java：如何将透明渐变背景添加到 JFrame

Question

java: I want to use the Gradient style Transparent Background to JFrame. On the top the transparency should be 100% but when going down it should go on decreasing and at the bottom it should be 20%

I know i can use the images already having such effect but i want to provide the themes facility and allowing user to use their favorite images but allow transparency at the run time.

Answer 1

Sun added support for translucent backgrounds to java in 6u10 but it is not formally described in the API. In Java 7 the functionality was formally added to the API via the setBackground(), setOpacity(), and setShape() methods of the Window class.

The behavior is described by Oracle here

Towards the bottom there is a code example for the gradient effect.

The technique will only work if the underlying OS window manager supports it. X11 (Linux) requires a compositing window manager to be installed and configured correctly. This is documented in the known issues of the Java 7 release notes and in this bug .

Answer 2

I was actually working in a JFrame extended class with transluscent Gradients in JFrame

import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.GraphicsConfiguration;
import java.awt.Rectangle;
import javax.swing.JFrame;
import javax.swing.JLayeredPane;
import javax.swing.JPanel;
import javax.swing.JRootPane;

public class JFrameGradient extends JFrame
{
private static final long serialVersionUID = 7565267933439533086L;
private Color initialColor;
private Color finalColor;
public static final int VERTICAL = 0;
public static final int HORIZONTAL = 1;
private int orientation = VERTICAL;

private int MAX_WIDTH = 1;
private int MAX_HEIGHT = 1;

private int xInitial = 0;
private int xFinal = 0;
private int yInitial = 0;
private int yFinal = 0;

private int initialRedComponent;
private int initialGreenComponent;
private int initialBlueComponent;

private int finalRedComponent;
private int finalGreenComponent;
private int finalBlueComponent;

private int delta = 1;
private String title;
private GraphicsConfiguration gc;
private JFrame frame;
private Graphics g;
private double transparency;
private JPanel gradientPane = new JPanel(true);
private boolean isColorChanged = false;



 public JFrameGradient( Color initialColor, Color finalColor , double transparency )
{
    super();
    this.frame = this;
    setTransparency(transparency);
    initClass();
    initColor(initialColor, finalColor);
}

 public JFrameGradient( String title , Color initialColor, Color finalColor , double transparency)
 {
     super(title);
     this.title = title;
     setTransparency(transparency);
     initClass();
     initColor(initialColor, finalColor);
 }

 public JFrameGradient( GraphicsConfiguration gc , Color initialColor, Color finalColor , double transparency)
 {
     super(gc);
     this.setGc(gc);
     setTransparency(transparency);
     initClass();
     initColor(initialColor, finalColor);
 }

 public JFrameGradient( GraphicsConfiguration gc , String title , Color initialColor, Color finalColor , double transparency)
 {
     super( title , gc );
     this.title = title;
     this.setGc(gc);
     setTransparency(transparency);
     initClass();
     initColor(initialColor, finalColor);
 }

 public JFrameGradient(  double transparency)
 {
     this( Color.black , Color.white , transparency);
 }

 public JFrameGradient(String title , double transparency)
 {
     this( title , Color.black , Color.white , transparency);
 }

 public JFrameGradient( GraphicsConfiguration gc , double transparency)
 {
     this( gc , Color.black , Color.white , transparency);
 }

 public JFrameGradient( GraphicsConfiguration gc , String title , double transparency)
 {
     this( gc , title , Color.black , Color.white , transparency);
 }

 public JFrameGradient()
 {
     this( Color.black , Color.white , 1);
 }

 public JFrameGradient(String title)
 {
     this( title , Color.black , Color.white , 1);
 }

 public JFrameGradient( GraphicsConfiguration gc)
 {
     this( gc , Color.black , Color.white , 1);
 }

 public JFrameGradient( GraphicsConfiguration gc , String title)
 {
     this( gc , title , Color.black , Color.white , 1);
 }

public Color getInitialColor()
{
    return initialColor;
}

public Color getFinalColor()
{
    return finalColor;
}

public void setInitialColor(Color initialColor)
{
    this.initialColor = initialColor;
    isColorChanged = true;
    if(isVisible())
    {
        repaint();
    }
}

public void setFinalColor(Color finalColor)
{
    this.finalColor = finalColor;
    isColorChanged = true;
    if(isVisible())
    {
        repaint();
    }
}

public String getTitle()
{
    return title;
}

public double getTransparency()
{
    return transparency;
}

public void setTransparency(double transparency)
{
    if( ( transparency >= 0.0) && (transparency <= 1.0) )
    {
        this.transparency = transparency;
    }
    else
    {
        this.transparency = 1.0;
    }
}

/**
 * @return the gc
 */
public GraphicsConfiguration getGc()
{
    return gc;
}

/**
 * @param gc the gc to set
 */
private void setGc(GraphicsConfiguration gc)
{
    this.gc = gc;
}

public int getOrientation()
{
    return orientation;
}

public void setOrientation(int orientation)
{
    this.orientation = orientation;
    if( isVisible())
    {
        repaint();
    }

}


private void initColor(Color initialColor, Color finalColor)
{
    this.initialColor = initialColor;
    this.finalColor = finalColor;

    this.initialRedComponent = initialColor.getRed();
    this.initialGreenComponent = initialColor.getGreen();
    this.initialBlueComponent = initialColor.getBlue();

    this.finalRedComponent = finalColor.getRed();
    this.finalGreenComponent = finalColor.getGreen();
    this.finalBlueComponent = finalColor.getBlue();

}

private void initClass()
{
    if( this != null)
    {
        frame = this;
        frame.add(gradientPane);
        frame.pack();
    }
}

@Override
public void paint(Graphics g)
{
    super.paint(g);
    paintGradient(g);
    Rectangle mask = null;

    for( Component c : getComponents() )
    {
        if( c instanceof JRootPane )
        {
            JRootPane rootPane = (JRootPane) c;
            rootPane.setDoubleBuffered(true);
            for( Component cRootPane : rootPane.getComponents())
            {
                 if( cRootPane instanceof JLayeredPane)
                 {
                    JLayeredPane cLayerPanels = (JLayeredPane) cRootPane;
                    cLayerPanels.setDoubleBuffered(true);
                    for( Component cLayerPanel : cLayerPanels.getComponents() )
                    {
                        if( cLayerPanel instanceof JPanel)
                        {
                            JPanel cPanels = (JPanel) cLayerPanel;
                            cPanels.setDoubleBuffered(true);

                            for( Component cPanel : cPanels.getComponents() )
                            {
                                if( cPanel instanceof JPanel)
                                {
                                    JPanel cPanels2 = (JPanel) cPanel;
                                    cPanels2.setDoubleBuffered(true);
                                     mask = frame.getBounds();
                                    for( Component cPanel2 : cPanels2.getComponents() )
                                    {
                                        mask.union(cPanel2.getBounds());
                                        cPanel2.paint(cPanel2.getGraphics());
                                    }

                                }
                            }
                        }
                    }
                }
            }
        }
    }
    g.setClip(mask);
}


private void paintGradient(Graphics g)
{
    if( isColorChanged == true)
    {
        initColor(initialColor, finalColor);
        isColorChanged = false;
    }

    if ( orientation == VERTICAL)
    {
        if ( this.getWidth() != 0 )
        {
            MAX_WIDTH = this.getWidth();
        }

        if ( this.getHeight() != 0)
        {
            MAX_HEIGHT = this.getHeight();
            xFinal = MAX_WIDTH;
            delta = MAX_HEIGHT;
        }

    } else if( orientation == HORIZONTAL )
    {
        if ( this.getHeight() != 0 )
        {
            MAX_HEIGHT = this.getHeight();
        }

        if ( this.getWidth() != 0)
        {
            MAX_WIDTH = this.getWidth();
            yFinal = MAX_HEIGHT;
            delta = MAX_WIDTH;
        }

    }

    if ( (this.initialColor != null ) && (this.finalColor != null) )
    {

        if ( delta == 0)
        {
            delta = 1;
        }

         if( orientation == VERTICAL)
         {
             for( int n = 0 ; n < MAX_HEIGHT ; n++)
             {
                 calculateColor(g, n);
                 g.drawLine(xInitial, n, xFinal, n);
             }
         } else if (orientation == HORIZONTAL)
         {
            for( int n = 0 ; n < MAX_WIDTH ; n++)
             {
                 calculateColor(g, n);
                 g.drawLine(n , yInitial, n , yFinal);
                 delta = Math.max( MAX_HEIGHT , MAX_WIDTH);
              }
          }



     }

    }

private void calculateColor(Graphics g, int n)
{
    int redComponent = 0;
    int greenComponent = 0;
    int blueComponent = 0;

    redComponent = interpolateComponent(n, initialRedComponent, finalRedComponent, delta);
     greenComponent = interpolateComponent(n, initialGreenComponent, finalGreenComponent, delta);
     blueComponent = interpolateComponent(n, initialBlueComponent, finalBlueComponent, delta);

     if( redComponent > 255)
     {
         redComponent = 255;
     } else if ( redComponent < 0)
     {
         redComponent = 0;
     }

     if( greenComponent > 255)
     {
         greenComponent = 255;
     } else if ( greenComponent < 0)
     {
         greenComponent = 0;
     }

     if( redComponent > 255)
     {
         blueComponent = 255;
     } else if ( redComponent < 0)
     {
         blueComponent = 0;
     }

     g.setColor( new Color(redComponent , greenComponent , blueComponent , (int) (255 * transparency) ));
}

private int interpolateComponent( int x , int xInit , int xFinal , int delta )
{
    int returnValue = 0 ;

    if ( xInit < xFinal ) {
        double slope =  (xFinal - xInit) / (double) delta ;

        returnValue = (int) ( xInit + slope * x );
    }
    else if( xFinal < xInit ) {
        double slope =  (xInit - xFinal) / (double) delta ;

        returnValue = (int) ( xInit - slope * x );
    } else {
        returnValue = xInit;
    }


    return returnValue;

}

@Override
public void setVisible(boolean aFlag)
{
    if (aFlag == true)
    {
        g = gradientPane.getGraphics();
        paint(g);
        frame.pack();
    }

        super.setVisible(aFlag);

}
public void setPreferredSize(int width, int height)
{
    setPreferredSize(new Dimension(width, height));
}

}

Answer 3

Only Mac OSX provides transparent/translucent frames in Java.

If you own a Mac, then you should start off by setting the background color to transparent:

frame.setBackground(new Color(0, 0, 0, 0));

Then -- I think (I don't own a Mac, yet:P) -- override the paintComponents(Graphics) method:

public void paintComponents(Graphics g)
{
     Graphics2D g2 = (Graphics2D) g;
     g2.setPaint(new GradientPaint(
     new Point(0, 0), 
     new Color(0.0f, 0.0f, 0.0f, 0.0f), 
     new Point(0, getHeight()), 
     new Color(0.0f, 0.0f, 0.0f, 0.8f)));
     super.paintComponents(g);
}