Using alpha in jpanel compoments

Question

hi all,
I am overhiden jpanel and yours components using alpha and happens which components are drawing too in area left superior, and I dont know, why this happens, I wish post code here , but is to long... I do alpha in images, and no problems with that, but in compoments I dont know how make this... thanks
      class painel extends JPanel{
          public void paintComponent(Graphics g) {
              System.out.println("pintando "+alpha);
            ((Graphics2D) g).setComposite(
                    AlphaComposite.getInstance(AlphaComposite.SRC_OVER,
                                               alpha));
            g.setColor(getBackground());
           // g.fillRect(0,0,getWidth(),getHeight());
             g.fillRect(0,0,getWidth(),getHeight());
}

Answer 1

I try setOpaque(true), but fail...
import java.awt.AlphaComposite;
import java.awt.Container;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.*;
public class FadingExemple extends JFrame {
    public FadingExemple(){
    public static void main(String[] args) throws Exception {
       JFrame f = new JFrame();
       f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
       FadingOut glassOut = new FadingOut();
       FadingIn glassIn = new FadingIn();
     JPanel contentPane = new JPanel();
       //contentPane.setLayout(new java.awt.GridLayout(10,10));
       contentPane.setLayout(new java.awt.FlowLayout());
       //for(int row = 0; row < 10; row++)
         //  for(int column = 0; column < 10; column++) {
              contentPane.add(new JButton("Fading"));
              contentPane.add(new JButton("323232"));
              contentPane.add(new JButton("2347676767"));
       f.setContentPane(contentPane);
       f.pack();
       f.setSize(400,400);
       f.setVisible(true);
       try{Thread.sleep(500);}
       catch(InterruptedException e) {e.printStackTrace();}
       f.setGlassPane(glassOut);
       glassOut.setVisible(true);
       //glassOut.beginFade();
glassOut.beginFade(0.70f);
       // usando glassOut e apos glassIn -> glassIn faz aparecer
       // usando somente glassIn -> glassIn faz desaparecer rapido
       try{Thread.sleep(900);}
       catch(InterruptedException e) {e.printStackTrace();}
       f.setGlassPane(glassIn);
       glassIn.setVisible(true);
       glassIn.beginFade();
    public static class FadingIn extends JPanel implements ActionListener
              private float opacity = 1f;
              private Timer fadeTimer;
                 public void beginFade() {
            fadeTimer = new javax.swing.Timer(75,this);
            fadeTimer.setInitialDelay(0);
            fadeTimer.start();
        public void actionPerformed(ActionEvent e) {
               opacity -= .01;
               System.out.println(opacity);
            if(opacity < 0) {
                opacity = 0;
                fadeTimer.stop();
                fadeTimer = null;
            repaint();
           public void paintComponent(Graphics g) {
        ((Graphics2D) g).setComposite(
                    AlphaComposite.getInstance(AlphaComposite.SRC_OVER,
                                               opacity));
            g.setColor(getBackground());
            g.fillRect(0,0,getWidth(),getHeight());
    public static class FadingOut extends JPanel
            implements ActionListener
        private float opacity = 0f;
        private Timer fadeTimer;
        public void beginFade() {
            fadeTimer = new javax.swing.Timer(75,this);
            fadeTimer.setInitialDelay(0);
            fadeTimer.start();
        public void beginFade(float opacity){
            this.opacity = opacity;
        public void actionPerformed(ActionEvent e) {
            opacity += .03;
            System.out.println(opacity);
            if(opacity > .5) {
                opacity = 0.5f;
                fadeTimer.stop();
                fadeTimer = null;
            repaint();
        public void paintComponent(Graphics g) {
            ((Graphics2D) g).setComposite(
                    AlphaComposite.getInstance(AlphaComposite.SRC_OVER,
                                               opacity));
            g.setColor(getBackground());
            g.fillRect(0,0,getWidth(),getHeight());
}