怎么在canvas上添加button或者textbox

刚看到的，或许对你有启示当然可以，但不是在Canvas添加。Canvas是不能添加控件的。可以用一个FrameLayout。将按钮和Canvas都放到FrameLayout里，FrameLayout类似photosshop的图层。可以实现控件重叠的效果。只要把button放在canvas上面，看着就像在canvas添加一样。

canvas中添加按钮，参考代码如下：

Button btn =new Button()

btn.Content ="电压表"

pcbCanvas.AddVisual(btn)

PCBCanvas.SetLeft(btn, 100)

PCBCanvas.SetTop(btn, 100)

import javax.swing.*

import javax.swing.border.*

import java.awt.*

import java.awt.event.*

import java.util.*

/**

 * @author Hardneedl

 */

final public class PaintDemo extends JApplet {

    private final static Dimension PREFERRED_SIZE = new Dimension(800, 600)

    public Dimension getPreferredSize() {return PREFERRED_SIZE}

    public Dimension getMinimumSize() {return PREFERRED_SIZE}

    private Brush brushprivate BrushCanvas canvas

    private JCheckBox ckGreen,ckRed,ckBlue

    private ButtonGroup rbGroup

    private JRadioButton rbSmall,rbMidel,rbBig

    public void init() {

        canvas=new BrushCanvas(brush = new StringBrush(){

            public Component getOwner() {

                return canvas

            }

        }

        ){

            public Dimension getPreferredSize() {

                return new Dimension(400, 450)

            }

        }

        ckGreen=new JCheckBox(new ColorValueAction("green", Color.GREEN,brush))

        ckRed=new JCheckBox(new ColorValueAction("red", Color.RED,brush))

        ckBlue=new JCheckBox(new ColorValueAction("blue", Color.BLUE,brush))

        rbGroup=new ButtonGroup()

        rbGroup.add(rbSmall=new JRadioButton(new IntegerValueAction("10",10,brush)))

        rbGroup.add(rbMidel=new JRadioButton(new IntegerValueAction("16",16,brush)))

        rbGroup.add(rbBig=new JRadioButton(new IntegerValueAction("50", 50,brush)))

        Container container = getContentPane()

        BoxLayout boxLayout=new BoxLayout(container,BoxLayout.Y_AXIS)

        container.setLayout(boxLayout)

        JComponent p = new JPanel()

        p.add(ckGreen)p.add(ckRed)p.add(ckBlue)

        container.add(p)

        JComponent p0 = new JPanel()

        p0.add(rbSmall)p0.add(rbMidel)p0.add(rbBig)

        container.add(p0)

        container.add(canvas)

    }

    public void start() {

        rbGroup.setSelected(rbBig.getModel(),true)

    }

}

/*整数值的动作，getValue("integer")返回代表的整数值*/

class IntegerValueAction extends AbstractAction{

    private int v

    private Observable observable=new Observable(){

        public void notifyObservers(Object arg) {

            setChanged()super.notifyObservers(arg)

        }

    }

    public IntegerValueAction(String t, int v,Observer observer) {

        super(t)

        this.v=v

        observable.addObserver(observer)

    }

    public void actionPerformed(ActionEvent e) {

        observable.notifyObservers(getValue("integer"))

    }

    public Object getValue(String key) {

        if (key.equalsIgnoreCase("integer")){

            return v

        }

        return super.getValue(key)

    }

}

class ColorValueAction extends AbstractAction{

    private Color v=new Color(0)

    private Observable observable=new Observable(){

        public void notifyObservers(Object arg) {

            setChanged()super.notifyObservers(arg)

        }

    }

    public ColorValueAction(String t, Color v, Observer observer) {

        super(t)

        this.v=v

        observable.addObserver(observer)

    }

    public void actionPerformed(ActionEvent e) {

        observable.notifyObservers(getValue("color"))

    }

    public Object getValue(String key) {

        if (key.equalsIgnoreCase("color")){

            return v

        }

        return super.getValue(key)

    }

}

/*画笔*/

interface Brush extends Observer{

    /**

     * 绘图

     * @param g 绘图环境

     */

    void paint(Graphics g)

    Component getOwner()

}

abstract class StringBrush implements Brush{

    private int fontSize = 14

    private Color color

    String getString(){

        return "请选择"

    }

    public void paint(Graphics g) {

        Graphics2D g2 = (Graphics2D)g.create()

        g2.setColor(color==null?Color.BLACK:color)

        g2.setFont(g2.getFont().deriveFont((float)fontSize))

        g2.translate(40,50)

        g2.drawString(getString()==null?"":getString(),0,0)

        g2.dispose()

    }

    public void update(Observable o, Object arg) {

        if (arg instanceof Integer) {

            fontSize = (int)arg

        }

        if (arg instanceof Color) {

            Color c = (Color)arg

            color=new Color(c.getRed(),c.getGreen(),c.getBlue())

        }

        Component owner = getOwner()

        if (owner!=null)owner.repaint()

    }

}

/*画布*/

class BrushCanvas extends JComponent{

    private Brush brush

    public BrushCanvas(Brush brush) {

        setBrush(brush)

    }

    void setBrush(Brush b){

        brush=b

    }

    protected void paintComponent(Graphics g) {

        super.paintComponent(g)

        if (brush!=null)

            brush.paint(g)

    }

}

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