Input asserts while keyboard is dismissed

Now we recreate the stub every time we try to connect to the keyboard. The
underlying message pipe in the stub cannot be re-used, which is why we
previously asserted.

Fixes #776

packages/flutter/lib/src/material/input.dart

@@ -80,7 +80,7 @@ const Curve _kTransitionCurve = Curves.ease;
 class _InputState extends State<Input> {
   String _value;
   EditableString _editableString;
-  KeyboardHandle _keyboardHandle = KeyboardHandle.unattached;
+  KeyboardHandle _keyboardHandle;
 
   // Used by tests.
   EditableString get editableValue => _editableString;
@@ -96,19 +96,22 @@ class _InputState extends State<Input> {
   }
 
   void dispose() {
-    if (_keyboardHandle.attached)
+    if (_isAttachedToKeyboard)
       _keyboardHandle.release();
     super.dispose();
   }
 
+  bool get _isAttachedToKeyboard => _keyboardHandle != null && _keyboardHandle.attached;
+
   void _attachOrDetachKeyboard(bool focused) {
-    if (focused && !_keyboardHandle.attached) {
-      _keyboardHandle = keyboard.show(_editableString.stub, config.keyboardType);
+    if (focused && !_isAttachedToKeyboard) {
+      _keyboardHandle = keyboard.show(_editableString.createStub(), config.keyboardType);
       _keyboardHandle.setText(_editableString.text);
       _keyboardHandle.setSelection(_editableString.selection.start,
                                    _editableString.selection.end);
-    } else if (!focused && _keyboardHandle.attached) {
+    } else if (!focused && _isAttachedToKeyboard) {
       _keyboardHandle.release();
+      _keyboardHandle = null;
       _editableString.didDetachKeyboard();
     }
   }
@@ -251,7 +254,7 @@ class _InputState extends State<Input> {
       behavior: HitTestBehavior.opaque,
       onTap: () {
         if (Focus.at(context)) {
-          assert(_keyboardHandle.attached);
+          assert(_isAttachedToKeyboard);
           _keyboardHandle.showByRequest();
         } else {
           Focus.moveTo(config.key);

packages/flutter/lib/src/services/keyboard.dart

@@ -10,19 +10,6 @@ import 'shell.dart';
 
 export 'package:mojo_services/keyboard/keyboard.mojom.dart';
 
-class _KeyboardConnection {
-
-  _KeyboardConnection() {
-    proxy = new KeyboardServiceProxy.unbound();
-    shell.connectToService(null, proxy);
-  }
-
-  KeyboardServiceProxy proxy;
-  KeyboardService get keyboardService => proxy.ptr;
-
-  static final _KeyboardConnection instance = new _KeyboardConnection();
-}
-
 /// An interface to the system's keyboard.
 ///
 /// Most clients will want to use the [keyboard] singleton instance.
@@ -40,11 +27,8 @@ class Keyboard {
 
   KeyboardHandle show(KeyboardClientStub stub, KeyboardType keyboardType) {
     assert(stub != null);
-    if (_currentHandle != null) {
-      if (_currentHandle.stub == stub)
-        return _currentHandle;
-      _currentHandle.release();
-    }
+    _currentHandle?.release();
+    assert(_currentHandle == null);
     _currentHandle = new KeyboardHandle._show(this, stub, keyboardType);
     return _currentHandle;
   }
@@ -67,16 +51,12 @@ class Keyboard {
 
 class KeyboardHandle {
 
-  KeyboardHandle._show(Keyboard keyboard, this.stub, KeyboardType keyboardType) : _keyboard = keyboard {
+  KeyboardHandle._show(Keyboard keyboard, KeyboardClientStub stub, KeyboardType keyboardType) : _keyboard = keyboard {
     _keyboard.service.show(stub, keyboardType);
     _attached = true;
   }
 
-  KeyboardHandle._unattached(Keyboard keyboard) : _keyboard = keyboard, stub = null, _attached = false;
-  static final unattached = new KeyboardHandle._unattached(keyboard);
-
   final Keyboard _keyboard;
-  final KeyboardClientStub stub;
 
   bool _attached;
   bool get attached => _attached;
@@ -111,4 +91,11 @@ class KeyboardHandle {
 
 }
 
-final Keyboard keyboard = new Keyboard(_KeyboardConnection.instance.keyboardService);
+KeyboardServiceProxy _initKeyboardProxy() {
+  KeyboardServiceProxy proxy = new KeyboardServiceProxy.unbound();
+  shell.connectToService(null, proxy);
+  return proxy;
+}
+
+final KeyboardServiceProxy _keyboardProxy = _initKeyboardProxy();
+final Keyboard keyboard = new Keyboard(_keyboardProxy.ptr);

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

@@ -64,7 +64,6 @@ class _KeyboardClientImpl implements KeyboardClient {
   }) {
     assert(onUpdated != null);
     assert(onSubmitted != null);
-    stub = new KeyboardClientStub.unbound()..impl = this;
     selection = new TextRange(start: text.length, end: text.length);
   }
 
@@ -84,7 +83,9 @@ class _KeyboardClientImpl implements KeyboardClient {
   TextRange selection = TextRange.empty;
 
   /// A keyboard client stub that can be attached to a keyboard service.
-  KeyboardClientStub stub;
+  KeyboardClientStub createStub() {
+    return new KeyboardClientStub.unbound()..impl = this;
+  }
 
   void _delete(TextRange range) {
     if (range.isCollapsed || !range.isValid) return;
@@ -196,7 +197,7 @@ class EditableString {
   /// A keyboard client stub that can be attached to a keyboard service.
   ///
   /// See [Keyboard].
-  KeyboardClientStub get stub => _client.stub;
+  KeyboardClientStub createStub() => _client.createStub();
 
   void didDetachKeyboard() {
     _client.composing = TextRange.empty;