set gradient in background container vertical in flutter code example

Example 1: flutter container background gradient

appBar: AppBar(

      title: Text('Flutter Demo'),
      flexibleSpace: Container(
        decoration: BoxDecoration(
          gradient: LinearGradient(
            begin: Alignment.centerLeft,
            end: Alignment.centerRight,
            colors: <Color>[
              Colors.red,
              Colors.blue
            ],
          ),
        ),
      ),
    ),

Example 2: add gradient bg to container in flutter

body: Container(
  decoration: BoxDecoration(
    gradient: LinearGradient(
      colors: [Colors.green, Colors.blue])
  ),
  child: Center(
    child: Text('Gradients are cool!',
      style: TextStyle(
        fontSize: 35,
        color: Colors.white,
      ),
    ),
  ),
),