Home >Java >javaTutorial >Why isn't my JPanel's paintComponent() method being called, and how can I fix it?

Why isn't my JPanel's paintComponent() method being called, and how can I fix it?

Patricia Arquette
Patricia ArquetteOriginal
2024-12-13 06:43:10459browse

Why isn't my JPanel's paintComponent() method being called, and how can I fix it?

Program not accessing method paintComponent() of extended JPanel class

The issue arises because the DrawPanelRemoteControl class's paintComponent() method is never called. The paintComponent() method is responsible for drawing the panel's contents, but in this case, it's not being executed because the imageLabel is not being repainted.

To resolve this issue, you need to make sure that the imageLabel is repainted whenever the byteArray is changed. You can do this by calling the imageLabel.repaint() method in the setNewImageGrayscale() method of the DrawPanelRemoteControl class. This will ensure that the paintComponent() method is executed and the new image is drawn.

Here's the updated code for the DrawPanelRemoteControl class:

import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.Toolkit;
import java.awt.Transparency;
import java.awt.color.ColorSpace;
import java.awt.image.BufferedImage;
import java.awt.image.ColorModel;
import java.awt.image.ComponentColorModel;
import java.awt.image.DataBuffer;
import java.awt.image.DataBufferByte;
import java.awt.image.MemoryImageSource;
import java.awt.image.Raster;
import java.awt.image.SampleModel;
import java.awt.image.WritableRaster;
import javax.swing.ImageIcon;
import javax.swing.JLabel;
import javax.swing.JPanel;

class DrawPanelRemoteControl extends JPanel
{
    private byte[] byteArray=null;
    private Image image;
    private JLabel imageLabel=new JLabel();
    private Dimension imageDimension;

    public DrawPanelRemoteControl(Dimension imageDimension)
    {
        this.imageDimension=imageDimension;
        add(imageLabel);
    }

    @Override
    protected void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        System.out.println(".");
        if(byteArray!=null)
        {
            image=getGrayscaleImageFromArray(byteArray,imageDimension.width,imageDimension.height);
            imageLabel.setIcon(new ImageIcon(image));
        }
    }

    private Image getGrayscaleImageFromArray(byte[] buffer, int width, int height)
    {
        ColorSpace cs = ColorSpace.getInstance(ColorSpace.CS_GRAY);
        int[] nBits = { 8 };
        ColorModel cm = new ComponentColorModel(cs, nBits, false, true,Transparency.OPAQUE, DataBuffer.TYPE_BYTE);
        SampleModel sm = cm.createCompatibleSampleModel(width, height);
        DataBufferByte db = new DataBufferByte(buffer, width * height);
        WritableRaster raster = Raster.createWritableRaster(sm, db, null);
        BufferedImage result = new BufferedImage(cm, raster, false, null);
        return result;
    }

    void setNewImageGrayscale(byte[] array)
    {
        this.byteArray=array;
        this.intArray=null;
        imageLabel.repaint();
    }
}

By calling imageLabel.repaint() in setNewImageGrayscale(), you're ensuring that the imageLabel is repainted whenever the byteArray is changed. This will cause the paintComponent() method to be executed and the new image will be drawn.

The above is the detailed content of Why isn't my JPanel's paintComponent() method being called, and how can I fix it?. For more information, please follow other related articles on the PHP Chinese website!

Statement:
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn