height * scale);
        setPreferredSize(size);

        frame = new JFrame();
    }

    public synchronized void start() {
        running = true;
        thread = new Thread(this, "Display");
        thread.start();

    }

    public synchronized void stop() {
        running = false;
        try {
            thread.join();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    public void run() {
        while (running) {
            update();
            render();
//          try {
//              Thread.sleep(40);
//          } catch (InterruptedException ex) {
//          }
        }

    }

    public void update() {

    }

    public void render() {
        BufferStrategy bs = getBufferStrategy();
        if (bs == null) {
            createBufferStrategy(3);
            return;
        }

        Graphics g = bs.getDrawGraphics();
        g.setColor(Color.RED);
        g.fillRect(0, 0, getWidth(), getHeight());
        g.dispose();
        bs.show();
    }

    public static void main(String[] args) {
        Game game = new Game();
        game.frame.setResizable(false);
        game.frame.setTitle("JJF");
        game.frame.add(game);
        game.frame.pack();
        game.frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        game.frame.setLocationRelativeTo(null);
        game.frame.setVisible(true);

        game.start();

    }

}

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