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209 lines
7.5 KiB
Java
209 lines
7.5 KiB
Java
EventDemo
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import java.awt.*;
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import java.awt.event.*;
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import java.applet.*;
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public class EventDemo extends Applet implements ActionListener, ItemListener, AdjustmentListener {
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// An applet that displays a shape and some text. Color of
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// shape and text is controlled by a vertical scroll bar.
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// Color of background is controlled by a horizontal scroll bar.
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// Text to be displayed can be entered in a TextField.
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// Shape to be displayed can be selected from a Choice componnet.
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// Bright or dim colors can be selected using a Chackbox.
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// The display area is implemented as a ColorCanvas; the
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// ColorCanvas class is defined later in this file.
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ColorCanvas display; // display area
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Choice shapeChoice; // for selecting which shape to display
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Checkbox brightColors;// for selecting bright or dim colors
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TextField text; // for entering the text to be displayed
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Scrollbar hScroll; // horizontal scroll bar
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Scrollbar vScroll; // vertical scroll bar
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public void init() { // set up contents of applet
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setBackground(Color.red); // background for applet
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Panel displayPanel = new Panel(); // to hold display and scroll bars
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displayPanel.setLayout(new BorderLayout());
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display = new ColorCanvas("Hello World",ColorCanvas.RECT);
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displayPanel.add(display, BorderLayout.CENTER);
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hScroll = new Scrollbar(Scrollbar.HORIZONTAL,50,1,0,100);
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displayPanel.add(hScroll, BorderLayout.SOUTH);
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vScroll = new Scrollbar(Scrollbar.VERTICAL,0,1,0,100);
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displayPanel.add(vScroll, BorderLayout.EAST);
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Panel topPanel = new Panel(); // for controls
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topPanel.setBackground(Color.white);
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topPanel.setLayout(new GridLayout(1,3,5,5));
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shapeChoice = new Choice();
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shapeChoice.add("Rectangle");
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shapeChoice.add("Oval");
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shapeChoice.add("RoundRect");
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topPanel.add(shapeChoice);
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brightColors = new Checkbox("Bright Colors");
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topPanel.add(brightColors);
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text = new TextField("Hello World");
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topPanel.add(text);
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setLayout(new BorderLayout(1,1)); // applies to applet itself
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add("Center", displayPanel);
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add("North", topPanel);
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setDisplayColors(); // defined below
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text.addActionListener(this); // set this applet to listen for events
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hScroll.addAdjustmentListener(this);
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vScroll.addAdjustmentListener(this);
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shapeChoice.addItemListener(this);
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brightColors.addItemListener(this);
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} // end of init()
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public Insets getInsets() { // leave border around edge of applet
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return new Insets(1,1,1,1);
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}
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void setDisplayColors() {
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// Set foreground and background colors of display,
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// depending on values of scroll bars and
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// on state of the checkbox. (Colors are made
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// using Color.getHSBColor(float,float,float),
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// which creates a color given a hue, a satuation,
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// and a brightness. The parameters must be between
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// 0.0 and 1.0.)
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float backgroundBrightness = hScroll.getValue() / 100.0F;
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float foregroundHue = vScroll.getValue() / 100.0F;
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float saturation = 1.0F;
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float brightness;
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if (brightColors.getState())
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brightness = 1.0F;
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else
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brightness = 0.6F;
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Color backgroundColor =
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Color.getHSBColor(0.0F,0.0F,backgroundBrightness); // A grayscale color
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Color foregroundColor =
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Color.getHSBColor(foregroundHue,1.0F,brightness);
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display.setBackground(backgroundColor);
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display.setForeground(foregroundColor);
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} // end of setDisplayColors()
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public void itemStateChanged(ItemEvent evt) { // from the ItemListener interface
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// An item event could have been generated by shapeChoice or brightColors.
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Object source = evt.getSource(); // object that generated the event
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if (source == shapeChoice) {
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// user has selected a shape; set the shape
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// that is shown in the display
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switch (shapeChoice.getSelectedIndex()) {
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case 0:
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display.setShape(ColorCanvas.RECT);
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break;
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case 1:
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display.setShape(ColorCanvas.OVAL);
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break;
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case 2:
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display.setShape(ColorCanvas.ROUNDED);
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break;
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}
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}
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else if (source == brightColors) {
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// user has changed the state of the checkbox;
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// reset the colors for the display,
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// and ask the system to redraw the display
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setDisplayColors();
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display.repaint();
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}
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} // end itemStateChanged()
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public void actionPerformed(ActionEvent evt) { // from the ActionListener interface
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// This can only be generated by the TextField, because the user has pressed
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// return. Set the display text to the contents of the TextField, text.
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display.setText(text.getText());
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} // end of actionPerformed()
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public void adjustmentValueChanged(AdjustmentEvent evt) {
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// User has changed the value of one of the scroll bars.
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// In thisprogram, it doesn't matter which one. Respond
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// by setting the display colors.
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setDisplayColors();
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display.repaint();
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} // end of adjustmentValueChanged()
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} // end of class Event Demo
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class ColorCanvas extends Canvas {
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// Display a shape and some text.
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// The canvas's setForeground() and setBackground()
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// methods should be called to set the colors to
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// be used for drawing.
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private String text; // text to be displayed
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private int shape; // code for shape to be displayed;
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private Font font; // used for displaying the text
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public final static int RECT = 0; // shape code for a rectangle
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public final static int OVAL = 1; // shape code for an oval
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public final static int ROUNDED = 2; // shape code for an round rect
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public ColorCanvas(String text, int shape) {
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this.text = text;
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this.shape = shape;
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font = new Font("Serif",Font.PLAIN,18);
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}
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public void setText(String text) {
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this.text = text;
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repaint();
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}
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public void setShape(int shape) {
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this.shape = shape;
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repaint();
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}
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public void paint(Graphics g) {
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int width = getSize().width; // get size of canvas
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int height = getSize().height;
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int shape_left = width / 9; // compute position and size of shape
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int shape_top = height / 3;
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int shape_width = (7*width / 9);
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int shape_height = (5*height / 9);
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switch (shape) { // draw the shape
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case RECT:
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g.fillRect(shape_left,shape_top,shape_width,shape_height);
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break;
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case OVAL:
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g.fillOval(shape_left,shape_top,shape_width,shape_height);
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break;
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case ROUNDED:
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g.fillRoundRect(shape_left,shape_top,shape_width,shape_height,24,24);
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break;
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}
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g.setFont(font);
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g.drawString(text,width/9,2*height/9); // draw the text
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}
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} // end of class ColorCanvas
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