positioned-tap-detector

pub package

Flutter widget allowing to receive tap callbacks, together with their position on the screen. It supports onTap, onDoubleTap and onLongPress gestures. Each callback function is invoked with TapPosition object that provides global and relative touch position. To adjust maximum time allowed between double-tap gesture consecutive taps, specify an additional doubleTapDelay parameter:

PositionedTapDetector(
  onTap: (position) => _printTap('Single tap', position),
  onDoubleTap: (position) => _printTap('Double tap', position),
  onLongPress: (position) => _printTap('Long press', position),
  doubleTapDelay: Duration(milliseconds: 500),
  child: ...,
)

void _printTap(String gesture, TapPosition position) => 
    print('$gesture: ${position.global}, ${position.relative}');

PositionedTapDetector demo

Controller

In case you need to wrap another GestureDetector below in the widget tree, pass an additional PositionedTapController parameter and invoke its callback methods whenever relevant gesture takes place:

final _controller = PositionedTapController();

Widget build(BuildContext context) {
  // ...
    child: PositionedTapDetector(
      // ...
      controller: _controller,
      child: GestureDetector(
        onTap: _handleTap,
        onTapDown: _controller.onTapDown,
        onLongPress: _controller.onLongPress,
        behavior: ...,
        child: ...,
      ),
    ),
}

void _handleTap() {
  // ...
  _controller.onTap();
}

Drawbacks

PositionedTapDetector will not invoke onDoubleTap callback in case there's GestureDetector underneath it in the widget tree that also specifies onDoubleTap parameter. Since Flutter framework doesn't invoke its onTapDown callback when detector is double-tapped, positioned detector is unable to receive tap positions and therefore detect double-tap gestures.

Libraries

positioned_tap_detector

Dart

dart:ui
Built-in types and core primitives for a Flutter application. [...]

Core

dart:async
Support for asynchronous programming, with classes such as Future and Stream. [...]
dart:collection
Classes and utilities that supplement the collection support in dart:core. [...]
dart:convert
Encoders and decoders for converting between different data representations, including JSON and UTF-8. [...]
dart:core
Built-in types, collections, and other core functionality for every Dart program. [...]
dart:developer
Interact with developer tools such as the debugger and inspector. [...]
dart:math
Mathematical constants and functions, plus a random number generator. [...]
dart:typed_data
Lists that efficiently handle fixed sized data (for example, unsigned 8 byte integers) and SIMD numeric types. [...]

VM

dart:io
File, socket, HTTP, and other I/O support for non-web applications. [...]
dart:isolate
Concurrent programming using isolates: independent workers that are similar to threads but don't share memory, communicating only via messages. [...]