[react-native] In React Native, how do I put a view on top of another view, with part of it lying outside the bounds of the view behind?

I'm trying to make a layout as per below with React Native.

How do I specify the position of B relative to A?

With iOS Interface Builder and autoconstraints, this can very explicitly be done and is a breeze. It's not so obvious how one might achieve this with React Native.

You can use zIndex for placing a view on top of another. It works like the CSS z-index property - components with a larger zIndex will render on top.

You can refer: Layout Props

Snippet:

    <ScrollView>
          <StatusBar backgroundColor="black" barStyle="light-content" />
          <Image style={styles.headerImage} source={{ uri: "http://www.artwallpaperhi.com/thumbnails/detail/20140814/cityscapes%20buildings%20hong%20kong_www.artwallpaperhi.com_18.jpg" }}>
            <View style={styles.back}>
              <TouchableOpacity>
                <Icons name="arrow-back" size={25} color="#ffffff" />
              </TouchableOpacity>
            </View>
            <Image style={styles.subHeaderImage} borderRadius={55} source={{ uri: "https://upload.wikimedia.org/wikipedia/commons/thumb/1/14/Albert_Einstein_1947.jpg/220px-Albert_Einstein_1947.jpg" }} />
          </Image>

const styles = StyleSheet.create({
    container: {
        flex: 1,
        backgroundColor: "white"
    },
    headerImage: {
        height: height(150),
        width: deviceWidth
    },
    subHeaderImage: {
        height: 110,
        width: 110,
        marginTop: height(35),
        marginLeft: width(25),
        borderColor: "white",
        borderWidth: 2,
        zIndex: 5
    },

add the following to the "floating" view

position: 'absolute'

you may also need to add a top and left value for positioning

see this example: https://rnplay.org/apps/OjzcxQ/edit

The above solutions were not working for me. I solved it by creating a View with the same background colour as the parent and added negative margin to move the image upwards.

<ScrollView style={{ backgroundColor: 'blue' }}>
  <View
    style={{
      width: '95%',
      paddingLeft: '5%',
      marginTop: 80,
      height: 800,
    }}>
    <View style={{ backgroundColor: 'white' }}>

      <Thumbnail square large source={{uri: uri}} style={{ marginTop: -30 }}/>
      <Text>Some Text</Text>
    </View>
  </View>
</ScrollView>

and I got the following result.

You can use react-native-view-overflow plugin for placing a view on top of another. It works like the CSS z-index property.

import ViewOverflow from 'react-native-view-overflow';

<ViewOverflow />
    <View style={[styles2.cardBox, { marginTop: 50 }]}>
    <View style={[styles2.cardItem]} >
      <Text style={styles2.cardHeader}>userList</Text>
    </View>
      <View style={[styles2.cardContent]}>
        <Text style={styles2.text}>overflow: "visible"</Text>
      </View>
      <View style={[styles2.cardItemFooter]} >
        <Text style={styles2.cardTextFooter}>...</Text>
      </View>
    </View>
  </ViewOverflow>

const styles2 = StyleSheet.create({
  cardBox: {
    borderLeftWidth: 0,
    borderTopWidth: 0,
    backgroundColor: "transparent",
    borderWidth: 1,
    borderColor: "#d0d0d0",
    width: '94%',
    alignSelf: 'center',
    height: 200,
    position: "relative",
    borderRadius: 15,
    overflow: "visible" // doesn't do anything
  },
  cardContent: {
    textAlign: "right",
    backgroundColor: "transparent",
    marginTop: 15,
    alignSelf: 'flex-end',
    padding: 5,
  },
  cardHeader: {
    color: '#fff',
    fontFamily: 'Vazir',
    fontSize: 12
  },
  cardItem: {
    backgroundColor: "#3c4252",
    borderRadius: 3,
    position: "absolute",
    top: -10,
    right: -5,
    width: 50,
    height: 20,
    paddingRight: 5,
  },
})

The easiest way to achieve this is with a negative margin.

const deviceWidth = RN.Dimensions.get('window').width

a: {
  alignItems: 'center',
  backgroundColor: 'blue',
  width: deviceWidth,
},
b: {
  marginTop: -16,
  marginStart: 20,
},

You can use this OverlayContainer. The trick is to use absolute with 100% size. Check below an example:

// @flow

import React from 'react'
import { View, StyleSheet } from 'react-native'

type Props = {
  behind: React.Component,
  front: React.Component,
  under: React.Component
}

// Show something on top of other
export default class OverlayContainer extends React.Component<Props> {
  render() {
    const { behind, front, under } = this.props

    return (
      <View style={styles.container}>
        <View style={styles.center}>
          <View style={styles.behind}>
            {behind}
          </View>
          {front}
        </View>
        {under}
      </View>
    )
  }
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    alignItems: 'center',
    height: '100%',
    justifyContent: 'center',
  },
  center: {
    width: '100%',
    height: '100%',
    alignItems: 'center',
    justifyContent: 'center',
  },
  behind: {
    alignItems: 'center',
    justifyContent: 'center',
    position: 'absolute',
    left: 0,
    top: 0,
    width: '100%',
    height: '100%'
  }
})

import React, {Component} from 'react';
import {StyleSheet, View} from 'react-native';


export default class App extends Component {
  render() {
    return (
       <View>// you need to wrap the two Views an another View
          <View style={styles.box1}></View>
          <View style={styles.box2}></View>
       </View> 
    );
  }
}

const styles = StyleSheet.create({
  box1:{
    height:100,
    width:100,
    backgroundColor:'red'
  },
  box2:{
    height:100,
    width:100,
    backgroundColor:'green',
    position: 'absolute',
    top:10,
    left:30

  },
});

You can use elevation property for Android if you don't mind the shadow.

{
  elevation:1
}