java - 无法使图像在 jpanel 上消失

Question

我正在为这个问题苦苦挣扎。我想通过按下按钮并在按钮监听器中设置标志来使面板上的图像消失。关键的 boolean 变量是 showImage，我希望它能够阻止加载图像。看来我无法从 butoon 监听器创建新图像。 包 com.pumpfundamentals.calc;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import java.io.File;
import java.text.DecimalFormat;

import javax.imageio.ImageIO;
import javax.swing.Box;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;

import com.pumpfundamentals.calc.CalcVel;



public class Calc extends JFrame{

    private static final long serialVersionUID = -6408828418879466758L;
    //private static final String imageURL = null;
    private static JFrame frame;
    private JPanel panel, panel3;
    private JButton buttonCalc, buttonView;
    private JLabel labelDia, labelFlow, labelVel, labelVelRes, labelRe, labelReRes;
    private JLabel labelFrict_par, labelFrict_parRes, labelFrict_fact, labelFrict_factRes;
    private JTextField diaInput, flowInput;

    public double v, dia, fl, re, f_par, fr_100, f_fact, eps=0.00015, v_round;
    public  boolean showImage = false;

    public Image vel_formula = null;

    private static BufferedImage image = null;
    private JLabel labelImage;

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            new Calc("img/vel_formula.png");
        }
        });
    }

    public Calc(String fileName) {

        this.setSize(1000, 800);
        this.setLocationRelativeTo(null);
        this.setResizable(false);
        this.setDefaultCloseOperation(EXIT_ON_CLOSE);
        this.setTitle("Pipe friction calculations");


        //frame = new JFrame();
        //panel = new JPanel();
        JPanel btnPanel  = new JPanel(new FlowLayout());

        //Box theBox = Box.createHorizontalBox();

        //panel3 = new JPanel();
        //panel.setLayout(new BorderLayout());

        //frame.add(panel);
        buttonView = new JButton("VIEW");
        buttonCalc = new JButton("CALC");
        labelDia = new JLabel("  Dia.  ");
        diaInput = new JTextField(5);
        diaInput.setText("0");
        labelFlow = new JLabel("  flow  ");
        flowInput = new JTextField(5);
        flowInput.setText("0");
        labelVel = new JLabel("  velocity (ft/s)  ");
        labelVelRes = new JLabel("___");
        labelVelRes.setForeground(Color.red);
        labelRe = new JLabel("  Re no.  ");
        labelReRes = new JLabel("___");
        labelReRes.setForeground(Color.red);
        labelFrict_par = new JLabel("  frict.param.  ");
        labelFrict_parRes = new JLabel("___");
        labelFrict_parRes.setForeground(Color.red);

        labelFrict_fact = new JLabel("  frict. fact. (ft/100 ft)  ");
        labelFrict_factRes = new JLabel("___");
        labelFrict_factRes.setForeground(Color.red);

        btnPanel.add(buttonView);
        btnPanel.add(buttonCalc);
        btnPanel.add(labelDia);
        btnPanel.add(diaInput);
        btnPanel.add(labelFlow);
        btnPanel.add(flowInput);
        btnPanel.add(labelVel);
        btnPanel.add(labelVelRes);
        btnPanel.add(labelRe);
        btnPanel.add(labelReRes);
        btnPanel.add(labelFrict_par);
        btnPanel.add(labelFrict_parRes);
        btnPanel.add(labelFrict_fact);
        btnPanel.add(labelFrict_factRes);

        //buttonPanel.add(theBox);
        //this.add(buttonPanel, BorderLayout.NORTH);


        //this.add(new ImageArea(fileName), BorderLayout.CENTER);

        ImageArea image = new ImageArea(fileName);

        Container cp = getContentPane();
        cp.setLayout(new BorderLayout());
        cp.add(image, BorderLayout.CENTER);
        cp.add(btnPanel, BorderLayout.NORTH);

        ListenForButton lForButton = new ListenForButton();
        buttonCalc.addActionListener(lForButton);
        buttonView.addActionListener(lForButton);
        //this.pack();
        this.setVisible(true);
    }

    @SuppressWarnings("serial")
    private class ImageArea extends JPanel{

        public ImageArea(String fileName) {

            try {
                image = ImageIO.read(new File(fileName));
                //System.out.println(showImage + " 3");
            }
            catch (Exception e){
                e.printStackTrace();
            }
        }

        public void paint(Graphics g) {
            //boolean show = false;
            Graphics2D g2 = (Graphics2D)g;
            System.out.println(showImage + " 1");
            if(showImage) g2.drawImage(image, 0, 10, 577, 743, null);
            /*
            if(!showImage) {
            g2.setColor(Color.BLACK);
            g2.fillRect(0, 10, 800, 440);
            }


            */
        }

    }

    private class ListenForButton implements ActionListener{

        public void actionPerformed(ActionEvent e) {
            if(e.getSource() == buttonCalc) {
                CalcVel vel = new CalcVel();
                v = vel.CalcVel(diaInput.getText(), flowInput.getText());
                labelVelRes.setText("  " + v);
                CalcRe rey = new CalcRe();
                re = rey.CalcRe(v, diaInput.getText());
                DecimalFormat df = new DecimalFormat("0.000E0");
                String reString = df.format(re).toLowerCase();
                labelReRes.setText("  " + reString);
                CalcFrict_par f_param = new CalcFrict_par();
                f_par = f_param.CalcFrict_par(eps, diaInput.getText(), re);
                labelFrict_parRes.setText("  " + f_par);
                CalcFrictFact f_fac = new CalcFrictFact();
                f_fact = f_fac.CalcFrictFact(f_par, v, diaInput.getText());
                labelFrict_factRes.setText("  " + f_fact);

            }
            else if(e.getSource() == buttonView) {
                //System.out.println("img/vel_formula.png");
                showImage = true;

                System.out.println(showImage + " 2");
                ImageArea image = new ImageArea("img/vel_formula.png");


            }
        }

    }



}

Answer 1

说实话，你的代码一团糟。我运行了你的代码，但没有任何图像显示出什么情况。您无需创建嵌套的 ImageArea 类，只需将图像放入 Label 中即可。

 labelImage = new JLabel();
 labelImage.setIcon(new ImageIcon(fileName));
 this.add(labelImage); // not sure in what panel you add the image

稍后，当您按下按钮时，您将执行以下操作:

else if (e.getSource() == buttonView)
    {
        // inverting the boolean
        showImage = !showImage;
        // setting the image visible or not
        labelImage.setVisible(showImage);
    }
}

所以你不需要重新绘制任何东西。

如果您提供包括 CalcVel 类的完整代码并确保图像显示，我可以尝试为您提供更具体的帮助。