react-native-signature-canvas

React Native Signature Component based Canvas for Android && IOS && expo

Supports Android and iOS and Expo
Pure JavaScript implementation with no native dependencies
Tested with RN 0.50
Core use signature_pad.js
Only depend on react and react native
Generates a base64 encoded png image of the signature Note: Expo support for React Native Signature Canvas v1.5.0 started with Expo SDK v33.0.0.

Installation(for React Native V0.60.0 or Expo SDK v35.0.0)

npm install --save react-native-signature-canvas

Installation(for React Native V0.5x.x or Expo SDK < v33)

npm install --save react-native-signature-canvas@1.4.2

Usage

import Signature from 'react-native-signature-canvas';

Properties

Prop	Type	Description
descriptionText	`string`	description text for signature
clearText	`string`	clear button text
confirmText	`string`	save button text
webStyle	`string`	webview style for overwrite default style, all style: https://github.com/YanYuanFE/react-native-signature-canvas/blob/master/h5/css/signature-pad.css
onOK	`function`	handle function when you click save button
onEmpty	`function`	handle function of empty signature when you click save button
onClear	`function`	handle function when you click clear button
onBegin	`function`	handle function when a new stroke is started
onEnd	`function`	handle function when the stroke has ended
customHtml	`function`	html string that lets you modify things like the layout or elements.
autoClear	`boolean`	is auto clear the signature after click confirm button
imageType	`string`	default is "", "image/jpeg"、"image/svg+xml", imageType of export signature
dataURL	`string`	default is "", Base64 string, Draws signature image from data URL.
penColor	`string`	default is "black", color of pen
backgroundColor	`string`	default is "rgba(0,0,0,0)", backgroundColor of canvas

Methods

Function	Description
readSignature()	Reads the current signature on the canvas and triggers either the onOK or onEmpty callbacks
clearSignature()	Clears the current signature

You need to use ref like:

import SignatureScreen from 'react-native-signature-canvas';

const Sign = ({text, onOK}) => {
  const ref = useRef();

  const handleSignature = signature => {
    console.log(signature);
    onOK(signature);
  };

  const handleEmpty = () => {
    console.log('Empty');
  }

  const handleClear = () => {
    console.log('clear success!');
  }

  const handleEnd = () => {
      ref.current.readSignature();
  }

  return (
    <SignatureScreen
        ref={ref}
        onEnd={handleEnd}
        onOK={handleSignature} 
        onEmpty={handleEmpty}
        onClear={handleClear}
        autoClear={true} 
        descriptionText={text}
    />
  );
}

export default Sign;

Save Base64 Image as File

If you use expo, you can use expo-file-system for save base64 image as local file, if you use react-native-cli, use react-native-fs.

import * as FileSystem from 'expo-file-system';

const handleSignature = signature => {
    const path = FileSystem.cacheDirectory + 'sign.png';
    FileSystem.writeAsStringAsync(path, signature.replace('data:image/png;base64,', ''), {encoding: FileSystem.EncodingType.Base64}).then(res => {
      console.log(res);
      FileSystem.getInfoAsync(path, {size: true, md5: true}).then(file => {
        console.log(file);
      })
    }).catch(err => {
      console.log("err", err);
    })
};

Basic parameters

<Signature
  // handle when you click save button
  onOK={(img) => console.log(img)}
  onEmpty={() => console.log("empty")}
  // description text for signature
  descriptionText="Sign"
  // clear button text
  clearText="Clear"
  // save button text
  confirmText="Save"
  // String, webview style for overwrite default style, all style: https://github.com/YanYuanFE/react-native-signature-canvas/blob/master/h5/css/signature-pad.css
  webStyle={`.m-signature-pad--footer
    .button {
      background-color: red;
      color: #FFF;
    }`
  }
  autoClear={true}
  imageType={"image/svg+xml"}
/>

If you create your own triggers for the readSignature and/or clearSignature you can hide the built in Clear and Save buttons with css styles passed into the webStyle property.

const webStyle = `.m-signature-pad--footer
	.save {
		display: none;
	}
	.clear {
		display: none;
	}
`;
...
  <Signature
    webStyle={webStyle}
    onOK={handleOK}
    onEmpty={handleEmpty}
    onEnd={handleEnd}
  />

Example

Android

import React from 'react';
import { StyleSheet, Text, View, Image } from 'react-native';
import Signature from 'react-native-signature-canvas';

export const SignatureScreen = () => {
  const [signature, setSign] = useState(null);

  const handleSignature = signature => {
    console.log(signature);
    setSign(signature);
  };

  const handleEmpty = () => {
    console.log('Empty');
  }

  const style = `.m-signature-pad--footer
    .button {
      background-color: red;
      color: #FFF;
    }`;
  return (
    <View style={{ flex: 1 }}>
      <View style={styles.preview}>
        {this.state.signature ? (
          <Image
            resizeMode={"contain"}
            style={{ width: 335, height: 114 }}
            source={{ uri: this.state.signature }}
          />
        ) : null}
      </View>
      <Signature
        onOK={this.handleSignature}
        onEmpty={this.handleEmpty}
        descriptionText="Sign"
        clearText="Clear"
        confirmText="Save"
        webStyle={style}
      />
    </View>
  );
}

const styles = StyleSheet.create({
  preview: {
    width: 335,
    height: 114,
    backgroundColor: "#F8F8F8",
    justifyContent: "center",
    alignItems: "center",
    marginTop: 15
  },
  previewText: {
    color: "#FFF",
    fontSize: 14,
    height: 40,
    lineHeight: 40,
    paddingLeft: 10,
    paddingRight: 10,
    backgroundColor: "#69B2FF",
    width: 120,
    textAlign: "center",
    marginTop: 10
  }
});

Using Typescript

To use Typescript just import SignatureViewRef and in useRef hook inform that the reference is of the SignatureViewRef type, with that the readSignature and clearSignature methods will be available.

import React, { useRef } from 'react';
import SignatureScreen, { SignatureViewRef } from 'react-native-signature-canvas';

interface Props {
  text: string;
  onOK: (signature) => void;
}

const Sign: React.FC<Props> = ({text, onOK}) => {
  const ref = useRef<SignatureViewRef>(null);

  const handleSignature = signature => {
    console.log(signature);
    onOK(signature);
  };

  const handleEmpty = () => {
    console.log('Empty');
  }

  const handleClear = () => {
    console.log('clear success!');
  }

  const handleEnd = () => {
      ref.current?.readSignature();
  }

  return (
    <SignatureScreen
        ref={ref}
        onEnd={handleEnd}
        onOK={handleSignature} 
        onEmpty={handleEmpty}
        onClear={handleClear}
        autoClear={true} 
        descriptionText={text}
    />
  );
}

export default Sign;

herarya/react-native-signature-canvas