通过按钮单击循环浏览Jlabel的图像时出现循环问题 [英] for loop issue when cycling through images for Jlabel with button click

问题描述

在java应用程序中我有一个Jlabel，我想在每次单击一个按钮时分配一个新图像，使用for循环我可以让它只显示跳过图像之间的所有最后一个图像，我知道那里我的逻辑中出现错误，也许我不应该使用for循环？任何建议

in a java aplication I have a Jlabel which i want to assign a new image to every time i click a button, using a for loop i can get it to just display the last image skipping all in between images, i know there is a error in my logic here maybe i should not be using a for loop?? any advice

 private String imageList[];
 ImageIcon image;
 imageList =  new String[] {"src\\Tour_Eiffel_Wikimedia_Commons.jpg","src\\Ben.jpg", "src\\Rio.jpg", "src\\Liberty.jpg", "src\\Pyramid.jpg"};

 //constructor setting first image to display on load
public GeographyGameGUI() {
       image = new ImageIcon(imageList[0]);
            imageLbl.setIcon(image);
 }

  //button method
   private void nextBtnActionPerformed(java.awt.event.ActionEvent evt) {                                        


      for (imgCount = 1; imgCount < imageList.length; imgCount++) {
            image = new ImageIcon(imageList[imgCount]);
            imageLbl.setIcon(image);

    }

如果我不使用for循环而只是使用计数器（在下面显示）我在按钮方法之外声明它正确地循环显示图像但运行到ArrayIndexOutOfBoundsException。这里最好的做法是什么？谢谢

if i dont use a for loop and simply use a counter (displayed below) which i declare outside of the button method it loops correctly displaying the images but runs into a ArrayIndexOutOfBoundsException. what is the best practice here? thanks

 image = new ImageIcon(imageList[imgCount]);
     imageLbl.setIcon(image);
    imgCount++;

推荐答案

从本质上讲，你阻止事件调度线程，防止它更新UI。有关更多详细信息，请参阅 Swing中的并发

You're, essentially, blocking the Event Dispatching Thread, prevent it from updating the UI. See Concurrency in Swing for more details

相反，您应该使用 javax.swing.Timer 来循环覆盖图像，允许UI在更改为下一个之前进行更新...

Instead, you should use a javax.swing.Timer to loop over the images, allowing the UI to update before changing to the next one...

请参阅如何使用Swing Timers 获取更多详细信息。

See How to use Swing Timers for more details.

Java数组是零索引的，这意味着数组中的第一个元素是一个位置 0 ，不是 1

Java arrays are zero indexed, this means that the first element in the array is a position 0, not 1

不要引用 src 直接在您的代码中，一旦构建和打包应用程序， src 目录将不存在

Don't reference src directly within your code, the src directory will not exist once the application is built and packaged

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class Test {

    public static void main(String[] args) {
        new Test();
    }

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private JLabel label;
        private String[] imageList = new String[] {"/Tour_Eiffel_Wikimedia_Commons.jpg","/Ben.jpg", "/Rio.jpg", "/Liberty.jpg", "/Pyramid.jpg"};

        public TestPane() {
            setLayout(new BorderLayout());
            label = new JLabel();
            add(label);

            JButton btn = new JButton("Play");
            btn.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    btn.setEnabled(false);
                    Timer timer = new Timer(1000, new ActionListener() {
                        private int count;
                        @Override
                        public void actionPerformed(ActionEvent e) {
                            if (count < imageList.length) {
                                try {
                                    label.setIcon(
                                            new ImageIcon(
                                                    ImageIO.read(
                                                            TestPane.this.getClass().getResource(imageList[count]))));
                                } catch (IOException exp) {
                                    exp.printStackTrace();
                                }
                                count++;
                            } else {
                                ((Timer)e.getSource()).stop();
                            }
                        }
                    });
                    timer.stop();
                }
            });
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

    }

}

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