I was wondering if it exists a way to continuously call a function on Flutter as long as a button (any kind of button is okay) is pressed.

For example:

GestureDetector(
 child: Container(),
 onLongPressStart: () {}, // Start of the function
 onLongPressEnd: () {}, // End of the function
)

CodePudding user response：

Change your onLongPressEnd to onLongPressUp. So it should be like:

GestureDetector(
  child: Container(),
  onLongPressStart: () {},
  onLongPressUp: () {}
);

CodePudding user response：

You could do something like

1. on long tap, start the timer and call the function
2. on long press end, stop the timer

Example:

Timer? timer;

GestureDetector(
          onLongPressStart: (detail) {
            setState(() {
              timer = Timer.periodic(const Duration(milliseconds: 250), (t) {
                print(Random().nextInt(1000)   9);
              });
            });
          },
          onLongPressEnd: (detail) {
            if (timer != null) {
              timer!.cancel();
            }
          },
          child: Container(
            child: const Text("press me"),
            padding: const EdgeInsets.all(16),
            color: kRedColor,
          ),
        ),

CodePudding user response：

You can use Timer for this case.

  //how often method will be called
  Duration delay = const Duration(milliseconds: 100);

  Timer? timer;

  void continuousWork() {
    debugPrint("I am working c ${timer!.tick}");
  }

  void onJobEnd() {
    debugPrint("Job END");
    timer?.cancel();
    timer = null;
  }

  void onJobStart() {
    if (timer != null) return;
    debugPrint("Job started");
    timer = Timer.periodic(delay, (timer) {
      continuousWork();
    });
  }

And use case will be using GestureDetector

GestureDetector(
  onTap: () {},
  onTapDown: (details) {
    onJobStart();
  },
  onTapUp: (v) {
    onJobEnd();
  },
  child: Text("tap"),
),

More about dart-async, and another way of doing this using CancelableOperation from async package