I found this code pretty useful for beginners to learn java programming and at the same time coming up with something fun and useful.
main.xml:
<?xml version="1.0" encoding="utf-8"?>
<!-- Demonstrates using a relative layout to create a form -->
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content">
<Button android:id="@+id/one"
android:layout_width="100px"
android:layout_height="100px"
android:layout_alignParentRight="true"
android:layout_marginLeft="5px"
android:text=" "
android:textSize="70px" />
<Button android:id="@+id/two"
android:layout_width="100px"
android:layout_height="100px"
android:layout_toLeftOf="@id/one"
android:layout_alignTop="@id/one"
android:layout_marginLeft="5px"
android:text=" "
android:textSize="70px" />
<Button android:id="@+id/three"
android:layout_width="100px"
android:layout_height="100px"
android:layout_toLeftOf="@id/two"
android:layout_alignTop="@id/two"
android:layout_marginLeft="5px"
android:text=" "
android:textSize="70px"
android:padding="0px"/>
<Button android:id="@+id/four"
android:layout_width="100px"
android:layout_height="100px"
android:layout_alignParentRight="true"
android:layout_marginLeft="5px"
android:layout_below="@id/one"
android:text=" "
android:textSize="70px" />
<Button android:id="@+id/five"
android:layout_width="100px"
android:layout_height="100px"
android:layout_toLeftOf="@id/four"
android:layout_alignTop="@id/four"
android:layout_marginLeft="5px"
android:text=" "
android:textSize="70px" />
<Button android:id="@+id/six"
android:layout_width="100px"
android:layout_height="100px"
android:layout_toLeftOf="@id/five"
android:layout_alignTop="@id/five"
android:layout_marginLeft="5px"
android:text=" "
android:textSize="70px" />
<Button android:id="@+id/seven"
android:layout_width="100px"
android:layout_height="100px"
android:layout_alignParentRight="true"
android:layout_marginLeft="5px"
android:layout_below="@id/four"
android:text=" "
android:textSize="70px" />
<Button android:id="@+id/eight"
android:layout_width="100px"
android:layout_height="100px"
android:layout_toLeftOf="@id/seven"
android:layout_alignTop="@id/seven"
android:layout_marginLeft="5px"
android:text=" "
android:textSize="70px" />
<Button android:id="@+id/nine"
android:layout_width="100px"
android:layout_height="100px"
android:layout_toLeftOf="@id/eight"
android:layout_alignTop="@id/eight"
android:layout_marginLeft="5px"
android:text=" "
android:textSize="70px" />
<TextView android:id="@+id/dialogue"
android:layout_width="fill_parent"
android:layout_below="@id/nine"
android:layout_height="wrap_content"
android:text="Click a button to start"
android:gravity="center_horizontal"
android:layout_marginTop="20px"
android:textSize="20px"/>
</RelativeLayout>
package com.games.tictactoe;
import java.util.Random;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
public class TicTacToe extends Activity {
int c[][];
int i, j, k = 0;
Button b[][];
TextView textView;
AI ai;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
setBoard();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
super.onCreateOptionsMenu(menu);
MenuItem item = menu.add("New Game");
return true;
}
public boolean onOptionsItemSelected(MenuItem item) {
setBoard();
return true;
}
// Set up the game board.
private void setBoard() {
ai = new AI();
b = new Button[4][4];
c = new int[4][4];
textView = (TextView) findViewById(R.id.dialogue);
b[1][3] = (Button) findViewById(R.id.one);
b[1][2] = (Button) findViewById(R.id.two);
b[1][1] = (Button) findViewById(R.id.three);
b[2][3] = (Button) findViewById(R.id.four);
b[2][2] = (Button) findViewById(R.id.five);
b[2][1] = (Button) findViewById(R.id.six);
b[3][3] = (Button) findViewById(R.id.seven);
b[3][2] = (Button) findViewById(R.id.eight);
b[3][1] = (Button) findViewById(R.id.nine);
for (i = 1; i <= 3; i++) {
for (j = 1; j <= 3; j++)
c[i][j] = 2;
}
textView.setText("Click a button to start.");
// add the click listeners for each button
for (i = 1; i <= 3; i++) {
for (j = 1; j <= 3; j++) {
b[i][j].setOnClickListener(new MyClickListener(i, j));
if(!b[i][j].isEnabled()) {
b[i][j].setText(" ");
b[i][j].setEnabled(true);
}
}
}
}
class MyClickListener implements View.OnClickListener {
int x;
int y;
public MyClickListener(int x, int y) {
this.x = x;
this.y = y;
}
public void onClick(View view) {
if (b[x][y].isEnabled()) {
b[x][y].setEnabled(false);
b[x][y].setText("O");
c[x][y] = 0;
textView.setText("");
if (!checkBoard()) {
ai.takeTurn();
}
}
}
}
private class AI {
public void takeTurn() {
if(c[1][1]==2 &&
((c[1][2]==0 && c[1][3]==0) ||
(c[2][2]==0 && c[3][3]==0) ||
(c[2][1]==0 && c[3][1]==0))) {
markSquare(1,1);
} else if (c[1][2]==2 &&
((c[2][2]==0 && c[3][2]==0) ||
(c[1][1]==0 && c[1][3]==0))) {
markSquare(1,2);
} else if(c[1][3]==2 &&
((c[1][1]==0 && c[1][2]==0) ||
(c[3][1]==0 && c[2][2]==0) ||
(c[2][3]==0 && c[3][3]==0))) {
markSquare(1,3);
} else if(c[2][1]==2 &&
((c[2][2]==0 && c[2][3]==0) ||
(c[1][1]==0 && c[3][1]==0))){
markSquare(2,1);
} else if(c[2][2]==2 &&
((c[1][1]==0 && c[3][3]==0) ||
(c[1][2]==0 && c[3][2]==0) ||
(c[3][1]==0 && c[1][3]==0) ||
(c[2][1]==0 && c[2][3]==0))) {
markSquare(2,2);
} else if(c[2][3]==2 &&
((c[2][1]==0 && c[2][2]==0) ||
(c[1][3]==0 && c[3][3]==0))) {
markSquare(2,3);
} else if(c[3][1]==2 &&
((c[1][1]==0 && c[2][1]==0) ||
(c[3][2]==0 && c[3][3]==0) ||
(c[2][2]==0 && c[1][3]==0))){
markSquare(3,1);
} else if(c[3][2]==2 &&
((c[1][2]==0 && c[2][2]==0) ||
(c[3][1]==0 && c[3][3]==0))) {
markSquare(3,2);
}else if( c[3][3]==2 &&
((c[1][1]==0 && c[2][2]==0) ||
(c[1][3]==0 && c[2][3]==0) ||
(c[3][1]==0 && c[3][2]==0))) {
markSquare(3,3);
} else {
Random rand = new Random();
int a = rand.nextInt(4);
int b = rand.nextInt(4);
while(a==0 || b==0 || c[a][b]!=2) {
a = rand.nextInt(4);
b = rand.nextInt(4);
}
markSquare(a,b);
}
}
private void markSquare(int x, int y) {
b[x][y].setEnabled(false);
b[x][y].setText("X");
c[x][y] = 1;
checkBoard();
}
}
// check the board to see if someone has won
private boolean checkBoard() {
boolean gameOver = false;
if ((c[1][1] == 0 && c[2][2] == 0 && c[3][3] == 0)
|| (c[1][3] == 0 && c[2][2] == 0 && c[3][1] == 0)
|| (c[1][2] == 0 && c[2][2] == 0 && c[3][2] == 0)
|| (c[1][3] == 0 && c[2][3] == 0 && c[3][3] == 0)
|| (c[1][1] == 0 && c[1][2] == 0 && c[1][3] == 0)
|| (c[2][1] == 0 && c[2][2] == 0 && c[2][3] == 0)
|| (c[3][1] == 0 && c[3][2] == 0 && c[3][3] == 0)
|| (c[1][1] == 0 && c[2][1] == 0 && c[3][1] == 0)) {
textView.setText("Game over. You win!");
gameOver = true;
} else if ((c[1][1] == 1 && c[2][2] == 1 && c[3][3] == 1)
|| (c[1][3] == 1 && c[2][2] == 1 && c[3][1] == 1)
|| (c[1][2] == 1 && c[2][2] == 1 && c[3][2] == 1)
|| (c[1][3] == 1 && c[2][3] == 1 && c[3][3] == 1)
|| (c[1][1] == 1 && c[1][2] == 1 && c[1][3] == 1)
|| (c[2][1] == 1 && c[2][2] == 1 && c[2][3] == 1)
|| (c[3][1] == 1 && c[3][2] == 1 && c[3][3] == 1)
|| (c[1][1] == 1 && c[2][1] == 1 && c[3][1] == 1)) {
textView.setText("Game over. You lost!");
gameOver = true;
} else {
boolean empty = false;
for(i=1; i<=3; i++) {
for(j=1; j<=3; j++) {
if(c[i][j]==2) {
empty = true;
break;
}
}
}
if(!empty) {
gameOver = true;
textView.setText("Game over. It's a draw!");
}
}
return gameOver;
}
}
