Fix issue 21640: Assertion Error : '_listenerAttached': is not true (#30513)

packages/flutter/lib/src/rendering/editable.dart

diff --git a/packages/flutter/lib/src/rendering/editable.dart b/packages/flutter/lib/src/rendering/editable.dart
index eb0190b..78a5ecc 100644
--- a/packages/flutter/lib/src/rendering/editable.dart
+++ b/packages/flutter/lib/src/rendering/editable.dart
@@ -196,7 +196,6 @@
        _cursorColor = cursorColor,
        _backgroundCursorColor = backgroundCursorColor,
        _showCursor = showCursor ?? ValueNotifier<bool>(false),
-       _hasFocus = hasFocus ?? false,
        _maxLines = maxLines,
        _minLines = minLines,
        _expands = expands,
@@ -213,6 +212,7 @@
        _obscureText = obscureText {
     assert(_showCursor != null);
     assert(!_showCursor.value || cursorColor != null);
+    this.hasFocus = hasFocus ?? false;
     _tap = TapGestureRecognizer(debugOwner: this)
       ..onTapDown = _handleTapDown
       ..onTap = _handleTap;
@@ -707,7 +707,7 @@
 
   /// Whether the editable is currently focused.
   bool get hasFocus => _hasFocus;
-  bool _hasFocus;
+  bool _hasFocus = false;
   bool _listenerAttached = false;
   set hasFocus(bool value) {
     assert(value != null);
@@ -723,7 +723,6 @@
       RawKeyboard.instance.removeListener(_handleKeyEvent);
       _listenerAttached = false;
     }
-
     markNeedsSemanticsUpdate();
   }
 

packages/flutter/test/rendering/editable_test.dart

diff --git a/packages/flutter/test/rendering/editable_test.dart b/packages/flutter/test/rendering/editable_test.dart
index 63b6368..d5e28bc 100644
--- a/packages/flutter/test/rendering/editable_test.dart
+++ b/packages/flutter/test/rendering/editable_test.dart
@@ -422,4 +422,25 @@
     expect(updatedSelection.extentOffset, 5);
     expect(selectionChangedCount, 1);
   });
+
+  test('editable hasFocus correctly initialized', () {
+    // Regression test for https://github.com/flutter/flutter/issues/21640
+    final TextSelectionDelegate delegate = FakeEditableTextState();
+    final RenderEditable editable = RenderEditable(
+      text: const TextSpan(
+        style: TextStyle(height: 1.0, fontSize: 10.0, fontFamily: 'Ahem'),
+        text: '12345',
+      ),
+      textAlign: TextAlign.start,
+      textDirection: TextDirection.ltr,
+      locale: const Locale('en', 'US'),
+      offset: ViewportOffset.zero(),
+      textSelectionDelegate: delegate,
+      hasFocus: true,
+    );
+
+    expect(editable.hasFocus, true);
+    editable.hasFocus = false;
+    expect(editable.hasFocus, false);
+  });
 }