给TextField 赋值

在Android开发中 EditTextView 复制直接调用setText()方法即可，那么在flutter中我遍历所有TextField 属性后发现没有setText这个方法！很困惑

所有属性如下：

 const TextField({
    Key key,
    this.controller,    //编辑框的控制器，跟文本框的交互一般都通过该属性完成，如果不创建的话默认会自动创建
    this.focusNode,  //用于管理焦点
    this.decoration = const InputDecoration(),   //输入框的装饰器，用来修改外观
    TextInputType keyboardType,   //设置输入类型，不同的输入类型键盘不一样
    this.textInputAction,   //用于控制键盘动作（一般位于右下角，默认是完成）
    this.textCapitalization = TextCapitalization.none,
    this.style,    //输入的文本样式
    this.textAlign = TextAlign.start,   //输入的文本位置
    this.textDirection,    //输入的文字排列方向，一般不会修改这个属性
    this.autofocus = false,   //是否自动获取焦点
    this.obscureText = false,   //是否隐藏输入的文字，一般用在密码输入框中
    this.autocorrect = true,   //是否自动校验
    this.maxLines = 1,   //最大行
    this.maxLength,   //能输入的最大字符个数
    this.maxLengthEnforced = true,  //配合maxLength一起使用，在达到最大长度时是否阻止输入
    this.onChanged,  //输入文本发生变化时的回调
    this.onEditingComplete,   //点击键盘完成按钮时触发的回调，该回调没有参数，(){}
    this.onSubmitted,  //同样是点击键盘完成按钮时触发的回调，该回调有参数，参数即为当前输入框中的值。(String){}
    this.inputFormatters,   //对输入文本的校验
    this.enabled,    //输入框是否可用
    this.cursorWidth = 2.0,  //光标的宽度
    this.cursorRadius,  //光标的圆角
    this.cursorColor,  //光标的颜色
    this.keyboardAppearance,
    this.scrollPadding = const EdgeInsets.all(20.0),
    this.dragStartBehavior = DragStartBehavior.down,
    this.enableInteractiveSelection,
    this.onTap,    //点击输入框时的回调(){}
    this.buildCounter,
  })

仔细看这个所有属性的话你会发现
controller：//编辑框的控制器，跟文本框的交互一般都通过该属性完成，如果不创建的话默认会自动创建

给 _controller.value重新赋值就可以实现给TextField 赋值

  final _controller = TextEditingController();
 _controller.value = _controller.value.copyWith(
        text: text,
        selection:
            TextSelection(baseOffset: text.length, extentOffset: text.length),
        composing: TextRange.empty,
      );
    });

完整代码

// Flutter code sample for widgets.TextEditingController.1

// This example creates a [TextField] with a [TextEditingController] whose
// change listener forces the entered text to be lower case and keeps the
// cursor at the end of the input.

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

/// This Widget is the main application widget.
class MyApp extends StatelessWidget {
  static const String _title = 'Flutter Code Sample';

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: _title,
      home: MyStatefulWidget(),
    );
  }
}

class MyStatefulWidget extends StatefulWidget {
  MyStatefulWidget({Key key}) : super(key: key);

  @override
  _MyStatefulWidgetState createState() => _MyStatefulWidgetState();
}

class _MyStatefulWidgetState extends State<MyStatefulWidget> {
  final _controller = TextEditingController();

  void initState() {
    _controller.addListener(() {
      final text = _controller.text.toLowerCase();
      _controller.value = _controller.value.copyWith(
        text: text,
        selection:
            TextSelection(baseOffset: text.length, extentOffset: text.length),
        composing: TextRange.empty,
      );
    });
    super.initState();
  }

  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  Widget build(BuildContext context) {
    return Scaffold(
      body: Container(
        alignment: Alignment.center,
        padding: const EdgeInsets.all(6),
        child: TextFormField(
          controller: _controller,
          decoration: InputDecoration(border: OutlineInputBorder()),
        ),
      ),
    );
  }
}

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