Xamarin.Forms 目录选取器

Question

我想将文件保存在用户选择的文件夹中，这就是为什么我想向用户提供目录列表，用户将能够选择他想要导出数据的目录。不幸的是，我找不到 directory/folder 选择器的任何示例，我只是找到了一个对我没有用的文件选择器..

https://github.com/jfversluis/FilePicker-Plugin-for-Xamarin-and-Windows

是否有为 Xamarin.Forms 选择文件夹的组件？实际上我只是在做 Android 但我们使用 Xamarin.forms

Answer 1

有none我能想到的。使用 netstandard 一切都变得更加简单，因为您可以使用经典的 c# 文件 api 来获取文件夹。

您只需要知道特殊文件夹和 android 文件夹之间的映射（每个示例）：

System.Environment.SpecialFolder    Path
ApplicationData                     INTERNAL_STORAGE/.config
Desktop                             INTERNAL_STORAGE/Desktop
LocalApplicationData                INTERNAL_STORAGE/.local/share
MyDocuments                         INTERNAL_STORAGE
MyMusic                             INTERNAL_STORAGE/Music
MyPictures                          INTERNAL_STORAGE/Pictures
MyVideos                            INTERNAL_STORAGE/Videos
Personal                            INTERNAL_STORAGE

来源：https://docs.microsoft.com/en-US/xamarin/android/platform/files/

与 ios 相同：

https://docs.microsoft.com/en-US/xamarin/ios/app-fundamentals/file-system

不过实现起来真的很简单，枚举所有的文件夹，然后在一个ListView中显示即可。

编辑：关于实施的更多细节。

其实你要编码一个"directory explorer"，很简单，概念就在这里。

您的 Page

ListView

您的 Page

Cancel

Select

您的 ViewModel

CurrentPath

您将 CurrentPath 绑定到主页的 Title
您的 ViewModel

List<DirectoryViewModel> Directories

每次用户单击列表中的项目时：

您在当前路径中添加目录名称
您从新路径获取所有目录，并更新您的目录属性（不要忘记 RaisePropertyChange(nameof(Directories))）
ListView会相应更新

每次返回：

您删除了当前路径的最后一部分
和以前一样

如果你到达根路径“/”，点击返回时你什么都不做。

哦，你可以使用这个 Grid 组件来代替 ListView，会更好 ;)

https://github.com/roubachof/Sharpnado.Presentation.Forms#grid-Layout

Answer 2

您可以对其进行编辑以使其正常工作..

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using Android.App;
using Android.Content;
using Android.OS;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using Java.IO;
using Java.Util;

namespace Android.Basic.IO
{
    
    public class DirectoryPicker : ListActivity
    {


        public const String START_DIR = "startDir";
        public const String ONLY_DIRS = "onlyDirs";
        public const String SHOW_HIDDEN = "showHidden";
        public const String CHOSEN_DIRECTORY = "chosenDir";
        public const int PICK_DIRECTORY = 43522;
        private File dir;
        private Boolean showHidden = false;
        private bool onlyDirs = true;
        public override void OnCreate(Bundle savedInstanceState, PersistableBundle persistentState)
        {
            base.OnCreate(savedInstanceState, persistentState);
            Bundle extras = Intent.Extras;
            dir = OS.Environment.ExternalStorageDirectory;
            if (extras != null)
            {
                String preferredStartDir = extras.GetString(START_DIR);
                showHidden = extras.GetBoolean(SHOW_HIDDEN, false);
                onlyDirs = extras.GetBoolean(ONLY_DIRS, true);
                if (preferredStartDir != null)
                {
                    File startDir = new File(preferredStartDir);
                    if (startDir.IsDirectory)
                    {
                        dir = startDir;
                    }
                }
            }

            SetContentView(Resource.Layout.folder_chooser_activity);
            var title = dir.AbsolutePath.ToString();
            Title = (title);
            Button btnChoose = (Button)FindViewById(Resource.Id.btnChoose);
            String name = dir.Name;
            if (name.Length == 0)
                name = "/";
            btnChoose.Text = ("Choose " + "'" + name + "'");
            btnChoose.Click += delegate
              {
                  returnDir(dir.AbsolutePath);
              };
            ListView lv = this.ListView;
            lv.TextFilterEnabled = (true);

            if (!dir.CanRead())
            {
                Context context = ApplicationContext;
                String msg = "Could not read folder contents.";
                Toast.MakeText(context, msg, ToastLength.Long).Show();
                return;
            }
            var files = filter(dir.ListFiles(), onlyDirs, showHidden);
            String[] names = Names(files);
            ListAdapter = (new ArrayAdapter<String>(this, Resource.Layout.folder_chooser_item, names));
            lv.ItemClick += (ff, gg) =>
            {
                var position = gg.Position;
                if (!files[gg.Position].IsDirectory)
                    return;
                String path = files[position].AbsolutePath;
                var intent = new Intent(this, typeof(DirectoryPicker));
                intent.PutExtra(DirectoryPicker.START_DIR, path);
                intent.PutExtra(DirectoryPicker.SHOW_HIDDEN, showHidden);
                intent.PutExtra(DirectoryPicker.ONLY_DIRS, onlyDirs);
                StartActivityForResult(intent, PICK_DIRECTORY);
            };

        }

        protected void OnActivityResult(int requestCode, int resultCode, Intent data)
        {
            if (requestCode == PICK_DIRECTORY && resultCode == (int)Result.Ok)
            {
                Bundle extras = data.Extras;
                String path = (String)extras.Get(DirectoryPicker.CHOSEN_DIRECTORY);
                returnDir(path);
            }
        }

        private void returnDir(String path)
        {
            Intent result = new Intent();
            result.PutExtra(CHOSEN_DIRECTORY, path);
            SetResult(Result.Ok, result);
            Finish();
        }


        public List<File> filter(File[] file_list, bool onlyDirs, bool showHidden)
        {
            var files = new List<File>();
            foreach (var file in file_list)
            {
                if (onlyDirs && !file.IsDirectory)
                    continue;
                if (!showHidden && file.IsHidden)
                    continue;
                files.Add(file);
            }
            Collections.Sort(files);
            return files;
        }

        public String[] Names(List<File> files)
        {
            String[] names = new String[files.Count];
            int i = 0;
            foreach (var file in files)
            {
                names[i] = file.Name;
                i++;
            }
            return names;
        }
    }
}

作为结果启动activity然后在OnActivityResult

中捕获

if (requestCode == DirectoryPicker.PICK_DIRECTORY && resultCode == Result.Ok)
            {
                Bundle extras = data.Extras;
                String path = (String)extras.Get(DirectoryPicker.CHOSEN_DIRECTORY);
                // do stuff with path
            }

Xamarin.Forms 目录选取器

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