onPressed Flutter 属性故障

Question

• I created an extended class from a RaisedButton. When passing the onPressed parameter, the class rejects saying that the drive is null.

• The Class

class VecRaisedButton extends RaisedButton {
  VecRaisedButton({
    text,
    elevation,
    onPressed,
    colorButton = CorPrimaria,
    colorFont,
    splashColor: CorBranca
  }) :
    super(
      child:VecText(text: text, textAlign: TextAlign.center, color: colorFont),
      shape:RoundedRectangleBorder( borderRadius: BordaArredondadaApenas4(10, 10, 10, 10)),
      splashColor:splashColor,
      elevation:elevation,
      onPressed: () => onPressed,
      color:colorButton,
    );
}

• Class call

child: VecRaisedButton(
   text: "Enviar",
   colorFont: CorBranca,
   onPressed: Navigator.push(context, MaterialPageRoute(builder: (context) => Layout_Menu())),
)

Can anybody help me?

Answer 1

Change:

  elevation:elevation,
  onPressed: () => onPressed,

to:

  elevation: elevation,
  onPressed: onPressed, // just pass along the Function

and, this:

   colorFont: CorBranca,
   onPressed: Navigator.push(context, 

to this:

   colorFont: CorBranca,
   onPressed: () => Navigator.push(context, // onPressed takes a Function

However, in general you should compose new widgets rather than extending. That means making a class that extends StatelessWidget and then returning a correctly styled raised button in your new widget's build .