更改顏色 ListView.Builder onPressed Flutter

Question

我想改變顏色。 如果我選擇值為“einamal”（真）的索引，它將是綠色，否則（假）紅色。

List<String> _choices = <String>[ 'einmal','zweimal', 'dreimal', 'viemal' ];
List<bool> _hasBeenPressed = [true, false, false, false];

 Widget _buildChoice() {

    return Container(
      height: MediaQuery.of(context).size.height/4,
      child: ListView.builder(
          itemCount: _choices.length,
          itemBuilder: (BuildContext context, int index)
          {
            return RaisedButton(
              child: new Text(_choices[index]),
              textColor: _hasBeenPressed[index] ? Colors.white : Colors.green,
              color: _hasBeenPressed[index] ? Colors.green : Colors.white,
              onPressed: () =>
              {
                setState(() {
                  if(_choices[index] == 'einmal') {
                    _hasBeenPressed[index] = !_hasBeenPressed[index];
                  }
                })
              },
              shape: RoundedRectangleBorder(
                  borderRadius: BorderRadius.circular(30.0)
              ),
            );
          }
      ),

    );
  }

實現截圖

Answer 1

您需要另一個變量來存儲您的實際答案，在您的情況下，它將是，

String answer = "einmal";

現在，您只需要一個String來存儲用戶選擇的選項而不是列表，就像這樣，

String selected = "";

現在，每當用戶選擇一個選項時，更新您的selected ，就像這樣，

onPressed: () => {
  setState(() {
    selected = _choices[index];
  })
},

現在，用它來獲得正確的顏色，

textColor: selected == _choices[index] ? Colors.white : Colors.green,
color: selected == _choices[index]
         ? (selected == answer ? Colors.green : Colors.red)
         : Colors.white,

完整的代碼，

List<String> _choices = <String>['einmal', 'zweimal', 'dreimal', 'viemal'];
String answer = "einmal";

String selected = "";

Widget _buildChoice() {
  return Container(
    height: MediaQuery.of(context).size.height / 4,
    child: ListView.builder(
      itemCount: _choices.length,
      itemBuilder: (BuildContext context, int index) {
        return RaisedButton(
          child: new Text(_choices[index]),
          textColor:
              selected == _choices[index] ? Colors.white : Colors.green,
          color: selected == _choices[index]
              ? (selected == answer ? Colors.green : Colors.red)
              : Colors.white,
          onPressed: () => {
            setState(() {
              selected = _choices[index];
            })
          },
          shape: RoundedRectangleBorder(
              borderRadius: BorderRadius.circular(30.0)),
        );
      }),
  );
}