Crea%ng  Asha  Games:  Game  Pausing,  Device  Orienta%on,  Sensors,  Gestures  

Jussi  Pohjolainen  Tampere  University  of  Applied  Sciences  

GAME  PAUSING  

About  Game  Pausing  

•  Pause  game  when  – Phone  rings  – Back  –  buHon  is  pressed  

•  Remember  that  MIDlet's  pauseApp  –  method  is  never  called!  

•  In  GameCanvas,  implement  following  – public void showNotify() // resume – public void hideNotify() // pause

About  Gameloop  and  Threading  

•  Gameloop  is  implemented  using  Threading  – Thread thread = new Thread(Runnable x); – thread.start(); // calls run()

•  Gameloop  usually:  – while(gameIsOn) { …. Thread.sleep(ticks); }

•  How  to  pause  the  current  thread  in  midp?  

Synchroniza%on  •  Let's  first  look  at  synchroniza5on.  •  There  might  be  a  problem,  if  two  threads  accesses  the  same  

data  –  Two  people  each  have  a  ATM  cards  that  are  linked  to  only  one  account  –  What  happens  when  these  two  people  accesses  the  account  at  the  

same  %me?  

•  Withdrawal  is  two-­‐step  process  –  Check  the  balance  –  If  there's  enough  money  int  the  account,  make  the  withdrawal  

•  What  happens  if  1  and  2  are  separated?  

Locks  

•  We  must  guarantee  that  the  two  steps  are  never  split  apart.  Use  synchronized  keyword  

•  Synchroniza%on  works  with  locks.  Every  object  has  a  lock.  If  one  thread  has  picked  up  the  lock,  no  other  thread  can  use  the  synchronized  code.  

Examples  

•  Let's  look  at  some  synchroniza%on  examples  – https://dl.dropboxusercontent.com/u/874087/game-programming/examples/threading/Synchronized1.java

•  See  also  – Synchronized2.java -> Synchronized5.java

wait()  

•  Object  class  holds  a  method  wait()  – Causes  the  current  thread  to  wait  un%l  another  thread  invokes  the  no%fy()  method  for  this  object  

•  So  when  calling  wait()  it  pauses  the  current  thread  and  waits  that  some  other  thread  calls  no%fy()  or  no%fyAll()!  

// NOTICE! This example does not work, all exception handling and synchronized blocks

// are missing

class MyApp {

public static void main(String [] args) {

new MyApp();

}

public MyApp() {

MyThread mythread;

Thread thread = new Thread(mythread = new MyThread());

thread.start();

System.out.println("Sleeping");

Thread.sleep(2000);

// Resume from wait! Calls notify from the object that is in wait…

mythread.notify();

}

}

class MyThread implements Runnable {

public void run() {

// Let's wait until someone calls notify

wait();

System.out.println("Resumed!");

}

}

wait()  

•  When  calling  wait  and  no%fy,  it  must  be  inside  synchronized  block.  

 synchronized(this) { // Before calling notify, the thread calling this must // own a lock. notify(); } synchronized(this) { wait(); }

 

Game  Pausing  in  MIDlet  •  In  GameCanvas,  following  methods  are  called  when  phone  rings.  

           // Phone rings public void hideNotify()  {   pause(); // pause game – my own method }    // Phone ends public void showNotify()  {   resume(); // resume game – my own method }

pause() and  resume() public void resume() {

isPause = false;

synchronized(this) { notify(); // Notify that waiting thread can

// continue. }

} public void pause() {

isPause = true; }

Game  Loop  public void run() {

int i = 0;

while(true) {

checkIfPause();

checkCollisions();

moveSprites();

try {

Thread.sleep(100);

} catch (InterruptedException e) {

e.printStackTrace();

}

}

}

private void checkIfPause() {

synchronized(this) {

while(isPause) { // while, just in case

try {

wait(); // Wait in current thread

} catch (InterruptedException e) {

e.printStackTrace();

}

}

}

}

Back  BuHon  to  Game  Canvas  Command backCommand = new Command("Back", Command.BACK, 0); addCommand(backCommand); setCommandListener(this); // and the listener method public void commandAction(Command c, Displayable d) { if(isPause) { midlet.notifyDestroyed(); } else { pause(); } }

DEVICE  ORIENTATION  

Adjus%ng  Device's  Orienta%on  

•  MIDlets  can  use  Orienta5on  API  to  – Change  their  UI  orienta%on  – Determine  their  current  UI  orienta%on  – Determine  the  current  display  orienta%on  – Receive  a  no%fica%on  whenever  the  display  orienta%on  changes  

•  When  MIDlet  changes  it's  UI  orienta%on,  it  has  to  redraw  the  low-­‐level  components  that  it  uses.  

Supported  Orienta%ons  

•  ORIENTATION_LANDSCAPE •  ORIENTATION_LANDSCAPE_180 •  ORIENTATION_PORTRAIT •  ORIENTATION_PORTRAIT_180

Se^ng  UI  Orienta%on  

•  Add  following  to  JAD  file:  – Nokia-MIDlet-App-Orientation: manual

•  Now  it  supports  both  portrait  and  landscape  modes  

•  Add  orienta%on  listener  –  Orientation.addOrientationListener(orientationListener);

Orienta%on  Listener  Callback  /** Orientation listener callback */ public void displayOrientationChanged( int newDisplayOrientation ){

/** Check display orientation */

switch( newDisplayOrientation ){

case Orientation.ORIENTATION_PORTRAIT:

case Orientation.ORIENTATION_PORTRAIT_180:

/** Change MIDlet UI orientation to portrait */

Orientation.setAppOrientation(Orientation.ORIENTATION_PORTRAIT);

break;

case Orientation.ORIENTATION_LANDSCAPE:

case Orientation.ORIENTATION_LANDSCAPE_180:

/** Change MIDlet UI orientation to landscape */

Orientation.setAppOrientation(Orientation.ORIENTATION_LANDSCAPE);

break;

}

}

sizeChanged()

•  When  UI  Orienta%on  changes:    /** Java platform will call this when UI orientation has been changed */

protected void sizeChanged( int w, int h ){

/** Acquiring new Graphics Object since old is not valid anymore */

g = getGraphics( );

canDraw = true;

}

MOBILE  SENSOR  API  

Mobile  Sensors  

•  Mobile  Sensor  API  allows  MIDlets  to  fetch  data  from  the  sensors  of  the  mobile  device  

•  Sensor  consists  of  one  or  more  channels,  in  accelerometer  you  will  get  data  from  three  channels  (x,  y  and  z)  

•  Sensors  have  common  proper%es:    – accuracy  – max  and  min  value  

Available  Sensors  in  Asha  50X  •  Accelera5on  sensor    

–  measures  accelera%on  in  SI  units  for  x,  y  and  z  -­‐  axis.  

•  Orienta5on  sensor  –  provides  informa%on  of  devices  current  orienta%on  posi%on.  

•  Rota5on  sensor    –  provides  informa%on  of  devices  current  rota%on  degree.  

•  Double  tapping  sensor    –  provides  informa%on  of  double  taps  occurred  on  the  phone  sides.  

•  Proximity  sensor    –  indicates  if  an  obstacle  is  right  in  front  of  it  

•  BaLery  sensor    –  shows  baHery  charge  level  in  percentage.  Sensor  is  always  on.  

•  Charger  sensor  –  shows  whether  charger  is  connected.  Sensor  is  always  on.  

•  Signal  strength  sensor  –  shows  strength  of  network  connec%on  in  percentage.  Sensor  is  always  on.  

Using  Sensors  

Finding  and  Iden%fying  a  Sensor  // Find all sensors

SensorInfo[] sensorInfos =

SensorManager.findSensors(null, null);

for(int i=0; i<sensorInfos.length; i++) {

SensorInfo si = sensorInfos[i];

System.out.println(si.getUrl());

}

Finding  and  Iden%fying  a  Sensor  // Sensor type (quantity):

// acceleration

// orientation

// rotation

// double_tap

// proximity

// battery_charge

// charger_state

// network_field_intensity

// null

String type = "acceleration";

// Sensor Context type

// ambient

// device

// user

// vehicle

// null

String contextType = "user";

// Fetch all sensors with given information, should find only one.

SensorInfo[] si = SensorManager.findSensors(type, contextType);

// Retrieve the sensor url.

String sensorURL = si[0].getUrl();

Opening  a  sensor  connec%on  {

try {

// This may not be a good idea, fetch the URL from sensorinfo using sensor quantity and

// context type

String sensorURL = "sensor:acceleration;contextType=user;model=Nokia;location=NoLoc";

// How fast data is sent to listener!

final int BUFFER_SIZE = 1;

SensorConnection sensorConnection = (SensorConnection)Connector.open(sensorURL);

// this = any object that implements DataListener

sensorConnection.setDataListener(this, BUFFER_SIZE);

} catch (IOException e) {

e.printStackTrace();

}

}

// Datalistener interface method

public void dataReceived(SensorConnection sensor, Data[] data,

boolean isDataLost) {

System.out.println("Here!");

}

Case:  Accelera%on  listening  public void dataReceived(SensorConnection sensor, Data[] data,

boolean isDataLost) { // We have three channels. System.out.println("Channel amount: " + data.length); // Channel is Data object Data x = data[0]; // Each channel may hold several values. In this case // only one. double [] values = x.getDoubleValues(); System.out.println("Number of values " + values.length); // And the value is: System.out.println("x = " + values[0]); // Let's fetch the rest (y and z) in just on line System.out.println("y = " + data[1].getDoubleValues()[0]); System.out.println("z = " + data[2].getDoubleValues()[0]);

}

Case:  Accelera%on  listening  public void dataReceived(SensorConnection sensor, Data[] data,

boolean isDataLost) {

System.out.println("x = " + data[0].getDoubleValues()[0]);

System.out.println("y = " + data[1].getDoubleValues()[0]);

System.out.println("z = " + data[2].getDoubleValues()[0]);

}

Closing  connec%on  

•  Remember  to  close  the  connec%on  if  not  needed!  – sensorConnection.close();

GESTURES  API  

Really  Easy  to  Use  // STEP 1: Defines a GestureInteractiveZone for the

// whole screen and all Gesture types.

GestureInteractiveZone giz = new GestureInteractiveZone( GestureInteractiveZone.GESTURE_ALL );

// STEP 2: Register the GestureInteractiveZones for the

// GameCanvas object this.

GestureRegistrationManager.register( this, giz );

// STEP 3: Set the listener, source is this gamecanvas

// and listener is this also

GestureRegistrationManager.setListener(this, this);

Listener  public void gestureAction(Object container,

GestureInteractiveZone gestureInteractiveZone,

GestureEvent gestureEvent) {

switch(gestureEvent.getType()) {

case GestureInteractiveZone.GESTURE_TAP:

Debug.printInfo("MyGameCanvas", "gestureAction", "TAP", 2);

break;

...

case GestureInteractiveZone.GESTURE_LONG_PRESS:

Debug.printInfo("MyGameCanvas", "gestureAction", "LONG PRESS", 2);

break;

}

}

Listener  public void gestureAction(Object container,

GestureInteractiveZone gestureInteractiveZone,

GestureEvent gestureEvent) {

switch(gestureEvent.getType()) {

...

case GestureInteractiveZone.GESTURE_FLICK:

Debug.printInfo("MyGameCanvas", "gestureAction", "FLICK", 2);

Debug.printInfo("MyGameCanvas", "gestureAction",

"flick speed = " + gestureEvent.getFlickSpeed(), 2);

Debug.printInfo("MyGameCanvas", "gestureAction",

"flick direction = " + gestureEvent.getFlickDirection(), 2);

break;

}

}