在xna/monogame中从鼠标拖动中获取第一个和最后一个点

using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;

public class Game1 : Game
{
    private GraphicsDeviceManager _graphics;
    private SpriteBatch _spriteBatch;
    private Vector2 _startPoint;
    private Vector2 _endPoint;
    private bool _isDragging;

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

    protected override void Initialize()
    {
        // 初始化代码
        base.Initialize();
    }

    protected override void LoadContent()
    {
        _spriteBatch = new SpriteBatch(GraphicsDevice);
    }

    protected override void Update(GameTime gameTime)
    {
        MouseState mouseState = Mouse.GetState();

        if (mouseState.LeftButton == ButtonState.Pressed)
        {
            if (!_isDragging)
            {
                _startPoint = new Vector2(mouseState.X, mouseState.Y);
                _isDragging = true;
            }
            _endPoint = new Vector2(mouseState.X, mouseState.Y);
        }
        else
        {
            _isDragging = false;
        }

        base.Update(gameTime);
    }

    protected override void Draw(GameTime gameTime)
    {
        GraphicsDevice.Clear(Color.CornflowerBlue);

        _spriteBatch.Begin();
        if (_isDragging)
        {
            _spriteBatch.DrawLine(_startPoint, _endPoint, Color.Red);
        }
        _spriteBatch.End();

        base.Draw(gameTime);
    }
}