@devgeorep/react-native-signature-canvas

v1.0.0

Published

a year ago

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

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devgeorep

react-native react component ios android signature pad canvas expo

react-native-signature-canvas

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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)

yarn add react-native-signature-canvas

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

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

Methods

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;