github.com/mxmzb/react-native-gesture-detector

React Native Gesture Detector

Create and detect custom gestures on React Native.

Demos

Example app and usage

Feel free to run the included Expo app:

$ git clone https://github.com/mxmzb/react-native-gesture-detector.git
$ cd react-native-gesture-detector/example
$ yarn
$ yarn start

Check the code for the screens to see how they are done!

Intro

This package originated from a real life need to detect custom gestures. The idea for implementation originated from this stellar answer on StackOverflow. The result is not 100% foolproof, but rock solid, performant and extremely simple to use.

The package comes with another, insanely cool component GestureRecorder, which allows you to create gestures on the fly. Yep, just plug it in, paint the gesture and you will receive the coordinate data for your supercomplex, custom gesture. You can use it to just use the data points as a predefined gesture in your app, or you can even let your app users create their own custom gestures, if that fits your game plan!

Because the library significantly uses React hooks, you must use at least react@16.8.0.

Installation

$ yarn add react-native-gesture-detector
$ yarn add react-native-gesture-handler lodash # install peer dependencies

Quickstart

import GestureDetector, {
  GestureRecorder,
  GesturePath,
  Cursor,
} from "react-native-gesture-detector";

const gestures = {
  // this will result in the gesture shown in the first demo give above
  Coil: [
    { x: 10, y: -30 }, // This is a coordinate object
    { x: 25, y: -15 },
    { x: 40, y: -10 },
    { x: 55, y: -15 },
    { x: 70, y: -30 },
    { x: 85, y: -45 },
    { x: 90, y: -65 },
    { x: 85, y: -85 },
    { x: 70, y: -100 },
    { x: 55, y: -115 },
    { x: 40, y: -130 },
    { x: 20, y: -130 },
    { x: 0, y: -130 },
    { x: -20, y: -130 },
    { x: -35, y: -115 },
    { x: -50, y: -100 },
    { x: -65, y: -85 },
    { x: -80, y: -70 },
    { x: -80, y: -55 },
    { x: -80, y: -30 },
    { x: -80, y: -15 },
    { x: -80, y: 0 },
    { x: -65, y: 15 },
    { x: -50, y: 30 },
    { x: -35, y: 45 },
    { x: -20, y: 60 },
    { x: 0, y: 65 },
    { x: 20, y: 70 },
    { x: 40, y: 70 },
  ],
};

const CoilExample = () => (
  <GestureDetector
    onGestureFinish={gesture => console.log(`Gesture "${gesture}" finished!`)}
    onProgress={({ gesture, progress }) => {
      console.log(`Gesture: ${gesture}, progress: ${progress}`);
    }}
    onPanRelease={() => {
      console.log("User released finger!");
    }}
    gestures={gestures}
    slopRadius={35}
  >
    {({ coordinate }) => (
      <View style={{ position: "relative", width: "100%", height: "100%" }}>
        <GesturePath path={gestures["Coil"]} color="green" slopRadius={35} />
        {coordinate && <Cursor {...coordinate} />}
      </View>
    )}
  </GestureDetector>
);

const RecordGestureExample = () => {
  // finishedGesture will look like gestures["Coil"] from the top
  const [finishedGesture, setFinishedGesture] = useState([]);

  return (
    <GestureRecorder onPanRelease={gesture => setFinishedGesture(gesture)}>
      {({ gesture }) => (
        <View style={{ position: "relative", width: "100%", height: "100%" }}>
          <GesturePath path={gesture} color="green" slopRadius={35} />
        </View>
      )}
    </GestureRecorder>
  );
};

Documentation and API

GestureDetector

GestureDetector is a render props component. The child function has the form children({ coordinate: { x: number, y: number } })

Prop	Default	Type	Description
slopRadius	50	number	The radius in px from a coordinate. The resulting circle is the area in which the user can move the finger
gestures	{}	{ [key: string]: [{ x: number, y: number }] }	An object with one or more gestures. A gesture is an array of { x, y } objects, which symbolize the exact coordinates you want the user to pass
onProgress	({ progress, gesture }) => {}	function	A callback, which is called on each predefined gesture coordinate passed by the user.
onGestureFinish	(gesture) => {}	function	A callback, which is called when the user finishes a gesture. Receives the gesture key of the finished gesture.
onPanRelease	() => {}	function	Callback, when the user releases the finger. Receives no arguments.

GestureRecorder

GestureRecorder is a render props component. The child function has the form children({ gesture: [{ x: string, y: string }, { x: string, y: string }, ...], gestureDirectionHistory: [{ x: string, y: string }, { x: string, y: string }, ...], offset: { x: number, y: number } }).

gesture is an array of coordinates. They are generated based on the pointDistance prop of the component.

gestureDirectionHistory will tell you accordingly to gesture which direction the gesture is moving there. This might give somewhat unreliable data currently. A direction object looks like { x: "left", y: "up" }.

offset will artificially add an horizontal and vertical offset to the coordinates. This does not change the detection of the defined gesture at all. It's just a helper to use with the GesturePath component to paint the path where you actually draw. Check the GestureRecorder example screen for more details on this.

Prop	Default	Type	Description
pointDistance	20	number	The minimum distance between points that you want to be recorded. So default wise, every 20px (or more, usually depending on the phone hardware and the speed of the finger moving over the display) the component will add another point to the gesture array
onCapture	() => {}	function	A callback, which is called every time the component is adding a coordinate to the gesture array
onPanRelease	(gesture) => {}	function	Callback, when the user releases the finger. Receives the fully drawn gesture in form of a coordinate array.

GesturePath

GesturePath is a helper component, which paints a gesture visually in a container. The container should have position: absolute; set in its style property. { x, y } is a coordinate object. An array of coordinate objects must be passed to paint the gesture on the screen. This component should be only used in development to define and refine gestures.

Prop	Default	Type	Description
path	[]	array	An array of coordinates to paint the gesture
slopRadius	50	number	The radius around each coordinate, in which the user touch event will be associated with the gesture (or rather the radius of the circle being painted for each coordinate, as this whole component has no functionality really and is purely visual)
color	black	string	A string of a valid CSS color property

Cursor

Paints a black, round indicator at the passed coordinate. The only useful situation is in development and you probably will use it like this, where coordinate is passed from the GestureDetector render props function:

{coordinate && <Cursor {...coordinate} />}

Prop	Default	Type	Description
x	0	number	The coordinate of the absolute center of the cursor relatively to the parent container.
y	0	number	The coordinate of the absolute center of the cursor relatively to the parent container.
throttleMs	50 in dev build, 25 in production build	number	A performance optimization. Sets the time delay between each rerender of the repositioned cursor. You probably don't want to touch this.

License

react-native-gesture-detector is licensed under the MIT.