Fix: MANAGE_EXTERNAL_STORAGE 권한 추가로 파일 쓰기 오류 해결

문제: Android 11+ Scoped Storage로 인해 EPERM (Operation not permitted) 에러 발생
- Storage Access Framework로 디렉토리 선택했지만 File API로 쓰기 시도
- 권한 부족으로 파일 업로드(STOR) 실패

해결:
- AndroidManifest.xml에 MANAGE_EXTERNAL_STORAGE 권한 추가
- MainActivity에서 Android 11+ (API 30+) 권한 요청 로직 추가
  * Environment.isExternalStorageManager()로 권한 확인
  * Settings.ACTION_MANAGE_APP_ALL_FILES_ACCESS_PERMISSION으로 설정 화면 이동
  * 서버 시작 전 권한 체크 추가
- 이 권한으로 외부 저장소 전체에 File API 접근 가능

사용자는 앱 실행 시 "All files access" 권한 활성화 필요

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

app/src/main/AndroidManifest.xml

@@ -12,6 +12,7 @@
     <uses-permission android:name="android.permission.READ_MEDIA_IMAGES" />
     <uses-permission android:name="android.permission.READ_MEDIA_VIDEO" />
     <uses-permission android:name="android.permission.READ_MEDIA_AUDIO" />
+    <uses-permission android:name="android.permission.MANAGE_EXTERNAL_STORAGE" />
 
     <application
         android:allowBackup="true"

app/src/main/java/be/gyu/android/server/ftp/MainActivity.java

@@ -13,6 +13,8 @@ import android.content.pm.PackageManager;
 import android.net.Uri;
 import android.os.Build;
 import android.os.Bundle;
+import android.os.Environment;
+import android.provider.Settings;
 import android.widget.Button;
 import android.widget.EditText;
 import android.widget.TextView;
@@ -145,20 +147,21 @@ public class MainActivity extends AppCompatActivity {
     }
 
     private void requestPermissions() {
-        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
-            // Android 13+
-            if (ContextCompat.checkSelfPermission(this, Manifest.permission.READ_MEDIA_IMAGES)
-                    != PackageManager.PERMISSION_GRANTED) {
-                ActivityCompat.requestPermissions(this,
-                        new String[]{
-                                Manifest.permission.READ_MEDIA_IMAGES,
-                                Manifest.permission.READ_MEDIA_VIDEO,
-                                Manifest.permission.READ_MEDIA_AUDIO
-                        },
-                        PERMISSION_REQUEST_CODE);
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
+            // Android 11+ - Need MANAGE_EXTERNAL_STORAGE
+            if (!Environment.isExternalStorageManager()) {
+                try {
+                    Intent intent = new Intent(Settings.ACTION_MANAGE_APP_ALL_FILES_ACCESS_PERMISSION);
+                    intent.setData(Uri.parse("package:" + getPackageName()));
+                    startActivity(intent);
+                    Toast.makeText(this, "Please grant 'All files access' permission", Toast.LENGTH_LONG).show();
+                } catch (Exception e) {
+                    Intent intent = new Intent(Settings.ACTION_MANAGE_ALL_FILES_ACCESS_PERMISSION);
+                    startActivity(intent);
+                }
             }
         } else if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
-            // Android 6.0 - 12
+            // Android 6.0 - 10
             if (ContextCompat.checkSelfPermission(this, Manifest.permission.READ_EXTERNAL_STORAGE)
                     != PackageManager.PERMISSION_GRANTED) {
                 ActivityCompat.requestPermissions(this,
@@ -172,6 +175,15 @@ public class MainActivity extends AppCompatActivity {
     }
 
     private void startFTPServer() {
+        // Check permission first
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
+            if (!Environment.isExternalStorageManager()) {
+                Toast.makeText(this, "Please grant 'All files access' permission first", Toast.LENGTH_LONG).show();
+                requestPermissions();
+                return;
+            }
+        }
+
         if (!config.hasRootDirectory()) {
             Toast.makeText(this, "Please select a root directory first", Toast.LENGTH_LONG).show();
             return;