更改安卓端的文件访问方式，优化导入逻辑 (#64)

* Refactor import function & Allow import local comics without copying them to local path.

* android: use file_picker instead, support directory access for android 10

* Improve import logic

* Fix sql query.

* Add ability to remove invalid favorite items.

* Perform sort before choosing cover

* Revert changes of "use file_picker instead".

* Try catch on "check update"

* Added module 'flutter_saf'

* gitignore

* remove unsupported arch in build.gradle

* Use flutter_saf to handle android's directory and files, improve import logic.

* revert changes of 'requestLegacyExternalStorage'

* fix cbz import

* openDirectoryPlatform

* Remove double check on source folder

* use openFilePlatform

* remove unused import

* improve local comic's path handling

* bump version

* fix pubspec format

* return null when comic folder is empty

lib/foundation/favorites.dart

@@ -4,6 +4,7 @@ import 'package:flutter/foundation.dart';
 import 'package:sqlite3/sqlite3.dart';
 import 'package:venera/foundation/appdata.dart';
 import 'package:venera/foundation/image_provider/local_favorite_image.dart';
+import 'package:venera/foundation/local.dart';
 import 'package:venera/foundation/log.dart';
 import 'dart:io';
 
@@ -496,6 +497,22 @@ class LocalFavoritesManager with ChangeNotifier {
     notifyListeners();
   }
 
+  Future<int> removeInvalid() async {
+    int count = 0;
+    await Future.microtask(() {
+      var all = allComics();
+      for(var c in all) {
+        var comicSource = c.type.comicSource;
+        if ((c.type == ComicType.local && LocalManager().find(c.id, c.type) == null) 
+          || (c.type != ComicType.local && comicSource == null)) {
+          deleteComicWithId(c.folder, c.id, c.type);
+          count++;
+        }
+      }
+    });
+    return count;
+  }
+
   Future<void> clearAll() async {
     _db.dispose();
     File("${App.dataPath}/local_favorite.db").deleteSync();

lib/foundation/image_provider/cached_image.dart

@@ -3,6 +3,7 @@ import 'dart:io';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:venera/network/images.dart';
+import 'package:venera/utils/io.dart';
 import 'base_image_provider.dart';
 import 'cached_image.dart' as image_provider;
 
@@ -24,7 +25,7 @@ class CachedImageProvider
   @override
   Future<Uint8List> load(StreamController<ImageChunkEvent> chunkEvents) async {
     if(url.startsWith("file://")) {
-      var file = File(url.substring(7));
+      var file = openFilePlatform(url.substring(7));
       return file.readAsBytes();
     }
     await for (var progress in ImageDownloader.loadThumbnail(url, sourceKey, cid)) {

lib/foundation/local.dart

@@ -71,12 +71,13 @@ class LocalComic with HistoryMixin implements Comic {
         downloadedChapters = List.from(jsonDecode(row[8] as String)),
         createdAt = DateTime.fromMillisecondsSinceEpoch(row[9] as int);
 
-  File get coverFile => File(FilePath.join(
-        LocalManager().path,
-        directory,
+  File get coverFile => openFilePlatform(FilePath.join(
+        baseDir,
         cover,
       ));
 
+  String get baseDir => directory.contains("/") ? directory : FilePath.join(LocalManager().path, directory);
+
   @override
   String get description => "";
 
@@ -341,12 +342,12 @@ class LocalManager with ChangeNotifier {
       throw "Invalid ep";
     }
     var comic = find(id, type) ?? (throw "Comic Not Found");
-    var directory = Directory(FilePath.join(path, comic.directory));
+    var directory = openDirectoryPlatform(comic.baseDir);
     if (comic.chapters != null) {
       var cid = ep is int
           ? comic.chapters!.keys.elementAt(ep - 1)
           : (ep as String);
-      directory = Directory(FilePath.join(directory.path, cid));
+      directory = openDirectoryPlatform(FilePath.join(directory.path, cid));
     }
     var files = <File>[];
     await for (var entity in directory.list()) {
@@ -392,10 +393,10 @@ class LocalManager with ChangeNotifier {
       String id, ComicType type, String name) async {
     var comic = find(id, type);
     if (comic != null) {
-      return Directory(FilePath.join(path, comic.directory));
+      return openDirectoryPlatform(FilePath.join(path, comic.directory));
     }
     var dir = findValidDirectoryName(path, name);
-    return Directory(FilePath.join(path, dir)).create().then((value) => value);
+    return openDirectoryPlatform(FilePath.join(path, dir)).create().then((value) => value);
   }
 
   void completeTask(DownloadTask task) {
@@ -454,7 +455,7 @@ class LocalManager with ChangeNotifier {
 
   void deleteComic(LocalComic c, [bool removeFileOnDisk = true]) {
     if(removeFileOnDisk) {
-      var dir = Directory(FilePath.join(path, c.directory));
+      var dir = openDirectoryPlatform(FilePath.join(path, c.directory));
       dir.deleteIgnoreError(recursive: true);
     }
     //Deleting a local comic means that it's nolonger available, thus both favorite and history should be deleted.