Programma non accede metodo paintComponent() della classe JPanel esteso

Question

Questa è la JFrame

package client.connection; 

import java.awt.Dimension; 
import java.io.ObjectInputStream; 
import java.io.ObjectOutputStream; 
import javax.swing.JFrame; 


class DrawFrameRemoteControl extends JFrame 
{ 
    private DrawPanelRemoteControl imagePanel; 
    private ClientRemoteControlConnection clientRemoteControlConnection; 
    private ObjectInputStream clientInputStream; 
    private ObjectOutputStream clientOutputStream; 
    private Dimension imageDimension; 
    private Dimension serverDimension; 

    public DrawFrameRemoteControl(Dimension imageDimension,ClientRemoteControlConnection clientRemoteControlConnection,ObjectInputStream clientInputStream,ObjectOutputStream clientOutputStream,Dimension serverDimension) 
    { 
     super("Remote Desktop Control"); 

     this.clientRemoteControlConnection=clientRemoteControlConnection; 
     this.clientInputStream=clientInputStream; 
     this.clientOutputStream=clientOutputStream; 
     this.imageDimension=imageDimension; 
     this.serverDimension=serverDimension; 

     imagePanel=new DrawPanelRemoteControl(imageDimension); 
     add(imagePanel); 


     setSize(imageDimension.width,imageDimension.height); 
     setResizable(false); 
     setDefaultCloseOperation(EXIT_ON_CLOSE); 
     setVisible(true); 
     setLocationRelativeTo(null); 
    } 

    void drawNewImageGrayscale(byte[] array) 
    { 
     imagePanel.setNewImageGrayscale(array); 
     imagePanel.repaint(); 
    } 
} 

e questo è il JPanel esteso Aula

package client.connection; 

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; 
    } 
} 

Ho provato il debug del codice, anche se imagePanel.repaint() viene eseguito più volte, il programma non raggiunge mai il metodo paintComponent() della classe DrawPanelRemoteControl.

Qualcuno può darmi un'idea del perché questo potrebbe accadere? Ha qualcosa a che fare con l'oggetto imageDimension?

Informazioni aggiuntive: In main() metodo, viene creato un oggetto DrawFrameRemoteControl ed è drawNewImageGrayscale(byte[] arr) metodo è in corso di aggiornamento dal main() ogni secondo.

Answer 1

Non è chiaro il motivo per cui si sta passando intorno allo byte[], ma sembra che si desideri aggiornare il Icon di un componente con una miniatura grigia. L'esempio seguente crea icone in scala di grigi dalle icone di esempio esistenti e utilizza setIcon() per eseguire l'aggiornamento. Un approccio simile funziona con qualsiasi Image. Vedere anche questo example che suggerisce ColorConvertOp e questo example che aggiorna componenti interi piuttosto che icone.

import java.awt.Color; 
import java.awt.EventQueue; 
import java.awt.Graphics2D; 
import java.awt.GraphicsConfiguration; 
import java.awt.GraphicsDevice; 
import java.awt.GraphicsEnvironment; 
import java.awt.GridLayout; 
import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 
import java.awt.image.BufferedImage; 
import java.awt.image.ColorConvertOp; 
import java.util.ArrayList; 
import java.util.Collections; 
import java.util.List; 
import javax.swing.Icon; 
import javax.swing.ImageIcon; 
import javax.swing.JFrame; 
import javax.swing.JPanel; 
import javax.swing.JToggleButton; 
import javax.swing.Timer; 
import javax.swing.UIManager; 

/** 
* @see https://stackoverflow.com/a/12228640/230513 
* @see https://stackoverflow.com/a/7935040/230513 
*/ 
public class GrayIcons extends JPanel { 

    private List<Icon> list = new ArrayList<Icon>(); 
    private List<JToggleButton> buttons = new ArrayList<JToggleButton>(); 
    private Timer timer = new Timer(1000, new ActionListener() { 

     @Override 
     public void actionPerformed(ActionEvent e) { 
      update(); 
     } 
    }); 

    public GrayIcons() { 
     this.setLayout(new GridLayout(1, 0)); 
     list.add(getGray(UIManager.getIcon("OptionPane.errorIcon"))); 
     list.add(getGray(UIManager.getIcon("OptionPane.informationIcon"))); 
     list.add(getGray(UIManager.getIcon("OptionPane.warningIcon"))); 
     list.add(getGray(UIManager.getIcon("OptionPane.questionIcon"))); 
     for (Icon icon : list) { 
      JToggleButton jtb = new JToggleButton(icon); 
      buttons.add(jtb); 
      this.add(jtb); 
     } 
     timer.start(); 
    } 

    private void update() { 
     Collections.shuffle(list); 
     int index = 0; 
     for (JToggleButton b : buttons) { 
      b.setIcon(list.get(index++)); 
     } 
    } 

    /** 
    * @see https://stackoverflow.com/q/5830533/230513 
    * @see https://stackoverflow.com/a/3106550/230513 
    */ 
    private Icon getGray(Icon icon) { 
     final int w = icon.getIconWidth(); 
     final int h = icon.getIconHeight(); 
     GraphicsEnvironment ge = 
      GraphicsEnvironment.getLocalGraphicsEnvironment(); 
     GraphicsDevice gd = ge.getDefaultScreenDevice(); 
     GraphicsConfiguration gc = gd.getDefaultConfiguration(); 
     BufferedImage image = gc.createCompatibleImage(w, h); 
     Graphics2D g2d = image.createGraphics(); 
     g2d.setPaint(new Color(0x00f0f0f0)); 
     g2d.fillRect(0, 0, w, h); 
     icon.paintIcon(null, g2d, 0, 0); 
     BufferedImage gray = new BufferedImage(w, h, BufferedImage.TYPE_BYTE_GRAY); 
     ColorConvertOp op = new ColorConvertOp(
      image.getColorModel().getColorSpace(), 
      gray.getColorModel().getColorSpace(), null); 
     op.filter(image, gray); 
     return new ImageIcon(gray); 
    } 

    private void display() { 
     JFrame f = new JFrame("GrayIcons"); 
     f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     f.add(this); 
     f.pack(); 
     f.setLocationRelativeTo(null); 
     f.setVisible(true); 
    } 

    public static void main(String[] args) { 
     EventQueue.invokeLater(new Runnable() { 

      @Override 
      public void run() { 
       new GrayIcons().display(); 
      } 
     }); 
    } 
}