模态路由中叠加层条目的语义顺序

我们更改了模态路由中叠加层条目的语义遍历顺序。无障碍辅助功能（如“对讲”或“语音旁白”）现在会首先聚焦模态路由的范围，而不是其模态屏障。

模态路由有两个叠加层条目：作用域（scope）和模态屏障（modal barrier）。作用域是模态路由的实际内容，而模态屏障是当模态路由的作用域不覆盖整个屏幕时，路由的背景。如果模态路由的 `barrierDismissible` 返回 `true`，则模态屏障会变得可供无障碍功能聚焦，因为用户可以点击模态屏障来弹出模态路由。此更改特意使无障碍功能先聚焦作用域，再聚焦模态屏障。

我们在模态路由的两个叠加层条目上方添加了额外的语义节点。这些语义节点表示这两个叠加层条目的语义遍历顺序。这也改变了语义树的结构。

如果更新后您的测试因语义树更改而开始失败，您可以通过预期模态路由叠加层条目上方的新节点来迁移代码。

迁移前的代码

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;
}

迁移后的代码

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;
}

发布版本：1.19.0
稳定版本中：1.20

API 文档

模态路由中叠加层条目的语义顺序

概述

背景

变更说明

迁移指南

时间线

参考资料