I want to increment my price by the percentage that the user types in the UI, how do I do the math of that?

for example with simple math you do it like this

1. Increase the value by 1%: 1.45 x 1.01 = 1.4645
2. Decrease the value by 1%: 1.45 x 0.99 = 1.4355
3. Increase the value by 10%: 1.45 x 1.10 = 1.595
4. Decrease the value by 1%: 1.45 x 0.90 = 1.305

But I don’t know how to do it with flutter because the user is gonna put a value from 1 to 1000 in the percentage that he wants to add.

How to change that value to match the equation above?

CodePudding user response：

If x is the percentage the user fills in the UI and y is the value, then you do:

(x / 100   1) × y

x is positive for increase and negative for decreasing percentage.

CodePudding user response：

The above answer will solve the problem. Just writing an answer to show you by codes.

class MyWidget extends StatefulWidget {
  
  @override
  State<MyWidget> createState() => _MyWidgetState();
}

class _MyWidgetState extends State<MyWidget> {
  double originalPrice = 50;
  TextEditingController textController = TextEditingController();
int defaultPercentage = 1;
  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        TextField(
         controller: textController,
          onChanged:(val){
            setState((){});
          }
        ),
        Text("Original Price : $originalPrice"),
        Text("Price in % ${originalPrice (originalPrice*(int.tryParse(textController.text)?? defaultPercentage)/100)})")
      ],
    );
  }
}