Flutter：具有TextFormField标题和字幕的ListTile

Question

当我尝试创建带有包含TextFormField标题的ListTile时，我无法添加字幕，否则字幕会爆炸。

这是一个简单的例子：

ListTile(
  title: TextFormField(
    initialValue: 'foo',
  ),
  subtitle: const Text('bar'),
),

当我将此代码段添加到代码中并运行它时，我得到：

I/flutter (20366):   RenderParagraph#3f385 relayoutBoundary=up8 NEEDS-PAINT
I/flutter (20366): ════════════════════════════════════════════════════════════════════════════════════════════════════
I/flutter (20366): Another exception was thrown: RenderBox was not laid out: _RenderListTile#76527 relayoutBoundary=up7 NEEDS-PAINT
I/flutter (20366): Another exception was thrown: RenderBox was not laid out: RenderPadding#61d3e relayoutBoundary=up6 NEEDS-PAINT
I/flutter (20366): Another exception was thrown: RenderBox was not laid out: RenderSemanticsAnnotations#eaf9a relayoutBoundary=up5 NEEDS-PAINT
I/flutter (20366): Another exception was thrown: RenderBox was not laid out: RenderPointerListener#479d1 relayoutBoundary=up4 NEEDS-PAINT
I/flutter (20366): Another exception was thrown: RenderBox was not laid out: RenderSemanticsGestureHandler#1419c relayoutBoundary=up3 NEEDS-PAINT
I/flutter (20366): Another exception was thrown: 'package:flutter/src/rendering/shifted_box.dart': Failed assertion: line 310 pos 12: 'child.hasSize': is not true.
I/flutter (20366): Another exception was thrown: NoSuchMethodError: The method '<=' was called on null.
D/        (20366): HostConnection::get() New Host Connection established 0xd0a0ab40, tid 20389
W/        (20366): Unrecognized GLES max version string in extensions:

这是错误还是只是无效的请求？

我的最终目标是创建一个显示标签和单位的TextFormField。例如，一个字段，用户可以在其中输入以英尺为单位的测量距离的值。