如何在不修改 Flutter 中默认提供的行为的情况下更改 appbar 的抽屉/后退按钮图标的大小？

Question

I am trying to change the size of the icons ("Back" provided by Navigator and "Drawer" provided by Scaffold) in appbar in my ThemeData, modifying iconTheme and primaryIconTheme:

ThemeData(
    primarySwatch: Colors.blue,
    iconTheme: IconThemeData(color: Colors.grey, size: 32),
    primaryIconTheme: IconThemeData(color: Colors.grey, size: 32)
  ),

This lines only changes the color of the icons, but the size does not change.

I do not need to change the behavior that Flutter handles this button, only the size of them.

Answer 1

The AppBar widget uses a BackButton widget, so that change is not possible unless you modify it from the framework in a different branch, but the best approach is to use the Leading property and the condition ModalRoute.of(context)?.canPop to check whether the current route can be popped. For example:

AppBar( leading: ModalRoute.of(context)?.canPop == true ? IconButton( icon: Icon( Icons.arrow_back, size: 60, ), ) : null, title: Text( "Example", ), )

Answer 2

Luis' answer is mostly complete, but note that you will need to define the onPressed callback in the IconButton, shown below:

AppBar(
      leading: ModalRoute.of(context)?.canPop == true
          ? IconButton(
              icon: Icon(
                Icons.arrow_back,
                size: 60,
                onPressed: () => Navigator.of(context).pop(),
              ),
            )
          : null,
      title: Text(
        "Example",
      ),
    )