我是新来的人，当我单击“提交”按钮时，什么都没有发生？

问题描述

这是代码！ 实际上，这是一个非常新的反应，我正在做一个将要执行的项目，但是在执行此操作时，我却坚持在列表项中渲染输入字段的输出。如果还有其他解决方案，例如没有列表组，那将非常有帮助！

我在做实际的错误时，请有人看一下 预先感谢！

import React,{ Component,Fragment } from "react";
class MainPage extends Component {
  state = { data: "" };
  handleChange = (e) => {
    e.preventDefault();};
  handleSubmit = (e) => {
    e.preventDefault();

    this.setState({ data: e.target.value });
  };



render() {
    const mystyle = {
      padding: "16px 16px 16px 60px",textAlign: "start",fontSize: "24px",fontFamily: 'Helvetica Neue",Helvetica,Arial,sans-serif',width: "500px",};

return (
  <Fragment>
    <h1 className="display-1 text-center" style={{ color: "#f7c6c6" }}>
      todos
    </h1>
    <form className="todo-form" onSubmit={this.handleSubmit}>
      <input
        type="text"
        onChange={this.handleChange.bind(this)}
        className="new-todo shadow-lg p-3 mb-5 bg-white rounded"
        style={mystyle}
        placeholder="What needs to be done?"
      />

      <button className="btn btn-primary btn-sm ml-3">Submit</button>

      <ul className="list-group">
        <li
          className="list-group-item disabled p-3 mb-5 w-50 p-3 mx-auto "
          style={{ width: "200px",fontSize: "24px" }}
        >
          {this.state.data}
        </li>
      </ul>
    </form>
  </Fragment>
);}}

导出默认的MainPage；

解决方法

import React,{ Component,Fragment } from "react";
class MainPage extends Component {
  state = { data: "" };

  handleSubmit = (e) => {
    e.preventDefault();

    alert(data)
  };



render() {
    const mystyle = {
      padding: "16px 16px 16px 60px",textAlign: "start",fontSize: "24px",fontFamily: 'Helvetica Neue",Helvetica,Arial,sans-serif',width: "500px",};

return (
  <Fragment>
    <h1 className="display-1 text-center" style={{ color: "#f7c6c6" }}>
      todos
    </h1>
    <form className="todo-form" onSubmit={this.handleSubmit}>
      <input
        type="text"
        onChange={(e) => this.setState({data: e.target.value})}
        className="new-todo shadow-lg p-3 mb-5 bg-white rounded"
        style={mystyle}
        placeholder="What needs to be done?"
      />

      <button className="btn btn-primary btn-sm ml-3">Submit</button>

      <ul className="list-group">
        <li
          className="list-group-item disabled p-3 mb-5 w-50 p-3 mx-auto "
          style={{ width: "200px",fontSize: "24px" }}
        >
          {this.state.data}
        </li>
      </ul>
    </form>
  </Fragment>
);}}

,

尝试一下：

state = { data: "",FinalDataValue:"" };
 handleChange = (e) => {
e.preventDefault();
this.setState({ data: e.target.value });};


handleSubmit = (e) => {
e.preventDefault();
this.setState({ FinalDataValue:this.state.data });};

并在渲染列表中将其写为：

<li
      className="list-group-item disabled p-3 mb-5 w-50 p-3 mx-auto "
      style={{ width: "200px",fontSize: "24px" }}
    >
      {this.state.FinalDataValue}
    </li>

,

您的代码中存在一些问题：

1. 您要提交按钮。为此，您需要添加type="submit"

<button className="btn btn-primary btn-sm ml-3" type="submit">
    Submit
</button>

1. 您需要为input维护两个状态，为todo's维护第二个状态。这样，您始终可以在用户提交表单时追加现有的待办事项：

state = { data: [],input: "" };

1. 最后一次保存的是onSubmit，但还没有保存e.target.value，相反，您需要保存在onHandleChage

这里是完整代码：

import React,Fragment } from "react";

class MainPage extends Component {
  state = { data: [],input: "" };
  handleChange = (e) => {
    e.preventDefault();
    this.setState({ input: e.target.value });
  };
  handleSubmit = (e) => {
    e.preventDefault();
    this.setState({ data: [...this.state.data,this.state.input],input: "" });
  };

  render() {
    const mystyle = {
      padding: "16px 16px 16px 60px",width: "500px"
    };

    return (
      <Fragment>
        <h1 className="display-1 text-center" style={{ color: "#f7c6c6" }}>
          todos
        </h1>
        <form className="todo-form" onSubmit={this.handleSubmit}>
          <input
            type="text"
            onChange={this.handleChange.bind(this)}
            value={this.state.input}
            className="new-todo shadow-lg p-3 mb-5 bg-white rounded"
            style={mystyle}
            placeholder="What needs to be done?"
          />

          <button className="btn btn-primary btn-sm ml-3" type="submit">
            Submit
          </button>

          <ul className="list-group">
            {this.state.data.map((data,i) => {
              return (
                <li
                  className="list-group-item disabled p-3 mb-5 w-50 p-3 mx-auto "
                  style={{ width: "200px",fontSize: "24px" }}
                  key={"todo-" + i}
                >
                  {data}
                </li>
              );
            })}
          </ul>
        </form>
      </Fragment>
    );
  }
}

export default function App() {
  return (
    <div className="App">
      <MainPage />
    </div>
  );
}

以下是演示：https://codesandbox.io/s/xenodochial-banzai-qwxfu?file=/src/App.js:0-1762