About.java

package com.example.sudoku;

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

public class About extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.about);
    }
}

about.xml

<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:padding="10dip"
    >
	<TextView
		android:id="@+id/about_title"
	    android:layout_width="wrap_content" 
	    android:layout_height="wrap_content" 
	    android:text="@string/about_text"
	    />
</ScrollView>

arrays.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
	<array name="difficulty">
		<item>@string/easy_label</item>
		<item>@string/medium_label</item>
		<item>@string/hard_label</item>
	</array>
</resources>

main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
	android:background="@color/background"
    android:orientation="horizontal"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:padding="15dip"
    >
 <LinearLayout 
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    android:paddingRight="20dip"
    android:paddingLeft="20dip"
    >
<TextView  
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:text="@string/main_title"
    android:layout_gravity="center"
    android:layout_marginBottom="20dip"
    android:textSize="24.5sp"
    />
<TableLayout
	android:layout_width="wrap_content"
	android:layout_height="wrap_content"
	android:layout_gravity="center"
	android:stretchColumns="*" >
	<TableRow>
		<Button
			android:id="@+id/continue_button"
			android:text="@string/continue_label" />
	
		<Button
			android:id="@+id/new_button"
			android:text="@string/new_game_label" />
	</TableRow>
	<TableRow>
		<Button
			android:id="@+id/about_button"
			android:text="@string/about_label" />
		
		<Button
			android:id="@+id/exit_button"
			android:text="@string/exit_label" />
	</TableRow>
	</TableLayout>
</LinearLayout>
</LinearLayout>

main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
	android:background="@color/background"
    android:orientation="horizontal"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:padding="30dip"
    >
    <LinearLayout
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    >
<TextView  
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:text="@string/main_title"
    android:layout_gravity="center"
    android:layout_marginBottom="25dip"
    android:textSize="24.5sp"
    />

<Button
	android:id="@+id/continue_button"
	android:layout_width="fill_parent"
	android:layout_height="wrap_content"
	android:text="@string/continue_label" />
	
<Button
	android:id="@+id/new_button"
	android:layout_width="fill_parent"
	android:layout_height="wrap_content"
	android:text="@string/new_game_label" />
	
<Button
	android:id="@+id/about_button"
	android:layout_width="fill_parent"
	android:layout_height="wrap_content"
	android:text="@string/about_label" />

<Button
	android:id="@+id/exit_button"
	android:layout_width="fill_parent"
	android:layout_height="wrap_content"
	android:text="@string/exit_label" />
</LinearLayout>
</LinearLayout>

menu.xml

<?xml version="1.0" encoding="utf-8"?>
<menu
  xmlns:android="http://schemas.android.com/apk/res/android">
  <item android:id="@+id/settings"
	android:title="@string/settings_label"
	android:alphabeticShortcut="@string/settings_shortcut" />
</menu>

Prefs.java

package com.example.sudoku;

import android.os.Bundle;
import android.preference.PreferenceActivity;

public class Prefs extends PreferenceActivity {
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		addPreferencesFromResource(R.xml.settings);
	}
}

settings.xml

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen
  xmlns:android="http://schemas.android.com/apk/res/android">
  <CheckBoxPreference
	android:key="music"
	android:title="@string/music_title"
	android:summary="@string/music_summary"
	android:defaultValue="true" />
  <CheckBoxPreference
	android:key="hints"
	android:title="@string/hints_title"
	android:summary="@string/hints_summary"
	android:defaultValue="true" />
</PreferenceScreen>

strings.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string name="app_name">Sudoku</string>
    <string name="main_title">Android Sudoku</string>
    <string name="about_title">About Android Sudoku</string>
    <string name="continue_label">Continue</string>
    <string name="new_game_label">New Game</string>
    <string name="about_label">About</string>
    <string name="exit_label">Exit</string>
    <string name="about_text">\
    Sudoku is a logic based number placement puzzle. 
    Starting with a partially completed 9x9 grid, the 
    objective is to fill the grid so that each 
    row, each column, and each of the 3x3 boxes 
    (also called <i>blocks</i>) contains the digits 
    1 to 9 exactly once.
    </string>
    <string name="settings_label">Settings...</string>
	<string name="settings_title">Sudoku settings</string>
	<string name="settings_shortcut">s</string>
	<string name="music_title">Music</string>
	<string name="music_summary">Play background music</string>
	<string name="hints_title">Hints</string>
	<string name="hints_summary">Show hints during play</string>
    
    <string name="new_game_title">Difficulty</string>
	<string name="easy_label">Easy</string>
	<string name="medium_label">Medium</string>
	<string name="hard_label">Hard</string>
    
</resources>

Sudoku.java

package com.example.sudoku;

import android.app.Activity;
import android.os.Bundle;
import android.content.Intent;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.util.Log;


public class Sudoku extends Activity implements OnClickListener{
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        //Set up click listeners
        View continueButton = findViewById(R.id.continue_button);
        continueButton.setOnClickListener(this);
        View newButton = findViewById(R.id.new_button);
        newButton.setOnClickListener(this);
        View aboutButton = findViewById(R.id.about_button);
        aboutButton.setOnClickListener(this);
        View exitButton = findViewById(R.id.exit_button);
        exitButton.setOnClickListener(this);
        
    }
    
    public void onClick(View v){
    	switch (v.getId()) {
    	case R.id.about_button:
    		Intent i = new Intent(this, About.class);
    		startActivity(i);
    		break;
    	case R.id.new_button:
    		openNewGameDialog();
    		break;
    	case R.id.exit_button:
    		finish();
    		break;
    	}
    }
    
    private static final String TAG = "Sudoku";
    
    private void openNewGameDialog(){
    	new AlertDialog.Builder(this)
	    	.setTitle(R.string.new_game_title)
	    	.setItems(R.array.difficulty,
	    	new DialogInterface.OnClickListener() {
	    		public void onClick(DialogInterface dialoginterface,
	    			int i) {
	    			startGame(i);
	    		}
    	})
    	.show();
    }
    
    //Start a new game
    private void startGame(int i) {
    	Log.d(TAG, "clicked on " + i);
    	// Start game here...
    	}


    @Override
    public boolean onCreateOptionsMenu(Menu menu){
    	super.onCreateOptionsMenu(menu);
    	MenuInflater inflater = getMenuInflater();
    	inflater.inflate(R.menu.menu, menu);
    	return true;
    }
    
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
	    switch (item.getItemId()) {
	    case R.id.settings:
	    startActivity(new Intent(this, Prefs.class));
	    return true;
	    // More items go here (if any) ...
	    }
	    return false;
    }
}