Android井字游戏（二）游戏界面

图片与代码可见书配套官网下载

1 棋盘

1.1  先将游戏界面所需的图片放于“drawable-xxhdpi”文件夹中，后缀xxhdpi表示超高密度。

然后将图片封装到drawable中一个名为tile.xml的文件中

<?xml version="1.0" encoding="utf-8"?>

<level-list xmlns:android="http://schemas.android.com/apk/res/android" >
    <item
        android:drawable="@drawable/x_blue"
        android:maxLevel="0" />
    <item
        android:drawable="@drawable/o_red"
        android:maxLevel="1" />
    <item
        android:drawable="@drawable/tile_empty"
        android:maxLevel="2" />
    <item
        android:drawable="@drawable/tile_available"
        android:maxLevel="3" />
</level-list>

每个格子都有4种可能的状态：X、O、空 和 可下。

下面是格子为空时的定义，在文件tile_empty.xml中

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <stroke
        android:width="@dimen/stroke_width"
        android:color="@color/dark_border_color"/>
    <corners android:radius="@dimen/corner_radius"/>
</shape>

下面是格子可下时的定义，在文件tile_available.xml中

<?xml version="1.0" encoding="utf-8"?>

<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <stroke
        android:width="@dimen/stroke_width"
        android:color="@color/dark_border_color"/>
    <solid android:color="@color/available_color"/>
    <corners android:radius="@dimen/corner_radius"/>
</shape>

1.2 小棋盘

由排列成3×3网格的9个格子组成，通过指定行号和列号确定每个格子的位置。

以下文件是位于layout的small_board.xml

<GridLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:background="@drawable/tile_background"
    android:elevation="@dimen/elevation_low"
    android:padding="@dimen/small_board_padding"
    tools:context=".GameActivity">

    <ImageButton android:id="@+id/small1" style="@style/TileButton"
        android:layout_column="0" android:layout_row="0"/>
    <ImageButton android:id="@+id/small2" style="@style/TileButton"
        android:layout_column="1" android:layout_row="0"/>
    <ImageButton android:id="@+id/small3" style="@style/TileButton"
        android:layout_column="2" android:layout_row="0"/>
    <ImageButton android:id="@+id/small4" style="@style/TileButton"
        android:layout_column="0" android:layout_row="1"/>
    <ImageButton android:id="@+id/small5" style="@style/TileButton"
        android:layout_column="1" android:layout_row="1"/>
    <ImageButton android:id="@+id/small6" style="@style/TileButton"
        android:layout_column="2" android:layout_row="1"/>
    <ImageButton android:id="@+id/small7" style="@style/TileButton"
        android:layout_column="0" android:layout_row="2"/>
    <ImageButton android:id="@+id/small8" style="@style/TileButton"
        android:layout_column="1" android:layout_row="2"/>
    <ImageButton android:id="@+id/small9" style="@style/TileButton"
        android:layout_column="2" android:layout_row="2"/>
</GridLayout>

修改styles.xml

<?xml version="1.0" encoding="utf-8"?>

<resources>
   <!-- Base application theme. -->
   <style name="AppTheme"
          parent="android:Theme.Holo.Light.NoActionBar.Fullscreen">
      <!-- Customize your theme here. -->
   </style>

   <style name="TileButton">
      <item name="android:layout_width">@dimen/tile_size</item>
      <item name="android:layout_height">@dimen/tile_size</item>
      <item name="android:layout_margin">@dimen/tile_margin</item>
      <item name="android:background">#00000000</item>
      <item name="android:padding">@dimen/tile_padding</item>
      <item name="android:scaleType">centerCrop</item>
      <item name="android:src">@drawable/tile</item>
   </style>
</resources>

1.3 背景信息

drawable中tile_background.xml的定义如下

<?xml version="1.0" encoding="utf-8"?>

<level-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:drawable="@drawable/tile_blue"
        android:maxLevel="0"/>
    <item
        android:drawable="@drawable/tile_red"
        android:maxLevel="1"/>
    <item
        android:drawable="@drawable/tile_gray"
        android:maxLevel="2"/>
    <item
        android:drawable="@drawable/tile_purple"
        android:maxLevel="3"/>
</level-list>

用蓝色格子表示格子被玩家X占用，红色表示被玩家O占用，灰色表示未被玩家占用，紫色表示被两个玩家占用（即表示两个玩家平手）。分别在tile_blue.xml,  tile_red.xml,  tile_gray.xml,  tile_purple.xml 中定义，如下。

<!--blue-->
<?xml version="1.0" encoding="utf-8"?>

<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <stroke
        android:width="@dimen/stroke_width"
        android:color="@color/dark_border_color"/>
    <solid android:color="@color/blue_color"/>
    <corners android:radius="@dimen/corner_radius"/>
</shape>

<!--red-->
<?xml version="1.0" encoding="utf-8"?>

<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <stroke
        android:width="@dimen/stroke_width"
        android:color="@color/dark_border_color"/>
    <solid android:color="@color/red_color"/>
    <corners android:radius="@dimen/corner_radius"/>
</shape>

<!--gray-->
<?xml version="1.0" encoding="utf-8"?>

<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <stroke
        android:width="@dimen/stroke_width"
        android:color="@color/dark_border_color"/>
    <solid android:color="@color/gray_color"/>
    <corners android:radius="@dimen/corner_radius"/>
</shape>

<!--purple-->
<?xml version="1.0" encoding="utf-8"?>

<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <stroke
        android:width="@dimen/stroke_width"
        android:color="@color/dark_border_color"/>
    <solid android:color="@color/purple_color"/>
    <corners android:radius="@dimen/corner_radius"/>
</shape>

1.4 大棋盘

large_board.xml

<GridLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    tools:context=".GameActivity">

    <include android:id="@+id/large1" layout="@layout/small_board"
        android:layout_width="wrap_content" android:layout_height="wrap_content"
        android:layout_margin="@dimen/small_board_margin"
        android:layout_column="0" android:layout_row="0"/>
    <include android:id="@+id/large2" layout="@layout/small_board"
        android:layout_width="wrap_content" android:layout_height="wrap_content"
        android:layout_margin="@dimen/small_board_margin"
        android:layout_column="1" android:layout_row="0"/>
    <include android:id="@+id/large3" layout="@layout/small_board"
        android:layout_width="wrap_content" android:layout_height="wrap_content"
        android:layout_margin="@dimen/small_board_margin"
        android:layout_column="2" android:layout_row="0"/>
    <include android:id="@+id/large4" layout="@layout/small_board"
        android:layout_width="wrap_content" android:layout_height="wrap_content"
        android:layout_margin="@dimen/small_board_margin"
        android:layout_column="0" android:layout_row="1"/>
    <include android:id="@+id/large5" layout="@layout/small_board"
        android:layout_width="wrap_content" android:layout_height="wrap_content"
        android:layout_margin="@dimen/small_board_margin"
        android:layout_column="1" android:layout_row="1"/>
    <include android:id="@+id/large6" layout="@layout/small_board"
        android:layout_width="wrap_content" android:layout_height="wrap_content"
        android:layout_margin="@dimen/small_board_margin"
        android:layout_column="2" android:layout_row="1"/>
    <include android:id="@+id/large7" layout="@layout/small_board"
        android:layout_width="wrap_content" android:layout_height="wrap_content"
        android:layout_margin="@dimen/small_board_margin"
        android:layout_column="0" android:layout_row="2"/>
    <include android:id="@+id/large8" layout="@layout/small_board"
        android:layout_width="wrap_content" android:layout_height="wrap_content"
        android:layout_margin="@dimen/small_board_margin"
        android:layout_column="1" android:layout_row="2"/>
    <include android:id="@+id/large9" layout="@layout/small_board"
        android:layout_width="wrap_content" android:layout_height="wrap_content"
        android:layout_margin="@dimen/small_board_margin"
        android:layout_column="2" android:layout_row="2"/>
</GridLayout>

其中<include>用于创建一个由属性layout指定的布局实例，并设置其他属性，再将视图放到父布局的指定位置。

1.5 组合在一起

将整个棋盘封装在一起

<!--fragment_game.xml-->
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    tools:context=".GameActivity">

    <include
        layout="@layout/large_board"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

</RelativeLayout>

<!--activity_game.xml-->
<FrameLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".TicTacToeActivity">

    <ImageView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:scaleType="centerCrop"
        android:src="@drawable/sandy_beach"/>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center"
        android:orientation="vertical">

        <fragment
            android:id="@+id/fragment_game"
            class="org.example.tictactoe.GameFragment"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            tools:layout="@layout/fragment_game"/>
        <!-- Control fragment goes here... -->

    </LinearLayout>

</FrameLayout>

2 开始游戏

2.1 将 “开始游戏” 和 “继续游戏” 按钮的功能加入，修改MainFragment.java

package org.example.tictactoe;

import android.app.AlertDialog;
import android.app.Fragment;
import android.content.DialogInterface;import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class MainFragment extends Fragment {

    private AlertDialog mDialog;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView =
                inflater.inflate(R.layout.fragment_main, container, false);
        // Handle buttons here...
        View newButton = rootView.findViewById(R.id.new_button);
        View continueButton = rootView.findViewById(R.id.continue_button);
        View aboutButton = rootView.findViewById(R.id.about_button);
        newButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(getActivity(), GameActivity.class);
                getActivity().startActivity(intent);
            }
        });
        continueButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(getActivity(), GameActivity.class);
                intent.putExtra(GameActivity.KEY_RESTORE, true);
                getActivity().startActivity(intent);
            }
        });
        aboutButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
                builder.setMessage(R.string.about_text);
                builder.setCancelable(false);
                builder.setPositiveButton(R.string.ok_label,
                        new DialogInterface.OnClickListener() {
                            @Override
                            public void onClick(DialogInterface dialogInterface, int i) {
                                // nothing
                            }
                        });
                mDialog = builder.show();
            }
        });
        return rootView;
    }

    @Override
    public void onPause() {
        super.onPause();
        // Get rid of the about dialog if it's still up
        if (mDialog != null)
            mDialog.dismiss();
    }
}

其中 Intent 为红色， 将鼠标放置该单词上， 使用快捷键Alt + Enter 导入该类。

2.2 编写 GameActivity.java

2.2.1 方法onCreate()在活动启动时被调用。它根据前面创建的XML文件layout/activity_game.xml创建视图。

package org.example.tictactoe;

import android.app.Activity;
import android.app.AlertDialog;
import android.app.Dialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.util.Log;

public class GameActivity extends Activity {
    public static final String KEY_RESTORE = "key_restore";
    public static final String PREF_RESTORE = "pref_restore";
    private GameFragment mGameFragment;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_game);
        // 在此处恢复游戏
    }
}

每次在程序中添加新活动时，都必须修改AndroidManifest.xml以引用它。在application元素末尾添加以下代码。

<activity
    android:name="org.example.tictactoe.GameActivity">
</activity>

2.2.2 继续游戏

继续扩充GameActivity.java 代码

public class GameActivity extends Activity {
    //KEY_RESTORE是传递给新活动的标志的名称，用于将棋盘恢复到以前冻结的状态
    public static final String KEY_RESTORE = "key_restore";
    public static final String PREF_RESTORE = "pref_restore";
    private GameFragment mGameFragment;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_game);
        // 此处恢复游戏

        //getFragmentManager获取一个指向跟踪所有片段的对象的句柄
        //使用findFragmentById获取指向游戏片段的引用
        mGameFragment = (GameFragment) getFragmentManager()
                .findFragmentById(R.id.fragment_game);

        //对Intent实例调用方法getBooleanExtra()以获得KEY_RESTORE的值
        boolean restore = getIntent().getBooleanExtra(KEY_RESTORE, false);

        //若restore为true，就使用getPreferences()获取指向该活动的Android首项管理器的句柄
        //再调用getString()获取PREF_RESTORE的值
        if (restore) {
            String gameData = getPreferences(MODE_PRIVATE)
                    .getString(PREF_RESTORE, null);
            if (gameData != null) {
                //使用putState来修改游戏的状态
                mGameFragment.putState(gameData);
            }
        }
        Log.d("UT3", "restore = " + restore);
    }
}

2.2.3 保存游戏

每当有活动不再处于运行状态时，就要保存游戏。在GameActivity.java添加以下方法

@Override
    protected void onPause() {
        super.onPause();
        //getState获取游戏数据
        String gameData = mGameFragment.getState();
        //getPreferences获取指向首选项存储区的句柄，为首选项创建一个编辑器(edit)
        //使用键PREF_RESTORE保存游戏数据(putString),并将修改存储到首选项存储区(commit)
        getPreferences(MODE_PRIVATE).edit()
                .putString(PREF_RESTORE, gameData)
                .commit();
        // Log.d负责将一条调试消息写入日志
        Log.d("UT3", "state = " + gameData);
    }

2.2.4 重新开始游戏

public void restartGame() {
     mGameFragment.restartGame();
}

2.2.5 宣布获胜方

 public void reportWinner(final Tile.Owner winner) {
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setMessage(getString(R.string.declare_winner, winner));
        builder.setCancelable(false);
        builder.setPositiveButton(R.string.ok_label,
                new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface, int i) {
                        finish();
                    }
                });
        final Dialog dialog = builder.create();
        dialog.show();

        // Reset the board to the initial position
        mGameFragment.initGame();
    }

上述代码使用AlterDialog.Builder类创建了一个消息框，其中包含一行文本和一个ok按键。用户点击ok活动将结束，即关闭游戏屏幕返回主菜单。

2.3 编写GameFragment.java

2.3.1 定义

方法onCreateView用于创建视图。

package org.example.tictactoe;

import android.app.Fragment;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageButton;

import java.util.HashSet;
import java.util.Set;

public class GameFragment extends Fragment {
   //此处定义数据结构
   @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setRetainInstance(true);            // 设备配置发生变化时保留该片段
        initGame();                         //  设置所有数据结构
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView =
                inflater.inflate(R.layout.large_board, container, false);
        initViews(rootView);
        updateAllTiles();
        return rootView;
    }
}

2.3.2  数据结构

//此处定义数据结构

// mLargeIds和mSmallIds都是常量数组，分别用于将数字映射到小棋盘和格子资源id
static private int mLargeIds[] = {R.id.large1, R.id.large2, R.id.large3,
        R.id.large4, R.id.large5, R.id.large6, R.id.large7, R.id.large8,
        R.id.large9,};
static private int mSmallIds[] = {R.id.small1, R.id.small2, R.id.small3,
        R.id.small4, R.id.small5, R.id.small6, R.id.small7, R.id.small8,
        R.id.small9,};

// 以下三个表示不同层级的格子。最顶层有1个，最底层有81个
private Tile mEntireBoard = new Tile(this);
private Tile mLargeTiles[] = new Tile[9];
private Tile mSmallTiles[][] = new Tile[9][9];
// mPlayer 玩家id
private Tile.Owner mPlayer = Tile.Owner.X;
// mAvailable是列表，包含给定时点可下的所有格子
private Set<Tile> mAvailable = new HashSet<Tile>();
// mLastLarge和mLastSmall是最后一步棋的索引
private int mLastLarge;
private int mLastSmall;

2.3.3 初始化游戏

创建片段时，在方法onCreate()中调用了方法initGame()，该方法将所有的数据结构初始化为起始状态。

    public void initGame() {
        Log.d("UT3", "init game");
        mEntireBoard = new Tile(this);
        // 创建所有格子
        for (int large = 0; large < 9; large++) {
            mLargeTiles[large] = new Tile(this);
            for (int small = 0; small < 9; small++) {
                mSmallTiles[large][small] = new Tile(this);
            }
            mLargeTiles[large].setSubTiles(mSmallTiles[large]);
        }
        mEntireBoard.setSubTiles(mLargeTiles);

        // 设置先下棋子的玩家可下的格子
        mLastSmall = -1;
        mLastLarge = -1;
        setAvailableFromLastMove(mLastSmall);
    }

2.3.4  初始化视图

    private void initViews(View rootView) {
        mEntireBoard.setView(rootView);
        for (int large = 0; large < 9; large++) {
            View outer = rootView.findViewById(mLargeIds[large]);
            mLargeTiles[large].setView(outer);

            for (int small = 0; small < 9; small++) {
                ImageButton inner = (ImageButton) outer.findViewById
                        (mSmallIds[small]);
                final int fLarge = large;
                final int fSmall = small;
                final Tile smallTile = mSmallTiles[large][small];
                smallTile.setView(inner);
                inner.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View view) {
                        if (isAvailable(smallTile)) {
                            makeMove(fLarge, fSmall);
                            switchTurns();
                        }
                    }
                });
            }
        }
    }

2.3.5 将棋子下到格子中

每下一个棋子就要判断是否有玩家已取得胜利，若有，则游戏结束宣布winner；若没有，游戏继续。

    private void makeMove(int large, int small) {
        mLastLarge = large;
        mLastSmall = small;
        Tile smallTile = mSmallTiles[large][small];
        Tile largeTile = mLargeTiles[large];
        smallTile.setOwner(mPlayer);
        setAvailableFromLastMove(small);
        Tile.Owner oldWinner = largeTile.getOwner();
        Tile.Owner winner = largeTile.findWinner();
        if (winner != oldWinner) {
            largeTile.setOwner(winner);
        }
        winner = mEntireBoard.findWinner();
        mEntireBoard.setOwner(winner);
        updateAllTiles();
        if (winner != Tile.Owner.NEITHER) {
            ((GameActivity)getActivity()).reportWinner(winner);
        }
    }

2.3.6 让另一个玩家接着下棋

切换mPlayer的值即可。

    private void switchTurns() {
        mPlayer = mPlayer == Tile.Owner.X ? Tile.Owner.O : Tile
                .Owner.X;
    }

2.3.7 重新开始游戏

    public void restartGame() {
        initGame();
        initViews(getView());
        updateAllTiles();
    }

2.3.8 计算可下棋的格子

根据终极版井字游戏的规则，一个玩家下棋后，对手接下来只能在这步棋所处的格子对应的小棋盘中下棋。

// 用于清空可下棋格子列表，以便能够在其中添加格子
private void clearAvailable() {
    mAvailable.clear();
}

// 用于将一个格子加入可下棋格子列表中
private void addAvailable(Tile tile) {
    mAvailable.add(tile);
}

// 用于判断指定的格子是否可下棋
public boolean isAvailable(Tile tile) {
    return mAvailable.contains(tile);
}

private void setAvailableFromLastMove(int small) {
    clearAvailable();
    // 让目标小棋盘所有空格子都可下棋
    if (small != -1) {
        for (int dest = 0; dest < 9; dest++) {
            Tile tile = mSmallTiles[small][dest];
            if (tile.getOwner() == Tile.Owner.NEITHER)
                addAvailable(tile);
        }
    }
    // 若目标小棋盘没空格子，则令整个棋盘的空格子都可下棋
    if (mAvailable.isEmpty()) {
        setAllAvailable();
    }
}

private void setAllAvailable() {
    for (int large = 0; large < 9; large++) {
        for (int small = 0; small < 9; small++) {
            Tile tile = mSmallTiles[large][small];
            if (tile.getOwner() == Tile.Owner.NEITHER)
                addAvailable(tile);
        }
    }
}

2.3.9 处理状态

要将游戏当前状态转换为序列化形式存储下来。注意的是，明确每个格子由哪个玩家占领，还必须跟踪上一步棋子，因为接下来判断哪些地方可下棋取决于上一步棋子。

/** 创建包含游戏状态的字符串 */
    public String getState() {
        StringBuilder builder = new StringBuilder();
        builder.append(mLastLarge);
        builder.append(',');
        builder.append(mLastSmall);
        builder.append(',');
        for (int large = 0; large < 9; large++) {
            for (int small = 0; small < 9; small++) {
                builder.append(mSmallTiles[large][small].getOwner().name());
                builder.append(',');
            }
        }
        return builder.toString();
    }

    /** 根据给定的字符串恢复游戏状态 */
    public void putState(String gameData) {
        String[] fields = gameData.split(",");
        int index = 0;
        mLastLarge = Integer.parseInt(fields[index++]);
        mLastSmall = Integer.parseInt(fields[index++]);
        for (int large = 0; large < 9; large++) {
            for (int small = 0; small < 9; small++) {
                Tile.Owner owner = Tile.Owner.valueOf(fields[index++]);
                mSmallTiles[large][small].setOwner(owner);
            }
        }
        setAvailableFromLastMove(mLastSmall);
        updateAllTiles();
    }

接下来，重新计算可下棋格子列表，并更新所有格子的drawable状态。

    private void updateAllTiles() {
        mEntireBoard.updateDrawableState();
        for (int large = 0; large < 9; large++) {
            mLargeTiles[large].updateDrawableState();
            for (int small = 0; small < 9; small++) {
                mSmallTiles[large][small].updateDrawableState();
            }
        }
    }

2.4  定义Tile.java

Tile类 表示任何层次的棋盘格子。

2.4.1 Tile类的轮廓

Tile对象包含占据者和视图，还可能包含一系列格子。Tile类包含构造函数Tile，还包含占据者、视图和子格子的获取函数和设置函数。另外，它还包含管理drawale状态的代码以及判断谁是占据者的代码。

package org.example.tictactoe;

import android.graphics.drawable.Drawable;
import android.view.View;
import android.widget.ImageButton;

public class Tile {

    public enum Owner {
        X, O /* letter O */, NEITHER, BOTH
    }

    // 这些级别是在drawable中定义的
    private static final int LEVEL_X = 0;
    private static final int LEVEL_O = 1; // letter O
    private static final int LEVEL_BLANK = 2;
    private static final int LEVEL_AVAILABLE = 3;
    private static final int LEVEL_TIE = 3;

    private final GameFragment mGame;
    private Owner mOwner = Owner.NEITHER;
    private View mView;
    private Tile mSubTiles[];

    public Tile(GameFragment game) {
        this.mGame = game;
    }

    public View getView() {
        return mView;
    }

    public void setView(View view) {
        this.mView = view;
    }

    public Owner getOwner() {
        return mOwner;
    }

    public void setOwner(Owner owner) {
        this.mOwner = owner;
    }

    public Tile[] getSubTiles() {
        return mSubTiles;
    }

    public void setSubTiles(Tile[] subTiles) {
        this.mSubTiles = subTiles;
    }
}

2.4.2 管理drawable状态的代码

    // 通过调用getLevel来确定等级，然后根据视图泪习性，对视图背景或drawable调用setLevel
    public void updateDrawableState() {
        if (mView == null) return;
        int level = getLevel();
        if (mView.getBackground() != null) {
            mView.getBackground().setLevel(level);
        }
        if (mView instanceof ImageButton) {
            Drawable drawable = ((ImageButton) mView).getDrawable();
            drawable.setLevel(level);
        }
    }

    private int getLevel() {
        int level = LEVEL_BLANK;
        switch (mOwner) {
            case X:
                level = LEVEL_X;
                break;
            case O: // letter O
                level = LEVEL_O;
                break;
            case BOTH:
                level = LEVEL_TIE;
                break;
            case NEITHER:
                level = mGame.isAvailable(this) ? LEVEL_AVAILABLE : LEVEL_BLANK;
                break;
        }
        return level;
    }

2.4.3 编写确定占用者的代码

    public Owner findWinner() {
        // 如果已确定占用者，就返回它
        if (getOwner() != Owner.NEITHER)
            return getOwner();

        int totalX[] = new int[4];
        int totalO[] = new int[4];
        countCaptures(totalX, totalO);
        if (totalX[3] > 0) return Owner.X;
        if (totalO[3] > 0) return Owner.O;

        // 检查是否平局
        int total = 0;
        for (int row = 0; row < 3; row++) {
            for (int col = 0; col < 3; col++) {
                Owner owner = mSubTiles[3 * row + col].getOwner();
                if (owner != Owner.NEITHER) total++;
            }
            if (total == 9) return Owner.BOTH;
        }

        // 未被玩家占用
        return Owner.NEITHER;
    }

2.4.4 方法countCaptures()

如果有占用者，就返回他；否则，计算两玩家占据的格子数。若有一个玩家占据了3个连成一条线的格子那么该玩家为占据者；否则检查小棋盘的所有格子是否否不为空。若是，则为平局，返回BOTH；否则，说明未被任何玩家占据，因此返回NEITHER.

    private void countCaptures(int totalX[], int totalO[]) {
        int capturedX, capturedO;
        // 检查是否有一个玩家的3个棋子成一行
        for (int row = 0; row < 3; row++) {
            capturedX = capturedO = 0;
            for (int col = 0; col < 3; col++) {
                Owner owner = mSubTiles[3 * row + col].getOwner();
                if (owner == Owner.X || owner == Owner.BOTH) capturedX++;
                if (owner == Owner.O || owner == Owner.BOTH) capturedO++;
            }
            totalX[capturedX]++;
            totalO[capturedO]++;
        }

        // 检查是否有一个玩家的3个棋子成一列
        for (int col = 0; col < 3; col++) {
            capturedX = capturedO = 0;
            for (int row = 0; row < 3; row++) {
                Owner owner = mSubTiles[3 * row + col].getOwner();
                if (owner == Owner.X || owner == Owner.BOTH) capturedX++;
                if (owner == Owner.O || owner == Owner.BOTH) capturedO++;
            }
            totalX[capturedX]++;
            totalO[capturedO]++;
        }

        // 检查是否有一个玩家的3个棋子成对角线
        capturedX = capturedO = 0;
        for (int diag = 0; diag < 3; diag++) {
            Owner owner = mSubTiles[3 * diag + diag].getOwner();
            if (owner == Owner.X || owner == Owner.BOTH) capturedX++;
            if (owner == Owner.O || owner == Owner.BOTH) capturedO++;
        }
        totalX[capturedX]++;
        totalO[capturedO]++;
        capturedX = capturedO = 0;
        for (int diag = 0; diag < 3; diag++) {
            Owner owner = mSubTiles[3 * diag + (2 - diag)].getOwner();
            if (owner == Owner.X || owner == Owner.BOTH) capturedX++;
            if (owner == Owner.O || owner == Owner.BOTH) capturedO++;
        }
        totalX[capturedX]++;
        totalO[capturedO]++;
    }

首先，计算各行的X和O的数量，然后计算各列的X和O的数量，最后计算对角线的。结果是通过两个数组返回的：表示玩家X的数组totalX和表示玩家O的数组totalO。

2.5 控制游戏

玩游戏时，用户可能想重新开始或返回主菜单。以下提供一种返回主菜单的途径。定义在layout中fragment_control.xml

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    android:padding="@dimen/control_padding"
    tools:context=".GameActivity">

    <Button
        android:id="@+id/button_restart"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:elevation="@dimen/elevation_low"
        android:drawableTop="@drawable/restart"
        android:text="@string/restart_label"/>

    <Button
        android:id="@+id/button_main"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:elevation="@dimen/elevation_low"
        android:drawableTop="@drawable/home"
        android:text="@string/main_menu_label"/>

</LinearLayout>

其中所用到的图片位于drawable-xxhdpi中。接下来，要在activity_game.xml中包含一个新片段

<!-- -->
<fragment
            android:id="@+id/fragment_game_controls"
            class="org.example.tictactoe.ControlFragment"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            tools:layout="@layout/fragment_control"/>

最后，要编写处理该布局的代码ControlFragment.java

package org.example.tictactoe;

import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class ControlFragment extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView =
                inflater.inflate(R.layout.fragment_control, container, false);
        View main = rootView.findViewById(R.id.button_main);
        View restart = rootView.findViewById(R.id.button_restart);

        main.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                getActivity().finish();
            }
        });
        restart.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                ((GameActivity) getActivity()).restartGame();
            }
        });
        return rootView;
    }
}

通过Main Menu按钮结束当前活动，与返回按钮效果相同。Restart按钮假定控制片段嵌入在GameActivity中，因此会将当前活动转换为GameActivity，并调用前面定义的重新开始游戏的方法。

2.6 参数定义

以下定义程序所使用的一些参数。

    <!-- dimens.xml-->
    <dimen name="activity_horizontal_margin">8dp</dimen>
    <dimen name="activity_vertical_margin">8dp</dimen>
    <dimen name="tile_size">30dp</dimen>
    <dimen name="tile_margin">0dp</dimen>
    <dimen name="tile_padding">3dp</dimen>
    <dimen name="control_padding">20dp</dimen>
    <dimen name="small_board_padding">2dp</dimen>
    <dimen name="small_board_margin">2dp</dimen>
    <dimen name="elevation_low">4dp</dimen>

    <!-- colors.xml -->
    <color name="dark_border_color">#4f4f4f</color>
    <color name="available_color">#7fbf7f</color>
    <color name="blue_color">#7f7fff</color>
    <color name="gray_color">#bfbfbf</color>
    <color name="purple_color">#7f007f</color>
    <color name="red_color">#ff7f7f</color>

    <!-- strings.xml -->
    <string name="restart_label">Restart</string>
    <string name="main_menu_label">Main Menu</string>
    <string name="declare_winner">%1$s is the winner</string>

定义横向模式，即不同版本的activity_game.xml 和 fragment_control.xml , 存储在res/layout-land中，-land表示横向模式。

<!-- activity_game.xml -->
<FrameLayout
   xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:tools="http://schemas.android.com/tools"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   tools:context=".TicTacToeActivity">

   <ImageView
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:scaleType="centerCrop"
      android:src="@drawable/sandy_beach"/>

   <LinearLayout
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:gravity="center"
      android:baselineAligned="false"
      android:orientation="horizontal">

      <fragment
         android:id="@+id/fragment_game"
         class="org.example.tictactoe.GameFragment"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         tools:layout="@layout/fragment_game"/>

      <fragment
         android:id="@+id/fragment_game_controls"
         class="org.example.tictactoe.ControlFragment"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         tools:layout="@layout/fragment_control"/>
   </LinearLayout>

</FrameLayout>

<!-- fragment_control.xml -->
<LinearLayout
   xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:tools="http://schemas.android.com/tools"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:orientation="vertical"
   android:padding="@dimen/control_padding"
   tools:context=".GameActivity">

   <Button
      android:id="@+id/button_restart"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:drawableTop="@drawable/restart"
      android:elevation="@dimen/elevation_low"
      android:text="@string/restart_label"/>

   <Button
      android:id="@+id/button_main"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:drawableTop="@drawable/home"
      android:elevation="@dimen/elevation_low"
      android:text="@string/main_menu_label"/>

</LinearLayout>

然后，就可以运行了。

摘自《Hello, Android》