Java:使用 Swing 制作安全动画

Java: Safe Animations with Swing(Java:使用 Swing 制作安全动画)

问题描述

我正在创建一个使用 JFrame、JPanel、JLabel 和所有其他类型的摆动组件的程序.

I am creating a program that uses JFrame, JPanel, JLabel and all other sorts of swing components.

我想做的是在专门用于此动画的单独 JPanel 上创建 2D 动画.所以我将覆盖paintComponent (Graphics g) 方法.

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.

我有使用 for 循环 + 线程制作动画的经验，但我听说使用 swing 线程不安全.

I have experience making animations with for loops + Threads, but I am hearing that threads are not safe with swing.

因此，使用 Runnable 接口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)，请举一个小例子说明如何最好地使用它(或网页链接).

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).

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.

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.

我还添加了一些快速评论.

I have also added some quick comments.

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.
    }
}

推荐答案

Jimmy，我认为你误解了 Swing 中线程的工作方式.您必须使用称为 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情况，我不会在此讨论).您可以使用摆动计时器来设置循环任务以在事件调度线程上运行.请参阅如何使用 Swing 计时器的示例.http://download.oracle.com/javase/tutorial/uiswing/misc/timer.html

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

您还应该阅读 Event Dispatch Thread 以便了解它在 Swing 中的位置 http://download.oracle.com/javase/tutorial/uiswing/concurrency/dispatch.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

Java 还在 SwingUtilities 类中提供了多种使用 Swing 的方法，特别是 invokeLater 和 invokeAndWait，它们将在事件调度线程.

Java also provides a variety of methods for working with Swing in the SwingUtilities class, notably invokeLater and invokeAndWait which will run code on the event dispatch thread.

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