flutter - 无论如何在颤动中改变textlengthlimit指标的属性？

Question

我只想在文本表单字段中获取输入文本计数器和最大长度

TextFormField(
              controller: newusrname, //u can ignore this controller
              maxLength: 30,       //this is the limit i have set           
              decoration: InputDecoration(
                prefixIcon: Icon(Icons.account_box),
                labelText: "Username",
                labelStyle: TextStyle(
                  fontSize: 20.0,
                ),
                border: OutlineInputBorder(
                    borderRadius: BorderRadius.circular(8.0)),
              ),
            ),

标签： flutter

Answer 1

试试这个

  TextEditingController _controller = new TextEditingController();
  String text = ""; // empty string to carry what was there before it

  int maxLength = 30;
TextFormField(
              controller: _controller,
              decoration: InputDecoration(
                prefixIcon: Icon(Icons.account_box),
                labelText: "Username",
                suffix: Text("${_controller.text.length}/$maxLength"),
                labelStyle: TextStyle(
                  fontSize: 20.0,
                ),
                border: OutlineInputBorder(
                    borderRadius: BorderRadius.circular(8.0)),
              ),
                onChanged: (String newVal) {
                  setState(() {
                    if (newVal.length <= maxLength) {
                      text = newVal;
                    } else {
                      _controller.value = new TextEditingValue(
                          text: text,
                          selection: new TextSelection(
                              baseOffset: maxLength,
                              extentOffset: maxLength,
                              affinity: TextAffinity.downstream,
                              isDirectional: false),
                          composing: new TextRange(start: 0, end: maxLength));
                      _controller.text = text;
                    }
                  });
                },

            ),