React Native Signature Canvas

A React Native component for capturing signatures or drawing on a canvas with a smooth, native feel. Works on iOS, Android, and Expo.

Features

• ✅ Cross-platform support (iOS, Android, Expo)
• ✅ Smooth, responsive drawing experience with optimized performance
• ✅ Customizable pen color, size, and background
• ✅ Support for background and overlay images
• ✅ Export signatures as PNG, JPEG, or SVG
• ✅ Undo/redo functionality
• ✅ Drawing and erasing modes
• ✅ Full TypeScript support with enhanced type definitions
• 🆕 Advanced error handling with automatic recovery
• 🆕 Performance monitoring and optimization
• 🆕 Flexible WebView customization via webviewProps
• 🆕 Enhanced security with configurable restrictions
• 🆕 Memory management and leak prevention

Installation

For React Native ≥ 0.60.0 or Expo SDK ≥ 35.0.0

yarn add react-native-signature-canvas

or

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

This package depends on react-native-webview. If you're using React Native CLI (not Expo), you'll need to install react-native-webview separately:

yarn add react-native-webview
cd ios && pod install

For React Native < 0.60.0 or Expo SDK < 33.0.0

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

Basic Usage

import React, { useRef, useState } from 'react';
import { StyleSheet, View, Image } from 'react-native';
import SignatureCanvas from 'react-native-signature-canvas';

const SignatureScreen = () => {
  const [signature, setSignature] = useState(null);
  const [isLoading, setIsLoading] = useState(false);
  const ref = useRef();

  const handleSignature = (signature) => {
    console.log('Signature captured:', signature);
    setSignature(signature);
    setIsLoading(false);
  };

  const handleEmpty = () => {
    console.log('Signature is empty');
    setIsLoading(false);
  };

  const handleClear = () => {
    console.log('Signature cleared');
    setSignature(null);
  };

  const handleError = (error) => {
    console.error('Signature pad error:', error);
    setIsLoading(false);
  };

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

  return (
    <View style={styles.container}>
      <View style={styles.preview}>
        {signature && (
          <Image
            resizeMode="contain"
            style={{ width: 335, height: 114 }}
            source={{ uri: signature }}
          />
        )}
      </View>
      <SignatureCanvas
        ref={ref}
        onEnd={handleEnd}
        onOK={handleSignature}
        onEmpty={handleEmpty}
        onClear={handleClear}
        onError={handleError}
        autoClear={true}
        descriptionText="Sign here"
        clearText="Clear"
        confirmText={isLoading ? "Processing..." : "Save"}
        penColor="#000000"
        backgroundColor="rgba(255,255,255,0)"
        webviewProps={{
          // Custom WebView optimization
          cacheEnabled: true,
          androidLayerType: "hardware",
        }}
      />
    </View>
  );
};

const styles = StyleSheet.create({
  container: {
    flex: 1,
  },
  preview: {
    width: 335,
    height: 114,
    backgroundColor: '#F8F8F8',
    justifyContent: 'center',
    alignItems: 'center',
    marginTop: 15,
  },
});

export default SignatureScreen;

Props

| Prop | Type | Default | Description | |------|------|---------|-------------| | androidHardwareAccelerationDisabled | boolean | false | Disable hardware acceleration on Android | | autoClear | boolean | false | Auto clear signature after clicking the Confirm button | | backgroundColor | string | rgba(255,255,255,0) | Background color of the canvas | | bgHeight | number | 0 | Height of the background image | | bgWidth | number | 0 | Width of the background image | | bgSrc | string | null | Background image source URI | | clearText | string | Clear | Clear button text | | confirmText | string | Confirm | Save button text | | customHtml | (injectedJavaScript: string) => string | null | Custom HTML template for the canvas | | dataURL | string | "" | Base64 string to draw saved signature | | descriptionText | string | Sign above | Description text for signature | | dotSize | number | null | Radius of a single dot | | imageType | string | image/png | Image type for export (image/png, image/jpeg, image/svg+xml) | | minWidth | number | 0.5 | Minimum width of a line | | maxWidth | number | 2.5 | Maximum width of a line | | nestedScrollEnabled | boolean | false | Enable nested scrolling for use inside a ScrollView | | showsVerticalScrollIndicator | boolean | true | Show vertical scroll indicator in WebView | | onOK | function | - | Callback after saving non-empty signature | | onEmpty | function | - | Callback after trying to save an empty signature | | onClear | function | - | Callback after clearing the signature | | onGetData | function | - | Callback when getData() is called | | onBegin | function | - | Callback when a new stroke is started | | onEnd | function | - | Callback when the stroke has ended | | onLoadEnd | function | - | Callback when the WebView canvas load ended | | onUndo | function | - | Callback when undo() is called | | onRedo | function | - | Callback when redo() is called | | onDraw | function | - | Callback when drawing is enabled | | onErase | function | - | Callback when erasing is enabled | | onChangePenColor | function | - | Callback after changing the pen color | | onChangePenSize | function | - | Callback after changing the pen size | | overlayHeight | number | 0 | Height of the overlay image | | overlayWidth | number | 0 | Width of the overlay image | | overlaySrc | string | null | Overlay image source URI (must be PNG with transparent background) | | penColor | string | black | Color of the pen | | rotated | boolean | false | Rotate signature pad 90 degrees | | style | object | - | Style of the wrapper view | | scrollable | boolean | false | Enable scrolling in the signature pad | | trimWhitespace | boolean | false | Trim image whitespace | | webStyle | string | - | WebView style to override default style | | webviewContainerStyle | object | - | Style for the WebView container | | androidLayerType | none\|software\|hardware | hardware | Sets the Android WebView layer type | | onError | function | - | Callback when an error occurs | | webviewProps | object | {} | Additional props to pass to the underlying WebView |

Methods

Access these methods using a ref to the SignatureCanvas component.

| Method | Description | |--------|-------------| | clearSignature() | Clear the current signature | | changePenColor(color) | Change pen color | | changePenSize(minW, maxW) | Change pen size | | draw() | Enable drawing mode | | erase() | Enable erasing mode | | getData() | Triggers the onGetData callback with signature data | | readSignature() | Read the current signature and trigger callbacks | | undo() | Undo last stroke | | redo() | Redo last stroke |

WebView Customization (New!)

The webviewProps parameter allows you to customize the underlying WebView behavior while maintaining signature functionality:

<SignatureCanvas
  // ... other props
  webviewProps={{
    // Performance optimization
    cacheEnabled: true,
    androidLayerType: "hardware",
    androidHardwareAccelerationDisabled: false,
    
    // Security settings
    allowFileAccess: false,
    allowFileAccessFromFileURLs: false,
    mixedContentMode: "never",
    
    // UI customization
    decelerationRate: 'fast',
    bounces: false,
    
    // Any other WebView props...
  }}
/>

Performance Optimization Examples

// High-performance mode
<SignatureCanvas
  webviewProps={{
    cacheEnabled: true,
    androidLayerType: "hardware",
    androidHardwareAccelerationDisabled: false,
  }}
/>

// Low-memory mode
<SignatureCanvas
  webviewProps={{
    cacheEnabled: false,
    androidLayerType: "software",
    androidHardwareAccelerationDisabled: true,
  }}
/>

Error Handling (Enhanced!)

const [error, setError] = useState(null);

const handleError = (error) => {
  console.error('Signature error:', error);
  setError(error.message);
  // Error recovery is automatic, but you can handle it here
};

<SignatureCanvas
  onError={handleError}
  // Component automatically retries on recoverable errors
/>

{error && (
  <Text style={{ color: 'red' }}>Error: {error}</Text>
)}

Advanced Usage

Using a Background 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 }}>
  <SignatureCanvas
    ref={ref}
    bgSrc="https://example.com/background.jpg"
    bgWidth={imgWidth}
    bgHeight={imgHeight}
    webStyle={style}
    onOK={handleSignature}
  />
</View>

Using an Overlay Image

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 }}>
  <SignatureCanvas
    ref={ref}
    overlaySrc="https://example.com/overlay.png" // Must be PNG with transparent background
    overlayWidth={imgWidth}
    overlayHeight={imgHeight}
    webStyle={style}
    onOK={handleSignature}
  />
</View>

Using in a Modal

import React, { useState, useRef } from 'react';
import { StyleSheet, View, TouchableOpacity, Modal, Text } from 'react-native';
import SignatureCanvas from 'react-native-signature-canvas';

const SignatureModal = ({ onSignature }) => {
  const [show, setShow] = useState(false);
  const ref = useRef();
  
  const handleSignature = (signature) => {
    onSignature(signature);
    setShow(false);
  };

  return (
    <View>
      <TouchableOpacity onPress={() => setShow(true)}>
        <Text>Open Signature Pad</Text>
      </TouchableOpacity>
      
      {show && (
        <Modal>
          <SignatureCanvas
            ref={ref}
            onOK={handleSignature}
            onEmpty={() => console.log('Empty')}
            descriptionText="Sign here"
            penColor="rgba(255,117,2,1)"
          />
        </Modal>
      )}
    </View>
  );
};

Scrollable Signature Canvas

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

const ScrollableSignature = () => {
  const [scrollEnabled, setScrollEnabled] = useState(true);
  const signatureRef = useRef(null);

  return (
    <ScrollView scrollEnabled={scrollEnabled}>
      <View style={styles.container}>
        <SignatureCanvas
          ref={signatureRef}
          style={styles.canvas}
          onBegin={() => setScrollEnabled(false)}
          onEnd={() => setScrollEnabled(true)}
        />
      </View>
    </ScrollView>
  );
};

const styles = StyleSheet.create({
  container: {
    flex: 1,
    alignItems: 'center',
  },
  canvas: {
    width: '90%',
    height: 300,
    borderWidth: 1,
    borderColor: '#000',
  },
});

Performance & Reliability

Automatic Error Recovery

• Smart retry logic with exponential backoff
• Circuit breaker pattern to prevent cascading failures
• Memory leak prevention with automatic cleanup
• Performance monitoring with automatic optimization

Performance Features

• Debounced resize handling for smooth interaction
• Memory pressure detection with adaptive optimization
• Optimized rendering with reduced re-renders
• Device-specific optimization based on hardware capabilities

Security Enhancements

• Configurable WebView security via webviewProps
• Input validation for all methods and callbacks
• XSS protection with content security policies
• File access restrictions by default

Migration Guide

From v4.6.x to v4.7.x

This version is fully backward compatible. New features:

// NEW: Enhanced error handling
<SignatureCanvas
  onError={(error) => console.error(error)} // New callback
/>

// NEW: WebView customization
<SignatureCanvas
  webviewProps={{ // New prop
    cacheEnabled: false,
    androidLayerType: "software"
  }}
/>

Troubleshooting

Common Issues

Issue: Signature pad not loading

// Solution: Add error handling and check WebView props
<SignatureCanvas
  onError={(error) => console.log('Error:', error)}
  onLoadEnd={() => console.log('Loaded successfully')}
  webviewProps={{
    startInLoadingState: true,
    renderLoading: () => <ActivityIndicator />
  }}
/>

Issue: Poor performance on older devices

// Solution: Use low-performance mode
<SignatureCanvas
  webviewProps={{
    androidLayerType: "software",
    androidHardwareAccelerationDisabled: true,
    cacheEnabled: false
  }}
/>

Issue: Memory issues

// Solution: The component now handles this automatically
// But you can customize via webviewProps if needed
<SignatureCanvas
  webviewProps={{
    cacheEnabled: false, // Reduce memory usage
    androidLayerType: "software" // Use software rendering
  }}
/>

API Reference

For detailed API documentation, see:

• WEBVIEW_PROPS.md - WebView customization guide
• TypeScript definitions - Complete type definitions

Core Technology

This component is built on:

• signature_pad.js for the core signature functionality
• React Native WebView for cross-platform rendering
• Enhanced with performance monitoring and error recovery systems

Contributing

Contributions are welcome! Please read our contributing guidelines and submit pull requests to help improve this component.

Development Setup

# Clone the repository
git clone https://github.com/YanYuanFE/react-native-signature-canvas.git

# Install dependencies
cd react-native-signature-canvas
npm install

# Run example apps
cd example/expo-app
npm install && npm start

Changelog

v4.7.x (Latest)

• 🆕 Added webviewProps for WebView customization
• 🆕 Enhanced error handling with automatic recovery
• 🆕 Performance monitoring and optimization
• 🆕 Memory leak prevention
• 🆕 Improved TypeScript definitions
• 🔧 Fixed global variable pollution in WebView JavaScript
• 🔧 Added input validation for all methods
• ⚡ Optimized rendering performance

View full changelog

License

MIT License - see LICENSE file for details.

Buy Me a Coffee ☕

If you find this project helpful, consider supporting its development with cryptocurrency donations:

Cryptocurrency Donations

| Currency | Address | QR Code | |----------|---------|----------| | Bitcoin (BTC) | bc1phyz9agr0m9l2w9pd8w85w4da2jt3wl4cre7vv0qq4uesm3fv00pscu96tux | | | Ethereum (ETH) | 0xf5dfe16b1e64e8e3a92063fb2922447e13b48945 | | | Solana (SOL) | 3VuhyeTj3hMSrmzq7NctHkgFxvJrmtAUQTzagEBEu3Vm | |

Other Ways to Support

• ⭐ Star this repository
• 🐛 Report bugs and issues
• 💡 Suggest new features
• 🤝 Contribute code improvements
• 📢 Share this project with others

Your support helps maintain and improve this open-source project. Thank you! 🙏

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