flutter - TextField inside of Row causes layout exception: Unable to calculate size

Question

I’m getting a rendering exception that I don’t understand how to fix. I’m attempting to create a column that has 3 rows.

Row [Image]

Row [TextField ]

Row [Buttons]

Here is my code to build the container:

Container buildEnterAppContainer(BuildContext context) {
    var container = new Container(
      padding: const EdgeInsets.all(8.0),
      child: new Column(
        mainAxisAlignment: MainAxisAlignment.start,
        children: <Widget>[
          buildImageRow(context),
          buildAppEntryRow(context),
          buildButtonRow(context)
        ],
      ),
    );
    return container;
  }

and my buildAppEntryRow code for the text container

Widget buildAppEntryRow(BuildContext context) {
    return new Row(
      children: <Widget>[
        new TextField(
          decoration: const InputDecoration(helperText: "Enter App ID"),
          style: Theme.of(context).textTheme.body1,
        )
      ],
    );
  }

When I run I get the following exception:

I/flutter ( 7674): BoxConstraints forces an infinite width.
I/flutter ( 7674): These invalid constraints were provided to RenderStack's layout() function by the following
I/flutter ( 7674): function, which probably computed the invalid constraints in question:
I/flutter ( 7674):   RenderConstrainedBox.performLayout (package:flutter/src/rendering/proxy_box.dart:256:13)
I/flutter ( 7674): The offending constraints were:
I/flutter ( 7674):   BoxConstraints(w=Infinity, 0.0<=h<=Infinity)

If i change buildAppEntryRow to just a TextField instead like this

 Widget buildAppEntryRow2(BuildContext context) {
    return new TextField(
      decoration: const InputDecoration(helperText: "Enter App ID"),
      style: Theme.of(context).textTheme.body1,
    );
  }

I no longer get the exception. What am I missing with the Row implementation that is causing it to not be able to calculate the size of that row?

Answer 1

(I assume you're using a Row because you want to put other widgets beside the TextField in the future.)

The Row widget wants to determine the intrinsic size of its non-flexible children so it knows how much space that it has left for the flexible ones. However, TextField doesn't have an intrinsic width; it only knows how to size itself to the full width of its parent container. Try wrapping it in a Flexible or Expanded to tell the Row that you're expecting the TextField to take up the remaining space:

      new Row(
        children: <Widget>[
          new Flexible(
            child: new TextField(
              decoration: const InputDecoration(helperText: "Enter App ID"),
              style: Theme.of(context).textTheme.body1,
            ),
          ),
        ],
      ),