sketchview.java

用JAVA开发的一个小型画图软件

        }    
        start = null;
      }

    public void mousePressed(MouseEvent e)  {
      if(e.isPopupTrigger()) {
        processPopupTrigger(e);
      } else if((button1Down = (e.getButton() == MouseEvent.BUTTON1))) {
        start = e.getPoint();                  // Save the cursor position in start
        g2D = (Graphics2D)getGraphics();                // Get graphics context
        g2D.setXORMode(getBackground());                // Set XOR mode
      }
    } 

    public void mouseDragged(MouseEvent e) {
      last = e.getPoint();                              // Save cursor position
      if(button1Down && (theApp.getWindow().getElementType() != TEXT)&& (mode == NORMAL)) {
        if(tempElement == null) {                       // Is there an element?
          tempElement = createElement(start, last);     // No, so create one
        } else {
          tempElement.draw(g2D);                        // Yes - draw to erase it
          tempElement.modify(start, last);              // Now modify it
        }
        tempElement.draw(g2D);                          // and draw it
      } else if(button1Down && mode == MOVE && selectedElement != null) {
        selectedElement.draw(g2D);                    // Draw to erase the element
        selectedElement.move(last.x-start.x, last.y-start.y);  // Move it
        selectedElement.draw(g2D);                     // Draw in its new position
        start = last;                                  // Make start current point
      } else if(button1Down && mode == ROTATE && selectedElement != null) {
        selectedElement.draw(g2D);                   // Draw to erase the element
        selectedElement.rotate(getAngle(selectedElement.getPosition(),
                                                                    start, last));
        selectedElement.draw(g2D);                  // Draw in its new position
        start = last;                               // Make start current point
      }
    }

    // Helper method for calculating the rotation angle
    double getAngle(Point position, Point start, Point last) {
      // Get perpendicular distance from last to the line from position to start
      double perp = Line2D.ptLineDist(position.x, position.y,
                                      last.x, last.y, start.x, start.y);
      // Get the distance from position to start
      double hypotenuse = position.distance(start);
      if(hypotenuse == 0.0) {                      // Make sure it's
        hypotenuse = 1.0;                          // non-zero
      }

      // Angle is the arc sine of perp/hypotenuse. Clockwise is positive angle
      return -Line2D.relativeCCW(position.x, position.y,
                                 start.x, start.y,
                                 last.x, last.y)*Math.asin(perp/hypotenuse);
    }

    public void mouseReleased(MouseEvent e) {
      if(e.isPopupTrigger()) {
        processPopupTrigger(e);
      } else if((e.getButton()==MouseEvent.BUTTON1) && (theApp.getWindow().getElementType() != TEXT) && mode == NORMAL) {
        button1Down = false;                     // Reset the button 1 flag
        if(tempElement != null) {
       theApp.getModel().add(tempElement);       // Add element to the model
          tempElement = null;                    // No temporary element now stored
        }
      } else if((e.getButton()==MouseEvent.BUTTON1) &&
                (mode == MOVE || mode == ROTATE)) {
        button1Down = false;                     // Reset the button 1 flag
        if(selectedElement != null) {
          repaint();
        }
        mode = NORMAL;
      }

      if(g2D != null) {
        g2D.dispose();                           // Release graphic context resource
        g2D = null;                              // Set it to null
      }
      start = last = null;                       // Remove the points
      selectedElement = tempElement = null;      // Reset elements
    }

    public void mouseClicked(MouseEvent e) {
      if((e.getButton()== MouseEvent.BUTTON1) && (theApp.getWindow().getElementType() == TEXT)) {
  
        start = e.getPoint();                  // Save cursor position - start of text
        String text = JOptionPane.showInputDialog(
                   (Component)e.getSource(),   // Used to get the frame
                   "Enter Text:",              // The message
                   "Dialog for Text Element",  // Dialog title
                   JOptionPane.PLAIN_MESSAGE); // No icon
   
        if(text != null && text.length()!= 0)  { // If we have text        
                                                 // create the element
          g2D = (Graphics2D)getGraphics();
          Font font = theApp.getWindow().getCurrentFont();
          tempElement = new Element.Text(
            font,                                    // The font
            text,                                    // The text
            start,                                   // Position of the  text
            theApp.getWindow().getElementColor(),    // The text color
            new java.awt.font.TextLayout(text, font, // The bounding rectangle
            g2D.getFontRenderContext()).getBounds().getBounds()
                                         );

          if(tempElement != null) {                  // If we created one
            theApp.getModel().add(tempElement);      // add it to the model
            tempElement = null;                      // and reset the field
          }
          g2D.dispose();                             // Release context resources
          g2D = null;
          start = null;
        }
      }
    }

    // Handle mouse moves
    public void mouseMoved(MouseEvent e) {
      Point currentCursor = e.getPoint();  // Get current cursor position

      for(Element element : theApp.getModel())  {  // Go through the list
        if(element.getBounds().contains(currentCursor)) { // Under the cursor?
          if(element==highlightElement) {          // If it's already highlighted
            return;                                // we are done
          }
          // The element under the cursor is not highlighted
          g2D = (Graphics2D)getGraphics();         // Get graphics context
 
          // Un highlight any old highlighted element
          if(highlightElement!=null)   {           // If an element is highlighted
            highlightElement.setHighlighted(false);// un-highlight it and
            highlightElement.draw(g2D);            // draw it normal color
          }

          element.setHighlighted(true);           // Set highlight for new element
          highlightElement = element;             // Store new highlighted element
          element.draw(g2D);                      // Draw it highlighted 
          g2D.dispose();                          // Release graphic context resources
          g2D = null;
          return;
        }
      }

      // Here there is no element under the cursor so...
      if(highlightElement!=null)   {            // If an element is highlighted
        g2D = (Graphics2D)getGraphics();        // Get graphics context
        highlightElement.setHighlighted(false); // ...turn off highlighting
        highlightElement.draw(g2D);             // Redraw the element
        highlightElement = null;                // No element highlighted
        g2D.dispose();                          // Release graphic context resources
        g2D = null;
      }
    }

    private Element createElement(Point start, Point end) {
      switch(theApp.getWindow().getElementType()) {
        case LINE:
          return new Element.Line(start, end, theApp.getWindow().getElementColor());   

        case RECTANGLE:
          return new Element.Rectangle(start, end, theApp.getWindow().getElementColor());

        case CIRCLE:
          return new Element.Circle(start, end, theApp.getWindow().getElementColor());

        case CURVE:
          return new Element.Curve(start, end, theApp.getWindow().getElementColor());

        default:
          assert false;                     // We should never get to here
       }
       return null;
    }

    private Point start;                     // Stores cursor position on press
    private Point last;                      // Stores cursor position on drag
    private Element tempElement;             // Stores a temporary element
    private boolean button1Down = false;     // Flag for button 1 state
    private Graphics2D g2D;                  // Temporary graphics context
  }
}