Create pick user dialog

lib/ui/dialogs/pick_user_dialog.dart

@@ -0,0 +1,63 @@
+import 'package:comunic/models/user.dart';
+import 'package:comunic/ui/widgets/dialogs/cancel_dialog_button.dart';
+import 'package:comunic/ui/widgets/dialogs/confirm_dialog_button.dart';
+import 'package:comunic/ui/widgets/pick_user_widget.dart';
+import 'package:comunic/ui/widgets/safe_state.dart';
+import 'package:comunic/utils/intl_utils.dart';
+import 'package:flutter/cupertino.dart';
+import 'package:flutter/material.dart';
+
+/// Pick user dialog
+///
+/// @author Pierre HUBERT
+
+/// Ask the user to pick a user
+///
+/// Returns null if no user was selected
+Future<int> showPickUserDialog(BuildContext context) async {
+  return await showDialog(context: context, builder: (c) => _PickUserDialog());
+}
+
+class _PickUserDialog extends StatefulWidget {
+  @override
+  __PickUserDialogState createState() => __PickUserDialogState();
+}
+
+class __PickUserDialogState extends SafeState<_PickUserDialog> {
+  User _user;
+
+  bool get _isValid => _user != null;
+
+  @override
+  Widget build(BuildContext context) {
+    return AlertDialog(
+      title: Text(tr("Choose a user")),
+      content: _buildContent(),
+      actions: <Widget>[
+        CancelDialogButton(),
+        ConfirmDialogButton(
+          value: _isValid ? _user.id : null,
+          enabled: _isValid,
+        ),
+      ],
+    );
+  }
+
+  Widget _buildContent() {
+    final size = MediaQuery.of(context).size;
+    print(size);
+    return Container(
+      width: size.width,
+      height: size.height,
+      child: Column(
+        children: <Widget>[
+          PickUserWidget(
+            onSelectUser: (u) => setState(() => _user = u),
+            label: tr("Search user..."),
+            onValueChange: (u) => setState(() => _user = null),
+          ),
+        ],
+      ),
+    );
+  }
+}