You are doing it in the wrong way, just try this simple method to hide the soft keyboard. you just need to wrap your whole screen in the GestureDetector method and onTap method write this code.

FocusScope.of(context).requestFocus(new FocusNode());

Here is the complete example:

new Scaffold(
   body: new GestureDetector(
      onTap: () {
         FocusScope.of(context).requestFocus(new FocusNode());
      },
      child: new Container(
         //rest of your code write here
      ),
   ),
)

Updated (May 2021)

return GestureDetector(
   onTap: () => FocusManager.instance.primaryFocus?.unfocus(),
   child: Scaffold(
      appBar: AppBar(
         title: Text('Login'),
      ),
      body: Body(),
   ),
);

This will work even when you touch the AppBar, new is optional in Dart 2. FocusManager.instance.primaryFocus will return the node that currently has the primary focus in the widget tree.

Conditional access in Dart with null-safety

You are doing it in the wrong way, just try this simple method to hide the soft keyboard. you just need to wrap your whole screen in the GestureDetector method and onTap method write this code.

FocusScope.of(context).requestFocus(new FocusNode());

Here is the complete example:

new Scaffold(
   body: new GestureDetector(
      onTap: () {
         FocusScope.of(context).requestFocus(new FocusNode());
      },
      child: new Container(
         //rest of your code write here
      ),
   ),
)

Updated (May 2021)

return GestureDetector(
   onTap: () => FocusManager.instance.primaryFocus?.unfocus(),
   child: Scaffold(
      appBar: AppBar(
         title: Text('Login'),
      ),
      body: Body(),
   ),
);

This will work even when you touch the AppBar, new is optional in Dart 2. FocusManager.instance.primaryFocus will return the node that currently has the primary focus in the widget tree.

Conditional access in Dart with null-safety