Java：使用 Swing 的安全动画
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Java: Safe Animations with Swing
提问by Jimmy Huch
I am creating a program that uses JFrame, JPanel, JLabel and all other sorts of swing components.
我正在创建一个使用 JFrame、JPanel、JLabel 和所有其他类型的 Swing 组件的程序。
What I want to do is create a 2D animation on a separate JPanel that is dedicated to this animation. So I will be overriding the paintComponent (Graphics g) method.
我想要做的是在专用于此动画的单独 JPanel 上创建 2D 动画。所以我将覆盖paintComponent (Graphics g) 方法。
I have experience making animations with for loops + Threads, but I am hearing that threads are not safe with swing.
我有使用 for 循环 + 线程制作动画的经验，但我听说线程对于 Swing 并不安全。
Due to this, is it safe for me to make an animation with the use of the Runnable interface? If not what shall I use (e.g. Timer) and please give a small example on how to best use it (or a link to a web page).
因此，使用 Runnable 界面制作动画对我来说安全吗？如果不是，我应该使用什么（例如计时器），请举一个关于如何最好地使用它的小例子（或一个网页链接）。
EDIT:
编辑：
Thanks to Jeff, I will be using Timer to create the animation. For future viewers of this question, here is a quick program I coded in about 5 minutes, excuse the dirty code.
感谢 Jeff，我将使用 Timer 来创建动画。对于这个问题的未来观众，这是我在大约 5 分钟内编写的一个快速程序，请原谅脏代码。
I have also added some quick comments.
我还添加了一些快速评论。
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class JFrameAnimation extends JFrame implements ActionListener
{
JPanel panel;
Timer timer;
int x, y;
public JFrameAnimation ()
{
super ();
setDefaultCloseOperation (EXIT_ON_CLOSE);
timer = new Timer (15, this); //@ First param is the delay (in milliseconds) therefore this animation is updated every 15 ms. The shorter the delay, the faster the animation.
//This class iplements ActionListener, and that is where the animation variables are updated. Timer passes an ActionEvent after each 15 ms.
}
public void run ()
{
panel = new JPanel ()
{
public void paintComponent (Graphics g) //The JPanel paint method we are overriding.
{
g.setColor (Color.white);
g.fillRect (0, 0, 500, 500); //Setting panel background (white in this case);
//g.fillRect (-1 + x, -1 + y, 50, 50); //This is to erase the black remains of the animation. (not used because the background is always redrawn.
g.setColor (Color.black);
g.fillRect (0 + x, 0 + y, 50, 50); //This is the animation.
}
}
;
panel.setPreferredSize (new Dimension (500, 500)); //Setting the panel size
getContentPane ().add (panel); //Adding panel to frame.
pack ();
setVisible (true);
timer.start (); //This starts the animation.
}
public void actionPerformed (ActionEvent e)
{
x++;
y++;
if (x == 250)
timer.stop (); //This stops the animation once it reaches a certain distance.
panel.repaint (); //This is what paints the animation again (IMPORTANT: won't work without this).
panel.revalidate (); //This isn't necessary, I like having it just in case.
}
public static void main (String[] args)
{
new JFrameAnimation ().run (); //Start our new application.
}
}
回答by Jeff Storey
Jimmy, I think you are misunderstanding how threads work in Swing. You must use a specific thread called the Event Dispatch Thread to do any updating on swing components (with a few specific exceptions I won't discuss here). You can use a swing timer to set a recurring task to run on the event dispatch thread. See this example of how to use Swing timers. http://download.oracle.com/javase/tutorial/uiswing/misc/timer.html
Jimmy，我认为您误解了线程在 Swing 中的工作方式。您必须使用一个名为 Event Dispatch Thread 的特定线程来对 Swing 组件进行任何更新（除了一些特定的例外，我不会在这里讨论）。您可以使用摆动计时器设置在事件调度线程上运行的重复任务。请参阅此示例了解如何使用 Swing 计时器。http://download.oracle.com/javase/tutorial/uiswing/misc/timer.html
You should also read up on the Event Dispatch Thread so you understand its place in Swing http://download.oracle.com/javase/tutorial/uiswing/concurrency/dispatch.html
您还应该阅读事件调度线程，以便了解它在 Swing 中的位置http://download.oracle.com/javase/tutorial/uiswing/concurrency/dispatch.html
Java also provides a variety of methods for working with Swing in the SwingUtilitiesclass, notably invokeLaterand invokeAndWaitwhich will run code on the event dispatch thread.
Java也提供了多种方法用于与Swing合作的SwingUtilities类，特别是invokeLater和invokeAndWait这将运行事件调度线程上的代码。
回答by Windust
While is good to understand the EDT and SwingUtilities (everybody doing Swing should do so) if you're going to be doing a lot of animation I would recommend to use the TimingFramework. This will allow you to concentrate a little more on design and will give you a better control on "rate". Inherently the timing framework uses a Swing timer so the callbacks are on the EDT. Part of the Filthy-rich clients collection, the author made the chapter available.
如果您要制作大量动画，那么了解 EDT 和 SwingUtilities 很好（每个使用 Swing 的人都应该这样做），但我建议您使用TimingFramework。这将使您更专注于设计，并让您更好地控制“速率”。本质上，计时框架使用 Swing 计时器，因此回调位于 EDT 上。作为 Filthy-rich clients 集合的一部分，作者提供了该章节。
Have fun!
玩得开心！
