android-signaturepad

Android Signature Pad

Android Signature Pad is an Android library for drawing smooth signatures. It uses variable width Bézier curve interpolation based on Smoother Signatures post by Square.

Features

• Bézier implementation for a smoother line
• Variable point size based on velocity
• Customizable pen color and size
• Bitmap and SVG support
• Data Binding

Installation

Latest version of the library can be found on Maven Central.

For Gradle users

Open your build.gradle and make sure that Maven Central repository is declared into repositories section:

   repositories {
       mavenCentral()
   }

Then, include the library as dependency:

implementation 'com.github.gcacace:signature-pad:1.4.0'

For Maven users

Add this dependency to your pom.xml:

<dependency>
  <groupId>com.github.gcacace</groupId>
  <artifactId>signature-pad</artifactId>
  <version>1.4.0</version>
  <type>aar</type>
</dependency>

Usage

Please see the /SignaturePad-Example app for a more detailed code example of how to use the library.

1. Add the SignaturePad view to the layout you want to show.

 <com.github.gcacace.signaturepad.views.SignaturePad
     xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
     android:id="@+id/signature_pad"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     app:penColor="@android:color/black"
     />

1. Configure attributes.

• penMinWidth - The minimum width of the stroke (default: 3dp).
• penMaxWidth - The maximum width of the stroke (default: 7dp).
• penColor - The color of the stroke (default: Color.BLACK).
• velocityFilterWeight - Weight used to modify new velocity based on the previous velocity (default: 0.9).
• clearOnDoubleClick - Double click to clear pad (default: false)

1. Configure signature events listener

An OnSignedListener can be set on the view:

mSignaturePad = (SignaturePad) findViewById(R.id.signature_pad);
mSignaturePad.setOnSignedListener(new SignaturePad.OnSignedListener() {

     @Override
     public void onStartSigning() {
         //Event triggered when the pad is touched
     }

    @Override
    public void onSigned() {
        //Event triggered when the pad is signed
    }

    @Override
    public void onClear() {
        //Event triggered when the pad is cleared
    }
});

1. Get signature data

• getSignatureBitmap() - A signature bitmap with a white background.
• getTransparentSignatureBitmap() - A signature bitmap with a transparent background.
• getSignatureSvg() - A signature Scalable Vector Graphics document.

Data Binding

The SignaturePad view has custom Data Binding attribute setters for all the listener events:

 <com.github.gcacace.signaturepad.views.SignaturePad
     xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:bind="http://schemas.android.com/apk/res-auto"
     android:id="@+id/signature_pad"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     bind:onStartSigning="@{activity.onStartSigning}"
     bind:onSigned="@{activity.onSigned}"
     bind:onClear="@{activity.onClear}" />

Cordova Plugin

Thanks to netinhoteixeira, there is a Cordova plugin using that library. Please refer to https://github.com/netinhoteixeira/cordova-plugin-signature-view.

NativeScript Plugin

Thanks to bradmartin, there is a NativeScript plugin. Please refer to https://github.com/bradmartin/nativescript-signaturepad.

Configuration changes (rotation, backgrounding)

The signature is preserved across configuration changes such as screen rotation and process backgrounding: it is saved in the view's instance state and restored automatically. getSignatureSvg() is also restored after a rotation.

Note: a signature drawn before a rotation is restored in its original coordinate space and scaled to fit the new orientation. Strokes added after a rotation are captured in the new orientation's coordinate space; the on-screen bitmap stays correct, but such strokes and the pre-rotation strokes live in different coordinate spaces within the same SVG document.

Contributing

Contributions are welcome! Please read CONTRIBUTING.md for how to build, test, and open a pull request, and note the Code of Conduct. Security issues should be reported privately — see SECURITY.md.

License

Copyright 2014-2025 Gianluca Cacace

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.