Java – how to fade into JPanel and children?
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Java
I know I can fade in the panel by adding an alpha value to the background color and background color Timer However, how do I dilute a panel with subcomponents (such as jlabel)?
edit
_fadeTimer = new Timer(40,new ActionListener() { @Override public void actionPerformed(ActionEvent e) { if (_alpha == 255) { _fadeTimer.stop(); } else { pnl_hint.setBackground(new Color( bgColor.getRed(),bgColor.getGreen(),bgColor.getBlue(),(_alpha += 1))); pnl_hint.updateUI(); } } }); _fadeTimer.start();
Solution
Another option is to capture a screenshot of the panel and let it draw the added alpha synthesis itself
This is a small demonstration (although I'm not sure it's really clean):
import java.awt.AlphaComposite; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.image.BufferedImage; import java.net.MalformedURLException; import java.net.URL; import javax.swing.ImageIcon; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JPanel; import javax.swing.JTextField; import javax.swing.SwingUtilities; import javax.swing.Timer; public class TestFading { private static class FadingPanel extends JPanel { private BufferedImage buffer; private boolean isFading = false; private long start; private float alpha = 1.0f; @Override public void paint(Graphics g) { if (isFading) {// During fading,we prevent child components from being painted g.clearRect(0,getWidth(),getHeight()); ((Graphics2D) g).setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER,alpha)); g.drawImage(buffer,this);// We only draw an image of them with an alpha } else { super.paint(g); } } public void fade(int time) { start = System.currentTimeMillis(); buffer = new BufferedImage(getWidth(),getHeight(),BufferedImage.TYPE_INT_ARGB); this.print(buffer.getGraphics());// Draw the current components on the buffer isFading = true; final int timeInMillis = time * 1000; final Timer t = new Timer(50,null); t.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { long elapsed = System.currentTimeMillis() - start; if (elapsed > timeInMillis) { start = 0; isFading = false; buffer = null; repaint(); t.stop(); } else { alpha = 1.0f - (float) elapsed / timeInMillis; repaint(); } } }); t.start(); } } protected void initUI() throws MalformedURLException { JFrame frame = new JFrame(TestFading.class.getSimpleName()); frame.setDefaultCloSEOperation(JFrame.EXIT_ON_CLOSE); final FadingPanel panel = new FadingPanel(); JTextField textfield = new JTextField(60); JLabel image = new JLabel(new ImageIcon(new URL("http://helios.gsfc.nasa.gov/image_mag_stamp.jpg"))); JButton button = new JButton("Fade"); button.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { // I use an invoke later to allow the button to release itself SwingUtilities.invokelater(new Runnable() { @Override public void run() { panel.fade(5);// Fade the panel in 5s. } }); } }); panel.add(textfield); panel.add(image); panel.add(button); frame.add(panel); frame.setSize(400,300); frame.setVisible(true); } public static void main(String[] args) { SwingUtilities.invokelater(new Runnable() { @Override public void run() { try { new TestFading().initUI(); } catch (MalformedURLException e) { e.printStackTrace(); } } }); } }
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