java - 无法获取图像以Java显示

我正在做一个SwingBot，无法弄清楚如何显示图像。它可以正常编译，但不可见。我究竟做错了什么？ This is my image.它位于与我的代码Java文件相同的目录下的名为“ images”的文件夹中。

import javax.swing.JFrame;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import javax.swing.JComponent;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Line2D;
import java.awt.Color;
import java.awt.Polygon;
import java.awt.image.BufferedImage;
import java.io.File;
import javax.imageio.ImageIO;
import java.io.IOException;
import java.util.Scanner;



public class SwingBot
{
public static void main(String[] args)
{

    // contruction of new JFrame object
    JFrame frame = new JFrame();

    // mutators
    frame.setSize(400,400);
    frame.setTitle("SwingBot");

    // program ends when window closes
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    Robot r = new Robot();

    frame.add(r);

    // voila!
    frame.setVisible(true);


    // your Scanner-based command loop goes here

    int noend = 0;
    System.out.println("Enter Commands");
    while(noend == 0)
    {

    Scanner input = new Scanner(System.in);

    String command = input.next();

    if(command.equals("left"))
        r.moveBot(10,0);

    if(command.equals("right"))
        r.moveBot(-10,0);

    if(command.equals("down"))
        r.moveBot(0,10);

    if(command.equals("up"))
        r.moveBot(0,-10);

    // call methods on the Robot instance like w.moveBot(10,10) in response to
    // user input



 }

}

public static class Robot extends JComponent
{
    private Rectangle rect = new Rectangle(10,10);
    private BufferedImage image;

    public void ImagePanel()
    {
        try
        {
            image = ImageIO.read(new File("images/flower.png"));
        }
        catch (IOException ex)
        {
            // handle exception...
        }
    }

    public void paintComponent(Graphics g)
    {
        Graphics2D g2 = (Graphics2D) g;


        // set the color
        //g2.setColor(Color.BLUE);




        g.drawImage(image, 0, 0, null);


    }


    public void moveBot(int x, int y)
    {
        // move the rectangle
        rect.translate(x,y);

        // redraw the window
        repaint();
    }

}

}

最佳答案

这很容易被忽略，只是因为它太奇怪了。您有方法ImagePanel()。我认为可以肯定地假设，您从ImagePanel那里获得的代码是类，而ImagePanel()是构造函数，并且您刚刚添加了void，因为您收到一条错误消息，指出该方法需要返回类型。

相反，您应该做的是将public ImagePanel()变成public Robot()，以便您的Robot类具有构造函数。当前，您实例化Robot，但是由于从未调用方法ImagePanel()，因此图像从未初始化。


您可能需要仔细阅读what is a Constructor的一些基本知识
将public void ImagePanel()更改为public Robot()
不要从File对象加载图像。使用Robot.class.getResource("path/to/image.png")通过类路径加载它们。在Embedded Resources上查看信息
您应该在super.paintComponent方法中调用paintComponent

@Override
protected void paintComponent(Graphics g) {
    super.paintComponent(g);
}

绘画时，应覆盖getPreferredSize()的JComponent，以便组件具有首选的大小，然后只需pack()框架即可。

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

从事件调度线程运行Swing应用程序，但使用SwingUtilities.invokLater。见Initial Thread

public static void main(String[] args) {
    SwingUtilities.invokeLater(new Runnable(){
        public void run() {

        }
    });
}

见下面的例子

更新

import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.SwingUtilities;


public class SwingBot {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable(){
            public void run() {
                JFrame frame = new JFrame();
                frame.add(new Robot());
                frame.pack();
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public static class Robot extends JComponent {
        BufferedImage img;

        public Robot() {
            try {
                img = ImageIO.read(Robot.class.getResource("/images/android.jpg"));
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            g.drawImage(img, 0, 0, 300, 300, this);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(300, 300);
        }
    }
}

档案结构

ProjectRoot
         src
            somepackage
                 SwingBot.java
            images
                 android.jpg