边界在底部，右侧但不在左侧，顶部工作正常

Question

我关注：http://xbox.create.msdn.com/en-US/education/tutorial/2dgame/animating_the_player并且在实施动画期间出现了问题。但我不确定原因：

Game1.cs（我在这里更改的唯一方法是LoadContent（） - 方法和UpdatePlayer（） - 方法。

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Audio;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.GamerServices;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;
using Microsoft.Xna.Framework.Media;
using Microsoft.Xna.Framework.Input.Touch;

namespace Shooter
{
    /// <summary>
    /// This is the main type for your game
    /// </summary>
    public class Game1 : Microsoft.Xna.Framework.Game
    {
        GraphicsDeviceManager graphics;
        SpriteBatch spriteBatch;
        //Represents the player
        Player player;

        KeyboardState currentKeyboardState;
        KeyboardState previousKeyboardState;

        GamePadState currentGamePadState;
        GamePadState previousGamePadState;

        float playerMoveSpeed;

        public Game1()
        {
            graphics = new GraphicsDeviceManager(this);
            Content.RootDirectory = "Content";
        }

        /// <summary>
        /// Allows the game to perform any initialization it needs to before starting to run.
        /// This is where it can query for any required services and load any non-graphic
        /// related content.  Calling base.Initialize will enumerate through any components
        /// and initialize them as well.
        /// </summary>
        protected override void Initialize()
        {
            // TODO: Add your initialization logic here

            player = new Player();

            playerMoveSpeed = 8.0f;

            TouchPanel.EnabledGestures = GestureType.FreeDrag;

            base.Initialize();
        }

        /// <summary>
        /// LoadContent will be called once per game and is the place to load
        /// all of your content.
        /// </summary>
        protected override void LoadContent()
        {
            // Create a new SpriteBatch, which can be used to draw textures.
            spriteBatch = new SpriteBatch(GraphicsDevice);

            // TODO: use this.Content to load your game content here

            //Load the player resources

            // Load the player resources
            Animation playerAnimation = new Animation();
            Texture2D playerTexture = Content.Load<Texture2D>("shipAnimation");
            playerAnimation.Initialize(playerTexture, Vector2.Zero, 115, 69, 8, 30, Color.White, 1f, true);

            Vector2 playerPosition = new Vector2(GraphicsDevice.Viewport.TitleSafeArea.X, GraphicsDevice.Viewport.TitleSafeArea.Y
            + GraphicsDevice.Viewport.TitleSafeArea.Height / 2);
            player.Initialize(playerAnimation, playerPosition);



        }

        /// <summary>
        /// UnloadContent will be called once per game and is the place to unload
        /// all content.
        /// </summary>
        protected override void UnloadContent()
        {
            // TODO: Unload any non ContentManager content here
        }

        /// <summary>
        /// Allows the game to run logic such as updating the world,
        /// checking for collisions, gathering input, and playing audio.
        /// </summary>
        /// <param name="gameTime">Provides a snapshot of timing values.</param>
        protected override void Update(GameTime gameTime)
        {
            // Allows the game to exit
            if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)
                this.Exit();

            previousGamePadState = currentGamePadState;
            previousKeyboardState = currentKeyboardState;

            currentKeyboardState = Keyboard.GetState();
            currentGamePadState = GamePad.GetState(PlayerIndex.One);

            UpdatePlayer(gameTime);

            base.Update(gameTime);
        }

        private void UpdatePlayer(GameTime gameTime)
        {
            player.Update(gameTime);

            player.Position.X += currentGamePadState.ThumbSticks.Left.X *playerMoveSpeed;
            player.Position.Y -= currentGamePadState.ThumbSticks.Left.Y *playerMoveSpeed;

            if (currentKeyboardState.IsKeyDown(Keys.Left) || currentGamePadState.DPad.Left == ButtonState.Pressed)
            {
                player.Position.X -= playerMoveSpeed;
            }
            if (currentKeyboardState.IsKeyDown(Keys.Right) || currentGamePadState.DPad.Right == ButtonState.Pressed)
            {
                player.Position.X += playerMoveSpeed;
            }
            if (currentKeyboardState.IsKeyDown(Keys.Up) || currentGamePadState.DPad.Up == ButtonState.Pressed)
            {
                player.Position.Y -= playerMoveSpeed;
            }
            if (currentKeyboardState.IsKeyDown(Keys.Down) || currentGamePadState.DPad.Down == ButtonState.Pressed)
            {
                player.Position.Y += playerMoveSpeed;
            }

            //Make sure the player does not go out of bounds
            player.Position.X = MathHelper.Clamp(player.Position.X, 0, GraphicsDevice.Viewport.Width - player.Width);
            player.Position.Y = MathHelper.Clamp(player.Position.Y, 0, GraphicsDevice.Viewport.Height - player.Height);
        }

        /// <summary>
        /// This is called when the game should draw itself.
        /// </summary>
        /// <param name="gameTime">Provides a snapshot of timing values.</param>
        protected override void Draw(GameTime gameTime)
        {
            GraphicsDevice.Clear(Color.CornflowerBlue);

            // TODO: Add your drawing code here

            spriteBatch.Begin();

            player.Draw(spriteBatch);

            spriteBatch.End();

            base.Draw(gameTime);
        }
    }
}

Player.cs

using System;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;

namespace Shooter
{
    class Player
    {
        //Animation representing the player
        public Animation PlayerAnimation;

        //Position of the Player relative to the upper left side of the screen
        public Vector2 Position;

        //State of the player
        public bool Active;

        //Amount of hit points that player has
        public int Health;

        //Get the width of the player ship
        public int Width
        {
            get { return PlayerAnimation.FrameWidth; }
        }

        //Get the height of the player ship
        public int Height
        {
            get { return PlayerAnimation.FrameHeight; }
        }

        public void Initialize(Animation animation, Vector2 position)
        {
            PlayerAnimation = animation;

            //Set the starting position of the player around the middle of the screen and to the back
            Position = position;

            //Set the player to be active
            Active = true;

            //Set the player health
            Health = 100;
        }

        public void Update(GameTime gameTime)
        {
            PlayerAnimation.Position = Position;
            PlayerAnimation.Update(gameTime);
        }

        public void Draw(SpriteBatch spriteBatch)
        {
            PlayerAnimation.Draw(spriteBatch);
        }
    }
}

Animation.cs

using System;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.Graphics;

namespace Shooter
{
    class Animation
    {
        // The image representing the collection of images used for animation
        Texture2D spriteStrip;

        // The scale used to display the sprite strip
        float scale;

        // The time since we last updated the frame
        int elapsedTime;

        // The time we display a frame until the next one
        int frameTime;

        // The number of frames that the animation contains
        int frameCount;

        // The index of the current frame we are displaying
        int currentFrame;

        // The color of the frame we will be displaying
        Color color;

        // The area of the image strip we want to display
        Rectangle sourceRect = new Rectangle();

        // The area where we want to display the image strip in the game
        Rectangle destinationRect = new Rectangle();

        // Width of a given frame
        public int FrameWidth;

        // Height of a given frame
        public int FrameHeight;

        // The state of the Animation
        public bool Active;

        // Determines if the animation will keep playing or deactivate after one run
        public bool Looping;

        // Width of a given frame
        public Vector2 Position;

        public void Initialize(Texture2D texture, Vector2 position,
        int frameWidth, int frameHeight, int frameCount,
        int frametime, Color color, float scale, bool looping)
        {
            // Keep a local copy of the values passed in
            this.color = color;
            this.FrameWidth = frameWidth;
            this.FrameHeight = frameHeight;
            this.frameCount = frameCount;
            this.frameTime = frametime;
            this.scale = scale;

            Looping = looping;
            Position = position;
            spriteStrip = texture;

            // Set the time to zero
            elapsedTime = 0;
            currentFrame = 0;

            // Set the Animation to active by default
            Active = true;
        }

        public void Update(GameTime gameTime)
        {
            // Do not update the game if we are not active
            if (Active == false)
                return;

            // Update the elapsed time
            elapsedTime += (int)gameTime.ElapsedGameTime.TotalMilliseconds;

            // If the elapsed time is larger than the frame time
            // we need to switch frames
            if (elapsedTime > frameTime)
            {
                // Move to the next frame
                currentFrame++;

                // If the currentFrame is equal to frameCount reset currentFrame to zero
                if (currentFrame == frameCount)
                {
                    currentFrame = 0;
                    // If we are not looping deactivate the animation
                    if (Looping == false)
                        Active = false;
                }

                // Reset the elapsed time to zero
                elapsedTime = 0;
            }

            // Grab the correct frame in the image strip by multiplying the currentFrame index by the frame width
            sourceRect = new Rectangle(currentFrame * FrameWidth, 0, FrameWidth, FrameHeight);

            // Grab the correct frame in the image strip by multiplying the currentFrame index by the frame width
            destinationRect = new Rectangle((int)Position.X - (int)(FrameWidth * scale) / 2,
            (int)Position.Y - (int)(FrameHeight * scale) / 2,
            (int)(FrameWidth * scale),
            (int)(FrameHeight * scale));
        }

        public void Draw(SpriteBatch spriteBatch)
        {
            if (Active)
            {
                spriteBatch.Draw(spriteStrip, destinationRect, sourceRect, color);
            }
        }
    }
}

在Game1.cs中，这是检查边界的原因。但是，这部分教程没有改变，所以我不确定为什么它会开始发生，我错过了什么？你们有什么可以指出我做错了吗？

//Make sure the player does not go out of bounds
            player.Position.X = MathHelper.Clamp(player.Position.X, 0, GraphicsDevice.Viewport.Width - player.Width);
            player.Position.Y = MathHelper.Clamp(player.Position.Y, 0, GraphicsDevice.Viewport.Height - player.Height);

Answer 1

在查看代码之后，我最好的猜测是问题在于动画的绘制功能以及destinationRect的定义方式。

看起来游戏认为动画的中心是动画的左上角..

我想也许你想在动画的Update方法中设置destinationRect，如此

    // Grab the correct frame in the image strip by multiplying the currentFrame index by the frame width
    destinationRect = new Rectangle(
        (int)Position.X,
        (int)Position.Y,
        (int)(FrameWidth * scale),
        (int)(FrameHeight * scale));

矩形的X和Y坐标是动画的左上角而不是中心。