如何将小部件放置在表单小部件的底部？

Question

I have widget:

Scaffold(
  appBar: ...,
  body: Form(
    child: ListView(
      children: [
        ...
        ElevatedButton() // Save button
      ]
    )
  )
);

So, I want to place it to the bottom of the screen. I tried to place it inside Align widget but it doesn't work. Another thing is that I have ExpansionTile above and it can overflow the screen. In this case, there mustn't be any additional space between Activate and Save buttons. How to do it?

Answer 1

Use MainAxisAlignment.spaceBetween. Documentation:

Place the free space evenly between the children.

bool _hasExpansionTile = false;

Scaffold(
  appBar: ...,
  body: Column(mainAxisAlignment: _hasExpansionTile ? MainAxisAlignment.start : MainAxisAlignment.spaceBetween, /// Checking that the expansion tile is visible
        children: [
          Flexible(
             child: Form(
                child: Column(
                    children: [
                       ...
                    ],
                ),
             ),
          ),
          ElevatedButton(onPressed: (){}, child: Text("Send")),
        ],
      ),
);

Of course you must use setState(), when you changing the value of the _hasExpansionTile property.

Answer 2

You can use Spacer()

Scaffold( appBar: ...,
body: Form(
child: ListView(
  children: [
    ...
    Spacer(),
    ElevatedButton() // Save button
  ]
)

) );