模態路由中 Overlay 條目的語義順序

我們改變了模態路由中 Overlay 條目的語義遍歷順序。現在，無障礙讀屏軟體（如 TalkBack 或 VoiceOver）會先聚焦模態路由的作用域，而不是其模態障礙物。

模態路由有兩個 Overlay 條目：作用域（scope）和模態障礙物（modal barrier）。作用域是模態路由的實際內容，而模態障礙物是路由的背景，如果其作用域未覆蓋整個螢幕。如果模態路由的 barrierDismissible 返回 true，模態障礙物將變得可聚焦，因為使用者可以透過點選模態障礙物來關閉模態路由。此更改特意將無障礙焦點設定為先聚焦作用域，然後再聚焦模態障礙物。

我們在模態路由的兩個 Overlay 條目上方添加了額外的語義節點。這些語義節點表示這兩個 Overlay 條目的語義遍歷順序。這也改變了語義樹的結構。

如果更新後，您的測試因語義樹更改而失敗，您可以預期在模態路由 Overlay 條目上方出現一個新節點來遷移您的程式碼。

遷移前的程式碼

dartimport 'dart:ui';

import 'package:flutter_test/flutter_test.dart';
import 'package:flutter/rendering.dart';
import 'package:flutter/material.dart';

void main() {
  testWidgets('example test', (WidgetTester tester) async {
    final SemanticsHandle handle =
        tester.binding.pipelineOwner.ensureSemantics();

    // Build our app and trigger a frame.
    await tester.pumpWidget(MaterialApp(home: Scaffold(body: Text('test'))));

    final SemanticsNode root =
        tester.binding.pipelineOwner.semanticsOwner.rootSemanticsNode;

    final SemanticsNode firstNode = getChild(root);
    expect(firstNode.rect, Rect.fromLTRB(0.0, 0.0, 800.0, 600.0));

    // Fixes the test by expecting an additional node above the scope route.
    final SemanticsNode secondNode = getChild(firstNode);
    expect(secondNode.rect, Rect.fromLTRB(0.0, 0.0, 800.0, 600.0));

    final SemanticsNode thirdNode = getChild(secondNode);
    expect(thirdNode.rect, Rect.fromLTRB(0.0, 0.0, 800.0, 600.0));
    expect(thirdNode.hasFlag(SemanticsFlag.scopesRoute), true);

    final SemanticsNode forthNode = getChild(thirdNode);
    expect(forthNode.rect, Rect.fromLTRB(0.0, 0.0, 56.0, 14.0));
    expect(forthNode.label, 'test');
    handle.dispose();
  });
}

SemanticsNode getChild(SemanticsNode node) {
  SemanticsNode child;
  bool visiter(SemanticsNode target) {
    child = target;
    return false;
  }

  node.visitChildren(visiter);
  return child;
}

遷移後的程式碼

dartimport 'dart:ui';

import 'package:flutter_test/flutter_test.dart';
import 'package:flutter/rendering.dart';
import 'package:flutter/material.dart';

void main() {
  testWidgets('example test', (WidgetTester tester) async {
    final SemanticsHandle handle =
        tester.binding.pipelineOwner.ensureSemantics();

    // Build our app and trigger a frame.
    await tester.pumpWidget(MaterialApp(home: Scaffold(body: Text('test'))));

    final SemanticsNode root =
        tester.binding.pipelineOwner.semanticsOwner.rootSemanticsNode;

    final SemanticsNode firstNode = getChild(root);
    expect(firstNode.rect, Rect.fromLTRB(0.0, 0.0, 800.0, 600.0));

    // Fixes the test by expecting an additional node above the scope route.
    final SemanticsNode secondNode = getChild(firstNode);
    expect(secondNode.rect, Rect.fromLTRB(0.0, 0.0, 800.0, 600.0));

    final SemanticsNode thirdNode = getChild(secondNode);
    expect(thirdNode.rect, Rect.fromLTRB(0.0, 0.0, 800.0, 600.0));
    expect(thirdNode.hasFlag(SemanticsFlag.scopesRoute), true);

    final SemanticsNode forthNode = getChild(thirdNode);
    expect(forthNode.rect, Rect.fromLTRB(0.0, 0.0, 56.0, 14.0));
    expect(forthNode.label, 'test');
    handle.dispose();
  });
}

SemanticsNode getChild(SemanticsNode node) {
  SemanticsNode child;
  bool visiter(SemanticsNode target) {
    child = target;
    return false;
  }

  node.visitChildren(visiter);
  return child;
}