java - 将文本插入到 Java Canvas 上

Question

以下代码用于在按下按钮时插入文本:

if(actionNum == 4){
dropText = JOptionPane.showInputDialog(null, "Please enter the required text");
}

currentAction = actionNum;  

然后调用下面的段将文本绘制到 Canvas 上:

if(currentAction == 4){
 int w2 = getFontMetrics().stringWidth(dropText) / 2;
 aShape = drawString(dropText, textPoint.x - w2, textPoint.y);
}else

两个错误不断重复出现:

• Component 类中的方法 getFontMetrics 无法应用于给定类型:这里::行:259

• 找不到符号:这里::行:260

我试图添加到我正在使用的程序(一个绘图程序)中的代码可以在 here 中找到。

程序代码如下:

    import javax.swing.*;
    import javax.swing.event.ChangeEvent;
    import javax.swing.event.ChangeListener;

    import java.awt.event.*;
    import java.awt.*;
    import java.awt.geom.*;
    import java.text.DecimalFormat;
    import java.util.*;

    // Allows user text to be entered, for use in text
    // deployment to the canvas
    import java.io.*;
    import javax.swing.JOptionPane; 

    @SuppressWarnings("serial")
    public class Splat extends JFrame
    { 

    JButton brushBut, lineBut, clearBut, textBut, ellipseBut, rectBut,    strokeBut, fillBut;

    // Decleration of the string for use in text deployement on the canvas
 String dropText;
 private static final int W = 640;
    private static final int H = 480;
    private Point textPoint = new Point(W / 2, H / 2);
    private Point mousePoint;

    // Defines the arrays used on the DrawingBoard. These are Instantiated earlier
    // so that they may be cleared in the makeMeButtons method

    ArrayList<Shape> shapes = new ArrayList<Shape>();
    ArrayList<Color> shapeFill = new ArrayList<Color>();
    ArrayList<Color> shapeStroke = new ArrayList<Color>();
    ArrayList<Float> transPercent = new ArrayList<Float>();

    // Transparency slider

    JSlider transSlider;

    JLabel transLabel;

    // Limits the transparency float to 2 decimal points

    DecimalFormat dec = new DecimalFormat("#.##");

    // Standard 2D drawing rules for Java

    Graphics2D graphSettings;

    // Used to determine the shape/button selected

    int currentAction = 1;

    // Transparency of the shape

    float transparentVal = 1.0f;

    // Default stroke and fill colors

    Color strokeColor=Color.BLACK, fillColor=Color.BLACK;

    public static void main(String [] args)
    {
            new Splat();
    }

    public Splat()
    {
        // Define the defaults for the JFrame

        this.setSize(800, 600);
        this.setTitle("Splat");
        this.setFont(new Font("Serif", Font.ITALIC + Font.BOLD, 32));
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel buttonPanel = new JPanel();

        // Box that will hold the buttons

        Box theBox = Box.createHorizontalBox();

        // Make all the buttons by calling makeMeButtons and
        // makeMeColorButton

        brushBut = makeMeButtons("./src/brush.png", 1);
        lineBut = makeMeButtons("./src/Line.png", 2);
        clearBut = makeMeButtons("./src/Clear.png", 3);
        textBut = makeMeButtons("./src/Text.png", 4);
        ellipseBut = makeMeButtons("./src/Ellipse.png", 5);
        rectBut = makeMeButtons("./src/Rectangle.png", 6);

        // Make all the buttons in makeMeColorButton by passing the
        // button icon and true for stroke color or false for fill

        strokeBut = makeMeColorButton("./src/Stroke.png", 7, true);
        fillBut = makeMeColorButton("./src/Fill.png", 8, false);

        // Add the buttons to the box

        theBox.add(brushBut);
        theBox.add(lineBut);
        theBox.add(clearBut);
        theBox.add(textBut);
        theBox.add(ellipseBut);
        theBox.add(rectBut);
        theBox.add(strokeBut);
        theBox.add(fillBut);

        // Add the transparent label and slider

        transLabel = new JLabel("Transparent: 1");

        // Min value, Max value and starting value for slider

        transSlider = new JSlider(1, 99, 99);

        // Create an instance of ListenForEvents to handle events

        ListenForSlider lForSlider = new ListenForSlider();

        // Tell Java that you want to be alerted when an event
        // occurs on the slider

        transSlider.addChangeListener(lForSlider);

        theBox.add(transLabel);
        theBox.add(transSlider);

        // Add the box of buttons to the panel

        buttonPanel.add(theBox);

        // Position the buttons in the bottom of the frame

        this.add(buttonPanel, BorderLayout.SOUTH);

        // Make the drawing area take up the rest of the frame

        this.add(new DrawingBoard(), BorderLayout.CENTER);

        // Show the frame

        this.setVisible(true);
    }

    // Spits out buttons based on the image supplied
    // actionNum represents each shape to be drawn

    public JButton makeMeButtons(String iconFile, final int actionNum){
        JButton theBut = new JButton();
        Icon butIcon = new ImageIcon(iconFile);
        theBut.setIcon(butIcon);

        // Make the proper actionPerformed method execute when the
        // specific button is pressed
        // If the action number is 3 then the DrawingBoard is blanked instantly,
        // on the button press

        theBut.addActionListener(new ActionListener() {

            public void actionPerformed(ActionEvent e) {
                if(actionNum == 3)
                {
                    shapes.clear();
                    shapeFill.clear();
                    shapeStroke.clear();
                    transPercent.clear();
                    repaint();
                }
                else

                if(actionNum == 4){
                    dropText = JOptionPane.showInputDialog(null, "Please enter the required text");
                }

                    currentAction = actionNum;  
            }
        });

        return theBut;  
    }

    // Creates the Fill Colour and Stroke Colour Buttons

    public JButton makeMeColorButton(String iconFile, final int actionNum, final boolean stroke){
        JButton theBut = new JButton();
        Icon butIcon = new ImageIcon(iconFile);
        theBut.setIcon(butIcon);

        theBut.addActionListener(new ActionListener() {

            public void actionPerformed(ActionEvent e) {

                if(stroke){

                    // JColorChooser is a popup that lets you pick a color

                    strokeColor = JColorChooser.showDialog(null,  "Pick a Stroke", Color.BLACK);
                } else {
                    fillColor = JColorChooser.showDialog(null,  "Pick a Fill", Color.BLACK);
                }

            }
        });

        return theBut;  
    }

    private class DrawingBoard extends JComponent
    {

            Point drawStart, drawEnd;

            // Monitors events on the drawing area of the frame

            public DrawingBoard()
            {

                    this.addMouseListener(new MouseAdapter()
                      {

                        public void mousePressed(MouseEvent e)
                        {
        /*text input*/      if(currentAction == 4){
                                mousePoint = e.getPoint();
                                repaint();
                            }
                            else

                            if(currentAction != 1){

                            // When the mouse is pressed get x & y position

                            drawStart = new Point(e.getX(), e.getY());
                            drawEnd = drawStart;
                            repaint();

                            }

                            }

                        public void mouseReleased(MouseEvent e)
                            {

                            if(currentAction != 1){

                              // Create a shape using the starting x & y
                              // and finishing x & y positions

                            Shape aShape = null;

                            if (currentAction == 2){
                                aShape = drawLine(drawStart.x, drawStart.y,
                                        e.getX(), e.getY());
                            } else 

                            if(currentAction == 4){
                                int w2 = getFontMetrics().stringWidth(dropText) / 2;
                                aShape = drawString(dropText, textPoint.x - w2, textPoint.y);
                            } else

                            if (currentAction == 5){
                                aShape = drawEllipse(drawStart.x, drawStart.y,
                                        e.getX(), e.getY());
                            } else 

                            if (currentAction == 6) {

                                // Create a new rectangle using x & y coordinates

                                aShape = drawRectangle(drawStart.x, drawStart.y,
                                        e.getX(), e.getY());
                            }


                              // Add shapes, fills and colors to there ArrayLists

                              shapes.add(aShape);
                              shapeFill.add(fillColor);
                              shapeStroke.add(strokeColor);

                              // Add transparency value to ArrayList

                              transPercent.add(transparentVal);

                              drawStart = null;
                              drawEnd = null;

                              // repaint the drawing area

                              repaint();

                            }

                            }
                      } );

                    this.addMouseMotionListener(new MouseMotionAdapter()
                    {

                      public void mouseDragged(MouseEvent e)
                      {

                          if(currentAction == 4){
                            int dx = e.getX() - mousePoint.x;
                            int dy = e.getY() - mousePoint.y;
                            textPoint.setLocation(textPoint.x + dx, textPoint.y + dy);
                            mousePoint = e.getPoint();
                            repaint();
                          }
                          else

                          // If this is a brush have shapes go on the screen quickly

                          if(currentAction == 1){

                            int x = e.getX();
                            int y = e.getY();

                            Shape aShape = null;

                            // Make stroke and fill equal to eliminate the fact that this is an ellipse

                            strokeColor = fillColor;

                            aShape = drawBrush(x,y,5,5);

                            shapes.add(aShape);
                              shapeFill.add(fillColor);
                              shapeStroke.add(strokeColor);

                              // Add the transparency value

                              transPercent.add(transparentVal);
                        } 

                        // Get the final x & y position after the mouse is dragged

                        drawEnd = new Point(e.getX(), e.getY());
                        repaint();
                      }
                    } );
            }


            public void paint(Graphics g)
            {
                    // Class used to define the shapes to be drawn

                    graphSettings = (Graphics2D)g;

                    // Antialiasing cleans up the jagged lines and defines rendering rules

                    graphSettings.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALIAS_ON);

                    // Defines the line width of the stroke

                    graphSettings.setStroke(new BasicStroke(4));

                    // Iterators created to cycle through strokes and fills
                    Iterator<Color> strokeCounter = shapeStroke.iterator();
                    Iterator<Color> fillCounter = shapeFill.iterator();

                    // Iterator for transparency

                    Iterator<Float> transCounter = transPercent.iterator();

                    for (Shape s : shapes)
                    {

                        // Sets the shapes transparency value

                        graphSettings.setComposite(AlphaComposite.getInstance(
                                AlphaComposite.SRC_OVER, transCounter.next()));

                        // Grabs the next stroke from the color arraylist
                        graphSettings.setPaint(strokeCounter.next());

                        graphSettings.draw(s);

                        // Grabs the next fill from the color arraylist
                        graphSettings.setPaint(fillCounter.next());

                        graphSettings.fill(s);
                    }

                    // Guide shape used for drawing
                    if (drawStart != null && drawEnd != null)
                    {
                        // Makes the guide shape transparent

                        graphSettings.setComposite(AlphaComposite.getInstance(
                                AlphaComposite.SRC_OVER, 0.40f));

                        // Make guide shape gray for professional look

                        graphSettings.setPaint(Color.LIGHT_GRAY);

                        Shape aShape = null;

                        if (currentAction == 2){
                            aShape = drawLine(drawStart.x, drawStart.y,
                                    drawEnd.x, drawEnd.y);
                        } else 

                        if(currentAction == 4){
                            int w2 = g.getFontMetrics().stringWidth(dropText) / 2;
    g.drawString(dropText, textPoint.x - w2, textPoint.y);
                        }else

                        if (currentAction == 5){
                            aShape = drawEllipse(drawStart.x, drawStart.y,
                                    drawEnd.x, drawEnd.y);
                        } else 

                        if (currentAction == 6) {

                            // Create a new rectangle using x & y coordinates

                            aShape = drawRectangle(drawStart.x, drawStart.y,
                                    drawEnd.x, drawEnd.y);
                        }


                            graphSettings.draw(aShape);
                    }
            }

            private Rectangle2D.Float drawRectangle(
                    int x1, int y1, int x2, int y2)
            {
                // Get the top left hand corner for the shape
                // Math.min returns the points closest to 0

                    int x = Math.min(x1, x2);
                    int y = Math.min(y1, y2);

                    // Gets the difference between the coordinates and 

                    int width = Math.abs(x1 - x2);
                    int height = Math.abs(y1 - y2);

                    return new Rectangle2D.Float(
                            x, y, width, height);
            }

            // The other shapes will work similarly
            // More on this in the next tutorial

            private Ellipse2D.Float drawEllipse(
                    int x1, int y1, int x2, int y2)
            {
                    int x = Math.min(x1, x2);
                    int y = Math.min(y1, y2);
                    int width = Math.abs(x1 - x2);
                    int height = Math.abs(y1 - y2);

                    return new Ellipse2D.Float(
                            x, y, width, height);
            }

            private Line2D.Float drawLine(
                    int x1, int y1, int x2, int y2)
            {

                    return new Line2D.Float(
                            x1, y1, x2, y2);
            }

            private Ellipse2D.Float drawBrush(
                    int x1, int y1, int brushStrokeWidth, int brushStrokeHeight)
            {

                return new Ellipse2D.Float(
                        x1, y1, brushStrokeWidth, brushStrokeHeight);

            }

    }

 // Implements ActionListener so it can react to events on components

    private class ListenForSlider implements ChangeListener{

        // Called when the spinner is changed

        public void stateChanged(ChangeEvent e) {

            // Check if the source of the event was the button

            if(e.getSource() == transSlider){

                // Change the value for the label next to the spinner
                // Use decimal format to make sure only 2 decimals are ever displayed

                transLabel.setText("Transparent: " + dec.format(transSlider.getValue() * .01) );

                // Set the value for transparency for every shape drawn after

                transparentVal = (float) (transSlider.getValue() * .01);

            }

        }

    }

}

Answer 1

您需要:

import java.awt.FontMetrics;