Alien Game逻辑

在这最有一个部分你将创建game-specific logic和 helper方法和类。胜利就在眼前，你的第一个winphone7程序就要出现了，加油加油！！（感谢http://winphone.us/）。另外最近imagecup要开始了，帮小美女推一下，学生们有时间都去参加。为了帮大家了解imagecup和winphone7的开发，我可能会针对学生讲一些入门级webcast，有详细计划再通知大家。刚刚翻译了imagecup的winphone7的评判标准，觉得有一条很好玩，就是要让使用了你的程序的人想去买一部winphone，呵呵这个占20%，大家加油了。另外有人要源代码，我把最后成品的源代码放到下一篇“番外篇”了，大家感兴趣可以去下载。

1. 在 GameplayScreen.cs 文件里，创建一个新的helper 类(在GameplayScreen类之外)根据下面的代码:

(Code Snippet – Game Development with XNA – Gameplay Screen – Bullet class)

/// <summary>

/// Represents either an alien or player bullet

/// </summary>

public class Bullet

{

public Vector2 Position;

public Vector2 Velocity;

public bool IsAlive;

}

2. 在Bullet 类后面添加两个helper类:

(Code Snippet – Game Development with XNA – Gameplay Screen – Player and Alien classes)

/// <summary>

/// The player's state

/// </summary>

public class Player

{

public Vector2 Position;

public Vector2 Velocity;

public float Width;

public float Height;

public bool IsAlive;

public float FireTimer;

public float RespawnTimer;

public string Name;

public Texture2D Picture;

public int Score;

public int Lives;

}

/// <summary>

/// Data for an alien. The only difference between the ships

/// and the badguys are the texture used.

/// </summary>

public class Alien

{

public Vector2 Position;

public Texture2D Texture;

public Vector2 Velocity;

public float Width;

public float Height;

public int Score;

public bool IsAlive;

public float FireTimer;

public float Accuracy;

public int FireCount;

}

3. 添加如下GameplayScreen类的变量:

(Code Snippet – Game Development with XNA – Gameplay Screen – even more variables)

Player player;

List<Alien> aliens;

List<Bullet> alienBullets;

List<Bullet> playerBullets;

4. 在构造函数中初始化这些变量，如下所示:

(Code Snippet – Game Development with XNA – Gameplay Screen – Player and Alien Initialization)

public GameplayScreen()

{

...

player = new Player();

playerBullets = new List<Bullet>();

aliens = new List<Alien>();

alienBullets = new List<Bullet>();

Accelerometer = new Accelerometer();

if (AccelerometerSensor.Default.State == SensorState.Ready)

{

...

}

...

}

5. 初始化player变量Width 和 Height在LoadContent 方法中 (初始化ParticleSystem之后):

(Code Snippet – Game Development with XNA – Gameplay Screen – Player Initialization in LoadContent method)

public override void LoadContent()

{

...

particles = new ParticleSystem(ScreenManager.Game.Content, ScreenManager.SpriteBatch);

player.Width = tankTexture.Width;

player.Height = tankTexture.Height;

base.LoadContent();

}

6. 下面的一小段代码将添加游戏的逻辑。他们将根据用户的输入来改变“player1”的移动。导航到 HandleInput 的方法，并找到以下行：

//TODO: Update player Velocity over X axis #1

在它的后面添加如下代码段:

(Code Snippet – Game Development with XNA – Gameplay Screen – Player Movements 1 in HandleInput method)

player.Velocity.X = movement;

7. 找到以下行 (在HandleInput 方法中):

//TODO: Update player velocity over X axis #2

在其后添加如下代码:

(Code Snippet – Game Development with XNA – Gameplay Screen – Player Movements 2 in HandleInput method)

player.Velocity.X = -1.0f;

8. 找到以下行 (在HandleInput 方法中):

//TODO: Update player velocity over X axis #3

在其后添加如下代码:

(Code Snippet – Game Development with XNA – Gameplay Screen – Player Movements 3 in HandleInput method)

player.Velocity.X = 1.0f;

9. 找到以下行 (在HandleInput 方法中):

//TODO: Update player velocity over X axis #4

在其后添加如下代码:

(Code Snippet – Game Development with XNA – Gameplay Screen – Player Movements 4 in HandleInput method)

player.Velocity.X = MathHelper.Min(input.CurrentGamePadStates[0].ThumbSticks.Left.X * 2.0f, 1.0f);

10. 找到以下行:

//TODO: Fire the bullet

更改"if"语句根据下面的代码片断：:

(Code Snippet – Game Development with XNA – Gameplay Screen – HandleInput firing the bullet code)

if (player.FireTimer <= 0.0f && player.IsAlive && !gameOver)

{

Bullet bullet = CreatePlayerBullet();

bullet.Position = new Vector2((int)(player.Position.X + player.Width / 2) - bulletTexture.Width / 2, player.Position.Y - 4);

bullet.Velocity = new Vector2(0, -256.0f);

player.FireTimer = 1.0f;

particles.CreatePlayerFireSmoke(player);

playerFired.Play();

}

else if (gameOver)

finishCurrentGame();

11. 创建 GameplayScreen 类中的以下方法：

此方法将创建Bullet类的一个实例。此实例使用在前面的代码段。

(Code Snippet – Game Development with XNA – Gameplay Screen – CreatePlayerBullet method)

/// <summary>

/// Returns an instance of a usable player bullet. Prefers reusing an /// existing (dead)

/// bullet over creating a new instance.

/// </summary>

/// <returns>A bullet ready to place into the world.</returns>

Bullet CreatePlayerBullet()

{

Bullet b = null;

for (int i = 0; i < playerBullets.Count; ++i)

{

if (playerBullets[i].IsAlive == false)

{

b = playerBullets[i];

break;

}

if (b == null)

{

b = new Bullet();

playerBullets.Add(b);

}

b.IsAlive = true;

return b;

}

12. 更改Update方法。在"base.Update(…)"方法调用之前，添加下面的蓝色突出显示的代码段：

此块的代码实际上提供了游戏的逻辑 – 它移动玩家和调用该方法来更新异型和重新计算子弹的位置。

(Code Snippet – Game Development with XNA – Gameplay Screen – Update method)

public override void Update(GameTime gameTime,

bool otherScreenHasFocus, bool coveredByOtherScreen)

{

float elapsed = (float)gameTime.ElapsedGameTime.TotalSeconds;

if (IsActive)

{

// Move the player

if (player.IsAlive == true)

{

player.Position += player.Velocity * 128.0f * elapsed;

player.FireTimer -= elapsed;

if (player.Position.X <= 0.0f)

player.Position = new Vector2(0.0f, player.Position.Y);

if (player.Position.X + player.Width >= worldBounds.Right)

player.Position = new Vector2(worldBounds.Right - player.Width, player.Position.Y);

}

Respawn(elapsed);

UpdateAliens(elapsed);

UpdateBullets(elapsed);

CheckHits();

if (player.IsAlive && player.Velocity.LengthSquared() > 0.0f)

particles.CreatePlayerDust(player);

particles.Update(elapsed);

}

base.Update(gameTime, otherScreenHasFocus, coveredByOtherScreen);

}

13. 向GameplayScreen 类中添加helper方法:

Note: 下面的代码段中添加大量的帮助器方法。方法用途如下：

重生：检查是否，玩家已经"死亡"但这场游戏还没有结束，如果这，它完成等待 respawnTimer结束后创建一个新的玩家实例屏幕的中间。

UpdateBullets：检查和更新屏幕上的玩家和异形子弹的位置。

UpdateAliens：移动异形，并计算是否发射子弹和朝哪个方向。

CheckHits：检查所有的子弹和玩家/异形的碰撞。它还将处理游戏逻辑，当命中发生时，进行让死亡，加分或者结束游戏等。

(Code Snippet – Game Development with XNA – Gameplay Screen – Helper update methods)

/// <summary>

/// Handles respawning the player if we are playing a game and the player is dead.

/// </summary>

/// <param name="elapsed">Time elapsed since Respawn was called last.</param>

void Respawn(float elapsed)

{

if (gameOver)

return;

if (!player.IsAlive)

{

player.RespawnTimer -= elapsed;

if (player.RespawnTimer <= 0.0f)

{

// See if there are any bullets close...

int left = worldBounds.Width / 2 - tankTexture.Width / 2 - 8;

int right = worldBounds.Width / 2 + tankTexture.Width / 2 + 8;

for (int i = 0; i < alienBullets.Count; ++i)

{

if (alienBullets[i].IsAlive == false)

continue;

if (alienBullets[i].Position.X >= left || alienBullets[i].Position.X <= right)

return;

}

player.IsAlive = true;

player.Position = new Vector2(worldBounds.Width / 2 - player.Width / 2, worldBounds.Bottom - groundTexture.Height + 2 - player.Height);

player.Velocity = Vector2.Zero;

player.Lives--;

}

/// <summary>

/// Moves all of the bullets (player and alien) and prunes "dead" bullets.

/// </summary>

/// <param name="elapsed"></param>

void UpdateBullets(float elapsed)

{

for (int i = 0; i < playerBullets.Count; ++i)

{

if (playerBullets[i].IsAlive == false)

continue;

playerBullets[i].Position += playerBullets[i].Velocity * elapsed;

if (playerBullets[i].Position.Y < -32)

{

playerBullets[i].IsAlive = false;

hitStreak = 0;

}

for (int i = 0; i < alienBullets.Count; ++i)

{

if (alienBullets[i].IsAlive == false)

continue;

alienBullets[i].Position += alienBullets[i].Velocity * elapsed;

if (alienBullets[i].Position.Y > worldBounds.Height - groundTexture.Height - laserTexture.Height)

alienBullets[i].IsAlive = false;

}

/// <summary>

/// Moves the aliens and performs their "thinking" by determining if they

/// should shoot and where.

/// </summary>

/// <param name="elapsed">The elapsed time since UpdateAliens was called last.</param>

private void UpdateAliens(float elapsed)

{

// See if it's time to spawn an alien;

alienSpawnTimer -= elapsed;

if (alienSpawnTimer <= 0.0f)

{

SpawnAlien();

alienSpawnTimer += alienSpawnRate;

}

for (int i = 0; i < aliens.Count; ++i)

{

if (aliens[i].IsAlive == false)

continue;

aliens[i].Position += aliens[i].Velocity * elapsed;

if ((aliens[i].Position.X < -aliens[i].Width - 64 && aliens[i].Velocity.X < 0.0f) ||

(aliens[i].Position.X > worldBounds.Width + 64 && aliens[i].Velocity.X > 0.0f))

{

aliens[i].IsAlive = false;

continue;

}

aliens[i].FireTimer -= elapsed;

if (aliens[i].FireTimer <= 0.0f && aliens[i].FireCount > 0)

{

if (player.IsAlive)

{

Bullet bullet = CreateAlienBullet();

bullet.Position.X = aliens[i].Position.X + aliens[i].Width / 2 - laserTexture.Width / 2;

bullet.Position.Y = aliens[i].Position.Y + aliens[i].Height;

if ((float)random.NextDouble() <= aliens[i].Accuracy)

{

bullet.Velocity = Vector2.Normalize(player.Position - aliens[i].Position) * 64.0f;

}

else

{

bullet.Velocity = new Vector2(-8.0f + 16.0f * (float)random.NextDouble(), 64.0f);

}

alienFired.Play();

}

aliens[i].FireCount--;

}

/// <summary>

/// Performs all bullet and player/alien collision detection. Also handles game logic

/// when a hit occurs, such as killing something, adding score, ending the game, etc.

/// </summary>

void CheckHits()

{

if (gameOver)

return;

for (int i = 0; i < playerBullets.Count; ++i)

{

if (playerBullets[i].IsAlive == false)

continue;

for (int a = 0; a < aliens.Count; ++a)

{

if (aliens[a].IsAlive == false)

continue;

if ((playerBullets[i].Position.X >= aliens[a].Position.X && playerBullets[i].Position.X <= aliens[a].Position.X + aliens[a].Width) && (playerBullets[i].Position.Y >= aliens[a].Position.Y && playerBullets[i].Position.Y <= aliens[a].Position.Y + aliens[a].Height))

{

playerBullets[i].IsAlive = false;

aliens[a].IsAlive = false;

hitStreak++;

player.Score += aliens[a].Score * (hitStreak / 5 + 1);

if (player.Score > highScore)

highScore = player.Score;

if (player.Score > nextLife)

{

player.Lives++;

nextLife += nextLife;

}

levelKillCount--;

if (levelKillCount <= 0)

AdvanceLevel();

particles.CreateAlienExplosion(new Vector2(aliens[a].Position.X + aliens[a].Width / 2, aliens[a].Position.Y + aliens[a].Height / 2));

alienDied.Play();

}

if (player.IsAlive == false)

return;

for (int i = 0; i < alienBullets.Count; ++i)

{

if (alienBullets[i].IsAlive == false)

continue;

if ((alienBullets[i].Position.X >= player.Position.X + 2 && alienBullets[i].Position.X <= player.Position.X + player.Width - 2) && (alienBullets[i].Position.Y >= player.Position.Y + 2 && alienBullets[i].Position.Y <= player.Position.Y + player.Height))

{

alienBullets[i].IsAlive = false;

player.IsAlive = false;

hitStreak = 0;

player.RespawnTimer = 3.0f;

particles.CreatePlayerExplosion(new Vector2(player.Position.X + player.Width / 2, player.Position.Y + player.Height / 2));

playerDied.Play();

if (player.Lives <= 0)

{

gameOver = true;

}

/// <summary>

/// Advances the difficulty of the game one level.

/// </summary>

void AdvanceLevel()

{

baseLevelKillCount += 5;

levelKillCount = baseLevelKillCount;

alienScore += 25;

alienSpawnRate -= 0.3f;

alienMaxAccuracy += 0.1f;

if (alienMaxAccuracy > 0.75f)

alienMaxAccuracy = 0.75f;

alienSpeedMin *= 1.35f;

alienSpeedMax *= 1.35f;

if (alienSpawnRate < 0.33f)

alienSpawnRate = 0.33f;

if (transitionFactor == 1.0f)

{

transitionRate = -0.5f;

}

else

{

transitionRate = 0.5f;

}

14. 在GameplayScreen 类中添加如下代码:

Note: 下面的代码片断还增加了大量的帮助器方法。他们的目的是，如下所示： CreateAlienBullet：创建的异形的子弹，将用于异形向玩家开火。

SpawnAlien：初始化一个新的异形实例，设置了的初始位置、速度，选择颜色纹理等。

CreateAlien：创建新异形的实例，并将其添加到异形集合

(Code Snippet – Game Development with XNA – Gameplay Screen – Helper aliens methods)

/// <summary>

/// Returns an instance of a usable alien bullet. Prefers reusing an existing (dead)

/// bullet over creating a new instance.

/// </summary>

/// <returns>A bullet ready to place into the world.</returns>

Bullet CreateAlienBullet()

{

Bullet b = null;

for (int i = 0; i < alienBullets.Count; ++i)

{

if (alienBullets[i].IsAlive == false)

{

b = alienBullets[i];

break;

}

if (b == null)

{

b = new Bullet();

alienBullets.Add(b);

}

b.IsAlive = true;

return b;

}

/// <summary>

/// Creates an instance of an alien, sets the initial state, and places it into the world.

/// </summary>

private void SpawnAlien()

{

Alien newAlien = CreateAlien();

if (random.Next(2) == 1)

{

newAlien.Position.X = -64.0f;

newAlien.Velocity.X = random.Next((int)alienSpeedMin, (int)alienSpeedMax);

}

else

{

newAlien.Position.X = worldBounds.Width + 32;

newAlien.Velocity.X = -random.Next((int)alienSpeedMin, (int)alienSpeedMax);

}

newAlien.Position.Y = 24.0f + 80.0f * (float)random.NextDouble();

// Aliens

if (transitionFactor > 0.0f)

{

switch (random.Next(4))

{

case 0:

newAlien.Texture = badguy_blue;

break;

case 1:

newAlien.Texture = badguy_red;

break;

case 2:

newAlien.Texture = badguy_green;

break;

case 3:

newAlien.Texture = badguy_orange;

break;

}

else

{

newAlien.Texture = alienTexture;

}

newAlien.Width = newAlien.Texture.Width;

newAlien.Height = newAlien.Texture.Height;

newAlien.IsAlive = true;

newAlien.Score = alienScore;

float duration = screenHeight / newAlien.Velocity.Length();

newAlien.FireTimer = duration * (float)random.NextDouble();

newAlien.FireCount = 1;

newAlien.Accuracy = alienMaxAccuracy;

}

/// <summary>

/// Returns an instance of a usable alien instance. Prefers reusing an existing (dead)

/// alien over creating a new instance.

/// </summary>

/// <returns>An alien ready to place into the world.</returns>

Alien CreateAlien()

{

Alien b = null;

for (int i = 0; i < aliens.Count; ++i)

{

if (aliens[i].IsAlive == false)

{

b = aliens[i];

break;

}

if (b == null)

{

b = new Alien();

aliens.Add(b);

}

b.IsAlive = true;

return b;

}

15. .导航到Draw方法，并添加下面的蓝色突出显示的代码段，在Screen.SpriteBatch.Begin() 和 Screen.SpriteBatch.End() 之间：

这样更改方法方法将呼调用helper方法以在屏幕上绘制变化后的内容。

(Code Snippet – Game Development with XNA – Gameplay Screen – Draw method update)

public override void Draw(GameTime gameTime)

{

float elapsedTime = (float)gameTime.ElapsedGameTime.TotalSeconds;

ScreenManager.SpriteBatch.Begin();

DrawBackground(elapsedTime);

DrawAliens();

DrawPlayer();

DrawBullets();

particles.Draw();

DrawForeground(elapsedTime);

DrawHud();

ScreenManager.SpriteBatch.End();

}

16. 在Draw 方法后面添加如下方法:

Note: 下面的代码段中添加大量的绘图相关的Helper方法。方法用途如下： DrawPlayer：绘制玩家的坦克。

DrawAliens：绘制所有异形。

DrawBullets：绘制所有的子弹（玩家的和异形的）。

DrawForeground：作为前台绘制云，并将其移动。

DrawBackground：绘制草、丘陵、山地和太阳/月亮。此外处理白天和黑夜之间转换。

DrawHud：绘制分数、剩余的生命值和" GAME OVER "需要的时候。

drawString：绘制隐藏的文本的通用方法。

(Code Snippet – Game Development with XNA – Gameplay Screen – Draw methods)

/// <summary>

/// Draws the player's tank

/// </summary>

void DrawPlayer()

{

if (!gameOver && player.IsAlive)

{

ScreenManager.SpriteBatch.Draw(tankTexture, player.Position, Color.White);

}

/// <summary>

/// Draws all of the aliens.

/// </summary>

void DrawAliens()

{

for (int i = 0; i < aliens.Count; ++i)

{

if (aliens[i].IsAlive) ScreenManager.SpriteBatch.Draw(aliens[i].Texture, new Rectangle((int)aliens[i].Position.X, (int)aliens[i].Position.Y, (int)aliens[i].Width, (int)aliens[i].Height), Color.White);

}

/// <summary>

/// Draw both the player and alien bullets.

/// </summary>

private void DrawBullets()

{

for (int i = 0; i < playerBullets.Count; ++i)

{

if (playerBullets[i].IsAlive)

ScreenManager.SpriteBatch.Draw(bulletTexture, playerBullets[i].Position, Color.White);

}

for (int i = 0; i < alienBullets.Count; ++i)

{

if (alienBullets[i].IsAlive)

ScreenManager.SpriteBatch.Draw(laserTexture, alienBullets[i].Position, Color.White);

}

/// <summary>

/// Draw the foreground, which is basically the clouds. I think I had planned on one point

/// having foreground grass that was drawn in front of the tank.

/// </summary>

/// <param name="elapsedTime">The elapsed time since last Draw</param>

private void DrawForeground(float elapsedTime)

{

// Move the clouds. Movement seems like an Update thing to do, but this animations

// have no impact over gameplay.

cloud1Position += new Vector2(24.0f, 0.0f) * elapsedTime;

if (cloud1Position.X > screenWidth)

cloud1Position.X = -cloud1Texture.Width * 2.0f;

cloud2Position += new Vector2(16.0f, 0.0f) * elapsedTime;

if (cloud2Position.X > screenWidth)

cloud2Position.X = -cloud1Texture.Width * 2.0f;

ScreenManager.SpriteBatch.Draw(cloud1Texture, cloud1Position, Color.White);

ScreenManager.SpriteBatch.Draw(cloud2Texture, cloud2Position, Color.White);

}

/// <summary>

/// Draw the grass, hills, mountains, and sun/moon. Handle transitioning

/// between day and night as well.

/// </summary>

/// <param name="elapsedTime">The elapsed time since last Draw</param>

private void DrawBackground(float elapsedTime)

{

transitionFactor += transitionRate * elapsedTime;

if (transitionFactor < 0.0f)

{

transitionFactor = 0.0f;

transitionRate = 0.0f;

}

if (transitionFactor > 1.0f)

{

transitionFactor = 1.0f;

transitionRate = 0.0f;

}

Vector3 day = Color.White.ToVector3();

Vector3 night = new Color(80, 80, 180).ToVector3();

Vector3 dayClear = Color.CornflowerBlue.ToVector3();

Vector3 nightClear = night;

Color clear = new Color(Vector3.Lerp(dayClear, nightClear, transitionFactor));

Color tint = new Color(Vector3.Lerp(day, night, transitionFactor));

// Clear the background, using the day/night color

ScreenManager.Game.GraphicsDevice.Clear(clear);

// Draw the mountains

ScreenManager.SpriteBatch.Draw(mountainsTexture, new Vector2(0, screenHeight - mountainsTexture.Height), tint);

// Draw the hills

ScreenManager.SpriteBatch.Draw(hillsTexture, new Vector2(0, screenHeight - hillsTexture.Height), tint);

// Draw the ground

ScreenManager.SpriteBatch.Draw(groundTexture, new Vector2(0, screenHeight - groundTexture.Height), tint);

// Draw the sun or moon (based on time)

ScreenManager.SpriteBatch.Draw(sunTexture, sunPosition, new Color(255, 255, 255, (byte)(255.0f * (1.0f - transitionFactor))));

ScreenManager.SpriteBatch.Draw(moonTexture, sunPosition, new Color(255, 255, 255, (byte)(255.0f * transitionFactor)));

}

/// <summary>

/// Draw the hud, which consists of the score elements and the GAME OVER tag.

/// </summary>

void DrawHud()

{

float scale = 2.0f;

if (gameOver)

{

Vector2 size = menuFont.MeasureString("GAME OVER");

DrawString(menuFont, "GAME OVER", new Vector2(ScreenManager.Game.GraphicsDevice.Viewport.Width / 2 - size.X, ScreenManager.Game.GraphicsDevice.Viewport.Height / 2 - size.Y / 2), new Color(255, 64, 64), scale);

}

else

{

int bonus = 100 * (hitStreak / 5);

string bonusString = (bonus > 0 ? " (" + bonus.ToString(System.Globalization.CultureInfo.CurrentCulture) + "%)" : "");

// Score

DrawString(scoreFont, "SCORE: " + player.Score.ToString(System.Globalization.CultureInfo .CurrentCulture) + bonusString, new Vector2(leftOffset, topOffset), Color.Yellow, scale);

string text = "LIVES: " + player.Lives.ToString(System.Globalization.CultureInfo .CurrentCulture);

Vector2 size = scoreFont.MeasureString(text);

size *= scale;

// Lives

DrawString(scoreFont, text, new Vector2(screenWidth - leftOffset - (int)size.X, topOffset), Color.Yellow, scale);

DrawString(scoreFont, "LEVEL: " + (((baseLevelKillCount - 5) / 5) + 1).ToString(System.Globalization.CultureInfo.CurrentCulture), new Vector2(leftOffset, screenHeight - bottomOffset), Color.Yellow, scale);

text = "HIGH SCORE: " + highScore.ToString(System.Globalization.CultureInfo

.CurrentCulture);

size = scoreFont.MeasureString(text);

DrawString(scoreFont, text, new Vector2(screenWidth - leftOffset - (int)size.X * 2, screenHeight - bottomOffset), Color.Yellow, scale);

}

/// <summary>

/// A simple helper to draw shadowed text.

/// </summary>

void DrawString(SpriteFont font, string text,

Vector2 position, Color color)

{

ScreenManager.SpriteBatch.DrawString(font, text, new Vector2(position.X + 1, position.Y + 1), Color.Black);

ScreenManager.SpriteBatch.DrawString(font, text, position, color);

}

/// <summary>

/// A simple helper to draw shadowed text.

/// </summary>

void DrawString(SpriteFont font, string text,

Vector2 position, Color color, float fontScale)

{

ScreenManager.SpriteBatch.DrawString(font, text, new Vector2(position.X + 1, position.Y + 1), Color.Black, 0, new Vector2(0, font.LineSpacing / 2), fontScale, SpriteEffects.None, 0);

ScreenManager.SpriteBatch.DrawString(font, text, position, color, 0, new Vector2(0, font.LineSpacing / 2), fontScale, SpriteEffects.None, 0);

}

17. 找到 LoadContent 方法，在base.LoadContent() 调用后面体检如下代码：

public override void LoadContent()

{

...

player.Width = tankTexture.Width;

player.Height = tankTexture.Height;

base.LoadContent();

LoadHighscore();

Start();

}

18. 找到 UnloadContent 方法并在“particles = null;”之前的位置添加下面的代码段:

public override void UnloadContent()

{

SaveHighscore();

particles = null;

base.UnloadContent();

}

19. 创建一个区域loading/unloading high scores logic。我们需要通过Isolated Storage来读取Windows Phone 文件系统中的数据。用如下代码在GameplayScreen类中创建logic:

(Code Snippet – Game Development with XNA – Gameplay Screen – Highscore storage methods)

#region Highscore loading/saving logic

/// <summary>

/// Saves the current highscore to a text file. The StorageDevice was selected during screen loading.

/// </summary>

private void SaveHighscore()

{

using (IsolatedStorageFile isf = IsolatedStorageFile.GetUserStoreForApplication())

{

using (IsolatedStorageFileStream isfs = new IsolatedStorageFileStream("highscores.txt", FileMode.Create, isf))

{

using (StreamWriter writer = new StreamWriter(isfs))

{

writer.Write(highScore.ToString(System.Globalization.CultureInfo.InvariantCulture));

writer.Flush();

writer.Close();

}

/// <summary>

/// Loads the high score from a text file. The StorageDevice was selected during the loading screen.

/// </summary>

private void LoadHighscore()

{

using (IsolatedStorageFile isf = IsolatedStorageFile.GetUserStoreForApplication())

{

if (isf.FileExists("highscores.txt"))

{

using (IsolatedStorageFileStream isfs = new IsolatedStorageFileStream("highscores.txt", FileMode.Open, isf))

{

using (StreamReader reader = new StreamReader(isfs))

{

try

{

highScore = Int32.Parse(reader.ReadToEnd(), System.Globalization.CultureInfo.InvariantCulture);

}

catch (FormatException)

{

highScore = 10000;

}

finally

{

if (reader != null)

reader.Close();

}

#endregion

20. 在GameplayScreen 类中创建Start方法来开始一个新游戏:

(Code Snippet – Game Development with XNA – Gameplay Screen – Start method)

/// <summary>

/// Starts a new game session, setting all game states to initial values.

/// </summary>

void Start()

{

if (gameOver)

{

player.Score = 0;

player.Lives = 3;

player.RespawnTimer = 0.0f;

gameOver = false;

aliens.Clear();

alienBullets.Clear();

playerBullets.Clear();

Respawn(0.0f);

}

transitionRate = 0.0f;

transitionFactor = 0.0f;

levelKillCount = 5;

baseLevelKillCount = 5;

alienScore = 25;

alienSpawnRate = 1.0f;

alienMaxAccuracy = 0.25f;

alienSpeedMin = 24.0f;

alienSpeedMax = 32.0f;

alienSpawnRate = 2.0f;

alienSpawnTimer = alienSpawnRate;

nextLife = 5000;

}

21. 打开 ParticleSystem.cs文件

22. 添加如下命名申明:

(Code Snippet – Game Development with XNA – ParticleSystem – using statement)

using AlienGame;

23. 在这个步骤，你将添加两个方法。一个用来创建玩家控制坦克时泥土/灰尘的效果。一个用来创建玩家发射子弹时，火焰的效果。添加如下方法到ParticleSystem 类中:

(Code Snippet – Game Development with XNA – ParticleSystem – Helper player effects methods)

/// <summary>

/// Creates the mud/dust effect when the player moves.

/// </summary>

/// <param name="position">Where on the screen to create the effect.</param>

public void CreatePlayerDust(Player player)

{

for (int i = 0; i < 2; ++i)

{

Particle p = CreateParticle();

p.Texture = smoke;

p.Color = new Color(125, 108, 43);

p.Position.X = player.Position.X + player.Width * (float)random.NextDouble();

p.Position.Y = player.Position.Y + player.Height - 3.0f * (float)random.NextDouble();

p.Alpha = 1.0f;

p.AlphaRate = -2.0f;

p.Life = 0.5f;

p.Rotation = 0.0f;

p.RotationRate = -2.0f + 4.0f * (float)random.NextDouble();

p.Scale = 0.25f;

p.ScaleRate = 0.5f;

p.Velocity.X = -4 + 8.0f * (float)random.NextDouble();

p.Velocity.Y = -8 + 4.0f * (float)random.NextDouble();

}

/// <summary>

/// Creates the effect for when the player fires a bullet.

/// </summary>

/// <param name="position">Where on the screen to create the effect.</param>

public void CreatePlayerFireSmoke(Player player)

{

for (int i = 0; i < 8; ++i)

{

Particle p = CreateParticle();

p.Texture = smoke;

p.Color = Color.White;

p.Position.X = player.Position.X + player.Width / 2;

p.Position.Y = player.Position.Y;

p.Alpha = 1.0f;

p.AlphaRate = -1.0f;

p.Life = 1.0f;

p.Rotation = 0.0f;

p.RotationRate = -2.0f + 4.0f * (float)random.NextDouble();

p.Scale = 0.25f;

p.ScaleRate = 0.25f;

p.Velocity.X = -4 + 8.0f * (float)random.NextDouble();

p.Velocity.Y = -16.0f + -32.0f * (float)random.NextDouble();

}

24. 编译并运行该应用程序。选择"开始游戏"菜单项，并享受你自己编写的游戏吧。

Note: 在模拟器中我们使用桌面的键盘移动车辆，您需要首先按PAUSE /BREAK 键。这将开启或者关闭仿真程序软件输入面板 (SIP) 或者桌面的键盘。因为键盘不能同时作为仿真程序软件输入面板 (SIP)和桌面的键盘，这个问题将在后面的版本里解决。

图1

完工的游戏

恭喜你，你终于完成了一个属于你自己的winphone7手机程序。

在今天的部分的过程中，您创建包括玩家和异形的移动计算、命中的检测、屏幕绘制，和其他一些的 AlienGame 逻辑。

虽然这个游戏完成了，但是我想大家可能有更多的疑问和想改进的地方，那让我们进入

手把手教用XNA开发winphone7游戏中级教程

发表于 2010-11-13 04:29 爱喝可乐的猫阅读(1498) 评论(3) 编辑收藏举报

手把手教用XNA开发winphone7游戏（五）大结局

手把手教用XNA开发winphone7游戏中级教程