How do you change a style of a child when hovering over a parent using material-ui jss styles

19
votes

I'm using material-ui in react. Let's say I have this component with these styles

const useStyles = makeStyles(theme => ({
  outerDiv: {
    backgroundColor: theme.palette.grey[200],
    padding: theme.spacing(4),
    '&:hover': {
      cursor: 'pointer',
      backgroundColor: theme.palette.grey[100]
   }
  },
  addIcon: (props: { dragActive: boolean }) => ({
    height: 50,
    width: 50,
    color: theme.palette.grey[400],
    marginBottom: theme.spacing(2)
  })
}));

function App() {
  const classes = useStyles();
  return (
    <Grid container>
      <Grid item className={classes.outerDiv}>
        <AddIcon className={classes.addIcon} />
      </Grid>
    </Grid>
  );
}

I want to change the style of addIcon when hovering over outerDiv using the styles above.

Here's my example: https://codesandbox.io/s/trusting-mcnulty-b1gcd?fontsize=14&hidenavigation=1&theme=dark

2
reactjscss-selectorsmaterial-uijssonhover

2 Answers

51
votes

Below is an example of the correct syntax for v4 ("& $addIcon" nested within &:hover). Further down are some v5 examples.

import * as React from "react";
import { render } from "react-dom";
import { Grid, makeStyles } from "@material-ui/core";
import AddIcon from "@material-ui/icons/Add";

const useStyles = makeStyles(theme => ({
  outerDiv: {
    backgroundColor: theme.palette.grey[200],
    padding: theme.spacing(4),
    '&:hover': {
      cursor: 'pointer',
      backgroundColor: theme.palette.grey[100],
      "& $addIcon": {
        color: "purple"
      }
   }
  },
  addIcon: (props: { dragActive: boolean }) => ({
    height: 50,
    width: 50,
    color: theme.palette.grey[400],
    marginBottom: theme.spacing(2)
  })
}));

function App() {
  const classes = useStyles();
  return (
    <Grid container>
      <Grid item className={classes.outerDiv}>
        <AddIcon className={classes.addIcon} />
      </Grid>
    </Grid>
  );
}

const rootElement = document.getElementById("root");
render(<App />, rootElement);

Edit eager-tesla-xw2cg

Related documentation and answers:

For those who have started using Material-UI v5, the example below implements the same styles but leveraging the new sx prop.

import Grid from "@material-ui/core/Grid";
import { useTheme } from "@material-ui/core/styles";
import AddIcon from "@material-ui/icons/Add";

export default function App() {
  const theme = useTheme();
  return (
    <Grid container>
      <Grid
        item
        sx={{
          p: 4,
          backgroundColor: theme.palette.grey[200],
          "&:hover": {
            backgroundColor: theme.palette.grey[100],
            cursor: "pointer",
            "& .addIcon": {
              color: "purple"
            }
          }
        }}
      >
        <AddIcon
          className="addIcon"
          sx={{
            height: "50px",
            width: "50px",
            color: theme.palette.grey[400],
            mb: 2
          }}
        />
      </Grid>
    </Grid>
  );
}

Edit hover over parent

Here's another v5 example, but using Emotion's styled function rather than Material-UI's sx prop:

import Grid from "@material-ui/core/Grid";
import { createTheme, ThemeProvider } from "@material-ui/core/styles";
import AddIcon from "@material-ui/icons/Add";
import styled from "@emotion/styled/macro";

const StyledAddIcon = styled(AddIcon)(({ theme }) => ({
  height: "50px",
  width: "50px",
  color: theme.palette.grey[400],
  marginBottom: theme.spacing(2)
}));
const StyledGrid = styled(Grid)(({ theme }) => ({
  padding: theme.spacing(4),
  backgroundColor: theme.palette.grey[200],
  "&:hover": {
    backgroundColor: theme.palette.grey[100],
    cursor: "pointer",
    [`${StyledAddIcon}`]: {
      color: "purple"
    }
  }
}));
const theme = createTheme();
export default function App() {
  return (
    <ThemeProvider theme={theme}>
      <Grid container>
        <StyledGrid item>
          <StyledAddIcon />
        </StyledGrid>
      </Grid>
    </ThemeProvider>
  );
}

Edit hover over parent

And one more v5 example using Emotion's css prop:

/** @jsxImportSource @emotion/react */
import Grid from "@material-ui/core/Grid";
import { createTheme, ThemeProvider } from "@material-ui/core/styles";
import AddIcon from "@material-ui/icons/Add";

const theme = createTheme();
export default function App() {
  return (
    <ThemeProvider theme={theme}>
      <Grid container>
        <Grid
          item
          css={(theme) => ({
            padding: theme.spacing(4),
            backgroundColor: theme.palette.grey[200],
            "&:hover": {
              backgroundColor: theme.palette.grey[100],
              cursor: "pointer",
              "& .addIcon": {
                color: "purple"
              }
            }
          })}
        >
          <AddIcon
            className="addIcon"
            css={(theme) => ({
              height: "50px",
              width: "50px",
              color: theme.palette.grey[400],
              marginBottom: theme.spacing(2)
            })}
          />
        </Grid>
      </Grid>
    </ThemeProvider>
  );
}

Edit hover over parent

1
votes

Possibly an obvious point, but just to add to the answer above: if you are referencing a separate className, don't forget that you also need to create it in the makeStyles hook or else it won't work. For instance:

const useStyles = makeStyles({
  parent: {
    color: "red",
    "&:hover": {
      "& $child": {
        color: "blue" // will only apply if the class below is declared (can be declared empty)
      }
    }
  },
  // child: {} // THIS must be created / uncommented in order for the code above to work; assigning the className to the component alone won't work.
})

const Example = () => {
  const classes = useStyles()
  return (
    <Box className={classes.parent}>
      <Box className={classes.child}>
        I am red unless you create the child class in the hook
      </Box>
    </Box>
  )
}