使用 jpanel 变量在 Jframe 中加载图像

Question

我正在使用 netbeans 使用 swings 构建图像查看器。使用 netbeans swing builder GUI 我得到了以下代码，我在父 jframe 中放置了一个 jpanel。我现在要做的就是在 jpanel 中打开一个图像并将其添加到 jframe

代码如下：

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package javaapplication1;

import java.awt.Component;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.JPanel;

/**
 *
 * @author Tempo
 */
public class NewJFrame extends javax.swing.JFrame {

    /**
     * Creates new form NewJFrame
     */
    public NewJFrame() throws IOException {
        initComponents();
        final BufferedImage gray_img=ImageIO.read(new File("C:/Users/Tempo/Pictures/sucess.png"));
                    this.setBounds(0, 0, gray_img.getWidth(), gray_img.getHeight());
                    this.jPanel1 =new JPanel(){
                    @Override
                    public void paint(Graphics g) {
                            // TODO Auto-generated method stub
                            super.paint(g);
                            g.drawImage(gray_img, 0, 0, null);
                    }

                                    };
                    this.add(jPanel1);

    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        jPanel1 = new javax.swing.JPanel();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 440, Short.MAX_VALUE)
        );
        jPanel1Layout.setVerticalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 276, Short.MAX_VALUE)
        );

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(153, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(21, 21, 21)
                .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addContainerGap())
        );

        pack();
    }// </editor-fold>                        

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /*
         * Set the Nimbus look and feel
         */
        //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /*
         * If Nimbus (introduced in Java SE 6) is not available, stay with the
         * default look and feel. For details see
         * http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
         */
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

        /*
         * Create and display the form
         */
        java.awt.EventQueue.invokeLater(new Runnable() {

            public void run() {
                try {
                    NewJFrame frame=new NewJFrame();
//                    frame.setPreferredSize(new Dimension(800,600));
//                    frame.setMinimumSize(new Dimension(200,400));


                    frame.setVisible(true);
                } catch (IOException ex) {
                    Logger.getLogger(NewJFrame.class.getName()).log(Level.SEVERE, null, ex);
                }

            }
        });
    }
    // Variables declaration - do not modify                     
    private javax.swing.JPanel jPanel1;
    // End of variables declaration                   
}

当文件运行时，它只显示一个没有图像/（Jpanel）的空白jframe！

Answer 1

您没有对LayoutManager 提供任何约束，它似乎忽略了您的面板。

另一种解决方案是，在单独的类文件中使用所需的绘制例程创建自定义面板，编译项目，将自定义面板拖放到 NewJFrame 表单中

或者，在您掌握它之前，手动编码布局。它将让您更加了解正在发生的事情，并使将来更容易解决这些问题。

另外，除非您有充分的理由这样做，否则不要覆盖“paint”，最好改用paintComponent。

哦，这个this.setBounds(0, 0, gray_img.getWidth(), gray_img.getHeight()) 真是个坏主意。您可能会发现布局管理器已经覆盖了这些值。

最好将JScrollPane 用于可变宽度/高度组件。而且您可能需要提供首选尺寸详细信息