java：我想对 JFrame 使用渐变风格的透明背景。 顶部透明度应为 100%，但向下时应继续降低，底部应为 20%
我知道我可以使用已经具有这种效果的图像，但我想提供主题工具并允许用户使用他们最喜欢的图像，但在运行时允许透明。
【问题讨论】：
GradientPaint吗？
RescaleOp 会参与其中，但整个“渐变透明度”让我陷入了循环！我也会喜欢这个，所以我可以在下班后回来。 :)
标签： java swing jframe gradient
Sun 在 6u10 中为 java 添加了对半透明背景的支持，但在 API 中没有正式描述。 在 Java 7 中，该功能通过 Window 类的 setBackground()、setOpacity() 和 setShape() 方法正式添加到 API。
该行为由 Oracle here 描述
在底部有一个渐变效果的代码示例。
该技术只有在底层操作系统窗口管理器支持时才有效。 X11 (Linux) 需要正确安装和配置合成窗口管理器。这在 Java 7 发行说明的known issues 和此bug 中有记录。
【讨论】：
只有 Mac OSX 在 Java 中提供透明/半透明框架。
如果您拥有一台 Mac，那么您应该首先将背景颜色设置为透明：
frame.setBackground(new Color(0, 0, 0, 0));
然后 -- 我认为（我还没有 Mac，但：P） -- 覆盖 paintComponents(Graphics) 方法：
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);
}
【讨论】：
JFrame 没有 setOpaque(...) 方法。
我实际上是在一个 JFrame 扩展类中工作，在 JFrame 中使用半透明渐变
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));
}
}
【讨论】：