Question

我无法在JFrame上显示图片。跑步时车架完全变黑。这是我的代码：

import javax.swing.*;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.net.URISyntaxException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;

public class JFrameTesting extends JFrame {

    BufferedImage test = null;

    public static void main(String[] args) throws URISyntaxException {
        new JFrameTesting();
    }
    public JFrameTesting() throws URISyntaxException {
        JFrame frame = new JFrame("My first JFrame!");
        frame.setSize(400, 400);
        frame.setVisible(true);
        frame.setLocationRelativeTo(null);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        try {
            test = ImageIO.read(new File(getClass().getResource("test.png").toURI()));
        } catch (IOException ex) {
            Logger.getLogger(JFrameTesting.class.getName()).log(Level.SEVERE, null, ex);
        }
    }


    public void paint(Graphics g) {
        super.paint(g);
        g.drawImage(test, 200, 200, null);
    }
}

我不确定自己是否做错了什么。跑步时我没有任何错误。

提前致谢！

Answer 1

您尚未将图像实际添加到JFrame中。要显示图像，您需要将BufferedImage添加到组件上然后绘制它。你可以使用JLabel和ImageIcon来做到这一点。

function line_detect(wall,point){ // based on line formula of analytic geometry
    var a = (wall.p1[0] - wall.p2[0]) / (wall.p1[1] - wall.p2[1]);
    var b = wall.p1[1];
    var y = a*point[0]+b;
    if(y == point[1])
        return 0;
    else if(y > point[1])
        return 1;
    else return -1;
}

function range_detect(wall,point){
    if(point[0] > wall.p1[0]
    && point[0] > wall.p2[0])
        return 0;
    if(point[0] < wall.p1[0]
    && point[0] < wall.p2[0])
        return 0;
    if(point[1] > wall.p1[1]
    && point[1] > wall.p2[1])
        return 0;
    if(point[1] < wall.p1[1]
    && point[1] > wall.p2[1])
        return 0;
    return 1;
}

}

或者，如果需要，您可以跳过标签并绘制到组件上。在这种情况下，您将必须覆盖JPanel的draw方法。

public class JFrameTesting extends JFrame {

    BufferedImage test = null;
    ImageIcon image = new ImageIcon();

    public static void main(String[] args) throws URISyntaxException {
        new JFrameTesting();
    }
    public JFrameTesting() throws URISyntaxException {
        JFrame frame = new JFrame("My first JFrame!");
        try {
           test = ImageIO.read(new File(getClass().getResource("test.png").toURI()));
            image.setImage(test);
        } catch (IOException ex) {
            Logger.getLogger(JFrameTesting.class.getName()).log(Level.SEVERE, null, ex);
        }
        JLabel label = new JLabel();
        label.setIcon(image);
        frame.add(label);
        frame.setSize(400, 400);
        frame.setVisible(true);
        frame.setLocationRelativeTo(null);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }

另一个注意事项是，您正在扩展JFrame，但也在类中创建一个新的JFrame。您可以删除额外的JFrame和所有“框架”。该类本身是一个JFrame，因此您不需要额外的一个。

JPanel pane = new JPanel() {
        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            g.drawImage(image, 200, 200, null);
        }
    }; 
frame.add(pane);

另外，我相信ImageIO.read（...）方法可以将URI作为参数，因此您不必从中创建文件。

Answer 2

我的代码绘制图像，但需要重新绘制。为此，您需要使用鼠标更改框架的大小。

import javax.swing.*;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.net.URISyntaxException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;

public class JFrameTesting extends JFrame {

    BufferedImage test = null;

    public static void main(String[] args) throws URISyntaxException {
        new JFrameTesting();
    }
    public JFrameTesting() throws URISyntaxException {
        JFrame frame = new JFrame("My first JFrame!");
        frame.setSize(400, 400);
        frame.setVisible(true);
        frame.setLocationRelativeTo(null);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        try {
            System.out.println("init");
            test = ImageIO.read(new File(getClass().getResource("test.png").toURI()));
            System.out.println(test);
        } catch (IOException ex) {
            Logger.getLogger(JFrameTesting.class.getName()).log(Level.SEVERE, null, ex);
        }

        final JPanel pane = new JPanel() {
            @Override
            protected void paintComponent(Graphics g) {
                System.out.println("paint");
                super.paintComponent(g);
                g.drawImage(test, 0, 0, null);
            }
        };
        frame.add(pane);
        frame.repaint();
    }

    @Override
    public void paint(Graphics g) {
        super.paint(g);
        System.out.println("paint");
        g.drawImage(test, 200, 200, null);
    }
}

Answer 3

您可以尝试使用此代码。您需要在添加图像时在Jframe上加载JLabel。

BufferedImage test = null;

public static void main(String[] args) throws URISyntaxException {
    new JFrameTesting();
}
public JFrameTesting() throws URISyntaxException {
    JFrame frame = new JFrame("My first JFrame!");
    JLabel label = new JLabel();
    frame.setSize(800, 800);
    frame.setLocationRelativeTo(null);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    try {
        test = ImageIO.read(new File(getClass().getResource("test.png").toURI())); 
        frame.add( new JLabel(new ImageIcon(test)),BorderLayout.CENTER);
        frame.setIconImage(test);
        frame.setVisible(true);
        label.setVisible(true);
    } catch (IOException ex) {
        Logger.getLogger(JFrameTesting.class.getName()).log(Level.SEVERE, null, ex);
    }
}


public void paint(Graphics g) {
    super.paint(g);
    g.drawImage(test, 200, 200, null);
}

}

Java - BufferedImage没有出现在JFrame上

3 个答案: