1 mobile computing arrays copyright 2014 by janson industries assg1assg1 extracredit1extracredit1...

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Mobile Computing

Arrays

Copyright 2014 by Janson Industries

Assg1 ExtraCredit1Assg2 ExtraCredit2

Copyright 2014 by Janson Industries2

Topics▀ Arrays

▀ Looping/Iteration

▀ More GUI

▀ Timers

▀ Random numbers

▀ Touch listeners

▀ Media players


Tic Tac Toe▀ Last piece of our app requires

the extensive use of arrays

▀ An array is a programming data structure that holds multiple values

Think of it as a single row of storage spaces


Array▀ An array’s values

Must all be of the same type

Are referred to by an index (aka a subscript)

► The index begins at 0

Can be constant► Fixed values for program use

• Discount rates, zip codes, state abbrs

Can be changed► Multiple user or file input values

• Shopping cart items


Array▀ Arrays are fixed in length

i.e. Arrays have a size - the max number of values they can hold

▀ An array is assigned to a variable


Array▀ When creating an array

Specify the type of values it will hold

Specify the maximum number of values it will hold

Create and assign the array to a variable

▀ Syntax to create an array new arrayType[size]

► new String[3];► new int[6];


Using Arrays In Java▀ To use or access the array, must

assign to a variable

arrayType[ ] varName = new arrayType[size]

►String[] zipCodes = new String[3];

► int[] qtys = new int[6];


Array▀ String[] stateAbbrs = new String[4]; results in:

▀ To refer to a particular value, use the array variable name and index number in brackets

▀ stateAbbrs[2] = "FL"; results in

Index 0 1 2 3

Index 0 1 2 3

FL


Array▀ Let's be clear:

stateAbbrs[2] = "FL“; results in data being put into the third position of the array

stateAbbrs[4] = "GA" results in?Index 0 1 2 3

FL

An out of bounds error!


Looping▀ WHILE and DO WHILE allow

looping based on a condition

▀ FOR allows looping for a set number of iterations based on a

Starting value

Increment value

Ending value


Looping▀ WHILE allows looping based on a

condition

▀ FOR allows a certain number of iterations

while (eof == 0) {

statements to be repeated;

}

for (int j = 0; j < 10; j++) {


}


Looping▀ DO WHILE checks the condition

after the statements are executed

Therefore, the loop will be executed at least once

do {


} while (eof == 0)


Looping▀ BREAK and CONTINUE

provide exits from a loop

▀ Results in: j = 0

j = 1

for (int j = 0; j < 5; j++) {

if (j == 2) {

break;

}

System.out.println("j = " + j);

}


Looping

▀ Results in:

for (int j = 0; j < 5; j++) {

if (j == 2) {

continue;}

System.out.println(“j = “ + j);

}

j = 0

j = 1

j = 3

j = 4


Loops and Arrays▀ Loops very good way to process

arrays

▀ For example we could easily initialize an array with a for loop

String[] arrayOfStrings = new String[5];

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

arrayOfStrings[i] =

new String("This string has the value " + i);

}


Loops and Arrays▀ Could display the array’s

contents with this

▀ Ewwwwww…

System.out.println(arrayOfStrings[0]);






Loops and Arrays▀ Much more elegantly

▀ Results in:

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

System.out.println(arrayOfStrings[i]);

}

This string has the value 0This string has the value 1This string has the value 2This string has the value 3This string has the value 4


Nested Loops▀ Sometimes loops within loops

needed

▀ What do you think would be the output of this

for (int i = 1; i <= 5; i++) {

for (int j = 1; j <= i; j++) {

System.out.print(i);

}

}

122333444455555


Nested Loops▀ How about this

for (int i = 1; i <= 5; i++) {

for (int j = 1; j <= i; j++) {

System.out.print(i);

}

System.out.println("");

}

122333444455555


Tic Tac Toe▀ Need a playing board

New XML layout: TableLayout

▀ Each square will have a button

When clicked, button text changed to X or O and button disabled

Need a click handler method

▀ Will have a text view at bottom to give players info


Will take the numbers off later


tttboard XML▀ New layout (TableLayout) and a

couple new attributes:

Gravity controls both vertical and horizontal alignment

dp stands for density independent pixels ► Buttons will size correctly for different

screen resolutions

layout_marginTop controls space between title bar and layout


<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

android:orientation="vertical" android:layout_width="fill_parent"android:layout_height="fill_parent" android:gravity="center_horizontal"android:background="#000000"><TableLayout android:id="@+id/play_grid"

android:layout_width="fill_parent" android:layout_height="wrap_content"android:layout_marginTop="5dp">

<TableRow android:gravity="center_horizontal"><Button android:id="@+id/one" android:layout_width="100dp"

android:layout_height="100dp" android:text="1" android:textSize="70dp" android:onClick="clickHandler"/>

<Button android:id="@+id/two" android:layout_width="100dp"android:layout_height="100dp" android:text="2"android:textSize="70dp" android:onClick="clickHandler" />

<Button android:id="@+id/three" android:layout_width="100dp"android:layout_height="100dp" android:text="3"android:textSize="70dp" android:onClick="clickHandler"/>

</TableRow>

tttboard XML


tttboard XML

25

<TextView android:id="@+id/information" android:layout_width="fill_parent"android:layout_height="wrap_content" android:text="info"android:gravity="center_horizontal" android:layout_marginTop="20dp"android:textSize="20dp" android:textColor="#ffffff" />

</LinearLayout>

▀ Need a new activity called TTTActivity

▀ TTTActivity needs variables for An array of Buttons TextView


package my.first.pkg;

import android.app.Activity;import android.os.Bundle;import android.widget.Button;import android.widget.TextView;

public class TTTActivity extends Activity {private Button tttButtons[];private TextView infoTV;private int boardSize = 9;public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.tttboard); tttButtons = new Button[boardSize]; tttButtons[0] = (Button) findViewById(R.id.one); tttButtons[1] = (Button) findViewById(R.id.two); tttButtons[2] = (Button) findViewById(R.id.three); tttButtons[3] = (Button) findViewById(R.id.four); tttButtons[4] = (Button) findViewById(R.id.five); tttButtons[5] = (Button) findViewById(R.id.six); tttButtons[6] = (Button) findViewById(R.id.seven); tttButtons[7] = (Button) findViewById(R.id.eight); tttButtons[8] = (Button) findViewById(R.id.nine); infoTV = (TextView) findViewById(R.id.information); }

} 26

Get the buttonsAnd text view


Tic Tac Toe▀ Need to initialize the board

Take the numbers off

Enable the buttons

Prompt the players to start

▀ Will create a new method called start to do this


TTTActivity▀ Need to code click handler to

Change button text to correct symbol

Disable the clicked button

Prompt the other player to go►Must have a new class level variable to

keep track of who’s turn it is

►start() must initialize to Xprivate String whosTurn;

whosTurn = "X";


import android.view.View;import android.graphics.Color; : : : :private String whosTurn;

: : : : public void clickHandler(View target){ for (int i = 0; i < tttButtons.length; i++) { if (target == tttButtons[i]){ tttButtons[i].setEnabled(false); tttButtons[i].setText(whosTurn); if (whosTurn == "X"){ tttButtons[i].setTextColor(Color.GREEN); whosTurn = "O"; } else { tttButtons[i].setTextColor(Color.RED); whosTurn = "X";} infoTV.setText("It's " + whosTurn + "'s turn now." ); break; } } }

Click Handler


public boolean onOptionsItemSelected(MenuItem item) {if (item.getItemId() == R.id.browser) {

Intent intent = new Intent(Intent.ACTION_VIEW);intent.setData(Uri.parse("http://fscj.edu"));startActivity(intent);

} else {if (item.getItemId() == R.id.order) {

Intent intent = new Intent("my.first.pkg.ShowOrder");startActivity(intent);

} else {if (item.getItemId() == R.id.end) {

finish();} else {

String actionName = "my.first.pkg.TTTActivity";Intent intent = new Intent(actionName);startActivity(intent);

}}

}return true;

}

Tic Tac Toe▀ Modify HowdyActivity to run it


Tic Tac Toe▀ Add Tic Tac Toe activity to the

AndroidManifest.xml

▀ Run app, display menu, choose Play Tic Tac Toe

<activity android:name="TTTActivity" android:label="Tic Tac Toe" > <intent-filter> <action android:name="my.first.pkg.TTTActivity" /> <category android:name="android.intent.category.DEFAULT" /> </intent-filter></activity>


Graded Assg 1

▀ Create a method called checkForGameOver that

Checks for a winner and ties►Use loops to check for winners

Displays the messages►X won►O won►It’s a tie


Graded Assg 1

▀ Have the program keep track of how many wins for X and O and how many ties

▀ Add a textview beneath the message to display the number of wins for X and O and ties


Graded Assg 1▀ Add a menu and

function, so that the user can start a new game

▀ Store menu definition in a file called new_game.xml


Example after 5 games


Whack a Square▀ Program will randomly display a

square on the screen for a second

▀ If user touches square, they get a point

▀ Will need a timer and random number generator to move the square around

▀ Game lasts 30 seconds


Will keep score & display a timer to count down the time left to play


Created new project, package, activity and layout. Changed layout to above.


WhackaSquare Activity

▀ For displaying, can draw a View on the screen (aka canvas) from within the program

▀ Instead of xml layout

▀ Create a class that is a View

▀ Then draw the view on the screen


WhackaSquare

▀ Create a new View class called SquareCtrl to display the square, sense hits, keep score

▀ Make its superclass View

▀ Implement OnTouchListener

▀ Generate inherited abstract methods


Will have an error

Hover over red squiggly, select first suggested fix to insert constructor


Should look like this


Whack a Square▀ SquareCtrl needs class level variables for

▀ X and Y location coordinates for the square

▀ Number of clicks, hits, success percentage

▀ Have Eclipse generate getters and setters▀ Select the code, ALT+SHIFT+S, Generate Getters and

Setters

private int xCord, yCord;private double attempts, score, percentage;


WhackaSquare▀ SquareCtrl needs a new method called move which will

▀ Generate random numbers to be used to calculate the x and y coordinates

▀ Do this by▀ Getting the current width and height of the screen▀ Multiplying them by the random number (a decimal value between 0

and 1)


Random Number Generators▀ Not really random

▀ Complicated algorithm to imitate randomness

▀ Random method needs a “seed” number

▀ Traditionally use the current time’s milliseconds


X and Y Coordinates▀ When specified for location of square, indicates

the upper left location of the square

▀ So can’t have coords at bottom or rightmost of screen because part of square would be off screen

▀ Also need to not put square in score area at bottom


import java.util.Random; : : :protected void move(){

Random randomNumGenerator = new Random();randomNumGenerator.setSeed(System.currentTimeMillis());int w = this.getWidth()-20;int h = this.getHeight()-40;float randomNum = randomNumGenerator.nextFloat();this.setxCord((int)(randomNum * w));randomNum = randomNumGenerator.nextFloat();this.setyCord((int)(randomNum * h));

}

SquareCtrl - move()


SquareCtrl - onDraw()▀ When component is placed on

screen, its onDraw() invoked

▀ Override onDraw() and change to:

▀ Call move()

▀ Set background color to black

▀ Draw a 20x20 pixel red square at the random location

▀ Display score, percentage, time left


▀ Need to import graphics.*

▀ Need class level variables to calculate time

▀ In constructor, attach the listener to the view and set start time

import android.graphics.*; : : :int elapsedTime, startTime, timeLeft;String timeLeftString;

54

SquareCtrl - onDraw()

this.setOnTouchListener(this);startTime = (int)System.currentTimeMillis()/1000;


protected void onDraw(Canvas canvas) {super.onDraw(canvas);move();canvas.drawColor(Color.BLACK);Paint squareColor = new Paint();squareColor.setColor(Color.RED);canvas.drawRect(xCord, yCord, xCord+20, yCord+20, squareColor);Paint scoreColor = new Paint();scoreColor.setColor(Color.WHITE);scoreColor.setTextSize(20);canvas.drawText("Score: " + (int)score + " Attempts: " +

(int)attempts + " Percentage: " + (int)percentage + "%", 10, this.getHeight()- 5, scoreColor);

elapsedTime = (int)System.currentTimeMillis()/1000 - startTime ;timeLeft = 30 - elapsedTime;if (timeLeft <= 0){timeLeft = 0;} //so negative time not showntimeLeftString = String.valueOf(timeLeft);canvas.drawText(timeLeftString, this.getWidth()-25, this.getHeight()- 5, scoreColor);

}55

SquareCtrl - onDraw()


SquareCtrl - detectHit(int x, int y)▀ When screen touched, will invoke detectHit

▀ Supply location of touch

▀ Must calculate if touch within square boundary

▀ See if location is within the width and height of square location


SquareCtrl - detectHit(int x, int y)

protected boolean detectHit(int x, int y) {if ((x >= xCord && x <= xCord + 20) && (y >= yCord && y <= yCord + 20)) {

return true;} else {

return false;}

}


SquareCtrl - onTouch()▀ When screen touched, the

onTouchListener’s onTouch method is invoked

▀ Must extract location of touch from event object and invoke detectHit


SquareCtrl - onTouch()

public boolean onTouch(View v, MotionEvent event) {attempts = attempts + 1; // calc number of touchesif(detectHit((int)event.getX(), (int)event.getY())){

score = score + 1;}percentage = (score/attempts) * 100;return false;

}

▀ Change onTouch to this


Timers▀ Classes that enable you to schedule “tasks”

▀ Schedule means that a task can be:

▀ Set to run at a particular day and time (one shot timer)

▀ To be run repeatedly at some interval


Timers & Tasks

TaskCreates

task

Invokes schedule() passing task &

interval

Creates

timer

App

Invokesrun()

1

2

Timer


Timers▀ To create and use a Timer

▀Code a TimerTask subclass to perform the task

▀Create a TimerTask subclass variable and object (passing what it needs to perform the task– a SquareCtrl variable/object) and assign the TimerTask object to the variable

▀Create a Timer variable, a Timer object and assign the object to the variable

▀Using the Timer objects schedule method, specify the TimerTask subclass and timing


Timers▀ Our app will need two Timers and two

TimerTasks

▀ One Timer (timer) to run WaSqTimerTask, which invokes the SquareCtrl’s move method every second

▀ One Timer (endOfGameTimer) to run the EndGame TimerTask, which cancels the first Timer (timer), after approx 30 seconds


TimerTasks▀ Create a subclass of TimerTask

▀ WaSqTimerTask

▀ Create a method called run (that will be invoked by the timer)

▀ WaSqTimerTask needs a SquareCtrl object and, in run, executes its move function

▀ Will also invoke postInvalidate to force the view to be redrawn


WhackaSquare

Invokesmove()

SquareControl

sq

WaSqTimerTask

Creates

sq

Creates

task

Invokes schedule() passing task &

interval

Creates

timer

WaSq

Invokesrun()

1

2

3

Timer


WaSqTimerTaskpackage com.mygames.www;

import java.util.TimerTask;

public class WaSqTimerTask extends TimerTask {SquareCtrl sc;public WaSqTimerTask(SquareCtrl s){

sc = s;} public void run() {

sc.move(); //execute the move methodsc.postInvalidate(); //forces a draw

}

}


EndGame TimerTask

▀ Will need the original Timer object - timer (created to run the game and change the square location )

▀ Will invoke that timers cancel method to end the game


EndGame TimerTaskpackage com.mygames.www;

import java.util.Timer;import java.util.TimerTask;

public class EndGame extends TimerTask { Timer gameTimer;

public EndGame(Timer t){gameTimer = t;

}

public void run() {gameTimer.cancel();

}}


Pulling It All Together▀ WhackaSquare activity needs to create

▀ The initial SquareCtrl View and put it in on the screen

▀ The timer to run WaSqTimerTask every second

▀ The timer to run EndGame after 30.5 seconds


WhackaSquarepackage com.mygames.www;

import java.util.Date;import java.util.Timer;import android.app.Activity;import android.os.Bundle;

public class WhackaSquare extends Activity {private SquareCtrl sq;private Timer timer, endOfGameTimer;private WaSqTimerTask task; private EndGame endGameTask;

public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState);

setTitle("Whack a Square"); sq = new SquareCtrl(this.getBaseContext()); setContentView(sq); //puts SquareCtrl on screen


Timer Schedule Method▀ Must specify the task to be

performed

▀ For recurring execution: must specify when to invoke the task’s run method and how often thereafter to call the run method

▀ In milliseconds


Timer Schedule Method▀ For one time execution must

specify

▀ The task to be performed

▀ The date/time to execute the task

▀ We will retrieve the current date/time and add 30.5 seconds to it

▀ Extra half a second to let SquareCtrl start up


WhackaSquare task = new WaSqTimerTask(sq); // creates timer task

timer = new Timer(); // creates timer timer.schedule(task, 0, 1000); // timer set to 1 second

endOfGameTimer = new Timer(); // creates 2nd timer endGameTask = new EndGame(timer); // sends 1st timer

// end time set to 30.5 seconds from now Date endTime = new Date(System.currentTimeMillis() + 30500);

// timer set to execute 30.5 seconds from now endOfGameTimer.schedule(endGameTask, endTime);}

}


▀ Run to test


App Probs – Extra Credit 1▀ Have to change source code to

rerun and can’t end game

▀ Add a menu with options to play a new game or exit the application

▀ If new game need to reset score and time

▀ Add options to change speed and size of square


New menu


App Probs – Extra Credit 1▀ If set to easy, make square 25%

bigger and move every 1.25 seconds

▀ If set to hard, make square 25% smaller and move every .75 seconds


MusicPlayer▀ New app will have an initial

splash screen controlled by a handler

▀ Then display a list of songs, images and buttons

▀ When song button pressed, song will play


Initial splash screen displayed for 5 seconds


Then main screen with song images, text and play/pause buttons


Create a new projectClick Next for next 3 screens


Add a new activity


MusicPlayer

▀ Need to copy/import the splash image (from class website) into the drawable-hdpi folder in the res folder

▀ Then create a new xml layout file called splash in the layout folder in res


Right click layout folder, New, Android XML File

Specify the file name, make sure LinearLayout is selected, click Finish


MusicPlayer▀ Add a TextView that:

▀ Fills the layout▀ Has the splash image specified for the

background▀ Text centered horizontally at the bottom

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" >

<TextView android:id="@+id/textView1" android:layout_width="fill_parent"android:layout_height="fill_parent" android:background="@drawable/splashimage" android:text="My Homemade Music Player"android:gravity="bottom|center_horizontal" android:textSize="35sp">

</TextView></LinearLayout>


MusicPlayer▀ Need to change MusicPlayerMain

to display the splash pagepackage my.musicproj.com;

import android.os.Bundle;import android.app.Activity;import android.view.Menu;import android.view.MenuItem;import android.support.v4.app.NavUtils;

public class MusicPlayerMain extends Activity { public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.splash); } public boolean onCreateOptionsMenu(Menu menu) { getMenuInflater().inflate(R.menu.music_player_main, menu); return true; }}


Run to test


MusicPlayer▀ Only want the splash page to be

displayed for 5 seconds

▀ Will use a Handler to delay the display of the main screen

▀ Alternative to a timer

▀ A Handlers postDelayed method lets you specify a time delay and a Runnable object to be executed


Handlers

▀ The Handler will execute the Runnable object’s run method

▀ In run, create a new intent to display the main screen

▀ Have MusicPlayerMain invoke a Handlers postDelayed method and create and pass a Runnable object


Handlers▀ New concept: an object’s method(s)

can be overridden

▀ Just like an object’s property values can be set, method(s) can be defined when an object is created

▀ After the keyword new and class name, in {} specify the new method

new Handler().postDelayed(new Runnable(){ public void run() {

String actionName = "my.musicproj.com.Player";Intent intent = new Intent(actionName);startActivity(intent);

} }, 5000);


Handlers▀ This statement creates Handler and

Runnable objects

▀ Does not assign the objects to variables

▀ When Runnable object created, run method defined

▀ And passed to the postDelayed method with time delay in milliseconds

new Handler().postDelayed(new Runnable(){ public void run() {


} }, 5000);


MusicPlayerMainpackage my.musicproj.com;

: : : :import android.content.Intent;import android.os.Handler;

: : : :public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.splash); new Handler().postDelayed(new Runnable(){ public void run() {


} }, 5000); }

: : : :


Music Player▀ Need the new activity defined

in the manifest file

▀ Have to create Player class to display main layout

<activity android:name="Player" android:label="Play Music" > <intent-filter> <action android:name="my.musicproj.com.Player" /> <category android:name="android.intent.category.DEFAULT" /> </intent-filter></activity>


Player▀ Simply displays the main screen

for the music player

package my.musicproj.com;

import android.app.Activity;import android.os.Bundle;

public class Player extends Activity {

protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);this.setContentView(R.layout.main);

}

}


MusicPlayer▀ Run to test

▀ Splash should be displayed for 5 seconds

▀ Then Hello world screen (generated by Eclipse) will be displayed

▀ Want to change generic main to list songs that can be played and look like this…


Main screen


Themes▀ Predefined colors and

components

▀ Used instead of specifying individual component properties

▀ layout background color▀ text color

▀ In the Activity definition (in the Manifest) specify the theme

<activity android:name="Player" android:label="Play Music" android:theme="@android:style/Theme.Black">


Black background, white text


MusicPlayer

▀ Need to copy artist images into the drawable-hdpi folder in the res folder


main.xml▀ For each song, show:

▀ A picture of the artist

▀ Name of the song

▀ A play button

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

android:orientation="vertical" android:layout_width="fill_parent"android:layout_height="fill_parent"><LinearLayout

android:orientation="horizontal" android:layout_width="wrap_content"android:layout_height="wrap_content"><ImageView android:id="@+id/artist1" android:src="@drawable/artist1"

android:layout_width="90dip" android:layout_height="90dip" />


Main Screen<Button android:id="@+id/one" android:layout_width= "80dp"

android:onClick="clickHandler" android:layout_height="45dp"android:text="Play" android:textSize="20dp" android:layout_gravity="center_vertical"android:gravity="center_vertical|center_horizontal" />

</LinearLayout><TextView android:layout_width="fill_parent"

android:layout_height="wrap_content" android:text="Afraid To Fail"android:layout_gravity="center_horizontal" />

<LinearLayout android:orientation="horizontal" android:layout_width="wrap_content"android:layout_height="wrap_content"><ImageView android:id="@+id/artist2"

android:layout_width="90dip" android:layout_height="90dip"android:src="@drawable/artist2" />

<Button android:id="@+id/two" android:layout_width= "80dp"android:onClick="clickHandler" android:layout_height="45dp"android:text="Play" android:textSize="20dp" android:layout_gravity="center_vertical"android:gravity="center_vertical|center_horizontal" />

</LinearLayout><TextView android:layout_width="fill_parent"

android:layout_height="wrap_content" android:text="Crazy About You"android:layout_gravity="center_horizontal" />

</LinearLayout>


MusicPlayer

▀ Time to test

▀ Takes a lot longer to load because of the image files

▀ Splash screen displayed

▀ Then 5 seconds later...


Main screen displayed


Music Files▀ Traditionally stored in res

folder in a subfolder called raw

▀ Need to create the raw folder then copy/import the mp3 files into it


Player▀ Have to add function to play songs

after button clicked

▀ Will need variables for the buttons and two media players

▀ Must add OnClickListeners to the buttons and create an onClick method

▀ onClick determines which button was clicked and plays song


Variables

import android.media.MediaPlayer;import android.widget.Button;

public class Player extends Activity {

Button oneBtn, twoBtn;MediaPlayer oneMP, twoMP;

: : :

▀ MediaPlayers are objects that will allow music to be played


package my.musicproj.com;

import android.app.Activity;import android.os.Bundle;import android.media.MediaPlayer;import android.widget.Button;import android.view.View;import android.view.View.OnClickListener;

public class Player extends Activity implements OnClickListener {Button oneBtn, twoBtn;MediaPlayer oneMP, twoMP;

protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);this.setContentView(R.layout.main);oneBtn = (Button)this.findViewById(R.id.one);twoBtn = (Button)this.findViewById(R.id.two);oneBtn.setOnClickListener(this);twoBtn.setOnClickListener(this);

}

public void onClick(View v){}} 107

Buttons


MediaPlayers▀ Create the MediaPlayer object

with the static MediaPlayer method create()

▀ And specify the song file to tie to the media player

: : : protected void onCreate(Bundle savedInstanceState) {

: : : twoBtn.setOnClickListener(this); oneMP = MediaPlayer.create(this, R.raw.song1); twoMP = MediaPlayer.create(this, R.raw.song2);}


MediaPlayers▀ Three methods to control

the music

▀ start()

▀ pause()

▀ stop()▀ To use MediaPlayer after it is

stopped, must invoke prepare()


onClick▀ When first button is pushed,

start the first media player

▀ When second button is pushed start the second media player

public void onClick(View v){if (oneBtn == (Button) v) {

oneMP.start();} else {

twoMP.start();}

}


App Problems

▀ If you click the first button and then the second both songs play

▀ No way to stop song once started


Graded Assg 2 ▀ When play button clicked change

text on button to pause

▀ When play button clicked, check to see if other song is playing (use MP’s isPlaying()), if it is, pause it and change that buttons text to play

▀ When pause btn clicked, pause the song, change text to play


Assg 2

▀ Initial display

▀ First button clicked▀ First song played▀ Text changed to Pause


Assg 2▀ First button clicked again

▀ First song paused ▀ Text changed to Play

▀ First button clicked again▀ First song resumed▀ Text changed to Pause


▀ First button clicked▀ Second song paused▀ Second button text changed to Play▀ First song played▀ First button text changed to Pause

115

▀ Second button clicked▀ First song paused▀ First button text changed to Play▀ Second song played▀ Second button text changed to Pause


Extra Credit Assg 2

▀ In Whack A Square, add sounds for hits and misses


package my.other.music;

import java.io.IOException;import android.app.Activity;import android.media.MediaPlayer;import android.os.Bundle;

public class Main extends Activity { MediaPlayer urlMP; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); urlMP = new MediaPlayer(); try {

urlMP.setDataSource("http://web.fscj.edu/Janson/CIS2930/sample.mp3"); urlMP.prepare();

} catch (IllegalArgumentException e) {e.printStackTrace();

} catch (IllegalStateException e) {e.printStackTrace();

} catch (IOException e) {e.printStackTrace();

} urlMP.start(); }}

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Other Options▀ Can run music from a URL

▀ You’ll notice how much faster the app loads/installs


Must add <uses-permission android:name="android.permission.INTERNET" />

to Manifest


Other Options▀ Run music from the phone’s SD card▀ We defined SD card earlier when we created the emulator

▀ But if you didn’t, you can change


Other Options

▀ Specify 100 (MB)


Go to DDMS perspective, click File Explorer, then sdcard


To move a file onto SD Card, click the Push file onto device button


Select file, click Open


sdcard folder wont look any different

Indictes the folder to expand, in this case storage


Scroll down and expand storage and then sdcard folder and you’ll see the

uploaded file


package my.other.music;

import java.io.IOException;import android.app.Activity;import android.media.MediaPlayer;import android.os.Bundle;

public class Main extends Activity { MediaPlayer urlMP; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); urlMP = new MediaPlayer(); try {

urlMP.setDataSource("/sdcard/sample.mp3"); urlMP.prepare();

} catch (IllegalArgumentException e) {e.printStackTrace();

} catch (IllegalStateException e) {e.printStackTrace();

} catch (IOException e) {e.printStackTrace();

} urlMP.start(); }}

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Other Options▀ Run music

from SD card

▀ Also will load & install faster


MediaPlayer▀ When finished with MP, execute its release method

▀ Frees up memory

▀ But more importantly, failure to release▀ May lead to continuous battery consumption ▀ Playback failure for other applications


MediaPlayer▀ For example, Player's onPause()

could have the releases

▀ Then move all the media player creations to onRestart()

▀ Also, should have a menu or button to close app that calls onDestroy()

▀ In onDestroy(), call finish() which release all resources

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