[various] Enable use_build_context_synchronously (flutter#6585)

Enables the `use_build_context_synchronously` lint, and fixes violations.

Part of flutter/flutter#76229

Author: stuartmorgan-g

analysis_options.yaml

@@ -241,7 +241,7 @@ linter:
     - unnecessary_to_list_in_spreads
     - unrelated_type_equality_checks
     - unsafe_html
-    # - use_build_context_synchronously # LOCAL CHANGE - Needs to be enabled and violations fixed.
+    - use_build_context_synchronously
     # - use_colored_box # not yet tested
     # - use_decorated_box # not yet tested
     # - use_enums # not yet tested

packages/file_selector/file_selector/CHANGELOG.md

@@ -1,5 +1,6 @@
 ## NEXT
 
+* Updates example code for `use_build_context_synchronously` lint.
 * Updates minimum Flutter version to 3.0.
 
 ## 0.9.2+2

packages/file_selector/file_selector/example/lib/get_directory_page.dart

@@ -22,10 +22,12 @@ class GetDirectoryPage extends StatelessWidget {
       // Operation was canceled by the user.
       return;
     }
-    await showDialog<void>(
-      context: context,
-      builder: (BuildContext context) => TextDisplay(directoryPath),
-    );
+    if (context.mounted) {
+      await showDialog<void>(
+        context: context,
+        builder: (BuildContext context) => TextDisplay(directoryPath),
+      );
+    }
   }
 
   @override

packages/file_selector/file_selector/example/lib/open_image_page.dart

@@ -29,10 +29,12 @@ class OpenImagePage extends StatelessWidget {
     final String fileName = file.name;
     final String filePath = file.path;
 
-    await showDialog<void>(
-      context: context,
-      builder: (BuildContext context) => ImageDisplay(fileName, filePath),
-    );
+    if (context.mounted) {
+      await showDialog<void>(
+        context: context,
+        builder: (BuildContext context) => ImageDisplay(fileName, filePath),
+      );
+    }
   }
 
   @override

packages/file_selector/file_selector/example/lib/open_multiple_images_page.dart

@@ -32,10 +32,12 @@ class OpenMultipleImagesPage extends StatelessWidget {
       // Operation was canceled by the user.
       return;
     }
-    await showDialog<void>(
-      context: context,
-      builder: (BuildContext context) => MultipleImagesDisplay(files),
-    );
+    if (context.mounted) {
+      await showDialog<void>(
+        context: context,
+        builder: (BuildContext context) => MultipleImagesDisplay(files),
+      );
+    }
   }
 
   @override

packages/file_selector/file_selector/example/lib/open_text_page.dart

@@ -32,10 +32,12 @@ class OpenTextPage extends StatelessWidget {
     final String fileName = file.name;
     final String fileContent = await file.readAsString();
 
-    await showDialog<void>(
-      context: context,
-      builder: (BuildContext context) => TextDisplay(fileName, fileContent),
-    );
+    if (context.mounted) {
+      await showDialog<void>(
+        context: context,
+        builder: (BuildContext context) => TextDisplay(fileName, fileContent),
+      );
+    }
   }
 
   @override

packages/file_selector/file_selector_ios/CHANGELOG.md

@@ -1,5 +1,6 @@
 ## NEXT
 
+* Updates example code for `use_build_context_synchronously` lint.
 * Updates minimum Flutter version to 3.0.
 
 ## 0.5.0+2

packages/file_selector/file_selector_ios/example/lib/open_image_page.dart

@@ -29,10 +29,12 @@ class OpenImagePage extends StatelessWidget {
     final String fileName = file.name;
     final String filePath = file.path;
 
-    await showDialog<void>(
-      context: context,
-      builder: (BuildContext context) => ImageDisplay(fileName, filePath),
-    );
+    if (context.mounted) {
+      await showDialog<void>(
+        context: context,
+        builder: (BuildContext context) => ImageDisplay(fileName, filePath),
+      );
+    }
   }
 
   @override

packages/file_selector/file_selector_ios/example/lib/open_multiple_images_page.dart

@@ -34,10 +34,12 @@ class OpenMultipleImagesPage extends StatelessWidget {
       // Operation was canceled by the user.
       return;
     }
-    await showDialog<void>(
-      context: context,
-      builder: (BuildContext context) => MultipleImagesDisplay(files),
-    );
+    if (context.mounted) {
+      await showDialog<void>(
+        context: context,
+        builder: (BuildContext context) => MultipleImagesDisplay(files),
+      );
+    }
   }
 
   @override

packages/file_selector/file_selector_ios/example/lib/open_text_page.dart

@@ -26,10 +26,12 @@ class OpenTextPage extends StatelessWidget {
     final String fileName = file.name;
     final String fileContent = await file.readAsString();
 
-    await showDialog<void>(
-      context: context,
-      builder: (BuildContext context) => TextDisplay(fileName, fileContent),
-    );
+    if (context.mounted) {
+      await showDialog<void>(
+        context: context,
+        builder: (BuildContext context) => TextDisplay(fileName, fileContent),
+      );
+    }
   }
 
   @override