react-native-signature-canvas

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

• Supports Android and iOS and Expo
• Tested with RN 0.69
• Core use signature_pad.js
• 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)

yarn add react-native-signature-canvas

or

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

This package depends on react-native-webview and it is particularly needed when you are using React Native CLI. To install react-native-webview follow the steps mentioned here

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

npm install --save [email protected]

Usage

Basic

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

Custom

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

Properties

| Prop | Type | Description | |:------------------------------------|:----------------------------------------:|:------------------------------------------------------------------------------------------------------------------------------------------------------| | androidHardwareAccelerationDisabled | boolean | androidHardwareAccelerationDisabled for react-native-webview. Default is false | | autoClear | boolean | should auto clear the signature after clicking the Confirm button | | backgroundColor | string | default is "rgba(255,255,255,0)" (transparent), background color of the canvas | | bgHeight | number | height of the background image | | bgWidth | number | width of the background image | | bgSrc | string | background image source uri (url) | | clearText | string | clear button text | | confirmText | string | save button text | | customHtml | (injectedJavaScript: string) => string | html string that lets you modify things like the layout or elements | | dataURL | string | default is "", Base64 string, draws saved signature from dataURL. | | descriptionText | string | description text for signature | | dotSize | number | radius of a single dot (not stroke width) | | imageType | string | "image/png" (default), "image/jpeg"、"image/svg+xml", imageType of exported signature | | minWidth | number | minimum width of a line. Defaults to 0.5 | | maxWidth | number | maximum width of a line. Defaults to 2.5 | | nestedScrollEnabled | boolean | enable nested scrolling for use inside of a scrollview | | showsVerticalScrollIndicator | boolean | Boolean value that determines whether a vertical scroll indicator is shown in the WebView, The default value is true. | | onOK | function | callback function after saving non-empty signature | | onEmpty | function | callback function after trying to save an empty signature | | onClear | function | callback function after clearing the signature | | onGetData | function | callback function when getData() is called
| onBegin | function | callback function when a new stroke is started | | onEnd | function | callback function when the stroke has ended | | onLoadEnd | function | callback function when the webview canvas load ended | | onUndo | function | callback function when undo() is called | | onRedo | function | callback function when redo() is called | | onDraw | function | callback function when drawing is enabled | | onErase | function | callback function when erasing is enabled | | onChangePenColor | function | callback function after changing the pen color | | onChangePenSize | function | callback function after changing the pen size
| overlayHeight | number | height of the overlay image | | overlayWidth | number | width of the overlay image | | overlaySrc | string | overlay image source uri (url) must be .png with a transparent background
| penColor | string | default is "black", color of pen | | rotated | boolean | rotate signature pad 90 degrees | | style | object | style of wrapper view | | trimWhitespace | boolean | trim image whitespace | | 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 | | androidLayerType | none、software、hardware | Sets the android webview layerType |

Methods

| Function | Description | | :-------------------- | :-----------------------------------------------------------------------------------------------| | clearSignature() | Clear the current signature | | changePenColor(color) | Change pen color | | changePenSize(minW, maxW) | Change pen size | | draw() | Enable drawing signature | | erase() | Enable erasing signature | | getData() | Triggers the onGetData callback with a single data JSON string | | readSignature() | Reads the current signature on the canvas and triggers either the onOK or onEmpty callbacks | | undo() | Undo last stroke | | redo() | Redo last stroke |

To call the methods use the useRef hook:

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

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

  // Called after ref.current.readSignature() reads a non-empty base64 string
  const handleOK = (signature) => {
    console.log(signature);
    onOK(signature); // Callback from Component props
  };

  // Called after ref.current.readSignature() reads an empty string
  const handleEmpty = () => {
    console.log("Empty");
  };

  // Called after ref.current.clearSignature()
  const handleClear = () => {
    console.log("clear success!");
  };

  // Called after end of stroke
  const handleEnd = () => {
    ref.current.readSignature();
  };

  // Called after ref.current.getData()
  const handleData = (data) => {
    console.log(data);
  };

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

export default Sign;

Using a background image

You can use a non-erasable background image to draw your signature on using the bgSrc prop. Make sure to provide the width and height of the image.

const imgWidth = 300;
const imgHeight = 200;
const style = `.m-signature-pad {box-shadow: none; border: none; } 
              .m-signature-pad--body {border: none;}
              .m-signature-pad--footer {display: none; margin: 0px;}
              body,html {
              width: ${imgWidth}px; height: ${imgHeight}px;}`;
...
<View style={{ width: imgWidth, height: imgHeight }}>
  <SignatureScreen
    ref={ref}
    bgSrc="https://via.placeholder.com/300x200/ff726b"
    bgWidth={imgWidth}
    bgHeight={imgHeight}
    webStyle={style}
    onOK={handleOK}
  />
</View>

Using an overlay image

An overlay is a non-erasable image that can be used as a guideline similar to a colouring book. Make sure the image format is .png and that it has a transparent background. Also, don't forget to provide the width and height of the image. Use the overlaySrc prop to provide the link.

const imgWidth = 256;
const imgHeight = 256;
const style = `.m-signature-pad {box-shadow: none; border: none; } 
              .m-signature-pad--body {border: none;}
              .m-signature-pad--footer {display: none; margin: 0px;}
              body,html {
              width: ${imgWidth}px; height: ${imgHeight}px;}`;
...
<View style={{ width: imgWidth, height: imgHeight }}>
  <SignatureScreen
    ref={ref}
    overlaySrc="http://pngimg.com/uploads/circle/circle_PNG63.png"
    overlayWidth={imgWidth}
    overlayHeight={imgHeight}
    webStyle={style}
    onOK={handleOK}
  />
</View>

Save Base64 Image as File

If you're using expo, you can use expo-file-system to save the base64 image as a local file; if you're working with react-native-cli, use react-native-fs.

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

const handleOK = (signature) => {
  const path = FileSystem.cacheDirectory + "sign.png";
  FileSystem.writeAsStringAsync(
    path,
    signature.replace("data:image/png;base64,", ""),
    { encoding: FileSystem.EncodingType.Base64 }
  )
    .then(() => FileSystem.getInfoAsync(path))
    .then(console.log)
    .catch(console.error);
};

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}
  />

Custom Button for Confirm and Clear

import React, { useRef } from "react";
import { StyleSheet, View, Button } from "react-native";
import SignatureScreen from "react-native-signature-canvas";

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

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

  const handleClear = () => {
    ref.current.clearSignature();
  };

  const handleConfirm = () => {
    console.log("end");
    ref.current.readSignature();
  };

  const style = `.m-signature-pad--footer {display: none; margin: 0px;}`;

  return (
    <View style={styles.container}>
      <SignatureScreen ref={ref} onOK={handleOK} webStyle={style} />
      <View style={styles.row}>
        <Button title="Clear" onPress={handleClear} />
        <Button title="Confirm" onPress={handleConfirm} />
      </View>
    </View>
  );
};

export default Sign;

const styles = StyleSheet.create({
  container: {
    flex: 1,
    alignItems: "center",
    justifyContent: "center",
    height: 250,
    padding: 10,
  },
  row: {
    display: "flex",
    flexDirection: "row",
    justifyContent: "space-between",
    width: "100%",
    alignItems: "center",
  },
});

Example

• Android

• iOS

import React, { useState } 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 handleOK = (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}>
        {signature ? (
          <Image
            resizeMode={"contain"}
            style={{ width: 335, height: 114 }}
            source={{ uri: signature }}
          />
        ) : null}
      </View>
      <Signature
        onOK={handleOK}
        onEmpty={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 regular ref 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;

Example inside ScrollView

When using react-native-signature-canvas inside a ScrollView, you will only get a point on the canvas and the ScrollView will handle the gesture making it unused for the canvas. The work around is to use the scrollEnabled prop of ScrollView. Here an example:

import React, {useState} from 'react';
import {ScrollView, View} from 'react-native';
import Signature from 'react-native-signature-canvas';

const SignInScroll = () => {
  const [scrollEnabled, setScrollEnabled] = useState(true);

  return (
    <ScrollView scrollEnabled={scrollEnabled}>
      <View style={{height: 300}}>
        <Signature
          onOK={(img) => console.log(img)}
          onBegin={() => setScrollEnabled(false)}
          onEnd={() => setScrollEnabled(true)}
          descriptionText="Sign"
          clearText="Clear"
          confirmText="Save"
          imageType="image/jpeg"
        />
      </View>
    </ScrollView>
  );
};

export default SignInScroll;