從fildlabelText創建動態文本-有解無憂

我正在嘗試創建一個TextInput用于自定義的新小部件，TextFormField但我無法自定義labelText。我需要labelText為我發送建構式TextFormField并顯示這個字串。

class TextInput extends StatelessWidget {


 final TextEditingController textControler;
 final String textLabelHint;
 const TextInput({Key? key, required this.textControler,required this.textLabelHint}) : super(key: key);

@override
Widget build(BuildContext context) {
  return Padding(
    padding: const EdgeInsets.only(top: 10.0),
    child: TextFormField(
    controller: textControler,
    decoration: const InputDecoration(
      border: OutlineInputBorder(),
      labelText: textLabelHint, 
    ),
  ),
);
  }
}

但我有問題：

labelText: textLabelHint, //Invalid constant value.

uj5u.com熱心網友回復：

出現此錯誤是因為textLabelHint最終類屬性（不是 const）可能會根據建構式值而更改。但是，您嘗試傳遞此值的位置是InputDecoration您標記為const. 因此，錯誤表明了這一點。

要解決此問題，請const洗掉InputDecoration:

class TextInput extends StatelessWidget {
 final TextEditingController textControler;
 final String textLabelHint;
 const TextInput({Key? key, required this.textControler,required this.textLabelHint}) : super(key: key);

@override
Widget build(BuildContext context) {
  return Padding(
    padding: const EdgeInsets.only(top: 10.0),
    child: TextFormField(
    controller: textControler,
    decoration: InputDecoration( // <-- Notice the removed const
      border: OutlineInputBorder(),
      labelText: textLabelHint, 
    ),
  ),
);

uj5u.com熱心網友回復：

const您需要從中洗掉decoration: const InputDecoration(...)，因為textLabelHint它不是一個const值：

class TextInput extends StatelessWidget {
  final TextEditingController textControler;
  final String textLabelHint;
  const TextInput(
      {Key? key, required this.textControler, required this.textLabelHint})
      : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: const EdgeInsets.only(top: 10.0),
      child: TextFormField(
        controller: textControler,
        decoration: InputDecoration(
          border: OutlineInputBorder(),
          labelText: textLabelHint,
        ),
      ),
    );
  }
}

uj5u.com熱心網友回復：

嘗試這個：

class TextInput extends StatelessWidget {


 final TextEditingController textControler;
 final String textLabelHint;
 const TextInput({Key? key, required this.textControler,required this.textLabelHint}) : super(key: key);

@override
Widget build(BuildContext context) {
  return Padding(
    padding: const EdgeInsets.only(top: 10.0),
    child: TextFormField(
    controller: textControler,
    decoration: InputDecoration(
      border: OutlineInputBorder(),
      labelText: textLabelHint, 
    ),
  ),
);
  }
}

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標籤：扑镖

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