学习笔记31（手把手教用XNA开发WINPHONE7游戏5--完结篇）

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)

C#

/// <summary>

///Represents either an alien or player bullet

/// </summary>

publicclassBullet

{

publicVector2Position;

publicVector2Velocity;

publicboolIsAlive;

}

2.在Bullet类后面添加两个helper类:

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

C#

/// <summary>

///The player's state

/// </summary>

publicclassPlayer

{

publicVector2Position;

publicVector2Velocity;

publicfloatWidth;

publicfloatHeight;

publicboolIsAlive;

publicfloatFireTimer;

publicfloatRespawnTimer;

publicstringName;

publicTexture2DPicture;

publicintScore;

publicintLives;

}

/// <summary>

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

///and the badguys are the texture used.

/// </summary>

publicclassAlien

{

publicVector2Position;

publicTexture2DTexture;

publicVector2Velocity;

publicfloatWidth;

publicfloatHeight;

publicintScore;

publicboolIsAlive;

publicfloatFireTimer;

publicfloatAccuracy;

publicintFireCount;

}

3.添加如下GameplayScreen类的变量:

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

C#

Playerplayer;

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)

C#

publicGameplayScreen()

{

...

player =newPlayer();

playerBullets =newList<Bullet>();

aliens =newList<Alien>();

alienBullets =newList<Bullet>();

Accelerometer =newAccelerometer();

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)

C#

publicoverridevoidLoadContent()

{

...

particles =newParticleSystem(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：

C#

//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)

C#

player.Velocity.X = movement;

7.找到以下行(在HandleInput方法中):

C#

//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)

C#

player.Velocity.X = -1.0f;

8.找到以下行(在HandleInput方法中):

C#

//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)

C#

player.Velocity.X = 1.0f;

9.找到以下行(在HandleInput方法中):

C#

//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)

C#

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

10.找到以下行:

C#

//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)

C#

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

{

Bulletbullet = CreatePlayerBullet();

bullet.Position =newVector2((int)(player.Position.X + player.Width / 2) - bulletTexture.Width / 2, player.Position.Y - 4);

bullet.Velocity =newVector2(0, -256.0f);

player.FireTimer = 1.0f;

particles.CreatePlayerFireSmoke(player);

playerFired.Play();

}

elseif (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)

C#

/// <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>

BulletCreatePlayerBullet()

{

Bulletb =null;

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

{

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

{

b = playerBullets[i];

break;

}

}

if(b ==null)

{

b =newBullet();

playerBullets.Add(b);

}

b.IsAlive =true;

returnb;

}

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)

C#

publicoverridevoidUpdate(GameTimegameTime,

boolotherScreenHasFocus,boolcoveredByOtherScreen)

{

floatelapsed = (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 =newVector2(0.0f, player.Position.Y);

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

player.Position =newVector2(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)

C#

/// <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>

voidRespawn(float elapsed)

{

if(gameOver)

return;

if(!player.IsAlive)

{

player.RespawnTimer -= elapsed;

if(player.RespawnTimer <= 0.0f)

{

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

intleft = worldBounds.Width / 2 - tankTexture.Width / 2 - 8;

intright = worldBounds.Width / 2 + tankTexture.Width / 2 + 8;

for(inti = 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 =newVector2(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>

voidUpdateBullets(float elapsed)

{

for(inti = 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(inti = 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>

privatevoid UpdateAliens(floatelapsed)

{

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

alienSpawnTimer -= elapsed;

if(alienSpawnTimer <= 0.0f)

{

SpawnAlien();

alienSpawnTimer += alienSpawnRate;

}

for(inti = 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)

{

Bulletbullet = 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 =newVector2(-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>

voidCheckHits()

{

if(gameOver)

return;

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

{

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

continue;

for(inta = 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(newVector2(aliens[a].Position.X + aliens[a].Width / 2, aliens[a].Position.Y + aliens[a].Height / 2));

alienDied.Play();

}

}

}

if(player.IsAlive ==false)

return;

for(inti = 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(newVector2(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>

voidAdvanceLevel()

{

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)

C#

/// <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>

BulletCreateAlienBullet()

{

Bulletb =null;

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

{

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

{

b = alienBullets[i];

break;

}

}

if(b ==null)

{

b =newBullet();

alienBullets.Add(b);

}

b.IsAlive =true;

returnb;

}

/// <summary>

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

/// </summary>

privatevoid SpawnAlien()

{

AliennewAlien = 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))

{

case0:

newAlien.Texture = badguy_blue;

break;

case1:

newAlien.Texture = badguy_red;

break;

case2:

newAlien.Texture = badguy_green;

break;

case3:

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;

floatduration = 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>

AlienCreateAlien()

{

Alienb =null;

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

{

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

{

b = aliens[i];

break;

}

}

if(b ==null)

{

b =newAlien();

aliens.Add(b);

}

b.IsAlive =true;

returnb;

}

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)

C#

publicoverridevoidDraw(GameTimegameTime)

{

floatelapsedTime = (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)

C#

/// <summary>

///Draws the player's tank

/// </summary>

voidDrawPlayer()

{

if(!gameOver && player.IsAlive)

{

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

}

}

/// <summary>

///Draws all of the aliens.

/// </summary>

voidDrawAliens()

{

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

{

if(aliens[i].IsAlive) ScreenManager.SpriteBatch.Draw(aliens[i].Texture, newRectangle((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>

privatevoid DrawBullets()

{

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

{

if(playerBullets[i].IsAlive)

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

}

for(inti = 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>

privatevoid DrawForeground(floatelapsedTime)

{

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

// have no impact over gameplay.

cloud1Position +=newVector2(24.0f, 0.0f) * elapsedTime;

if(cloud1Position.X > screenWidth)

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

cloud2Position +=newVector2(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>

privatevoid DrawBackground(floatelapsedTime)

{

transitionFactor += transitionRate * elapsedTime;

if(transitionFactor < 0.0f)

{

transitionFactor = 0.0f;

transitionRate = 0.0f;

}

if(transitionFactor > 1.0f)

{

transitionFactor = 1.0f;

transitionRate = 0.0f;

}

Vector3day =Color.White.ToVector3();

Vector3night =newColor(80, 80, 180).ToVector3();

Vector3dayClear =Color.CornflowerBlue.ToVector3();

Vector3nightClear = night;

Colorclear =newColor(Vector3.Lerp(dayClear, nightClear, transitionFactor));

Colortint =newColor(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,newVector2(0, screenHeight - mountainsTexture.Height), tint);

// Draw the hills

ScreenManager.SpriteBatch.Draw(hillsTexture,newVector2(0, screenHeight - hillsTexture.Height), tint);

// Draw the ground

ScreenManager.SpriteBatch.Draw(groundTexture,newVector2(0, screenHeight - groundTexture.Height), tint);

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

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

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

}

/// <summary>

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

/// </summary>

voidDrawHud()

{

floatscale = 2.0f;

if(gameOver)

{

Vector2size = menuFont.MeasureString("GAME OVER");

DrawString(menuFont,"GAME OVER",newVector2(ScreenManager.Game.GraphicsDevice.Viewport.Width / 2 - size.X, ScreenManager.Game.GraphicsDevice.Viewport.Height / 2 - size.Y / 2),newColor(255, 64, 64), scale);

}

else

{

intbonus = 100 * (hitStreak / 5);

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

// Score

DrawString(scoreFont,"SCORE: "+ player.Score.ToString(System.Globalization.CultureInfo.CurrentCulture) + bonusString,newVector2(leftOffset, topOffset),Color.Yellow, scale);

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

Vector2size = scoreFont.MeasureString(text);

size *= scale;

// Lives

DrawString(scoreFont, text,newVector2(screenWidth - leftOffset - (int)size.X, topOffset), Color.Yellow, scale);

DrawString(scoreFont,"LEVEL: "+ (((baseLevelKillCount - 5) / 5) + 1).ToString(System.Globalization.CultureInfo.CurrentCulture),newVector2(leftOffset, screenHeight - bottomOffset),Color.Yellow, scale);

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

.CurrentCulture);

size = scoreFont.MeasureString(text);

DrawString(scoreFont, text,newVector2(screenWidth - leftOffset - (int)size.X * 2, screenHeight - bottomOffset),Color.Yellow, scale);

}

}

/// <summary>

///A simple helper to draw shadowed text.

/// </summary>

voidDrawString(SpriteFont font,stringtext,

Vector2position,Color color)

{

ScreenManager.SpriteBatch.DrawString(font, text,newVector2(position.X + 1, position.Y + 1),Color.Black);

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

}

/// <summary>

///A simple helper to draw shadowed text.

/// </summary>

voidDrawString(SpriteFont font,stringtext,

Vector2position,Color color,floatfontScale)

{

ScreenManager.SpriteBatch.DrawString(font, text,newVector2(position.X + 1, position.Y + 1),Color.Black, 0,newVector2(0, font.LineSpacing / 2), fontScale, SpriteEffects.None, 0);

ScreenManager.SpriteBatch.DrawString(font, text, position, color, 0,newVector2(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：

C#

publicoverridevoidLoadContent()

{

...

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:

C#

publicoverridevoidUnloadContent()

{

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)

C#

#regionHighscore loading/saving logic

///<summary>

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

///</summary>

privatevoid SaveHighscore()

{

using(IsolatedStorageFileisf =IsolatedStorageFile.GetUserStoreForApplication())

{

using(IsolatedStorageFileStreamisfs =newIsolatedStorageFileStream("highscores.txt",FileMode.Create, isf))

{

using(StreamWriterwriter =newStreamWriter(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>

privatevoid LoadHighscore()

{

using(IsolatedStorageFileisf =IsolatedStorageFile.GetUserStoreForApplication())

{

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

{

using(IsolatedStorageFileStreamisfs =newIsolatedStorageFileStream("highscores.txt",FileMode.Open, isf))

{

using(StreamReaderreader =newStreamReader(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)

C#

///<summary>

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

///</summary>

voidStart()

{

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)

C#

usingAlienGame;

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)

C#

///<summary>

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

///</summary>

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

publicvoidCreatePlayerDust(Playerplayer)

{

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

{

Particlep = CreateParticle();

p.Texture = smoke;

p.Color =newColor(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>

publicvoidCreatePlayerFireSmoke(Playerplayer)

{

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

{

Particlep = 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。