下载保存文件接口，让用户选择保存路径

lib/data/repositories/message/save_file_to_disk_handler.dart

@@ -4,6 +4,7 @@ import 'package:appframe/services/dispatcher.dart';
 import 'package:dio/dio.dart';
 import 'package:file_picker/file_picker.dart';
 import 'package:path/path.dart' as path;
+import 'package:path_provider/path_provider.dart';
 
 class SaveFileToDisKHandler extends MessageHandler {
   @override
@@ -17,17 +18,25 @@ class SaveFileToDisKHandler extends MessageHandler {
       throw Exception('参数错误');
     }
 
-    // 让用户选择保存目录
-    String? selectedDirectory = await FilePicker.platform.getDirectoryPath();
-    // 获取filePath中的文件名，以及后缀名
-    var fileName = path.basenameWithoutExtension(filePath);
-    var ext = path.extension(filePath);
+    var fileName = params['fileName'] as String? ?? '';
+
+    // 临时目录
+    var dir = await getTemporaryDirectory();
+    // 要保存的文件名和扩展名
+    String saveFileName, ext;
+    if (fileName.isEmpty) {
+      saveFileName = path.basenameWithoutExtension(filePath);
+      ext = path.extension(filePath);
+    } else {
+      saveFileName = path.basenameWithoutExtension(fileName);
+      ext = path.extension(fileName);
+    }
     // 要保存的路径
-    var targetPath = path.join(selectedDirectory!, '$fileName.$ext');
+    var targetPath = path.join(dir.path, '$saveFileName.$ext');
     // 如果文件存在，则在文件名后添加数字
     int i = 1;
     while (File(targetPath).existsSync()) {
-      targetPath = path.join(selectedDirectory, '$fileName($i).$ext');
+      targetPath = path.join(dir.path, '$saveFileName($i).$ext');
       i++;
     }
 
@@ -36,11 +45,14 @@ class SaveFileToDisKHandler extends MessageHandler {
       if (resp.statusCode != 200) {
         throw Exception('文件下载失败');
       }
+
+      await FilePicker.platform.saveFile(bytes: File(targetPath).readAsBytesSync(), fileName: fileName);
+
       return true;
     } else {
-      // 将filePath路径的文件保存到targetPath
-      final f = await File(filePath).copy(targetPath);
+      var f = File(filePath);
       if (f.existsSync()) {
+        await FilePicker.platform.saveFile(bytes: f.readAsBytesSync(), fileName: fileName);
         return true;
       } else {
         return false;