Css Reactjs：有没有办法将图片居中？

我写了一个网站，你可以在这里看到：

我现在很担心这个屏幕：

我想居中的图标，已经尝试了很多，但它仍然没有工作，因为我不知道我如何可以应用样式到它。在这里您可以看到我的代码：

import React from 'react';
import { Button, Grid } from '@material-ui/core';
import { withStyles } from '@material-ui/core/styles';
import AppContext from '../utils/AppContext';
import { Header } from '../Layout';
import SOSButton from './SOSButton';
import axios from 'axios';
import CONST from '../utils/Constants';
import AmbulanceIcon from '../utils/icons/Ambulance-small.png';
const styles = theme => ({
  container: {
    justifyContent: 'center',
    alignItems: 'center',
    // background: 'white',
    border: 'black',
    'border-width': 'medium',
    'margin-top': '80px',
    background: 'rgba(255, 255, 255, 0.8)',
    'border-radius': '20px'
  },
  item: {
    // background: 'red',
    width: '100%',
    //background: 'white',
    'text-align': 'center',
    'border-radius': '5px',
    'margin-top': '10px'
  },
  icon: {
    height: '50px',
    width: '50px'
  }
});

class Landingpage extends React.Component {
  static contextType = AppContext;

  constructor(props) {
    super(props);
    this.classes = props.classes;
    this.state = {};
    this.handleDirectSOS = this.handleDirectSOS.bind(this);
    this.onSubmit = this.onSubmit.bind(this);
  }

  componentDidMount() {
    console.log(this.context);

    if (this.context.onBoardingStatus === false) {
      console.log('IN IF');
      this.props.history.push('/onboarding');
    }
  }
  handleDirectSOS() {
    console.log('direct SOS');
    this.props.history.push('/emergency_sent');
  }

  onSubmit(e) {
    console.log('in OnSubmit');
    axios
      .post(CONST.URL + 'emergency/create', {
        id: 1,
        data: this.state
      })
      .then(res => {
        console.log(res);
        console.log(res.data);
      })
      .catch(err => {
        console.log(err);
      });
  }

  render() {
    return (
      <React.Fragment>
        <Header title="Send out SOS" />
        <Grid
          container
          className={this.classes.container}
          direction="column"
          spacing={2}
        >
          <Grid
            item
            sm={12}
            className={(this.classes.item, this.classes.forwardbutton)}
          >
            <div className={this.classes.imageContainer}>
            <img src={AmbulanceIcon} alt="AmbulanceIcon" />{' '}
            </div>
            <SOSButton onSubmit={this.onSubmit} />
          </Grid>
        </Grid>
      </React.Fragment>
    );
  }
}

export default withStyles(styles)(Landingpage);

谢谢你的帮助

编辑：图片现在居中，但按“立即获取帮助”后不再居中

我不理解这一点，因为按钮的更改仅在SOS按钮文件中管理，该文件不包含或操纵徽标：

import React from 'react';
import { withRouter } from 'react-router-dom';
import Button from '@material-ui/core/Button';
import { withStyles } from '@material-ui/core/styles';

const styles = theme => ({
  sosbutton: {
    background: '#e45050',
    'text-align': 'center',
    'margin-top': '30px',
    height: '80%',
    width: '100%'
  }
});
class SOSButton extends React.Component {
  constructor(props) {
    super(props);
    this.classes = props.classes;
    this.state = {
      timerOn: false
    };
    this.timerStart = this.timerStart.bind(this);
    this.timerStop = this.timerStop.bind(this);
    this.tick = this.tick.bind(this);
    this.counter = 3;
    this.counterStep = 1;
  }

  timerStart() {
    this.timerID = setInterval(() => this.tick(), 1000);
    this.setState({ timerOn: true });
  }

  timerStop() {
    clearInterval(this.timerID);
    this.counter = 3;
    this.setState({ timerOn: false });
    this.props.history.push('/');
  }

  tick() {
    this.counter = this.counter - this.counterStep;
    if (this.counter <= 0) {
      this.setState({ timerOn: false });
      this.timerStop();
      this.props.onSubmit();
      this.props.history.push('/emergency_sent');
    } else {
      this.setState({ timerOn: true });
    }
    console.log(this.counter);
  }

  render() {
    let timerOn = this.state.timerOn;
    let button;

    if (timerOn) {
      button = (
        <div>
          You have {this.counter} seconds to cancel the emergency SOS. <br />
          <br />
          <Button size="large" color="primary" onClick={this.timerStop}>
            Press here to cancel emergency call!
          </Button>
        </div>
      );
    } else {
      button = (
        <Button className={this.classes.sosbutton} onClick={this.timerStart}>
          GET HELP NOW!
        </Button>
      );
    }

    console.log(button);
    return button;
  }
}

export default withRouter(withStyles(styles)(SOSButton));

---

请参见此处的新网站：

您的第一个问题是需要将样式更改为驼峰式。第二，您只需添加display flex并将内容对齐到中心，它就可以使您的图像居中

item: {
    // background: 'red',
    width: '100%',

    //background: 'white',
    textAlign: 'center',
    borderRadius': '5px',
    marginTop: '10px',
    display: "flex",
    justifyContent: "center
  },

您需要将img标记包装在它自己的div中，并相应地设置该div的样式。在本例中，我为该div提供了一个imageContainer类。见下文：

import React from 'react';
import { Button, Grid } from '@material-ui/core';
import { withStyles } from '@material-ui/core/styles';
import AppContext from '../utils/AppContext';
import { Header } from '../Layout';
import SOSButton from './SOSButton';
import axios from 'axios';
import CONST from '../utils/Constants';
import AmbulanceIcon from '../utils/icons/Ambulance-small.png';
const styles = theme => ({
  container: {
    justifyContent: 'center',
    alignItems: 'center',
    // background: 'white',
    border: 'black',
    'border-width': 'medium',
    'margin-top': '80px',
    background: 'rgba(255, 255, 255, 0.8)',
    'border-radius': '20px'
  },
  item: {
    // background: 'red',
    width: '100%',
    //background: 'white',
    'textAlign': 'center',
    'borderRadius': '5px',
    'marginTop': '10px'
  },
  icon: {
    height: '50px',
    width: '50px'
  },
  imageContainer: {
    display: 'flex';
    justifyContent: 'center'
    width: '250px'
  }
});

class Landingpage extends React.Component {
  static contextType = AppContext;

  constructor(props) {
    super(props);
    this.classes = props.classes;
    this.state = {};
    this.handleDirectSOS = this.handleDirectSOS.bind(this);
    this.onSubmit = this.onSubmit.bind(this);
  }

  componentDidMount() {
    console.log(this.context);

    if (this.context.onBoardingStatus === false) {
      console.log('IN IF');
      this.props.history.push('/onboarding');
    }
  }
  handleDirectSOS() {
    console.log('direct SOS');
    this.props.history.push('/emergency_sent');
  }

  onSubmit(e) {
    console.log('in OnSubmit');
    axios
      .post(CONST.URL + 'emergency/create', {
        id: 1,
        data: this.state
      })
      .then(res => {
        console.log(res);
        console.log(res.data);
      })
      .catch(err => {
        console.log(err);
      });
  }

  render() {
    return (
      <React.Fragment>
        <Header title="Send out SOS" />
        <Grid
          container
          className={this.classes.container}
          direction="column"
          spacing={2}
        >
          <Grid
            item
            sm={12}
            className={(this.classes.item, this.classes.forwardbutton)}
          >
            <div className={this.classes.imageContainer}>
                <img src={AmbulanceIcon} alt="AmbulanceIcon" />{' '}
            </div>
            <SOSButton onSubmit={this.onSubmit} />
          </Grid>
        </Grid>
      </React.Fragment>
    );
  }
}

export default withStyles(styles)(Landingpage);

---

我想你可能忘了展示：谢谢！请看一下问题的编辑，如果您也能帮助我解决这个问题，那就太好了。@pythonlearner在imageContainer类中，删除宽度：250px，它应该可以工作。