Refactor file export logic to handle Android platform and improve file saving process

Author: CodeDoctorDE

packages/lw_sysapi/lib/src/api/save.dart

@@ -7,6 +7,7 @@ import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 
 bool supportsShare() => kIsWeb || !Platform.isLinux;
+bool supportsSave() => kIsWeb || !Platform.isIOS;
 
 Future<void> exportFile({
   required BuildContext context,
@@ -18,7 +19,7 @@ Future<void> exportFile({
   required String label,
   bool share = false,
 }) async {
-  if (share && supportsShare()) {
+  if (share && supportsShare() || (!share && !supportsSave())) {
     return exportUsingShare(
       bytes: bytes,
       fileName: fileName,
@@ -27,12 +28,14 @@ Future<void> exportFile({
       label: label,
     );
   }
-  return save.exportFile(
-    bytes,
-    fileName,
-    fileExtension,
-    mimeType,
-    uniformTypeIdentifier,
-    label,
-  );
+  if (supportsSave()) {
+    return save.exportFile(
+      bytes,
+      fileName,
+      fileExtension,
+      mimeType,
+      uniformTypeIdentifier,
+      label,
+    );
+  }
 }

packages/lw_sysapi/lib/src/api/src/save.dart

@@ -1,6 +1,8 @@
+import 'dart:io';
 import 'dart:typed_data';
 
 import 'package:file_picker/file_picker.dart';
+import 'package:lw_sysapi/src/api/api.dart';
 
 Future<void> exportFile(
   Uint8List bytes,
@@ -10,11 +12,29 @@ Future<void> exportFile(
   String uniformTypeIdentifier,
   String label,
 ) async {
-  await FilePicker.platform.saveFile(
+  if (Platform.isAndroid) {
+    await platform.invokeMethod('saveFile', {
+      'mime': mimeType,
+      'data': bytes,
+      'name': '$fileName.$fileExtension',
+    });
+    return;
+  }
+  var file = await FilePicker.platform.saveFile(
     dialogTitle: label,
     fileName: '$fileName.$fileExtension',
     bytes: bytes,
     type: FileType.custom,
     allowedExtensions: [fileExtension],
   );
+  if (file == null) return;
+  if (!file.endsWith('.$fileExtension')) {
+    final dotIndex = file.lastIndexOf('.');
+    if (dotIndex != -1) {
+      file = file.substring(0, dotIndex);
+    }
+    file = '$file.$fileExtension';
+  }
+  final outputFile = File(file);
+  await outputFile.writeAsBytes(bytes);
 }