java - 将图像附加到 JLabel 的边框

Question

我想编写一个 JLabel 的自定义子类，它将在边框上附加两个图像，可以通过移动鼠标来移动它们。真实效果是这样的:

这是我的子类，我如何添加这些附加图像？

public class Rect extends JLabel{
    private int width,height;
    public Rect (int width,int height){
        this.width = width;
        this.height = height;
        setText("b1");
        repaint();
    }

    public void paintComponent(Graphics g){
        super.paintComponent(g);

        g.setColor(Color.red);
        g.drawRect(0, 0, this.width, this.height);
    }

    public void reDraw(){
        this.repaint();
    }

    public void setWidth(int width) {
        this.width = width;
        repaint();
    }

    public void setHeight(int height) {
        this.height = height;
        repaint();
    }
}

Answer 1

为此，您应该做 4 件事:

• 扩展 AbstractBorder 而不是 Jlabel，那么您可以轻松地将自定义边框添加到任何组件，而不仅仅是 jLabel。<
• 重写 paintBorder 方法，以便您可以绘制边框。
• 添加鼠标操作监听器以跟踪边框图像。
• 最后，您需要一些逻辑来管理边框图像。

我发现这个问题很有趣，所以我尝试做一些东西作为测试。结果很好，并且达到了您想要的效果，但需要一些工作才能使其看起来正确。请参阅下文了解每一点的分割。

查看代码之前的示例图像:

扩展AbstractBorder:

public class MyCustomBorder extends AbstractBorder
{
    private Color borderColour;
    private int borderThickness = 10;
    private Point firstSlider = new Point(0, 0);
    private Point secondSlider = new Point(0, 0);
    private BufferedImage firstSliderImage;
    private BufferedImage secondSliderImage;

    Boolean draggingFirst = false;
    Boolean draggingSecond = false;

    //See usage info
    public MyCustomBorder(Color colour, int thickness, Point firstSlider, BufferedImage firstSliderImage, Point secondSlider, BufferedImage secondSliderImage)
    {
        borderColour = colour;
        borderThickness = thickness;
        this.firstSlider = firstSlider;
        this.secondSlider = secondSlider;
        this.firstSliderImage = firstSliderImage;
        this.secondSliderImage = secondSliderImage;
    }

重写paintBorder方法和插图:

    @Override
    public void paintBorder(Component c, Graphics g, int x, int y, int width, int height)
    {
        super.paintBorder(c, g, x, y, width, height);
        Graphics2D g2d = null;

        if (g instanceof Graphics2D)
        {
            g2d = (Graphics2D) g;

            //Draw border fill (currently hard coded to white, but can be changed)
            g2d.setColor(Color.white);
            //Top
            g2d.fill(new Rectangle2D.Double(0, 0, width, borderThickness));
            //Left
            g2d.fill(new Rectangle2D.Double(0, 0, borderThickness, height));
            //Bottom
            g2d.fill(new Rectangle2D.Double(0, height-borderThickness, width, borderThickness));
            //Right
            g2d.fill(new Rectangle2D.Double(width-borderThickness, 0, borderThickness, height));

            //draw black seperator
            g2d.setColor(borderColour);
            //Top
            g2d.fill(new Rectangle2D.Double(borderThickness, borderThickness, width-(borderThickness*2), 1));
            //Left
            g2d.fill(new Rectangle2D.Double(borderThickness, borderThickness, 1, height-(borderThickness*2)));
            //Bottom
            g2d.fill(new Rectangle2D.Double(borderThickness, height-borderThickness-1, width-(borderThickness*2), 1));
            //Right
            g2d.fill(new Rectangle2D.Double(width-borderThickness-1, borderThickness, 1, height-(borderThickness*2)));

            //draw sliders an custom position       
            g2d.drawImage(scale(secondSliderImage), null, secondSlider.x, secondSlider.y);
            g2d.drawImage(scale(firstSliderImage), null, firstSlider.x, firstSlider.y);
        }
    }

    @Override
    public Insets getBorderInsets(Component c)
    {
        return (getBorderInsets(c, new Insets(borderThickness, borderThickness, borderThickness, borderThickness)));
    }

    @Override
    public Insets getBorderInsets(Component c, Insets insets)
    {
        insets.left = insets.top = insets.right = insets.bottom = borderThickness;
        return insets;
    }

    @Override
    public boolean isBorderOpaque()
    {
        return false;
    }
}

添加鼠标操作监听器:

    //listeners for dragging
    void addListeners(Component button)
    {
        button.addMouseMotionListener(new java.awt.event.MouseMotionAdapter()
        {
            public void mouseDragged(java.awt.event.MouseEvent evt)
            {   
            //Only drag if a slider was selected
            if (draggingFirst)
            {
                //update position of silder
                firstSlider = snapToEdge(evt.getPoint(), evt.getComponent());
                evt.getComponent().repaint();
            }
            else if (draggingSecond)
            {
                //update position of silder
                secondSlider = snapToEdge(evt.getPoint(), evt.getComponent());
                evt.getComponent().repaint();
            }
            }
        });
        button.addMouseListener(new java.awt.event.MouseAdapter()
        {
            //check if a slider was selected
            public void mousePressed(java.awt.event.MouseEvent evt)
            {
            if (isInside(evt.getPoint(), firstSlider))
            {
                draggingFirst = true;
            }
            else if (isInside(evt.getPoint(), secondSlider))
            {
                draggingSecond = true;
            }
            }
            public void mouseReleased(java.awt.event.MouseEvent evt)
            {
            //cancel selected slider
            draggingFirst = false;
            draggingSecond = false;
            }
        });
    }

逻辑:

    //check if a slider was selected
    private Boolean isInside(Point clicked, Point toCheck)
    {
        if (clicked.x > toCheck.x && clicked.x < toCheck.x + borderThickness)
        {
            if (clicked.y > toCheck.y && clicked.y < toCheck.y + borderThickness)
            {
            return true;
            }
        }
        return false;
    }

    //snap a sliders co-ords to as edge
    private Point snapToEdge(Point dragged, Component label)
    {   
        //work out how close to each edge
        int topEdge = dragged.y;
        int leftEdge = dragged.x;
        int rightEdge = label.getWidth()- dragged.x;
        int bottomEdge = label.getHeight() - dragged.y;

        //snap to slider co-ords to closest edge
        if (topEdge < leftEdge && topEdge < rightEdge && topEdge < bottomEdge)
        {
            dragged.y = 0;
        }
        else if (leftEdge < rightEdge && leftEdge < bottomEdge)
        {
            dragged.x = 0;
        }
        else if (rightEdge < bottomEdge)
        {
            dragged.x = label.getWidth()-borderThickness;
        }
        else
        {
            dragged.y = label.getHeight()-borderThickness;
        }
        return dragged;
    }

    //scale slider images to fit border size
    public BufferedImage scale(BufferedImage image)
    {
        BufferedImage resizedImage = null;
        if (image != null)
        {
            double border = borderThickness;
            resizedImage = new BufferedImage(borderThickness, borderThickness, TYPE_INT_ARGB);
            Graphics2D g = resizedImage.createGraphics();
            AffineTransform at = AffineTransform.getScaleInstance(border / (double)image.getWidth(), border / (double)image.getHeight());
            g.drawRenderedImage(image, at);
        }
        return resizedImage;
    }

要复制和粘贴的完整代码可以在此处找到:

https://github.com/sorifiend/customBorder/blob/master/MyCustomBorder.java

使用示例:

您可以将此代码放入表单类中，为大多数 swing 组件添加边框。在此示例中，我将其添加到名为 my_jLabel 的 jLabel 中:

   //Create border
   MyCustomBorder border = new MyCustomBorder(Color.BLACK, 10, new Point(0, 0), img1, new Point(0, 0), img2);

   //Add border to component called my_jLabel
   my_jLabel.setBorder(border);

   //Add action listeners for dragging sliders (very important)
   border.addListeners(my_jLabel);