RenderEditable 需要先布局，然后才能进行命中测试

RenderEditable 的实例在处理命中测试之前必须先进行布局。尝试在布局之前命中测试 RenderEditable 对象会导致断言失败，如下所示：

Failed assertion: line 123 pos 45: '!debugNeedsLayout': is not true.

为了在可选文本中支持手势识别器，RenderEditable 需要其文本跨度的布局信息，以确定哪个文本跨度接收指针事件。（在此更改之前，RenderEditable 对象在评估命中测试时不会考虑其文本。）为了实现这一点，布局被设为了在 RenderEditable 对象上执行命中测试的先决条件。

实际上，这很少成为问题。小部件库确保在对所有渲染对象进行任何命中测试之前都会执行布局。此问题仅可能在直接与渲染对象交互的代码中看到，例如自定义渲染对象的测试中。

如果您在命中测试 RenderEditable 时看到 '!debugNeedsLayout': is not true 断言错误，请先布局 RenderEditable，然后再进行命中测试。

迁移前的代码

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

void main() {
  test('attach and detach correctly handle gesture', () {
    final RenderEditable editable = RenderEditable(
      textDirection: TextDirection.ltr,
      offset: ViewportOffset.zero(),
      textSelectionDelegate: FakeEditableTextState(),
      startHandleLayerLink: LayerLink(),
      endHandleLayerLink: LayerLink(),
    );
    final PipelineOwner owner = PipelineOwner(onNeedVisualUpdate: () {});
    editable.attach(owner);
    // This throws an assertion error because
    // the RenderEditable hasn't been laid out.
    editable.handleEvent(const PointerDownEvent(),
        BoxHitTestEntry(editable, const Offset(10, 10)));
    editable.detach();
  });
}

class FakeEditableTextState extends TextSelectionDelegate {
  @override
  TextEditingValue textEditingValue;
  @override
  void hideToolbar() {}
  @override
  void bringIntoView(TextPosition position) {}
}

迁移后的代码

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

void main() {
  test('attach and detach correctly handle gesture', () {
    final RenderEditable editable = RenderEditable(
      textDirection: TextDirection.ltr,
      offset: ViewportOffset.zero(),
      textSelectionDelegate: FakeEditableTextState(),
      startHandleLayerLink: LayerLink(),
      endHandleLayerLink: LayerLink(),
    );
    // Lay out the RenderEditable first.
    editable.layout(BoxConstraints.loose(const Size(1000.0, 1000.0)));
    final PipelineOwner owner = PipelineOwner(onNeedVisualUpdate: () {});
    editable.attach(owner);
    editable.handleEvent(const PointerDownEvent(),
        BoxHitTestEntry(editable, const Offset(10, 10)));
    editable.detach();
  });
}

class FakeEditableTextState extends TextSelectionDelegate {
  @override
  TextEditingValue textEditingValue;
  @override
  void hideToolbar() {}
  @override
  void bringIntoView(TextPosition position) {}
}

发布版本：1.18.0
稳定版本中：1.20

API 文档

RenderEditable

RenderEditable 需要先布局，然后才能进行命中测试

概述

背景

迁移指南

时间线

参考资料