XNA Game Studio 游戲循環

在這部分中您將重點兩剩余部分的游戲 — — 重寫Update 和 Draw 功能。有些大大可能看過相關微軟的訓練包，我這里主要是幫一些初學者。希望各位大大包含，畢竟文章發出來還是有工作量的。大家覺得有用就好，要是沒有耽誤時間給大家道個歉。（感謝http://winphone.us/）

1.?????? 打開 BackgroundScreen.cs文件。

2.?????? 重寫基類Update 方法如下:

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

C#

public override void Update(GameTime gameTime, bool otherScreenHasFocus,

???????????????? ?bool coveredByOtherScreen)

{

?? base.Update(gameTime, otherScreenHasFocus, false);

}

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3.?????? 重寫基類方法繪制。 繪圖方法將繪制圖形設備上使用 Microsoft.Xna.Framewok.Graphics 命名空間中的 SpriteBatch 類。一組sprites被繪制的時候使用同樣的設置。改變 Draw 方法來匹配下面的代碼段：

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

C#

public override void Draw(GameTime gameTime)

{

?? SpriteBatch spriteBatch = ScreenManager.SpriteBatch;

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?? // Make the menu slide into place during transitions, using a

?? // power curve to make things look more interesting (this makes

?? // the movement slow down as it nears the end).

?? float transitionOffset = ???? (float)Math.Pow(TransitionPosition, 2);

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?? spriteBatch.Begin();

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?? // Draw Background

?? spriteBatch.Draw(background, new Vector2(0, 0),

???? new Color(255, 255, 255, TransitionAlpha));

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?? // Draw Title

?? spriteBatch.Draw(title, new Vector2(60, 55),

???? new Color(255, 255, 255, TransitionAlpha));

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?? spriteBatch.End();

}

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4.?????? 按 F5 編譯并運行該應用程序。

圖1

修改了updatae和Draw后的運行效果?

5.?????? 停止調試 (SHIFT + F5)，并返回到編輯應用程序。

6.?????? 將一個附加類添加到應用程序，并將其名稱設置為 GameplayScreen。

Note: 要創建一個新的類，在解決方案資源管理器中右鍵單擊 AlienGame 項目并選擇Add | Class.

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7.?????? 添加以下使用申明到新類：

(Code Snippet – Game Development with XNA – Gameplay Screen using statements )

C#

using AlienGameSample;

using Microsoft.Xna.Framework;

using Microsoft.Xna.Framework.Graphics;

using Microsoft.Xna.Framework.Audio;

using System.IO.IsolatedStorage;

using System.IO;

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8.?????? 從 GameScreen 派生：

C#

class GameplayScreen : GameScreen

{

}

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9.?????? 添加以下類變量 （將在比賽中使用它們）。 后面我們使用這些變量，處理游戲邏輯、 用戶輸入和繪圖：

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

C#

//

// Game Play Members

//

Rectangle worldBounds;

bool gameOver;

int baseLevelKillCount;

int levelKillCount;

float alienSpawnTimer;

float alienSpawnRate;

float alienMaxAccuracy;

float alienSpeedMin;

float alienSpeedMax;

int alienScore;

int nextLife;

int hitStreak;

int highScore;

Random random;

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//

// Rendering Members

//

Texture2D cloud1Texture;

Texture2D cloud2Texture;

Texture2D sunTexture;

Texture2D moonTexture;

Texture2D groundTexture;

Texture2D tankTexture;

Texture2D alienTexture;

Texture2D badguy_blue;

Texture2D badguy_red;

Texture2D badguy_green;

Texture2D badguy_orange;

Texture2D mountainsTexture;

Texture2D hillsTexture;

Texture2D bulletTexture;

Texture2D laserTexture;

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SpriteFont scoreFont;

SpriteFont menuFont;

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Vector2 cloud1Position;

Vector2 cloud2Position;

Vector2 sunPosition;

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// Level changes, nighttime transitions, etc

float transitionFactor; // 0.0f == day, 1.0f == night

float transitionRate; // > 0.0f == day to night

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ParticleSystem particles;

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//

// Audio Members

//

SoundEffect alienFired;

SoundEffect alienDied;

SoundEffect playerFired;

SoundEffect playerDied;

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//Screen dimension consts

const float screenHeight = 800.0f;

const float screenWidth = 480.0f;

const int leftOffset = 25;

const int topOffset = 50;

const int bottomOffset = 20;

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10.?? 游戲類構造函數定義 (在游戲屏幕和其他屏幕在游戲中的) 之間的屏幕轉換的速度和大小—— 在處理游戲的所有操作的地方。 添加此類構造函數，如下所示：:

(Code Snippet – Game Development with XNA – Gameplay Screen Constructor)

C#

public GameplayScreen()

{

?? random = new Random();

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?? worldBounds = new Rectangle(0, 0, (int)screenWidth, (int)screenHeight);

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?? gameOver = true;

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?? TransitionOnTime = TimeSpan.FromSeconds(0.0);

?? TransitionOffTime = TimeSpan.FromSeconds(0.0);

}

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11.?? 現在讓我們來創建內容的加載和卸載功能。 重寫基類的 LoadContent 和 UnloadContent 的方法。

添加 LoadContent 代碼段：:

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

C#

public override void LoadContent()

{

??? cloud1Texture = ScreenManager.Game.Content.Load<Texture2D>("cloud1");

??? cloud2Texture = ScreenManager.Game.Content.Load<Texture2D>("cloud2");

??? sunTexture = ScreenManager.Game.Content.Load<Texture2D>("sun");

??? moonTexture = ScreenManager.Game.Content.Load<Texture2D>("moon");

??? groundTexture = ScreenManager.Game.Content.Load<Texture2D>("ground");

??? tankTexture = ScreenManager.Game.Content.Load<Texture2D>("tank");

??? mountainsTexture = ScreenManager.Game.Content.Load<Texture2D>("mountains_blurred");

??? hillsTexture = ScreenManager.Game.Content.Load<Texture2D>("hills");

??? alienTexture = ScreenManager.Game.Content.Load<Texture2D>("alien1");

??? badguy_blue = ScreenManager.Game.Content.Load<Texture2D>("badguy_blue");

??? badguy_red = ScreenManager.Game.Content.Load<Texture2D>("badguy_red");

??? badguy_green = ScreenManager.Game.Content.Load<Texture2D>("badguy_green");

??? badguy_orange = ScreenManager.Game.Content.Load<Texture2D>("badguy_orange");

??? bulletTexture = ScreenManager.Game.Content.Load<Texture2D>("bullet");

??? laserTexture = ScreenManager.Game.Content.Load<Texture2D>("laser");

??? alienFired = ScreenManager.Game.Content.Load<SoundEffect>("Tank_Fire");

??? alienDied = ScreenManager.Game.Content.Load<SoundEffect>("Alien_Hit");

??? playerFired = ScreenManager.Game.Content.Load<SoundEffect>("Tank_Fire");

??? playerDied = ScreenManager.Game.Content.Load<SoundEffect>("Player_Hit");

??? scoreFont = ScreenManager.Game.Content.Load<SpriteFont>("ScoreFont");

??? menuFont = ScreenManager.Game.Content.Load<SpriteFont>("MenuFont");

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??? cloud1Position = new Vector2(224 - cloud1Texture.Width, 32);

??? cloud2Position = new Vector2(64, 80);

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??? sunPosition = new Vector2(16, 16);

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

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??? base.LoadContent();

}

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12.?? 添加UnloadContent代碼段:

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

C#

public override void UnloadContent()

{

??? particles = null;

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??? base.UnloadContent();

}

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13.?? 重寫基類Update功能：

Note: 我們將在做游戲邏輯的時候再來修改他。

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

C#

/// <summary>

/// Runs one frame of update for the game.

/// </summary>

/// <param name="gameTime">Provides a snapshot of timing values.</param>

public override void Update(GameTime gameTime,

bool otherScreenHasFocus, bool coveredByOtherScreen)

{

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

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?? base.Update(gameTime, otherScreenHasFocus, ?? coveredByOtherScreen);

}

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14.?? 重寫基類繪圖功能，當下的“游戲世界”是每秒30次。

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

C#

/// <summary>

/// Draw the game world, effects, and HUD

/// </summary>

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

public override void Draw(GameTime gameTime)

{

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

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?? ScreenManager.SpriteBatch.Begin();

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?? ScreenManager.SpriteBatch.End();

}

Note: The GameTime could be used to calculate the drawing locations of various game items.

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15.?? 打開 MainMenuScreen.cs，找到 StartGameMenuEntrySelected 方法，現在是空的，我們將以下代碼添加進去。 這段代碼的作用是當用戶點擊“START GAME”按鈕時，將 GameplayScreen 添加到ScreenManager：

(Code Snippet – Game Development with XNA – MainMenu Screen – GameMenuEntrySelected handler)

C#

void StartGameMenuEntrySelected(object sender, EventArgs e)

{

??? ScreenManager.AddScreen(new GameplayScreen());

}

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16.?? 編譯并運行該應用程序。 單擊"開始游戲"菜單項，可以看到主菜單從屏幕的下方滾動上來。

圖2

運行效果?

Note: 現在游戲的場景你還看不到，不過不要緊，明天我們就開始了，加油！！

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17.?? 停止調試并回到應用程序編輯狀態。

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在個章節，你創建了新的主游戲類，并重寫了游戲基類的功能。

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轉載于:https://www.cnblogs.com/zouyuntao/archive/2010/11/10/1874267.html

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