Question

我有一个小图库，我可以使用JButtons“next”和“previous”查看。它工作正常。

我想要做的是在点击它们时显示的图像上绘制一个矩形（只是框架，没有填充）。例如，如果我点击点（230,150），我希望我的矩形以左下角显示在该点上。

这是我的代码，我尝试过很多东西，但没有任何效果：

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.Rectangle2D;
import java.awt.Image;

public class rectOnGallery extends JFrame{

private static final long serialVersionUID = 1L;

private ImageIcon myImage1;
private ImageIcon myImage2;
private ImageIcon myImage3;
private ImageIcon myImage4;
JPanel ImageGallery = new JPanel();
private ImageIcon[] myImages = new ImageIcon[4];
private int curImageIndex=0;

int width;
int height;

public rectOnGallery(){

    double scale = 0.666667;
    width = (int) (scale * 612);
    height = (int) (scale * 792);

    myImage1 = new ImageIcon(((new ImageIcon("NewSign1.jpg")).getImage()).getScaledInstance(width, height, Image.SCALE_SMOOTH));
    myImage2 = new ImageIcon(((new ImageIcon("pdf2.jpg")).getImage()).getScaledInstance(width, height, Image.SCALE_SMOOTH));
    myImage3 = new ImageIcon(((new ImageIcon("pdfimg.jpg")).getImage()).getScaledInstance(width, height, Image.SCALE_SMOOTH));
    myImage4 = new ImageIcon(((new ImageIcon("images.jpg")).getImage()).getScaledInstance(width, height, Image.SCALE_SMOOTH));

    ImageGallery.add(new JLabel (myImage1));
    myImages[0]=myImage1;
    myImages[1]=myImage2;
    myImages[2]=myImage3;
    myImages[3]=myImage4;


     ImageGallery.addMouseListener(new MouseAdapter() {

         public void mouseClicked(MouseEvent evt) {
              if (myImages[curImageIndex] != null) {
                double x = (getWidth() - width) / 2;
                double y = (getHeight() - height) / 2;
                Rectangle2D.Double bounds = new Rectangle2D.Double(x, y, width, height);
                if (bounds.contains(evt.getPoint())) {
                  System.out.println("You clicked on " + evt.getX() + " x " + evt.getY());

                 **** HERE GOES SOMETHING THAT WRITES THE FRAME IN THE
                 **** POSITION (ent.getX() , evt.getY())

                }   
              }
         }
     });

     add(ImageGallery, BorderLayout.NORTH);

     JButton PREVIOUS = new JButton ("Previous");
     JButton NEXT = new JButton ("Next");

     JPanel buttons = new JPanel();
     buttons.setLayout(new GridLayout(1,4));
     buttons.add(PREVIOUS);
     buttons.add(NEXT);

     add(buttons, BorderLayout.SOUTH);

     //register listener
     PreviousButtonListener PreviousButton = new PreviousButtonListener ();
     NextButtonListener NextButton = new NextButtonListener ();

     //add listeners to corresponding componenets 
     PREVIOUS.addActionListener(PreviousButton);
     NEXT.addActionListener(NextButton);
}

private class PreviousButtonListener implements ActionListener {

    public void actionPerformed(ActionEvent e){

        if(curImageIndex>0 && curImageIndex <= 3){              
            ImageGallery.remove(0);
            curImageIndex -- ;
            ImageIcon TheImage= myImages[curImageIndex];
            ImageGallery.add(new JLabel (TheImage));
            ImageGallery.validate();
            ImageGallery.repaint(); 
        }
        else{
            ImageGallery.remove(0);
            ImageGallery.add(new JLabel (myImage1));
            curImageIndex=0;
            ImageGallery.validate();
            ImageGallery.repaint();
        }
    }
}

private class NextButtonListener implements ActionListener {

    public void actionPerformed(ActionEvent e){

        if(curImageIndex>=0 && curImageIndex < 3){
            ImageGallery.remove(0);
            curImageIndex ++ ;
            ImageIcon TheImage= myImages[curImageIndex];
            ImageGallery.add(new JLabel (TheImage));

            ImageGallery.validate();
            ImageGallery.repaint(); 
        }
        else{  
            ImageGallery.remove(0);
            ImageGallery.add(new JLabel (myImage4));
            curImageIndex=3;
            ImageGallery.validate();
            ImageGallery.repaint();
        }
    }
}

public static void main (String [] args){

    provaPosFirma frame = new provaPosFirma();

    frame.setSize(500, 600);
    frame.setVisible(true);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setLocationRelativeTo(null);
}
}

作为另一种选择，我还尝试在另一幅图像上绘制一个矩形的图像，但是这更有效。

我知道我做错了什么，这应该更容易，但我没有通过这个。如果你可以帮助我在显示器上绘制矩形或其他矩形图像，无论如何都会受到赞赏。

提前致谢

Answer 1

为此，您需要创建JPanel的自定义子类，并使用它而不是“ImageGallery”。然后，在该类中，重写paintComponent方法以绘制所需的矩形。所以代码看起来像这样。

class ImageGalleryPanel extends JPanel{
    private Point rectPosition = null;
    private Dimension rectSize; //Set the size of the rect

    public void setRectPosition(Point p){
        rectPosition = p;
    }

    private void drawRect(Graphics g){
        if(rectPosition != null){
            g.drawRect(rectPosition.x, rectPosition.y, rectSize.width, rectSize.height);
        }
    }

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

用此类替换JPanel“ImageGallery”，并指定要绘制的矩形的大小。如果您有评论绘制矩形，请添加以下行 -

ImageGallery.setRectPosition(evt.getPoint());
ImageGallery.repaint();

我没有测试这段代码，所以它可能有一些拼写错误，但这是绘制到JPanel时的基本想法。覆盖面板的绘制方法。然后，当你想绘制它时，将它的属性更改为它们应该是什么，并调用repaint（）。如果您只是尝试直接绘制它，那么将自动调用重绘方法，覆盖您所做的任何更改。

编辑 - 为了避免在矩形上绘制图像，您可以执行一些操作。您可以将paintComponent方法更改为“paint”或“paintChildren”，并将super.paintComponent函数调用更改为match。这将是快速和简单的，但被认为是不好的做法。我认为另一种方法是，不是覆盖JPanel的paintComponent，而是覆盖你要添加到它的JLabel。代码将完全相同，您只需将其应用于JLabel。

打印到JPanel上的图像

1 个答案: