import java.awt.*; import java.awt.event.*; import javax.swing.*; import java.util.ArrayList; /** * This panel lets the user place colored rectangles on a canvas * by clicking the canvas. The color of the rectangle is given * by a color palette that lies along the bottom of the applet. * Alt-clicking (or clicking with middle mouse button) on a rectangle * will delete it. Shift-clicking a rectangle will move it out in * front of all the other rectangles. The user can right-click-and-drag * to move the rectangles around. The rectangles are restricted so that * they cannot be moved entirely off the canvas. * * The main point of this class is to demonstrate the use of an * ArrayList. * * This class contains a main() routine so that it can be run as * a standalone application. The main routine simply opens a * window that uses a SimpleDrawRects panel as its content pane. * * This program depends on RainbowPalette.java. */ public class SimpleDrawRects extends JPanel { /** * When this class is run as an application, this main() routine opens * a frame that sues a SimpleDrawRects panel as its content pane. */ public static void main(String[] args) { JFrame window = new JFrame("SimpleDrawRects"); SimpleDrawRects content = new SimpleDrawRects(); window.setContentPane(content); window.pack(); window.setLocation(100,100); window.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE ); window.setResizable(false); window.setVisible(true); } /** * A palette of colors that appears at the bottom of the applet. The * RainbowPalette class is non-standard, and is defined in a separate file.. */ private RainbowPalette colorInput; /** * Constructor sets up the panel, with drawing area and palette. */ public SimpleDrawRects() { setBackground(Color.GRAY); setBorder(BorderFactory.createLineBorder(Color.GRAY,2)); setLayout(new BorderLayout(2,2)); RectPanel canvas = new RectPanel(); colorInput = new RainbowPalette(); add(canvas, BorderLayout.CENTER); add(colorInput, BorderLayout.SOUTH); } //-------------------------- Nested classes ------------------- /** * An object of type ColoredRect holds the data for one colored rectangle. */ private static class ColoredRect { int x, y, width, height; // Location and size of rect. Color color; // Color of rect. } /** * This class defined the drawing surface that is used for displaying * the rectangles. It also listens for mouse events on itself and * responds to them. The user adds a rectangle by (left) clicking on * the panel, can delete a rectangle by Alt-clicking, can move a * rectangle to the front by shift-clicking it, and can drag a rectangle * by right-clicking it. */ private class RectPanel extends JPanel implements MouseListener, MouseMotionListener { /** * The colored rectangles are represented by objects of type ColoredRect * that are stored in this ArrayList. */ private ArrayList rects; /* Variables for implementing dragging. */ private boolean dragging; // This is true when dragging is in progress. private ColoredRect dragRect; // The rect that is being dragged. private int offsetx, offsety; // The distance from the upper left corner of // the dragRect to the point where the user // clicked the rect. This offset is maintained \ // as the rect is dragged. /** * Constructor creates an ArrayList to hold the rectangle data and * sets up mouse listening. Background color is set to white, * and preferred size to 262-by-262. */ RectPanel() { setBackground(Color.WHITE); setPreferredSize(new Dimension(262,262)); rects = new ArrayList(); addMouseListener(this); addMouseMotionListener(this); } /** * Find the topmost rect that contains the point (x,y). Return null * if no rect contains that point. The rects in the ArrayList are * considered in reverse order so that if one lies on top of another, * the one on top is seen first and is returned. */ ColoredRect findRect(int x, int y) { for (int i = rects.size() - 1; i >= 0; i--) { ColoredRect rect = (ColoredRect)rects.get(i); if ( x >= rect.x && x < rect.x + rect.width && y >= rect.y && y < rect.y + rect.height ) return rect; // (x,y) is inside this rect. } return null; } /** * If rect != null, move it out in front of the other rects by moving * it to the last position in the ArrayList. */ void bringToFront(ColoredRect rect) { if (rect != null) { rects.remove(rect); // Remove rect from current position. rects.add(rect); // Put rect in the ArrayList in last position. repaint(); } } /** * If rect != null, remove it from the ArrayList and from the screen. */ void deleteRect(ColoredRect rect) { if (rect != null) { rects.remove(rect); repaint(); } } /** * Draw all the rects in the ArrayList. NOTE: A black border is drawn * around each rectangle. */ public void paintComponent(Graphics g) { super.paintComponent(g); // Fills with background color, white. for (int i = 0; i < rects.size(); i++) { ColoredRect rect = (ColoredRect)rects.get(i); g.setColor(rect.color); g.fillRect(rect.x, rect.y, rect.width, rect.height); g.setColor(Color.BLACK); g.drawRect(rect.x, rect.y, rect.width - 1, rect.height - 1); } } /** * Responds when the user clicks on the panel. */ public void mousePressed(MouseEvent evt) { if (dragging) // If dragging is already in progress, just return. return; if (evt.isMetaDown() || evt.isControlDown()) { // User right-clicked (or Command-clicked or control-clicked). // Start dragging the rect that the user clicked (if any). dragRect = findRect( evt.getX(), evt.getY() ); if (dragRect != null) { dragging = true; // Begin a drag operation. offsetx = evt.getX() - dragRect.x; offsety = evt.getY() - dragRect.y; } } else if (evt.isShiftDown()) { // User shift-clicked. More the rect that the user // clicked (if any) to the front. Note that findRect() // might return null, but bringToFront() accounts for that. bringToFront( findRect( evt.getX(), evt.getY() ) ); } else if (evt.isAltDown()) { // User alt-clicked or middle-clicked. Delete the rect // that the user clicked (if any). deleteRect( findRect( evt.getX(), evt.getY() ) ); } else { // This is a simple left-click. Make a new // rectangle and add it to the canvas. Every rectangle is // 60 pixels wide and 30 pixels tall. The point where the // user clicked is at the center of the rectangle. It's // color is the selected color in the colorInput palette. ColoredRect rect = new ColoredRect(); rect.x = evt.getX() - 30; rect.y = evt.getY() - 15; rect.width = 60; rect.height = 30; rect.color = colorInput.getSelectedColor(); rects.add(rect); repaint(); } } // end mousePressed() /** * Called when the user releases the mouse button. * End the current drag operation, if one is in progress. */ public void mouseReleased(MouseEvent evt) { if (dragging == false) return; dragRect = null; dragging = false; } /** * Called when the user drags the mouse. Continue the drag operation if * one is in progress. Move the rect that is being dragged to the current * mouse position. But clamp it so that it can't be more than halfway * off the screen. */ public void mouseDragged(MouseEvent evt) { if (dragging == false) return; dragRect.x = evt.getX() - offsetx; // Get new position of rect. dragRect.y = evt.getY() - offsety; /* Clamp (x,y) to a permitted range, as described above. */ if (dragRect.x < - dragRect.width / 2) dragRect.x = - dragRect.width / 2; else if (dragRect.x + dragRect.width/2 > getWidth()) dragRect.x = getWidth() - dragRect.width / 2; if (dragRect.y < - dragRect.height / 2) dragRect.y = - dragRect.height / 2; else if (dragRect.y + dragRect.height/2 > getHeight()) dragRect.y = getHeight() - dragRect.height / 2; /* Redraw the panel, with the rect in its new position. */ repaint(); } // end mouseDragged() public void mouseClicked(MouseEvent evt) { } public void mouseEntered(MouseEvent evt) { } public void mouseExited(MouseEvent evt) { } public void mouseMoved(MouseEvent evt) { } } // end nested class RectPanel } // end class SimpleDrawRects