functionframe.java

来自「一个一元曲线多项式数值演示例子」· Java 代码 · 共 216 行

package numbercruncher.graphutils;

import java.applet.*;
import java.net.*;

import java.awt.*;
import java.awt.event.*;

/**
 * The window that displays the image of all the functions to plot.
 * The user clicks on a function to select it.
 */
public class FunctionFrame
    extends Frame {
  /** image of functions */
  private Image image;
  /** image width */
  private int imageWidth;
  /** image height */
  private int imageHeight;
  /** true if image error occurred */
  private boolean imageError = false;
  /** error label */
  private TextArea errorText;

  /** image buffer */
  private Image buffer;
  /** buffer grapics context */
  private Graphics bg;

  /** function selection index */
  private int xSelection = 0;

  /** array of functions to plot */
  private Plottable functions[];
  /** root finder panel */
  private GraphPanel graphPanel;

  /**
   * Constructor.
   * @param functions the array of functions to plot
   * @param functionImageFileName the name of the function image file
   * @param title the frame title
   * @param graphPanel the graph panel
   */
  public FunctionFrame(Plottable functions[], String functionImageFileName,
                       String title, GraphPanel graphPanel) {
    this.functions = functions;
    this.graphPanel = graphPanel;

    initFrame(title);
    loadImage(functionImageFileName);
  }

  /**
   * Return the image.
   * @return the image
   */
  public Image getImage() {
    return image;
  }

  /**
   * Return the array of functions to plot.
   * @return the function array
   */
  public Plottable[] getFunctions() {
    return functions;
  }

  /**
   * Initialize the function frame.
   */
  private void initFrame(String title) {
    setTitle(title);
    setResizable(false);
    setBackground(Color.white);
    setLocation(25, 25);

    // Window event handlers.
    addWindowListener(new WindowAdapter() {
      public void windowOpened(WindowEvent ev) {
//                repaint();
        paint(FunctionFrame.this.getGraphics());
      }
    });

    // Mouse event handlers.
    addMouseListener(new MouseAdapter() {
      // Mouse click:  Select a function.
      public void mouseClicked(MouseEvent ev) {
        Insets in = getInsets();
        int x = ev.getX() - in.left;
        int y = ev.getY() - in.top;

        // Loop to find which function (if any) was clicked on.
        for (int i = 0; i < functions.length; ++i) {
          Rectangle r = functions[i].getRectangle();
          if (r.contains(x, y) && (i != xSelection)) {
            xSelection = i;
            repaint();

            graphPanel.chooseFunction(i); // callback
            break;
          }
        }
      }
    });
  }

  /**
   * Load the function image file.
   * @param functionImageFileName the file name of the image file
   */
  private void loadImage(String functionImageFileName) {
    Container parent = graphPanel.getParent();

    // Construct the URL string for the function image file.  For
    // a standalone application, the file should be in the current
    // working directory.  For an applet, the file should be in
    // the images subdirectory in the code base.
    String imageBase =
        (parent instanceof Frame)
        ? "file:///" + System.getProperty("user.dir") + "/"
        : ( (Applet) parent).getCodeBase() + "images/";
    String urlString = imageBase + functionImageFileName;

    try {
      // Load the function image file.
      URL url = new URL(urlString);
      image = Toolkit.getDefaultToolkit().getImage(url);

      // Wait for the image to load.
      MediaTracker tracker = new MediaTracker(this);
      tracker.addImage(image, 0);
      tracker.waitForID(0);

      imageWidth = image.getWidth(null);
      imageHeight = image.getHeight(null);

      // Did the image load sucessfully?
      if ( (imageWidth <= 0) && (imageHeight <= 0)) {
        throw new Exception("Could not find \"" + urlString + "\"");
      }

      repaint();
    }
    catch (Exception ex) {
      imageError = true;

      // Load the error message into the frame instead.
      errorText = new TextArea("Error loading function image file:\n");
      errorText.append(ex.getMessage());
      errorText.setForeground(GraphPanel.MAROON);
      errorText.setEditable(false);

      setLayout(new BorderLayout());
      add(errorText, BorderLayout.CENTER);

      // Display the error message.
      setSize(520, 100);
      setTitle("***** ERROR *****");
      setVisible(true);
    }
  }

  /**
   * Update the display without repainting the background.
   * @param g the graphics context
   */
  public void update(Graphics g) {
    paint(g);
  }

  /**
   * Paint the function frame.
   * @param g the graphics context
   */
  public void paint(Graphics g) {
    // If there was an error, display the error message.
    if (imageError) {
      super.paint(g);
      return;
    }

    Insets in = getInsets();
    g.translate(in.left, in.top);

    // Create the image buffer.
    if (buffer == null) {
      buffer = createImage(imageWidth, imageHeight);
      bg = buffer.getGraphics();
      bg.setColor(Color.white);
    }

    // Set the frame size to fit the image.
    setSize(imageWidth + in.left + in.right,
            imageHeight + in.top + in.bottom);

    // Draw the image into the buffer.
    bg.setPaintMode();
    bg.fillRect(0, 0, imageWidth, imageHeight);
    bg.drawImage(image, 0, 0, this);

    // Highlight the selected function.
    if (xSelection > -1) {
      Rectangle r = functions[xSelection].getRectangle();

      bg.setXORMode(Color.blue);
      bg.fillRect(r.x, r.y, r.width, r.height);
    }

    // Display the buffer.
    g.drawImage(buffer, 0, 0, this);
  }
}