React Native 中图像顶部的叠加按钮

Question

I'm trying to achieve the following effect in React Native:

The image has a button in the corner. The button is always within the corner of the image regardless of the image's size or aspect ratio, and no part of the image is clipped (it is always scaled down to fit fully within a box).

The trouble I'm having in React Native is that the Image component's size doesn't always match the scaled-down size of the image. If I fix the image's height to 300, set flex 1 to make the image's width expand to fill its contents, and the image is a portrait, the Image component with being the full width of the container, but the image within the component will have a width of much less. Therefore, the typical approach for having a view overlay another view doesn't work as I would like it to- my overlay also covers the padding around the image, and the button (anchored to the corner) appears outside of the image.

Here's what it looks like in React Native:

The X is a placeholder for the button. It is set to anchor to the top-left of a View that's a child of the same View that the Image is a child of. The backgroundColor of the image is set to green to demonstrate how the width of the Image component is different from the width of the picture that's inside the component.

The goal is that the X would be inside of the image regardless of its aspect ratio. I think I could do something based on grabbing the image's dimension and scaling the height and width of the Image component, but that sounds complicated and fragile. Is this possible in a responsive way with styling?

Demonstration code:

   <View
      style={{
        marginLeft: 7,
        marginRight: 7,
        backgroundColor: 'blue',
      }}
    >
      <View
        style={{
          height: 300,
          flex: 1,
        }}
      >
        <Image
          source={imageSource}
          style={{
            flex: 1,
            height: undefined,
            width: undefined,
            backgroundColor: 'green',
          }}
          resizeMode="contain"
        />
      </View>
      <View
        style={{
          position: 'absolute',
          right: 5,
          top: 5,
          backgroundColor: 'transparent',
        }}
      >
        <Text style={{ color: 'white' }}>X</Text>
      </View>
    </View>

Answer 1

From React-native v0.50.0 <Image> with nested content is no longer supported. Use <ImageBackground> instead.

<ImageBackground
  source={imageSource}
>
    <View>
        <Text>×</Text>
    </View>
</ImageBackground>

Answer 2

Here is how I accomplished that:

import React, { Component } from "react";
import { View, Image, StyleSheet } from "react-native";
import { Ionicons } from "@expo/vector-icons";

class MyCard extends Component {
  render() {
    return (
      <View style={styles.container}>
        <Image
          resizeMode="cover"
          style={styles.cover}
          source={{ uri: "https://picsum.photos/700" }}
        />
        <Ionicons style={styles.close} name="ios-close-circle" size={25} />
      </View>
    );
  }
}

export default MyCard;

const styles = StyleSheet.create({
  container: {
    margin: 5,
    width: 160,
    height: 200
  },
  cover: {
    flex: 1,
    borderRadius: 5
  },
  close: {
    margin: 5,
    position: "absolute",
    top: 0,
    left: 0,
    width: 25,
    height: 25,
    color: "tomato"
  }
});

Here is how it looks like :

Answer 3

Updated 29 Jun 2019

Now( react-native@0.60-RC ) there's a specific component to wrap elements as image background, ImageBackground . Go for the official documentation.

Following Gist has been changed.

---

Original Answer

We can use <Image/> display images, and we can use it as a background-image hack.

try this

<Image
  source={imageSource}
>
  <View>
    <Text>×</Text>
  </View>
</Image>

this gist is a full demo for your need.

or you can see it live at expo:

 <div data-snack-id="B1SsJ7m2b" data-snack-platform="ios" data-snack-preview="true" data-snack-theme="light" style="overflow:hidden;background:#fafafa;border:1px solid rgba(0,0,0,.16);border-radius:4px;height:505px;width:100%"></div> <script async src="https://snack.expo.io/embed.js"></script>

Answer 4

So the way you do this, as @ObooChin mentioned, is to use Image.getSize() to get the actual size of the image, then generate a height and width based on a) the maximum space you want the image to take up, and b) the aspect ratio of the actual image's dimensions.

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

export default class FlexibleThumbnail extends Component {

    constructor(props) {
        super(props)

        this.state = {
            imageWidth: 0,
            imageHeight: 0,
            source: null,
        }
    }

    componentWillMount() {
        this._updateState(this.props)
    }

    componentWillReceiveProps(nextProps) {
        this._updateState(nextProps)
    }

    _updateState(props) {
        const {source} = props;
        const height = props.maxHeight;
        const width = props.maxWidth || Dimensions.get('window').width;

        const imageUri = source.uri;

        Image.getSize(imageUri, (iw, ih) => {
            const {imageWidth, imageHeight} = /* some function that takes max height, width and image height, width and outputs actual dimensions image should be */

            this.setState({
                imageWidth,
                imageHeight,
                source,
            });
        });
    }

    render() {
        const {source, height, width, imageWidth, imageHeight} = this.state;

        const overlay = (/* JSX for your overlay here */);

        // only display once the source is set in response to getSize() finishing
        if (source) {
            return (
                <View style={{width: imageWidth, height: imageHeight}} >
                    <Image
                        style={[ imageStyle, {width: imageWidth, height: imageHeight} ]}
                        resizeMode="contain"
                        source={source}
                    />
                        <View style={{
                            position: 'absolute',
                            top: 0,
                            bottom: 0,
                            left: 0,
                            right: 0,
                            backgroundColor: 'transparent',
                        }}>
                            {overlay}
                        </View>
                </View>
            );
        }

        return (
            <View />
        )
    }
}

The attempt is still a bit rough, but I'm working on turning this into a library where you can specify max height, width, and the overlay you want to use, and it handles the rest: https://github.com/nudgeyourself/react-native-flexible-thumbnail .