瞎扯

新年上班第一天.

form表单

flutter不愧是个UI框架.
其实把它和ios android来比.是不能比的.
一个只是框架,ios和android是系统.还是不一样.
这点要想明白,

form这个概念,在安卓里面没有,在ios里应该也没有,在前端才有.

虽然android和ios都会写表单页面.但是没有一个专门的weight做这个事情

flutter不一样,专门提供了一个

weight

class Form extends StatefulWidget {
  /// Creates a container for form fields.
  ///
  /// The [child] argument must not be null.
  const Form({
    Key key,
    @required this.child,
    this.autovalidate = false,
    this.onWillPop,
    this.onChanged,
  }) : assert(child != null),
       super(key: key);

state

class FormState extends State<Form> {
  int _generation = 0;
  final Set<FormFieldState<dynamic>> _fields = Set<FormFieldState<dynamic>>();

  // Called when a form field has changed. This will cause all form fields
  // to rebuild, useful if form fields have interdependencies.
  void _fieldDidChange() {
    if (widget.onChanged != null)
      widget.onChanged();
    _forceRebuild();
  }

和前端十分类似.大致就是监听form下的每一个被TextFormField,FormField.包装的child.
也就是FormState的会add,每一个被FormField包装的weight.然后统一控制.

class FormField<T> extends StatefulWidget {
  /// Creates a single form field.
  ///
  /// The [builder] argument must not be null.
  const FormField({
    Key key,
    @required this.builder,
    this.onSaved, //保存规则
    this.validator, //校验规则
    this.initialValue, //初始化的值
    this.autovalidate = false, //自动校验
    this.enabled = true,
  }) : assert(builder != null),
       super(key: key);

这些其实和react很像,双向绑定,