[英]Java swing double buffering
i just started using double buffering and everything worked just fine until i wanted to add a JScrollPane to the screen so i later on can do some camera movements. 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,以便我以后可以做一些相机移动。 Everything shows up fine (my sprites) EXCEPT the ScrollBars of the JScrollPane.
一切都很好(我的精灵)除了JScrollPane的ScrollBars之外。 And i want them to be shown!
我希望它们能够被展示出来!
However if i resize the window, the scrollbars flicker, so i know they are there! 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! I can even use them if i'm fast enough.
如果我足够快,我甚至可以使用它们。 How come they dont show up at rendering?
他们怎么没有出现在渲染? :(
:(
Here is a SSCCE of the problem: 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 );
}
}
}
Drawing is performed on whole frame area, not on gameField
. 绘图在整个框架区域上执行,而不是在
gameField
上gameField
。 Actually, the only cause of temporary JScrollPane
appearing is that it calls paintImmediately
somewhere in mouse-drag handler. 实际上,临时
JScrollPane
出现的唯一原因是它在鼠标拖动处理程序中的某处调用paintImmediately
。
The first thing that comes to mind is to replace JPanel
with Canvas
, as I_Love_Thinking wrote, then get bufferStategy
from that canvas instance and use it for rendering. 我想到的第一件事是用
Canvas
替换JPanel
,就像I_Love_Thinking写的那样,然后从该画布实例获取bufferStategy
并将其用于渲染。 But unfortunately it not works as expected. 但不幸的是,它不能按预期工作。 Lightweight
JScrollPane
can't properly drive heavyweight Canvas
. 轻量级
JScrollPane
无法正常驱动重量级Canvas
。 Canvas refuses to draw content outside area (0, 0, viewport_width, viewport_height). Canvas拒绝在区域外绘制内容(0,0,viewport_width,viewport_height)。 This is known bug and it will not fixed.
这是已知的错误 ,它不会修复。 Mixing mixing heavyweight components with lightweight is bad idea.
混合重量级组件和轻量级是不好的主意。
Replacing JScrollPane
with heavyweight ScrollPane
seems working. 用重量级
ScrollPane
替换JScrollPane
似乎有效。 Almost. 几乎。 There are noticeable rendering artifacts on scroll bars under some circumstances.
在某些情况下,滚动条上会出现明显的渲染瑕疵。
At this point, I've decided to stop beating the wall and give up. 在这一点上,我决定停止敲打墙壁并放弃。 Scroll panes are the source of numerous problems and not worth to use for lazy scrolling.
滚动窗格是众多问题的根源,不值得使用延迟滚动。 It is time to look on scrolling from another view.
是时候从另一个视图看滚动了。 The
Canvas
is not game field itself, but window that we use to observe game world. Canvas
本身不是游戏领域,而是用于观察游戏世界的窗口。 This is well-known rendering strategy in gamedev. 这是gamedev中众所周知的渲染策略。 The size of canvas is exactly as observable area.
画布的大小与可观察区域完全相同。 When scrolling needed, we just render the world with some offset.
当需要滚动时,我们只是用一些偏移来渲染世界。 The value for offset may be taken from some external scrollbar.
offset的值可以从某个外部滚动条获取。
I suggest next changes: 我建议接下来的改变:
JScrollPane
JScrollPane
JScrollBar
under canvas. JScrollBar
。 The example is based on your code. 该示例基于您的代码。 This implementation not respects resizing of frame.
此实现不考虑帧的大小调整。 In real life some places need to be synchronized with size of viewport (that what scrollpane did before for us).
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)。 Also, example violates Swing threading rules and reads value of scrollbar from rendering thread.
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);
}
});
}
}
And another example , mostly based on code from Java Games: Active Rendering article. 另一个例子 ,主要基于Java Games:Active Rendering文章中的代码。 It properly synchronized with value of
JScrollBar
and size of Canvas
. 它与
JScrollBar
值和Canvas
大小正确同步。 Also, it does painting directly to Graphics
, obtained from BufferStrategy
instance (instead of intermediate BuffereImage
object). 此外,它直接绘制到
Graphics
,从BufferStrategy
实例(而不是中间BuffereImage
对象)获取。 The result is something like this: 结果是这样的:
Your game paints over your scroll pane 您的游戏涂在滚动窗格上
the resizing of the window shows your scroll pane for one moment because it the normal paint-method is called (no double-buffering) 窗口的大小调整显示您的滚动窗格片刻,因为它调用了普通的paint-method(没有双缓冲)
you have some possibilities... the second one is prettier but it's your choice and i dont know what exactly you wanna do with it... 你有一些可能性......第二个更漂亮,但它是你的选择,我不知道你究竟想用它做什么......
If you wanna control all the components in your jframe yourself: 如果你想自己控制你的jframe中的所有组件:
If you wanna use double-buffering on another component that you dont have to manage other components directly with the double buffering. 如果你想在另一个组件上使用双缓冲,那么你不必使用双缓冲来直接管理其他组件。
The best component for this is the Canvas. 最好的组件是Canvas。 It already has methods for double-buffering you can use.
它已经有你可以使用的双缓冲方法。
Long time ago I made this, so i can't exactly tell you how it works. 很久以前我做了这个,所以我不能确切地告诉你它是如何工作的。 But just look it up, it isn't hard.
但是看看它,并不难。
Your code is manipulating Swing objects on a background thread. 您的代码正在操作后台线程上的Swing对象。 This will not work.
这不行。
Read The Event Dispatch Thread and Concurrency in Swing . 阅读Swing中的事件调度线程和并发 。
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