showDialog<T> function

Future<T> showDialog <T>({@required BuildContext context, bool barrierDismissible: true, @Deprecated('Instead of using the "child" argument, return the child from a closure ' 'provided to the "builder" argument. This will ensure that the BuildContext ' 'is appropriate for widgets built in the dialog.') Widget child, WidgetBuilder builder })

Displays a Material dialog above the current contents of the app, with Material entrance and exit animations, modal barrier color, and modal barrier behavior (dialog is dismissible with a tap on the barrier).

This function takes a builder which typically builds a Dialog widget. Content below the dialog is dimmed with a ModalBarrier. The widget returned by the builder does not share a context with the location that showDialog is originally called from. Use a StatefulBuilder or a custom StatefulWidget if the dialog needs to update dynamically.

The context argument is used to look up the Navigator and Theme for the dialog. It is only used when the method is called. Its corresponding widget can be safely removed from the tree before the dialog is closed.

The child argument is deprecated, and should be replaced with builder.

Returns a Future that resolves to the value (if any) that was passed to Navigator.pop when the dialog was closed.

The dialog route created by this method is pushed to the root navigator. If the application has multiple Navigator objects, it may be necessary to call Navigator.of(context, rootNavigator: true).pop(result) to close the dialog rather than just Navigator.pop(context, result).

See also:

Implementation 

Future<T> showDialog<T>({
  @required BuildContext context,
  bool barrierDismissible = true,
  @Deprecated(
    'Instead of using the "child" argument, return the child from a closure '
    'provided to the "builder" argument. This will ensure that the BuildContext '
    'is appropriate for widgets built in the dialog.'
  ) Widget child,
  WidgetBuilder builder,
}) {
  assert(child == null || builder == null);
  assert(debugCheckHasMaterialLocalizations(context));
  return showGeneralDialog(
    context: context,
    pageBuilder: (BuildContext buildContext, Animation<double> animation, Animation<double> secondaryAnimation) {
      final ThemeData theme = Theme.of(context, shadowThemeOnly: true);
      final Widget pageChild =  child ?? Builder(builder: builder);
      return SafeArea(
        child: Builder(
          builder: (BuildContext context) {
            return theme != null
                ? Theme(data: theme, child: pageChild)
                : pageChild;
          }
        ),
      );
    },
    barrierDismissible: barrierDismissible,
    barrierLabel: MaterialLocalizations.of(context).modalBarrierDismissLabel,
    barrierColor: Colors.black54,
    transitionDuration: const Duration(milliseconds: 150),
    transitionBuilder: _buildMaterialDialogTransitions,
  );
}