从零开发游戏需要学习的c#模块，第二十六章（多种敌人与基础 AI）
本节课目标
创建三种敌人：史莱姆（慢）、骷髅（中速追人）、蝙蝠（快速随机移动）
敌人有独立的行为逻辑
不同敌人有不同外观和属性
敌人在地图上自主移动
第一步：创建敌人基类
右键项目 →添加→类，文件名Enemy.cs：
csharp
using Microsoft.Xna.Framework; using Microsoft.Xna.Framework.Graphics; using System; namespace MY_FIRST_GAME { public enum EnemyType { Slime, // 史莱姆：慢速随机移动 Skeleton, // 骷髅：追踪玩家 Bat // 蝙蝠：快速随机移动 } public class Enemy { public Vector2 Position; public EnemyType Type; public int Hp; public int MaxHp; public int Attack; public int ScoreValue; public float Speed; public bool IsAlive; protected Texture2D texture; protected Color color; protected Random rng; protected float changeTimer; protected float changeInterval; protected Vector2 moveDirection; public Enemy(EnemyType type, Vector2 position, GraphicsDevice graphicsDevice) { Type = type; Position = position; IsAlive = true; rng = new Random(); changeTimer = 0f; changeInterval = (float)(rng.NextDouble() * 2 + 1); // 根据类型设置属性 switch (type) { case EnemyType.Slime: Hp = 30; MaxHp = 30; Attack = 8; ScoreValue = 30; Speed = 40f; color = Color.Green; break; case EnemyType.Skeleton: Hp = 60; MaxHp = 60; Attack = 15; ScoreValue = 80; Speed = 80f; color = Color.White; break; case EnemyType.Bat: Hp = 15; MaxHp = 15; Attack = 5; ScoreValue = 20; Speed = 150f; color = Color.Purple; break; } // 创建纹理 int size = (type == EnemyType.Bat) ? 24 : 40; texture = new Texture2D(graphicsDevice, size, size); Color[] data = new Color[size * size]; if (type == EnemyType.Bat) { // 蝙蝠是三角形 for (int y = 0; y < size; y++) for (int x = 0; x < size; x++) { if (Math.Abs(x - size / 2) < y * 0.8f && y < size * 0.7f) data[y * size + x] = color; else data[y * size + x] = Color.Transparent; } } else if (type == EnemyType.Skeleton) { // 骷髅是菱形 for (int y = 0; y < size; y++) for (int x = 0; x < size; x++) { float dx = Math.Abs(x - size / 2f); float dy = Math.Abs(y - size / 2f); if (dx + dy < size / 2f) data[y * size + x] = color; else data[y * size + x] = Color.Transparent; } } else { // 史莱姆是圆形 for (int y = 0; y < size; y++) for (int x = 0; x < size; x++) { float dx = x - size / 2f; float dy = y - size / 2f; if (dx * dx + dy * dy < (size / 2f) * (size / 2f)) data[y * size + x] = color; else data[y * size + x] = Color.Transparent; } } texture.SetData(data); // 初始随机方向 float angle = (float)(rng.NextDouble() * Math.PI * 2); moveDirection = new Vector2((float)Math.Cos(angle), (float)Math.Sin(angle)); } public virtual void Update(float deltaTime, Vector2 playerPosition, TileMap tileMap) { changeTimer += deltaTime; switch (Type) { case EnemyType.Slime: UpdateSlime(deltaTime, tileMap); break; case EnemyType.Skeleton: UpdateSkeleton(deltaTime, playerPosition, tileMap); break; case EnemyType.Bat: UpdateBat(deltaTime, tileMap); break; } } // ★ 史莱姆：慢速随机移动 private void UpdateSlime(float deltaTime, TileMap tileMap) { if (changeTimer >= changeInterval) { changeTimer = 0f; changeInterval = (float)(rng.NextDouble() * 3 + 1); float angle = (float)(rng.NextDouble() * Math.PI * 2); moveDirection = new Vector2((float)Math.Cos(angle), (float)Math.Sin(angle)); } Vector2 newPos = Position + moveDirection * Speed * deltaTime; if (!tileMap.IsWall(newPos)) Position = newPos; else changeTimer = changeInterval; // 撞墙就换方向 } // ★ 骷髅：追踪玩家 private void UpdateSkeleton(float deltaTime, Vector2 playerPosition, TileMap tileMap) { Vector2 toPlayer = playerPosition - Position; if (toPlayer.Length() > 0) { moveDirection = Vector2.Normalize(toPlayer); } Vector2 newPos = Position + moveDirection * Speed * deltaTime; if (!tileMap.IsWall(newPos)) Position = newPos; } // ★ 蝙蝠：快速随机移动，频繁换向 private void UpdateBat(float deltaTime, TileMap tileMap) { if (changeTimer >= changeInterval) { changeTimer = 0f; changeInterval = (float)(rng.NextDouble() * 0.5 + 0.3); float angle = (float)(rng.NextDouble() * Math.PI * 2); moveDirection = new Vector2((float)Math.Cos(angle), (float)Math.Sin(angle)); } Vector2 newPos = Position + moveDirection * Speed * deltaTime; if (!tileMap.IsWall(newPos)) Position = newPos; else changeTimer = changeInterval; } public virtual void Draw(SpriteBatch spriteBatch) { spriteBatch.Draw(texture, Position, null, Color.White, 0f, new Vector2(texture.Width / 2, texture.Height / 2), 1f, SpriteEffects.None, 0f); } public Rectangle GetBounds() { return new Rectangle( (int)(Position.X - texture.Width / 2), (int)(Position.Y - texture.Height / 2), texture.Width, texture.Height); } } }第二步：改造Game1.cs
以下是需要修改的部分。为了节省篇幅，我只列出改动的地方，你按位置替换即可。
1. 替换敌人列表类型：
// 旧的
private List<Vector2> enemies = default!;
// 新的
private List<Enemy> enemies = default!;
2. 替换SpawnEnemies方法：
private void SpawnEnemies(int count) { for (int i = 0; i < count; i++) { Vector2 pos = tileMap.GetRandomEmptyPosition(rng); EnemyType type = (EnemyType)(rng.Next(3)); // 随机类型 enemies.Add(new Enemy(type, pos, GraphicsDevice)); } }3. 在Update的Game状态下更新敌人 AI：
// 在 CheckEnemyCollision 之前加 foreach (Enemy enemy in enemies) enemy.Update(deltaTime, player.Position, tileMap);4. 替换CheckEnemyCollision方法：
private void CheckEnemyCollision() { Rectangle playerRect = player.GetBounds(); for (int i = enemies.Count - 1; i >= 0; i--) { if (enemies[i].GetBounds().Intersects(playerRect)) { Enemy enemy = enemies[i]; enemies.RemoveAt(i); score += enemy.ScoreValue; enemiesDefeatedThisGame++; player.Hp -= enemy.Attack; particleSystem.EmitHitParticles(enemy.Position); try { hitSound?.Play(); } catch { } } } }5. 替换DrawGameWorld里的敌人绘制：
foreach (Enemy enemy in enemies) enemy.Draw(_spriteBatch);本节课学习任务到此结束，我是魔法阵维护师，关注我，下期更精彩！