从零开发游戏需要学习的c#模块，第十八章（2D 碰撞检测与金币收集）

这节课我们将要学习

1. 在地图上随机生成金币（黄色方块代替）

2. 玩家碰到金币后，金币消失，分数增加

3. 屏幕左上角显示实时分数

将game1替换为

using Microsoft.Xna.Framework;

using Microsoft.Xna.Framework.Graphics;

using Microsoft.Xna.Framework.Input;

using System;

using System.Collections.Generic;

namespace MY_FIRST_GAME

{

public class Game1 : Game

{

private GraphicsDeviceManager _graphics;

private SpriteBatch _spriteBatch;

// 玩家

private Texture2D playerTexture;

private Vector2 playerPosition;

private float playerSpeed = 200f;

// ★ 金币

private Texture2D coinTexture;

private List<Vector2> coins;

private Random rng;

private int score;

// 字体（显示分数用）

private SpriteFont font;

public Game1()

{

_graphics = new GraphicsDeviceManager(this);

Content.RootDirectory = "Content";

IsMouseVisible = true;

}

protected override void Initialize()

{

_graphics.PreferredBackBufferWidth = 800;

_graphics.PreferredBackBufferHeight = 600;

_graphics.ApplyChanges();

playerPosition = new Vector2(400, 300);

rng = new Random();

coins = new List<Vector2>();

score = 0;

// 生成 5 个金币

SpawnCoins(5);

base.Initialize();

}

protected override void LoadContent()

{

_spriteBatch = new SpriteBatch(GraphicsDevice);

// 加载玩家图片

using var stream = System.IO.File.OpenRead("Content/player.png");

playerTexture = Texture2D.FromStream(GraphicsDevice, stream);

// ★ 创建金币纹理（黄色 32x32 方块）

coinTexture = new Texture2D(GraphicsDevice, 32, 32);

Color[] data = new Color[32 * 32];

for (int i = 0; i < data.Length; i++)

data[i] = Color.Gold;

coinTexture.SetData(data);

// ★ 加载字体（需要先创建字体文件，见下方说明）

// font = Content.Load<SpriteFont>("font");

}

// ★ 生成金币

private void SpawnCoins(int count)

{

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

{

float x = rng.Next(50, 750);

float y = rng.Next(50, 550);

coins.Add(new Vector2(x, y));

}

}

protected override void Update(GameTime gameTime)

{

KeyboardState keyboard = Keyboard.GetState();

float speed = playerSpeed * (float)gameTime.ElapsedGameTime.TotalSeconds;

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

// 移动

if (keyboard.IsKeyDown(Keys.W) || keyboard.IsKeyDown(Keys.Up))

playerPosition.Y -= speed;

if (keyboard.IsKeyDown(Keys.S) || keyboard.IsKeyDown(Keys.Down))

playerPosition.Y += speed;

if (keyboard.IsKeyDown(Keys.A) || keyboard.IsKeyDown(Keys.Left))

playerPosition.X -= speed;

if (keyboard.IsKeyDown(Keys.D) || keyboard.IsKeyDown(Keys.Right))

playerPosition.X += speed;

// 限制玩家不超出窗口

playerPosition.X = Math.Clamp(playerPosition.X, 32, 768);

playerPosition.Y = Math.Clamp(playerPosition.Y, 32, 568);

// ★ 检测金币碰撞

CheckCoinCollision();

// ★ 金币捡完了重新生成

if (coins.Count == 0)

SpawnCoins(5);

if (keyboard.IsKeyDown(Keys.Escape))

Exit();

base.Update(gameTime);

}

// ★ 碰撞检测

private void CheckCoinCollision()

{

Rectangle playerRect = new Rectangle(

(int)playerPosition.X - 32,

(int)playerPosition.Y - 32,

64, 64

);

for (int i = coins.Count - 1; i >= 0; i--)

{

Rectangle coinRect = new Rectangle((int)coins[i].X, (int)coins[i].Y, 32, 32);

if (playerRect.Intersects(coinRect))

{

coins.RemoveAt(i); // 移除金币

score += 10; // 加分

}

}

}

protected override void Draw(GameTime gameTime)

{

GraphicsDevice.Clear(Color.CornflowerBlue);

_spriteBatch.Begin();

// 画所有金币

foreach (Vector2 coinPos in coins)

{

_spriteBatch.Draw(coinTexture, coinPos, Color.White);

}

// 画玩家（以图片中心为锚点）

_spriteBatch.Draw(

playerTexture,

playerPosition,

null,

Color.White,

0f,

new Vector2(playerTexture.Width / 2, playerTexture.Height / 2),

1f,

SpriteEffects.None,

0f

);

// ★ 画分数（暂时用窗口标题栏显示）

Window.Title = $"分数：{score} | 剩余金币：{coins.Count}";

_spriteBatch.End();

base.Draw(gameTime);

}

}

}

本节课学习的新内容

1. 碰撞检测：Rectangle.Intersects()

Rectangle playerRect = new Rectangle(玩家左上角X, 玩家左上角Y, 宽度, 高度);
Rectangle coinRect = new Rectangle(金币X, 金币Y, 32, 32);

if (playerRect.Intersects(coinRect))
{
    // 碰撞了！
}

2. 以图片中心为锚点画图

_spriteBatch.Draw(
    playerTexture,          // 纹理
    playerPosition,         // 位置
    null,                   // 不裁剪
    Color.White,            // 颜色
    0f,                     // 不旋转
    new Vector2(width/2, height/2),  // ★ 锚点设为中心
    1f,                     // 不缩放
    SpriteEffects.None,     // 不翻转
    0f                      // 深度
);

3. Math.Clamp 限制范围

playerPosition.X = Math.Clamp(playerPosition.X, 最小值, 最大值);

好了这节课就此结束，关注我，下期更精彩