/****************************************************************/ /* Written by Janette Duvall Copyright (c) 1998 */ /* */ /* this is just an example of easy animation */ /* It's easy because */ /* it doesn't double buffer */ /* it is not object oriented */ /* it is just one shape on the screen at a time */ /* */ /* It does show how to center things and calculate where */ /* a screen position. It has some really hokey work */ /* arounds for parts of java I'm still chasing. */ /* */ /* I hate these boxes. They are so ugly but they do intro */ /* duce what we do and make it obvious you don't want to */ /* read this. */ /* */ /****************************************************************/ import java.awt.Graphics; import java.awt.Color; import java.awt.Font; import java.awt.FontMetrics; public class GoOval extends java.applet.Applet implements Runnable { Thread myThread; int width, height; int xPos, yPos; Color color; int pass; // the font stuff FontMetrics fm; Font myfont; int margin; public void init() { color = Color.blue; width = 1; height = 50; xPos = 0; yPos = 0; pass = 1; // retrieve some font info so we don't run into the message myfont = new Font("Courier", Font.PLAIN, 12); fm = getFontMetrics(myfont); margin = 20 + fm.getHeight(); } public void start() { if ( myThread == null ) { myThread = new Thread(this); myThread.start(); } } public void run() { // set the variables that just work here int deltaX = 3; // needs to be bigger than 2 to escape int deltaY = 4; // now we loop while (true) { // if we run off the screen then go back small circles if ( ( height >= (size().height - margin) ) || width >= size().width ) { width = 1; height = 1; if ( ++pass > 5 ) { pass = 1; height = 50; color = nextColor(color); } else if ( pass == 3 ) { xPos = size().width / 2; yPos = ( size().height - margin ) / 2; } } // find the center according to the circle // pass 5 we move it around by changing the x and y switch (pass) { case 1: xPos = (size().width - ++width) / 2; yPos = (size().height - height - margin) / 2; break; case 3: // increment the width and height first width ++; height ++; // if we have hit a side BOUNCE if ( deltaX > 0 ) { if ( xPos + width > size().width ) deltaX = - deltaX; } else // we are less than zero { if ( xPos <= 0 ) deltaX = - deltaX; } if ( deltaY > 0 ) { if ( yPos + height > size().height - margin ) deltaY = - deltaY; } else { if ( yPos <= 0 ) deltaY = - deltaY; } xPos += deltaX; yPos += deltaY; break; default: xPos = (size().width - ++width) / 2; yPos = (size().height - ++height - margin) / 2; break; } // call the paint to show the picture repaint(); // now we sleep so the user can admire our work try { Thread.sleep(500); } catch(InterruptedException e) { System.out.println( " exception caught " + e); } } } public void stop() { if ( myThread != null ) { myThread.stop(); myThread = null; } } public void paint(Graphics g) { int stepSize = 8; // set the color to our saved color g.setColor( color ); // draw the oval switch ( pass ) { case 1: // the assignment really was just one dimensional growth g.drawString("Here is the assignment", 20, ( size().height - 20) ); g.fillOval( xPos, yPos, width, height ); break; case 2: // to show I can really do something I am doing 2-D growth g.drawString("I'm scoring brownie points here", 20, ( size().height - 20) ); g.fillOval( xPos, yPos, width, height ); break; case 5: // But really! one is boring so let's spice it up g.drawString("Look at this bulls eye", 20, ( size().height - 20) ); for ( int i = width; i >=0; i -= stepSize ) { // this works because height = width ( circle ) right now g.fillOval( xPos + (width - i)/2, yPos + (height - i)/2, i, i ); // change the color for the next circle if ( g.getColor() == color ) g.setColor( Color.white ); else g.setColor( color ); } break; case 4: // look at the cool 3-D on this bug! g.drawString("You gotta see my COOL bug", 20, ( size().height - 20) ); g.fillOval( xPos, yPos, width, height ); for ( int i = width - 8; i >=0; i -= stepSize ) { g.setColor( Color.white); g.fillOval( xPos, yPos, i, i ); g.setColor( color ); g.fillOval( xPos+stepSize/4, yPos+stepSize/4, i-stepSize/2, i-stepSize/2 ); } break; case 3: // This is the version that ' does everything ' // first we need to center the string and all that stuff String str = "Here is my eternal admiration version"; int strLen = fm.stringWidth(str); switch ( strLen / size().width ) { case 1: // the window is too small so make 2 lines // divide the string in half str = "Here is my eternal"; String str2 = "admiration version"; // Now do second line strLen = fm.stringWidth( str2 ); int xline2 = (size().width - strLen)/2; g.drawString( str2, xline2, size().height - 4 ); // We'll fall through to do the first line case 0: // center 1st line of text strLen = fm.stringWidth( str ); int xline1 = (size().width - strLen)/2; g.drawString(str, xline1, (size().height - 20) ); break; default: g.drawString("Grow Window", 10, (size().height - 20) ); break; } // switch for draw string // now it's time to draw the ball and watch it bounce int thisHeight = height; int thisWidth = width; // check the edge and squish the ball if ( xPos + width > size().width) thisWidth = width - (size().width - xPos); if ( yPos + height > size().height - margin ) thisHeight = height - (size().height - yPos); g.fillOval( xPos, yPos, width, height ); break; } // end of the switch } Color nextColor( Color thisColor ) { if ( thisColor == Color.blue ) thisColor = Color.red; else if ( thisColor == Color.red ) thisColor = Color.yellow; else if ( thisColor == Color.yellow ) thisColor = Color.orange; else if ( thisColor == Color.orange ) thisColor = Color.green; else if ( thisColor == Color.green ) thisColor = Color.pink; else if ( thisColor == Color.pink ) thisColor = Color.gray; else if ( thisColor == Color.gray ) thisColor = Color.cyan; else if ( thisColor == Color.cyan ) thisColor = Color.magenta; else thisColor = Color.blue; return (thisColor); } }