TextField/TextFormField Border in Flutter

The TextField and TextFormField widgets in Flutter are the most used widgets. It is used to get user input in a variety of forms such as email, password, phone, home address, etc. But after adding the default TextField/TextFormField, sometimes you might need to customize the border of TextField/TextFormField. So in this tutorial, we will see how to add and customize TextField/TextFormField border in Flutter.

How to add border to a TextField or TextFormField in Flutter

To add a border to a TextField/TextFormField in Flutter, you can specify the decoration property and then use the InputDecoration and OutlineInputBorder widget. The OutlineInputBorder widget has the borderSide widget which you can use to pass in the BorderSide widget with width and color parameter to create the border.

Here are step by step instructions the to add border to textfield/textformfield in Flutter:

1. Locate the file where you have placed the TextField/TextFormFieldwidget.
2. Inside the TextField/TextFormField widget, add the decoration parameter and assign the InputDecoration widget.
3. Inside the InputDecoration widget, add the enabledBorder parameter and assign the OutlineInputBorder widget.
4. Inside the OutlineInputBorder, add the BorderSide widget with color parameter and set the color of your choice.

Code Example:

const TextField(
  decoration: InputDecoration(
    enabledBorder: OutlineInputBorder(
      borderSide: BorderSide(
          width: 4, color: Colors.green), //<-- SEE HERE
    ),
  ),
)

How to add border radius or rounded border to TextField or TextFormField

To add border radius or create rounded border around the TextField/TextFormField widget, add the decoration property and then use OutlineInputBorder widget. The OutlineInputBorder widget accepts the borderRadius parameter. You can use the borderRadius parameter with BorderRadius.circular(50.0) to create the cricular border around the TextField.

Code Example:

TextField(
  decoration: InputDecoration(
    enabledBorder: OutlineInputBorder(
      borderSide:
          BorderSide(width: 4, color: Colors.green), //<-- SEE HERE
      borderRadius: BorderRadius.circular(20.0),
    ),
  ),
)

Display TextField or TextFormField error border

To display TextField/TextFormField error border, you can add the decoration parameter inside the TextField widget and then assign the InputDecoration widget. Inside the InputDecoration, you can add border for the error state by specifying errorBorder the parameter. You can assign the OutlineInputBorder widget and add border as usual.

Code Example:

const TextField(
  decoration: InputDecoration(
    errorBorder: OutlineInputBorder( //<-- SEE HERE
      borderSide: BorderSide(
          width: 3, color: Colors.redAccent), 
    ),
  ),
)

Display TextField or TextFormField focus border

To display TextField/TextFormField error border, you can add the decoration parameter inside the TextField widget and then assign the InputDecoration widget. Inside the InputDecoration, you can add border for the error state by specifying focusedBorder the parameter. You can assign the OutlineInputBorder widget and add border as usual.

Code Example:

const TextField(
  decoration: InputDecoration(
    focusedBorder: OutlineInputBorder( //<-- SEE HERE
      borderSide: BorderSide(
          width: 3, color: Colors.blueAccent), 
    ),
  ),
)

Show only the bottom border in TextField or TextFormField

To show only the bottom border in TextField/TextFormField, you can specify the decoration property and then use the InputDecoration and UnderlineInputBorder widget. The UnderlineInputBorder widget accepts the borderSide widget which you can use to create the border.

Code Example:

const TextField(
  decoration: InputDecoration(
    enabledBorder: UnderlineInputBorder( //<-- SEE HERE
      borderSide: BorderSide(
          width: 3, color: Colors.greenAccent), 
    ),
  ),
)

How to change TextField or TextFormField border width or size

To change the TextField/TextFormField border width, first add the border as usual and then simply modify the width value inside the BorderSide parameter.

Code Example:

TextField(
  decoration: InputDecoration(
    enabledBorder: OutlineInputBorder(
      borderSide:
          BorderSide(
          width: 5, //<-- SEE HERE
          color: Colors.greenAccent,),
      borderRadius: BorderRadius.circular(50.0),
    ),
  ),
),
//----------
const TextField(
  decoration: InputDecoration(
    enabledBorder: UnderlineInputBorder(
      borderSide: BorderSide(
        width: 3, //<-- SEE HERE
        color: Colors.greenAccent,
      ), 
    ),
  ),
)

Customize TextField or TextFormField border globally

In the previous section, we saw how to customize the TextField/TextFormField border at the page level. but sometimes you might be looking to have a common style across all the pages of your app. In that case, you might want to customize the TextField/TextFormField border color at the app level.

You can change the TextField/TextFormField border color globally by defining the inputDecorationTheme and then adding the OutlineInputBorder widget. Inside the OutlineInputBorder widget, you can specify which type of border you want to change. for example, enabledBorder, focusedBorder, and so on, and then assign the color.

Here’s how you do it:

1. Locate the MaterialApp widget.
2. Inside the MaterialApp, add the theme parameter with ThemeData class assigned.
3. Inside the ThemeData add the inputDecorationTheme parameter and then assign the InputDecorationTheme.
4. Inside the InputDecorationTheme add the enabledBorder parameter and then assign the OutlineInputBorder.
5. Inside the OutlineInputBorder add the borderSide parameter and then assign the BorderSide with color of your choice.

Code Example:

MaterialApp(
  title: 'Flutter Demo',
  theme: ThemeData(
    primarySwatch: Colors.blue,
    inputDecorationTheme: const InputDecorationTheme(
      enabledBorder: OutlineInputBorder(
        borderSide: BorderSide(width: 3, color: Colors.greenAccent),
      ),
      focusedBorder: OutlineInputBorder(
        borderSide: BorderSide(width: 3, color: Colors.amberAccent),
      ),
    ),
  ),
  home: ChangeTextFieldBorderColorDemo(),
);