The action for the world action control button. The button has three * states: CLEAR, RUNNING, and READY.
*In READY state, the button is labeled "Start the world". * The button press starts the world and changes * the state to RUNNING
*In RUNNING state, the button is labeled "Stop the world". * The world stops either when the program stops the timer, * or when the program ends the world, or when the user hits the button. * The button action changes the state to CLEAR
*In CLEAR state, the button is labeled "Clear the world". * The final state of the world with the appropriate * message is still visible. The button press clears the display and * changes the state to READY.
* * @author Viera K. Proulx * @since November 29, 2007 2007 * */ public class BigBangAction implements ActionListener{ /** *The only method we need.
*The button switches to state of the applet between three * states: CLEAR, RUNNING, and READY.
* *READY state displays a cleared Canvas. The button label indicates
* that the user can now Start the world. On activation
* it invokes the bigBang method for this world,
* with the speed given by the speed slider setting.
RUNNING state displays the running world. The button label * indicates that the user can Stop the world * if so desired. On activation of the button the currently running * world is terminated the state changes to CLEAR (see below). * It allows the user to interrupt an infinite loop * that may have been erroneously encoded in the program.
* *The change of state from RUNNING to CLEAR can also be triggered * by the program actions --- when the world ends. * *
CLEAR state displays the state of the world when the world ended.
* It contains any message the program produced in the
* endOfWorld
endOfTime
method, or it displays the * message STOP button ended the world. * *The button label indicates that the user can now Clear the
* world. On activation the Canvas panel is cleared (painted
* in light gray color) and the state is changed to READY.
*
* @param evt ignored, required by the ActionListener
* interface
*/
public void actionPerformed(ActionEvent evt){
/*
Button labels for each state:
String CLEAR = "CLEAR";
String RUNNING = "STOP ";
String READY = "START";
*/
// determine the current state of the button
currentState = bigButton.getText();
//----------------------------------------------------------------
// ignore all while the world is suspended (the applet is hidden)
if (stopped == true){}
//----------------------------------------------------------------
// process the READY state - change to RUNNING - if button pressed
else if (currentState.equals(READY)){
// start a new world, give it the canvas and button to stop the game
currentworld = getNewWorld();
currentworld.initWorld(theCanvas, bigButton);
// note that the world is running
currentState = RUNNING;
bigButton.setText(RUNNING);
// start the world
bbstart();
}
//----------------------------------------------------------------
// process the RUNNING state - change to CLEAR
// invoked by button press or endOfWorld or endOfTime
else if (currentState.equals(RUNNING)){
// print a message if world is stopped by the user's button press
// and inform the world of its demise
if (currentworld.worldExists == true){
theCanvas.drawString(new Posn(10, 20),
"STOP button ended the world");
}
// stop the timer, remove key listener, mark the world stopped
currentworld.stopWorld();
// now - change the applet so we can see that the world stopped
currentState = CLEAR;
bigButton.setText(CLEAR);
}
//---------------------------------------------------------------
// process the CLEAR state - change to READY -- if button pressed
else if (currentState.equals(CLEAR)){
// clear the canvas
redraw();
// now - change the applet to be ready for the next big bang
currentState = READY;
bigButton.setText(READY);
}
}
}
protected void signalEnd(){
currentState = CLEAR;
bigButton.setText(CLEAR);
}
/**
* Set up the applet for running the world interactions
*/
protected void bbstart(){
// set the speed for the timer
SPEED = getSpeed();
// now - change the applet so we can see that the world runs
bigButton.setText(currentState);
// give this world a Canvas and a way to notify the applet when done
currentworld.initWorld(theCanvas, this.bigButton);
// start the world
currentworld.bigBang(WIDTH, HEIGHT, SPEED);
// make the Canvas visible and responsive to key events
theCanvas.addNotify();
theCanvas.requestFocusInWindow();
}
/**
* The applet action on return from suspension and after init.
*/
public void start(){
stopped = false;
currentworld.worldStopped = false;
}
/**
* Process applet suspension:
* mark it stopped.
* If the world is currently running, end the world,
* stop the timer and remove the key listener
*/
public void stop(){
//if the world is running, end it, remove listeners and timer
if (currentworld.worldExists){
theCanvas.drawString(new Posn(10, 20),
"World stopped when not visible");
currentworld.stopWorld();
// now - change the applet so we can see that the world stopped
currentState = CLEAR;
bigButton.setText(CLEAR);
}
// note that the applet is stopped
stopped = true;
}
/**
* Draw the background for the entire applet panel
* in light gray color
*/
protected void redraw(){
Color back = Color.darkGray;
theCanvas.drawRect(new Posn(0, 0), WIDTH, HEIGHT, back);
}
/**
* Do nothing - we draw our own world images
*/
public void paint(){ }
}