Java swing双缓冲

Question

我刚刚开始使用双缓冲,一切正常,直到我想在屏幕上添加一个JScrollPane,所以我以后可以做一些相机移动.一切都很好(我的精灵)除了JScrollPane的ScrollBars之外.我希望它们能够被展示出来!

但是,如果我调整窗口大小,滚动条会闪烁,所以我知道它们在那里!如果我足够快,我甚至可以使用它们.他们怎么没有出现在渲染？:(

这是问题的SSCCE:

public class BufferStrategyDemo extends JFrame
{
    private BufferStrategy bufferStrategy;
    private JPanel gameField;
    private JScrollPane scroll;

    public BufferStrategyDemo()
    {

        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);        
        this.getContentPane().setPreferredSize(new Dimension(800, 600));
        this.pack();
        this.createBufferStrategy(2);

        this.gameField = new JPanel();
        this.gameField.setPreferredSize(new Dimension( 1400, 600 ));

        this.scroll = new JScrollPane( gameField );
        this.add( scroll, BorderLayout.CENTER );

        this.setVisible( true );
        this.bufferStrategy = this.getBufferStrategy();

        setupGameFieldContent();

        new Renderer( this, scroll , bufferStrategy ).start();
    }

    // Add some contents to gameField that shows up fine
    private void setupGameFieldContent()
    {
        // For ( all my sprites )
        //      gameField.add( sprite );

    }

    private class Renderer extends Thread
    {
        private BufferStrategy bufferStrategy;
        private JFrame window;
        private JScrollPane scroll;
        private Image imageOfGameField;

        public Renderer( JFrame window, JScrollPane scroll, BufferStrategy bufferStrategy )
        {
            this.bufferStrategy = bufferStrategy;
            this.window = window;
            this.scroll = scroll;
        }

        public void run()
        {
            while ( true )
            {
                Graphics g = null;
                try 
                {
                    g = bufferStrategy.getDrawGraphics();
                    drawSprites(g);
                } 
                finally { g.dispose(); }

                bufferStrategy.show(); // Shows everything except the scrollbars..
                Toolkit.getDefaultToolkit().sync(); 

                try { Thread.sleep( 1000/60 ) ; } 
                catch(InterruptedException ie) {}
            }
        }

        private void drawSprites( Graphics g )
        {
            Graphics2D g2d=(Graphics2D)g;

            //Also tried using the JPanels (gameField) createImage with same result
            imageOfGameField = this.scroll.createImage(800, 600 ); 
            Graphics screen = (Graphics2D)imageOfGameField.getGraphics();

            /**
             * For all my sprites, draw on the image
            for ( Sprite current : sprites )
                screen.drawImage( current.getImage(), current.getX(), current.getY(), current.getWidth() , current.getHeight(), null);
            */

            g2d.drawImage( imageOfGameField, 0, 0 , null );

        }
    }
}

Answer 1

绘图在整个框架区域上进行,而不是在gameField.实际上,临时JScrollPane出现的唯一原因是它paintImmediately在鼠标拖动处理程序中调用某个地方.

首先要想到的是JPanel用CanvasI_Love_Thinking写的替换,然后bufferStategy从该画布实例获取并使用它进行渲染.但不幸的是,它不能按预期工作.轻量级JScrollPane无法正常驾驶重量级Canvas.Canvas拒绝在区域外绘制内容(0,0,viewport_width,viewport_height).这是已知的错误,它不会修复.混合重量级组件和轻量级是不好的主意.

JScrollPane用重量级替换ScrollPane似乎有效.几乎.在某些情况下,滚动条上会出现明显的渲染瑕疵.

在这一点上,我决定停止敲打墙壁并放弃.滚动窗格是众多问题的根源,不值得使用延迟滚动.是时候从另一个视图看滚动了.该Canvas 不是游戏领域本身,而是窗口,我们用它来观察游戏世界.这是gamedev中众所周知的渲染策略.画布的大小与可观察区域完全相同.当需要滚动时,我们只是用一些偏移来渲染世界.offset的值可以从某个外部滚动条获取.

我建议接下来的改变:

1. 丢弃 JScrollPane
2. 将画布直接添加到框架.
3. JScrollBar在画布下添加单个水平.
4. 使用滚动条的值来移动渲染.

该示例基于您的代码.此实现不考虑帧的大小调整.在现实生活中,一些地方需要与视口的大小同步(滚动窗格之前为我们做的事情).此外,示例违反了Swing线程规则并从渲染线程中读取滚动条的值.

import java.awt.BorderLayout;
import java.awt.Canvas;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Toolkit;
import java.awt.image.BufferStrategy;
import java.awt.image.BufferedImage;

import javax.swing.JFrame;
import javax.swing.JScrollBar;

public class BufferStrategyDemo extends JFrame {
    private BufferStrategy bufferStrategy;
    private Canvas gameField;
    private JScrollBar scroll;

    public BufferStrategyDemo() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        getContentPane().setLayout(new BorderLayout());
        getContentPane().setPreferredSize(new Dimension(800, 600));

        gameField = new Canvas();
        gameField.setIgnoreRepaint(true);
        gameField.setPreferredSize(new Dimension(800, 580));
        getContentPane().add(gameField, BorderLayout.CENTER);

        scroll = new JScrollBar(JScrollBar.HORIZONTAL);
        scroll.setPreferredSize(new Dimension(800, 20));
        scroll.setMaximum(1400 - 800); // image width - viewport width
        getContentPane().add(scroll, BorderLayout.SOUTH);

        this.pack();

        gameField.createBufferStrategy(2);
        bufferStrategy = gameField.getBufferStrategy();

        new Renderer().start();
    }

    private class Renderer extends Thread {
        private BufferedImage imageOfGameField;

        public Renderer() {
            // NOTE: image size is fixed now, but better to bind image size to the size of viewport
            imageOfGameField = new BufferedImage(1400, 580, BufferedImage.TYPE_INT_ARGB);
        }

        public void run() {
            while (true) {
                Graphics g = null;
                try {
                    g = bufferStrategy.getDrawGraphics();
                    drawSprites(g);
                } finally {
                    g.dispose();
                }

                bufferStrategy.show(); 
                Toolkit.getDefaultToolkit().sync();

                try {
                    Thread.sleep(1000 / 60);
                } catch (InterruptedException ie) {
                }
            }
        }

        private void drawSprites(Graphics g) {
            Graphics2D g2d = (Graphics2D) g;

            Graphics g2d2 = imageOfGameField.createGraphics();
            g2d2.setColor(Color.YELLOW); // clear background
            g2d2.fillRect(0, 0, 1400, 580); // again, fixed width/height only for SSCCE
            g2d2.setColor(Color.BLACK);

            int shift = -scroll.getValue(); // here it is - get shift value

            g2d2.fillRect(100 + shift, 100, 20, 20); // i am ugly black sprite
            g2d2.fillRect(900 + shift, 100, 20, 20); // i am other black sprite
                                                     // located outside of default view

            g2d.drawImage(imageOfGameField, 0, 0, null);

            g2d2.dispose();
        }
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                BufferStrategyDemo mf = new BufferStrategyDemo();
                mf.setVisible(true);
            }
        });
    }
}

而另一个例子,主要是基于从代码Java游戏:活动渲染文章.它与价值JScrollBar和大小正确同步Canvas.此外,它直接绘制Graphics,从BufferStrategy实例(而不是中间BuffereImage对象)获取.结果是这样的: