Harden android startup path

os/android/app/src/main/java/com/alexbatalov/fallout2ce/FileUtils.java

@@ -13,18 +13,23 @@ import java.io.OutputStream;
 public class FileUtils {
 
     static boolean copyRecursively(ContentResolver contentResolver, DocumentFile src, File dest) {
+        if (dest == null || (!dest.exists() && !dest.mkdirs())) {
+            return false;
+        }
+
         final DocumentFile[] documentFiles = src.listFiles();
         for (final DocumentFile documentFile : documentFiles) {
+            final String name = documentFile.getName();
+            if (name == null || name.isEmpty()) {
+                return false;
+            }
+
             if (documentFile.isFile()) {
-                if (!copyFile(contentResolver, documentFile, new File(dest, documentFile.getName()))) {
+                if (!copyFile(contentResolver, documentFile, new File(dest, name))) {
                     return false;
                 }
             } else if (documentFile.isDirectory()) {
-                final File subdirectory = new File(dest, documentFile.getName());
-                if (!subdirectory.exists()) {
-                    subdirectory.mkdir();
-                }
-
+                final File subdirectory = new File(dest, name);
                 if (!copyRecursively(contentResolver, documentFile, subdirectory)) {
                     return false;
                 }
@@ -34,18 +39,22 @@ public class FileUtils {
     }
 
     private static boolean copyFile(ContentResolver contentResolver, DocumentFile src, File dest) {
-        try {
-            final InputStream inputStream = contentResolver.openInputStream(src.getUri());
-            final OutputStream outputStream = new FileOutputStream(dest);
+        final File parent = dest.getParentFile();
+        if (parent != null && !parent.exists() && !parent.mkdirs()) {
+            return false;
+        }
+
+        try (final InputStream inputStream = contentResolver.openInputStream(src.getUri());
+             final OutputStream outputStream = new FileOutputStream(dest)) {
+            if (inputStream == null) {
+                return false;
+            }
 
             final byte[] buffer = new byte[16384];
             int bytesRead;
             while ((bytesRead = inputStream.read(buffer)) != -1) {
                 outputStream.write(buffer, 0, bytesRead);
             }
-
-            inputStream.close();
-            outputStream.close();
         } catch (IOException e) {
             e.printStackTrace();
             return false;

os/android/app/src/main/java/com/alexbatalov/fallout2ce/ImportActivity.java

@@ -2,10 +2,12 @@ package com.alexbatalov.fallout2ce;
 
 import android.app.Activity;
 import android.app.ProgressDialog;
+import android.content.ActivityNotFoundException;
 import android.content.ContentResolver;
 import android.content.Intent;
 import android.net.Uri;
 import android.os.Bundle;
+import android.widget.Toast;
 
 import androidx.documentfile.provider.DocumentFile;
 
@@ -17,18 +19,18 @@ public class ImportActivity extends Activity {
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
-        Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT_TREE);
-        startActivityForResult(intent, IMPORT_REQUEST_CODE);
+        launchImportPicker();
     }
 
     @Override
     protected void onActivityResult(int requestCode, int resultCode, Intent resultData) {
         if (requestCode == IMPORT_REQUEST_CODE) {
             if (resultCode == Activity.RESULT_OK) {
-                final Uri treeUri = resultData.getData();
+                final Uri treeUri = resultData != null ? resultData.getData() : null;
                 if (treeUri != null) {
+                    grantImportPermissions(treeUri, resultData);
                     final DocumentFile treeDocument = DocumentFile.fromTreeUri(this, treeUri);
-                    if (treeDocument != null) {
+                    if (treeDocument != null && treeDocument.isDirectory()) {
                         copyFiles(treeDocument);
                         return;
                     }
@@ -42,20 +44,59 @@ public class ImportActivity extends Activity {
     }
 
     private void copyFiles(DocumentFile treeDocument) {
-        ProgressDialog dialog = createProgressDialog();
+        final ProgressDialog dialog = createProgressDialog();
         dialog.show();
 
         new Thread(() -> {
-            ContentResolver contentResolver = getContentResolver();
-            File externalFilesDir = getExternalFilesDir(null);
-            FileUtils.copyRecursively(contentResolver, treeDocument, externalFilesDir);
+            final ContentResolver contentResolver = getContentResolver();
+            final File externalFilesDir = getExternalFilesDir(null);
+            final boolean success = externalFilesDir != null
+                && FileUtils.copyRecursively(contentResolver, treeDocument, externalFilesDir);
 
-            startMainActivity();
-            dialog.dismiss();
-            finish();
+            runOnUiThread(() -> {
+                dialog.dismiss();
+
+                if (success) {
+                    startMainActivity();
+                } else {
+                    Toast.makeText(this, R.string.import_failed, Toast.LENGTH_LONG).show();
+                }
+
+                finish();
+            });
         }).start();
     }
 
+    private void launchImportPicker() {
+        final Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT_TREE);
+        intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION
+            | Intent.FLAG_GRANT_PERSISTABLE_URI_PERMISSION
+            | Intent.FLAG_GRANT_PREFIX_URI_PERMISSION);
+
+        try {
+            startActivityForResult(intent, IMPORT_REQUEST_CODE);
+        } catch (ActivityNotFoundException e) {
+            Toast.makeText(this, R.string.import_picker_unavailable, Toast.LENGTH_LONG).show();
+            finish();
+        }
+    }
+
+    private void grantImportPermissions(Uri treeUri, Intent resultData) {
+        int flags = Intent.FLAG_GRANT_READ_URI_PERMISSION;
+        if (resultData != null) {
+            flags = resultData.getFlags()
+                & (Intent.FLAG_GRANT_READ_URI_PERMISSION
+                | Intent.FLAG_GRANT_WRITE_URI_PERMISSION
+                | Intent.FLAG_GRANT_PERSISTABLE_URI_PERMISSION);
+        }
+
+        try {
+            getContentResolver().takePersistableUriPermission(treeUri, flags);
+        } catch (SecurityException ignored) {
+            // Some providers do not offer persistable grants. One-shot access is enough for import.
+        }
+    }
+
     private void startMainActivity() {
         Intent intent = new Intent(this, MainActivity.class);
         startActivity(intent);

os/android/app/src/main/res/values/strings.xml

@@ -2,4 +2,6 @@
     <string name="app_name">Fallout 2</string>
     <string name="loading_dialog_title">PLEASE STAND BY</string>
     <string name="loading_dialog_message">Copying files…</string>
+    <string name="import_failed">Failed to import game files. Please pick a valid Fallout 2 folder and try again.</string>
+    <string name="import_picker_unavailable">No compatible folder picker is available on this device.</string>
 </resources>