在 Unity 中实现 Windows 选择文件

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为 Windows 版的魔剑镇魂曲实现存档的导入导出功能

🥦实现思路

在 Windows 上实现存档的导入功能, 可以直接调用系统的文件管理器, 选择我们指定类型的文件, 之后代码中进行处理即可

🌵调用文件管理器

系统提供了 GetOpenFileName 函数, 可以调用 Windows 文件管理器, 以下是此函数的使用步骤

新建数据类

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[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
internal class OpenFileName
{
    public int structSize;
    public IntPtr dlgOwner;
    public IntPtr instance;
    public string filter;
    public string customFilter;
    public int maxCustFilter;
    public int filterIndex;
    public IntPtr file; // 新风格不能使用 string 存储返回值, 这里使用 IntPtr 存储返回值
    public int maxFile;
    public string fileTitle;
    public int maxFileTitle;
    public string initialDir;
    public string title;
    public int flags;
    public short fileOffset;
    public short fileExtension;
    public string defExt;
    public IntPtr custData;
    public IntPtr hook;
    public string templateName;
    public IntPtr reservedPtr;
    public int reservedInt;
    public int flagsEx;
}

引入 DLL

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/// <summary>
/// 打开文件对话框
/// </summary>
[DllImport("ComDLG32.dll", SetLastError = true, ThrowOnUnmappableChar = true, CharSet = CharSet.Auto)]
internal static extern bool GetOpenFileName([In, Out] OpenFileName openFileName);

准备数据

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var openFileName = new OpenFileName();

openFileName.structSize = Marshal.SizeOf(openFileName);
openFileName.filter = filter;
openFileName.fileTitle = new string(new char[64]);
openFileName.maxFileTitle = openFileName.fileTitle.Length;
openFileName.initialDir = defaultFolder;
openFileName.title = windowTitle;
openFileName.templateName = string.Empty;
openFileName.flags = 0x00000008 | 0x00000200 | 0x00000800 | 0x00001000 | 0x00080000;

// 分配 2KB 缓冲区
const int BUFFER_SIZE = 2048;
var fileBuffer = Marshal.AllocHGlobal(BUFFER_SIZE * Marshal.SystemDefaultCharSize);

// 清空缓冲区，防止残留数据影响
for (var index = 0; index < BUFFER_SIZE; index++)
{
    Marshal.WriteByte(fileBuffer, index, 0);
}

// 赋值缓冲区
openFileName.file = fileBuffer;
openFileName.maxFile = BUFFER_SIZE;

打开管理器

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// 选取文件
if (GetOpenFileName(openFileName) == false)
{
    selectData = null;
    return false;
}

处理返回值

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selectedFilesList.Clear();

var pointer = fileBuffer;

while (true)
{
    var file = Marshal.PtrToStringAuto(pointer);

    if (string.IsNullOrEmpty(file))
    {
        break;
    }

    selectedFilesList.Add(file);

    pointer += (file.Length + 1) * Marshal.SystemDefaultCharSize;
}

selectData = selectedFilesList;
return selectedFilesList.Count > 0;

释放内存

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// 释放分配的缓冲区内存
Marshal.FreeHGlobal(fileBuffer);

🦄总结

  1. 强烈建议使用新风格的文件管理器, 虽然旧风格的文件管理器返回的值用 空格 来分割, 处理起来更简单, 但是界面巨丑, 操作巨反人类
  2. 使用新风格的文件管理器时要注意, 一定不要使用 string 类型存储返回值, 因为返回值使用 \0 来分割, 而 C# 中的字符串认为 \0 是字符串的结束, 因此后面的信息就丢失了
  3. 记得及时释放申请的缓冲区内存

👀完整代码

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// ReSharper disable NotAccessedField.Global

using System;
using System.Collections.Generic;
using System.Runtime.InteropServices;

namespace Kuroha.Utility
{
    public class FileUtilWindows
    {
        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
        internal class OpenFileName
        {
            public int structSize;
            public IntPtr dlgOwner;
            public IntPtr instance;
            public string filter;
            public string customFilter;
            public int maxCustFilter;
            public int filterIndex;
            public IntPtr file; // 新风格不能使用 string 存储返回值, 这里使用 IntPtr 存储返回值
            public int maxFile;
            public string fileTitle;
            public int maxFileTitle;
            public string initialDir;
            public string title;
            public int flags;
            public short fileOffset;
            public short fileExtension;
            public string defExt;
            public IntPtr custData;
            public IntPtr hook;
            public string templateName;
            public IntPtr reservedPtr;
            public int reservedInt;
            public int flagsEx;
        }

        /// <summary>
        /// 打开文件对话框
        /// </summary>
        [DllImport("ComDLG32.dll", SetLastError = true, ThrowOnUnmappableChar = true, CharSet = CharSet.Auto)]
        internal static extern bool GetOpenFileName([In, Out] OpenFileName openFileName);

        private static readonly List<string> selectedFilesList = new List<string>();

        /// <summary>
        /// 选择多个文件并返回
        /// </summary>
        /// <param name="windowTitle">弹窗标题</param>
        /// <param name="defaultFolder">默认打开的文件夹</param>
        /// <param name="filter">文件后缀筛选</param>
        /// <param name="selectData">返回选择情况: 多个文件时, 首个数据为文件夹, 后续数据依次为文件名</param>
        /// <returns>未选择时返回 false, 选择文件时返回 true</returns>
        public static bool SelectFiles(string windowTitle, string defaultFolder, string filter, out List<string> selectData)
        {
            var openFileName = new OpenFileName();

            openFileName.structSize = Marshal.SizeOf(openFileName);
            openFileName.filter = filter;
            openFileName.fileTitle = new string(new char[64]);
            openFileName.maxFileTitle = openFileName.fileTitle.Length;
            openFileName.initialDir = defaultFolder;
            openFileName.title = windowTitle;
            openFileName.templateName = string.Empty;
            openFileName.flags = 0x00000008 | 0x00000200 | 0x00000800 | 0x00001000 | 0x00080000;

            // 分配 2KB 缓冲区
            const int BUFFER_SIZE = 2048;
            var fileBuffer = Marshal.AllocHGlobal(BUFFER_SIZE * Marshal.SystemDefaultCharSize);

            // 清空缓冲区，防止残留数据影响
            for (var index = 0; index < BUFFER_SIZE; index++)
            {
                Marshal.WriteByte(fileBuffer, index, 0);
            }

            // 赋值缓冲区
            openFileName.file = fileBuffer;
            openFileName.maxFile = BUFFER_SIZE;

            try
            {
                // 选取文件
                if (GetOpenFileName(openFileName) == false)
                {
                    selectData = null;
                    return false;
                }

                #region 处理返回值

                selectedFilesList.Clear();

                var pointer = fileBuffer;

                while (true)
                {
                    var file = Marshal.PtrToStringAuto(pointer);

                    if (string.IsNullOrEmpty(file))
                    {
                        break;
                    }

                    selectedFilesList.Add(file);

                    pointer += (file.Length + 1) * Marshal.SystemDefaultCharSize;
                }

                selectData = selectedFilesList;
                return selectedFilesList.Count > 0;

                #endregion
            }
            finally
            {
                // 释放分配的缓冲区内存
                Marshal.FreeHGlobal(fileBuffer);
            }
        }
    }
}