the acm java libraries - eastern illinois universitycfnkv/papers/tutorial-ccsc-mw2009.pdf · the...

The ACM Java Libraries

Andrew MertzWilliam Slough

Nancy Van Cleave

Mathematics and Computer Science DepartmentEastern Illinois University

October 10, 2009

CCSC:MW 2009, Saint Xavier University

Introduction

NetBeans and Java

The ACM Java Task Force (JTF) Libraries

Placing applets on web pages

How to learn about the ACM libraries:

This workshop

Textbooks

ACM Java Task Force Tutorial

Javadoc documentation


Textbook support for ACM libraries


ACM library galleries

EIU student work:http://www.eiu.edu/~mathcs/http

JTF demo gallery:http://jtf.acm.org/demos/index.html


http://www.eiu.edu/~mathcs/http

http://jtf.acm.org/demos/index.html

Installing the necessary software: NetBeans

www.netbeans.org/downloads/

Click on the Download NetBeans IDE Button

Run install


www.netbeans.org/downloads/

Installating the necessary software: ACM Java libraries

jtf.acm.org — obtain acm.zip

Create acmLibrary project in NetBeansFile → New Project

Within the Categories panel, select Java

Within the Projects, select Java Class Library

Click Next to proceed

For the project name, enter acmLibrary

Click on the Finish button

Move the acm.zip file to the acmLibrary/src directory

Unpack the zip file (into the acmLibrary/src directory)

Right–click on the acmLibrary project in NetBeans, andselect close (don’t shut down NetBeans)


jtf.acm.org

The Program class diagram

JApplet

Program

GraphicsProgram ConsoleProgram DialogProgram


A “Hello, world!” program

Create HelloProgram project

File → New Project

Within the Categories panel, select Java

Within the Projects, select Java Class Library

Click Next to proceed

For the project name, enter HelloProgram

Click on the Finish button

Make the acmLibrary available to this project

Right–click on Libraries, select Add Project

In the Add Project window choose acmLibrary

Click on Add Project / Jar files


Create a new Java program

Right–click on Source Packages, then select New → Other

Select Java from the categories

The file type to select is Empty Java File

Click Next, then replace the suggested class name NewEmptywith HelloProgram

Click the Finish button


A “Hello, world!” program: in a console window

import acm.graphics.*;import acm.program.*;

public class HelloProgram extends ConsoleProgram {public void run() {println("Hello, world!");

}}

Modifications:

Add a second line below the first with your name

Add a third line with your organization


A “Hello, world!” program: with dialog boxes


public class HelloProgram extends DialogProgram {public void run() {println("Hello, world!");println("Name here");println("Organization here");

}}

Modifications:

Change ConsoleProgram to DialogProgram

Change first two println statements to print statementswith \n to produce a single dialog window


A “Hello, world!” program: in a graphics window


public class HelloProgram extends GraphicsProgram {public void run() {add(new GLabel("Hello, world!", 100, 75));

}}

Modifications:

Move the output line down

Add lines for your name and organization


Placing applets on a web site

index.html

HelloProgram.html


Add2Quantities

import acm.program.*;

public class Add2Quantities extends ConsoleProgram {public void run() {

println("This program adds two values:");int a = readInt("Enter a: ");int b = readInt("Enter b: ");int sum = a + b;println("The sum is " + sum + ".");

}}

Modifications:

Convert to a DialogProgram

Different data types:int → double, readInt → readDoubleint → String, readInt → readLine


The acm.graphics model

The acm.graphics package uses a collage model in which youcreate an image by adding various objects to a canvas.

This is similar to a felt board that serves as a backdrop for coloredshapes that stick to the felt surface.

Note that newer objects can obscure those added earlier. Thislayering arrangement is called the stacking order or z-order.


The Java coordinate system

All distances and coordinates in the graphics library are measuredin pixels.

Coordinates in the graphics model are specified relative to theorigin in the upper left corner of the screen.

Coordinate values are specified as a pair of floating-point values(x, y) where the values for x increase as you move rightward acrossthe screen and the values for y increase as you move downward.


Partial class diagram for acm.graphics

java.awt.Container

GCanvas

GObject GCompound

GLabel

GRectGOval

GLine

GPolygon

GImageGArc

GTurtle


The GCanvas class

The GCanvas class represents the background canvas, a virtual feltboard.

When you use the acm.graphics package, you create pictures byadding various GObjects to a GCanvas.

For simple applications, you will not need to work with an explicitGCanvas object.

Programs that extend GraphicsProgram, automatically creates aGCanvas and resizes it so that it fills the program window.

Most of the methods defined for the GCanvas class are alsoavailable in a GraphicsProgram, thanks to delegation.


Methods in the GCanvas class

add(object) Adds the object to the canvas at the frontof the stack

add(object, x, y) Moves the object to (x, y) and then adds itto the canvas

remove(object) Removes the object from the canvas

removeAll() Removes all objects from the canvas

getElementAt(x, y) Returns the front most object at (x, y), ornull if none

getWidth() Returns the width in pixels of the canvas

getHeight() Returns the height in pixels of the canvas

setBackground(c) Sets the background color of the canvas


Methods in the GCanvas class

The following methods are available in GraphicsProgram only:

pause(milliseconds) Pauses the program for the specified time

waitForClick() Suspends the program until the user clicksthe mouse


Two forms of the add method

The add method comes in two forms.

add(object);

adds the object at the location currently stored in its internalstructure. You use this form when you have already set thecoordinates of the object, usually done when it was created.

The second form:

add(object, x, y);

which moves the object to the point (x, y) and then adds it there.This form is useful when you need to determine some property ofthe object before you know where to put it. If, for example, youwant to center a GLabel, you must first create it and then use itssize to determine its location.


Centering text


public class CenteredLabel extends GraphicsProgram {

public void run() {GLabel label = new GLabel("I am centered");add(label,

(getWidth() - label.getWidth()) / 2,(getHeight() - label.getHeight()) / 2);

}}


Methods common to GObjects

setLocation(x, y) Resets the location of the object to the specifiedpoint

move(dx, dy) Moves the object dx and dy pixels

movePolar(r, theta) Moves the object r pixels in the direction theta

getX() Returns the x coordinate of the object

getY() Returns the y coordinate of the object

getWidth() Returns the horizontal width of the object in pixels

getHeight() Returns the vertical height of the object in pixels

contains(x, y) Returns true if the object contains the specifiedpoint


Methods common to GObjects (continued)

setColor(c) Sets the color of the object

getColor() Returns the color currently assigned to the object

setVisible(flag) Sets visibility (false = invisible, true = visible)

isVisible() Returns true if the object is visible

sendToFront() Sends the object to the front of the stacking order

sendToBack() Sends the object to the back of the stacking order

sendForward() Sends the object forward one position in the stack-ing order

sendBackward() Sends the object backward one position in the stack-ing order


Sharing behavior through interfaces

There are some methods that apply to some GObject subclasses,but not others.

For example, you can call setFilled on GOvals or GRects.However, it does not make sense to call setFilled on a GLine.

In the acm.graphics package, there are three interfaces thatdefine methods for certain GObject subclasses:

GFillable

GResizable

GScalable


acm.graphics interfaces

GFillable (GArc, GOval, GPolygon, GRect)

setFilled(flag) Sets the fill state (false = outlined, true = filled)

isFilled() Returns the fill state

setFillColor(c) Sets the color used to fill the interior

getFillColor() Returns the fill color

GResizable (GImage, GOval, GRect)

setSize(width, height) Sets the dimensions of the object

setBounds(x, y, width, height) Sets the location and dimensions

GScalable (GArc, GCompound, GLine, GImage, GOval, GPolygon, GRect)

scale(sf) Scales both dimensions of the object by sf

scale(sx, sy) Scales the object by sx horizontally and sy vertically


Making a face


Exercise: Drawing a house


Encapsulated coordinates

The acm.graphics package defines three classes:

GPoint

GDimension

GRectangle

These combine geometric information about coordinates and sizesinto a single object.

GPoint encapsulates the x and y coordinates of a point

GDimension encapsulates width and height values that specifyan object’s size

GRectangle encapsulates all four of these values by specifyingboth the origin and size of a rectangle


Gathering input

Event driven model

Most of the time the program is waiting for something(an event) to occur

When an event occurs, the program responds appropriately

eventRespond to

an event

Event occursResponsecomplete

Wait for


The Java event model

In Java, you indicate what events you wish to respond to bydesignating some object as a listener for that event.

When the event occurs, a message is sent to the listener, whichtriggers the appropriate response.


Events the ACM library facilitates

Keyboard events: key presses and key releases. Identifies the keyand whether shift, control and/or alt are also pressed.

Mouse events: motion, button presses and button releases.Motion events tell where the position of the mouse is now, how farit moved and if any buttons are pressed.

Action events: GUI buttons pressed and other user-interfaceactions.


A simple event-driven program

import acm.graphics.*;import acm.program.*;import java.awt.event.*;

public class Dots extends GraphicsProgram {public void init() {addMouseListeners();

}

public void mouseClicked(MouseEvent e) {GOval dot = new GOval(DOT_SIZE, DOT_SIZE);dot.setFilled(true);add(dot,

e.getX() - DOT_SIZE/2,e.getY() - DOT_SIZE/2);

}private static final double DOT_SIZE = 20;

}


How it works

The addMouseListeners method of acm.program.Programenables mouse-event reporting.

Clicking the mouse generates a MouseEvent.

That event triggers a call to the mouseClicked method.

The program responds by adding a new GOval to the canvas.

Subsequent mouse clicks are treated in exactly the same way.


acm.util.RandomGenerator

The RandomGenerator class can generate pseudorandom integers,doubles, booleans, and colors.

Methods provided include:

nextBoolean(double p) Returns a random boolean valuewith the specified probability

nextColor() Returns a random opaque Color

nextDouble(double low, double high) Returns a random real numberin the specified range

nextInt(int low, int high) Returns a random integer in thespecified range


The GMath class

The GMath class has the following static methods:

sinDegrees(theta) Returns the sine of theta, measured in degrees

cosDegrees(theta) Returns the cosine of theta

tanDegrees(theta) Returns the tangent of theta

toRadians(degrees) Converts an angle from degrees to radians

toDegrees(radians) Converts an angle from radians to degrees

distance(x, y) Returns the distance from the origin to (x, y)

distance(x0, y0, x1, y1) Returns the distance from (x0, y0) to (x1, y1)

round(x) Returns the closest int to x

angle(x, y) Returns the angle in degrees formed by the lineconnecting the origin to the point (x, y)

angle(x0, y0, x1, y1) Returns the angle in degrees formed by the lineconnecting the points (x0, y0) and (x1, y1)


Adding a touch of color

public class Dots extends GraphicsProgram {public void init() {addMouseListeners();

}

public void mouseClicked(MouseEvent e) {GOval dot = new GOval(DOT_SIZE, DOT_SIZE);dot.setFilled(true);dot.setColor(rand.nextColor());add(dot,

e.getX() - DOT_SIZE/2,e.getY() - DOT_SIZE/2);

}

private static final double DOT_SIZE = 20;private static RandomGenerator rand =

new RandomGenerator();}


Responding to mouse events

1. Define an init method that calls addMouseListeners.

2. Write new definitions of any listener methods you need.

The most common mouse events and associated listener methods:

Method When invoked

mouseClicked(e) when the user clicks the mouse

mousePressed(e) when the mouse button is pressed

mouseReleased(e) when the mouse button is released

mouseMoved(e) when the user moves the mouse

mouseDragged(e) when the mouse is dragged with thebutton down

The parameter e is a MouseEvent object, which provides moredata about the event, such as the location of the mouse.


Lines

public class Lines extends GraphicsProgram {private GPoint lastPoint;

public void init() {lastPoint = new GPoint(getWidth()/2,getHeight()/2);addMouseListeners();

}

public void mouseClicked(MouseEvent e){add(new GLine(lastPoint.getX(), lastPoint.getY(),

e.getX(), e.getY()));lastPoint.setLocation(e.getX(), e.getY());

}}


DragLines

public class DragLines extends GraphicsProgram {public void init() {addMouseListeners();

}

public void mousePressed(MouseEvent e) {line = new GLine(e.getX(), e.getY(),

e.getX(), e.getY());add(line);

}

public void mouseDragged(MouseEvent e) {line.setEndPoint(e.getX(), e.getY());

}

private GLine line;}


Exercise: Dragging dots

Write a program that displays randomly colored dots whose size isbased on the amount the mouse is dragged.


DragObjects

public class DragObjects extends GraphicsProgram {public void init() {GRect rect = new GRect(100, 100, 150, 100);rect.setFilled(true);rect.setColor(Color.RED);add(rect);GOval oval = new GOval(300, 115, 100, 70);oval.setFilled(true);oval.setColor(Color.GREEN);add(oval);addMouseListeners();

}

public void mousePressed(MouseEvent e) {last = new GPoint(e.getPoint());gobj = getElementAt(last);

}

. . . continues on next slideCCSC:MW 2009, Saint Xavier University

DragObjects

public void mouseDragged(MouseEvent e) {if(gobj != null){gobj.move(e.getX() - last.getX(),

e.getY() - last.getY());last = new GPoint(e.getPoint());

}}

public void mouseClicked(MouseEvent e) {if (gobj != null) gobj.sendToFront();

}

private GObject gobj; /* The object being dragged */private GPoint last; /* The last mouse position */

}


Mouse listeners

The ACM Java Libraries simplifies the JFC approach to mouselisteners.

To maximize efficiency, Java defines two distinct listener interfaces.

The MouseListener interface responds to mouse events thathappen relatively infrequently, such as clicking the mouse button.

The MouseMotionListener interface responds to the much morerapid-fire events that occur when you move or drag the mouse.


GImage

The ACM Library makes displaying images very easy and you canstill use all of the other features of Swing.

import acm.graphics.*;import acm.program.*;import javax.swing.*;

public class ShowPicture extends GraphicsProgram {

public void run() {JFileChooser chooser = new JFileChooser();chooser.showOpenDialog(null);String filename = chooser.getSelectedFile().getPath();GImage image = new GImage(filename);setSize((int) image.getWidth(),

(int) image.getHeight());add(image);

}}


Animation

The pause method allows for simple animations.

double windowWidth = getWidth();double windowHeight = getHeight();

// calculate ball size and stepsdouble size = 0.06 * windowWidth;double dx = size / 8.0;double dy = size / 8.0;

. . . continues on next slide


Animation

GOval ball = new GOval(windowWidth/2.0,

windowHeight/2.0, size, size);

ball.setColor(Color.RED);

ball.setFilled(true); ball.setFillColor(Color.ORANGE);

add(ball);

int count = 0;

while (count < BOUNCES) {

if ((ball.getX() + size > windowWidth) ||

(ball.getX() <= 0.0)) {

dx = -dx;

count++;

}

if ((ball.getY() + size > windowHeight) ||

(ball.getY() <= 0.0)) {

dy = -dy;

count++;

}

ball.move(dx, dy);

pause(PAUSE_TIME);

}


Animation

Modify the bouncing ball demo to bounce an image around thescreen.


GPolygon

The GPolygon class can be used to represent closed polygonalshapes.

Initially, a GPolygon has no vertices. Vertices are added via thefollowing methods:

addArc(arcWidth, arcHeight,

start, sweep)

Adds a series of edges to simulatean arc

addEdge(dx, dy) Adds an edge using the given dis-placement from the last vertex

addPolarEdge(r, theta) Adds an edge using the given polarcoordinates

addVertex(x, y) Adds a vertex relative to the polygonorigin

The coordinates of vertices are expressed with respect to the originof the polygon (its location on a canvas).

GPolygons are resizable.


Drawing a diamond

public class Diamond extends GraphicsProgram {

public void run() {GPolygon diamond = new GPolygon();diamond.addVertex(-30, 0);diamond.addVertex(0, 40);diamond.addVertex(30, 0);diamond.addVertex(0, -40);diamond.setFilled(true);diamond.setFillColor(Color.BLUE);add(diamond, getWidth()/2, getHeight()/2);

}}


Exercise: Diamonds

Create a program that draws randomly sized and colored diamondswhere clicked.


GCompound

GCompound objects are like canvases, you can add other GObjectsto them.

Some of GCompound’s methods:

add(gobj) Adds an object to this GCompound

add(gobj, x, y) Adds an object at the point (x, y)

markAsComplete() Makes it illegal to add or remove elements

remove(gobj) Removes an object

removeAll() Removes all objects

The coordinates of vertices are expressed with respect to the originof the compound object (its location on a canvas).

GCompound objects are resizable.


Make a face as a compound object


Exercise: Draw a house as a compound object


Turtles

The GTurtle class enables graphics using a LOGO-like model of aturtle moving across the screen leaving a trail.

forward(distance) Moves the turtle forward

hideTurtle() Hides the turtle

left(angle) Turns the specified number of degrees to the left

penDown() Lowers the pen

penUp() Raises the pen

right(angle) Turns the specified number of degrees to the left

setDirection(dir) Sets the direction in which the turtle is moving

setLocation(x, y) Moves to the point (x, y) without drawing a line

setSpeed(speed) Sets the speed of the turtle, 0 (slowest) and 1(fastest)

showTurtle() Makes the turtle visible


Fractals

GTurtle can be very useful for many types of graphics, especiallyfractals.

The order 0 Koch snowflake is an equilateral triangle. The order nKoch snowflake replaces each line of the order n− 1 snowflakewith the following:


Fractals


Snowflakes

public class Koch_1 extends GraphicsProgram {

private GTurtle turtle = new GTurtle();private int order = 4;private double length = 300;

public void init() {setSize(600, 600);add(turtle, (getWidth() - length) / 2,

(getHeight() - length) / 2);turtle.setSpeed(0.8);turtle.penDown();

}



Snowflakes

private void zig(int order, double length) {if (order == 0) turtle.forward(length);else {zig(order - 1, length / 3.0);turtle.left(60);zig(order - 1, length / 3.0);turtle.right(120);zig(order - 1, length / 3.0);turtle.left(60);zig(order - 1, length / 3.0);

}}



Snowflakes

public void run() {zig(order, length);turtle.right(120);zig(order, length);turtle.right(120);zig(order, length);turtle.right(120);

}}


Exercise: Fractal

Make another fractal where the order 0 case is a square and theorder n case replaces each line of the order n− 1 case with thefollowing:

Note that there are 8 segments in the production rule.


Fractals


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