XNA（MonoGame）零异常

Posted 2021-04-24

我试图绘制屏幕我的播放器和一些实体，但我的播放器的更新方法我得到null异常...

我的SpriteManager

public override void Update(Microsoft.Xna.Framework.GameTime gameTime)
    {
        player.Update(gameTime, Game.Window.ClientBounds);

        foreach(Sprite s in spriteList)
        {
            s.Update(gameTime, Game.Window.ClientBounds);
            if(s.collisionRect.Intersects(player.collisionRect))
                Game.Exit();
        }
        base.Update(gameTime);
    }

和我的玩家类这就是我处理输入的方式

    public override Vector2 direction {
        get {
            Vector2 inputDirection = Vector2.Zero;

            KeyboardState keyboardState = Keyboard.GetState();
            if (keyboardState.IsKeyDown(Keys.Left))
                inputDirection.X -= 1;
            if (keyboardState.IsKeyDown(Keys.Right))
                inputDirection.X += 1;
            if (keyboardState.IsKeyDown(Keys.Up))
                inputDirection.Y -= 1;
            if (keyboardState.IsKeyDown(Keys.Down))
                inputDirection.Y += 1;

            return inputDirection * speed;
        }
    }

这是导致null异常的更新

        public override void Update(GameTime gameTime, Rectangle clientBounds) {
        position += direction;
        if(position.Y < 0)
            position.Y = 0;
        if(position.X < 0)
            position.X = 0;
        if(position.Y > clientBounds.Height - frameSize.Y)
            position.Y = clientBounds.Height - frameSize.Y;
         if(position.X > clientBounds.Width - frameSize.X)
            position.X = clientBounds.Width - frameSize.X;
        base.Update(gameTime, clientBounds);
    }

答案

我注意到的第一件事是需要标记：

    public override void Update(GameTime gameTime, Rectangle clientBounds) {
        position += direction;
        if(position.Y < 0)
            position.Y = 0;
        if(position.X < 0)
            position.X = 0;
        if(position.Y > clientBounds.Height - frameSize.Y)
            position.Y = clientBounds.Height - frameSize.Y;
         if(position.X > clientBounds.Width - frameSize.X)
            position.X = clientBounds.Width - frameSize.X;
        base.Update(gameTime, clientBounds);
    }

我注意到的第二件事是你的玩家类返回：inputDirection * speed; 但是没有变量设置为speed接受该返回。