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GestureDetector

A control that detects gestures.

Attempts to recognize gestures that correspond to its non-null callbacks.

If this control has a content, it defers to that child control for its sizing behavior. If it does not have a content, it grows to fit the parent instead.

Examples

Draggable containers

The following example demonstraits how a control can be freelly dragged inside a Stack.

The sample also shows that GestureDetector can have a child control (blue container) as well as be nested inside another control (yellow container) giving the same results.

import flet as ft

def main(page: ft.Page):
def on_pan_update1(e: ft.DragUpdateEvent):
c.top = max(0, c.top + e.delta_y)
c.left = max(0, c.left + e.delta_x)
c.update()

def on_pan_update2(e: ft.DragUpdateEvent):
e.control.top = max(0, e.control.top + e.delta_y)
e.control.left = max(0, e.control.left + e.delta_x)
e.control.update()

gd = ft.GestureDetector(
mouse_cursor=ft.MouseCursor.MOVE,
drag_interval=50,
on_pan_update=on_pan_update1,
)

c = ft.Container(gd, bgcolor=ft.colors.AMBER, width=50, height=50, left=0, top=0)

gd1 = ft.GestureDetector(
mouse_cursor=ft.MouseCursor.MOVE,
drag_interval=10,
on_vertical_drag_update=on_pan_update2,
left=100,
top=100,
content=ft.Container(bgcolor=ft.colors.BLUE, width=50, height=50),
)

page.add( ft.Stack([c, gd1], width=1000, height=500))

ft.app(target=main)

Properties

content

A child Control contained by the gesture detector.

mouse_cursor

The mouse cursor for mouse pointers that are hovering over the control. Possible values of MouseCursor enum:

  • ALIAS
  • ALL_SCROLL
  • BASIC
  • CELL
  • CLICK
  • CONTEXT_MENU
  • COPY
  • DISAPPEARING
  • FORBIDDEN
  • GRAB
  • GRABBING
  • HELP
  • MOVE
  • NO_DROP
  • NONE
  • PRECISE
  • PROGRESS
  • RESIZE_COLUMN
  • RESIZE_DOWN
  • RESIZE_DOWN_LEFT
  • RESIZE_DOWN_RIGHT
  • RESIZE_LEFT
  • RESIZE_LEFT_RIGHT
  • RESIZE_RIGHT
  • RESIZE_ROW
  • RESIZE_UP
  • RESIZE_UP_DOWN
  • RESIZE_UP_LEFT
  • RESIZE_UP_LEFT_DOWN_RIGHT
  • RESIZE_UP_RIGHT
  • RESIZE_UP_RIGHT_DOWN_LEFT
  • TEXT
  • VERTICAL_TEXT
  • WAIT
  • ZOOM_IN
  • ZOOM_OUT

drag_interval

Throttling in milliseconds for horizontal drag, vertical drag and pan update events. When a user moves a pointer a lot of events are being generated to do precise tracking. drag_interval allows sending drag update events to a Flet program every X milliseconds, thus preserving the bandwidth (web and mobile apps). Default is 0 - no throttling, all events are sent to a Flet program, very smooth tracking.

hover_interval

Throttling in milliseconds for on_hover event.

Events

multi_tap_touches

The minimum number of pointers to trigger on_multi_tap event.

on_double_tap

The user has tapped the screen with a primary button at the same location twice in quick succession.

on_double_tap_down

A pointer that might cause a double tap has contacted the screen at a particular location.

Triggered immediately after the down event of the second tap.

Event handler argument is an instance of TapEvent class.

on_enter

Triggered when a mouse pointer has entered this control.

Event handler argument is an instance of HoverEvent class.

on_exit

Triggered when a mouse pointer has exited this control.

Event handler argument is an instance of HoverEvent class.

on_horizontal_drag_end

A pointer that was previously in contact with the screen with a primary button and moving horizontally is no longer in contact with the screen and was moving at a specific velocity when it stopped contacting the screen.

Event handler argument is an instance of DragEndEvent class with the following properties:

  • primary_velocity - the velocity the pointer was moving along the primary axis when it stopped contacting the screen, in logical pixels per second.
  • velocity_x - x component of the pointer's velocity when it stopped contacting the screen.
  • velocity_y - y component of the pointer's velocity when it stopped contacting the screen.

on_horizontal_drag_start

A pointer has contacted the screen with a primary button and has begun to move horizontally.

Event handler argument is an instance of DragStartEvent class with the following properties:

  • local_x - x component of the local position at which the pointer contacted the screen.
  • local_y - y component of the local position at which the pointer contacted the screen.
  • global_x - x component of the global position at which the pointer contacted the screen.
  • global_y - y component of the global position at which the pointer contacted the screen.
  • timestamp - Recorded timestamp of the source pointer event that triggered the drag event.

on_horizontal_drag_update

A pointer that is in contact with the screen with a primary button and moving horizontally has moved in the horizontal direction.

Event handler argument is an instance of DragUpdateEvent class with the following properties:

  • delta_x - x component of the amount the pointer has moved in the coordinate space of the event receiver since the previous update.
  • delta_y - y component of the amount the pointer has moved in the coordinate space of the event receiver since the previous update.
  • local_x - x component of the local position in the coordinate system of the event receiver at which the pointer contacted the screen.
  • local_y - y component of the local position in the coordinate system of the event receiver at which the pointer contacted the screen.
  • global_x - x component of the pointer's global position when it triggered this update.
  • global_y - y component of the pointer's global position when it triggered this update.
  • primary_delta - the amount the pointer has moved along the primary axis in the coordinate space of the event receiver since the previous update.
  • timestamp - recorded timestamp of the source pointer event that triggered the drag event.

on_hover

Triggered when a mouse pointer has entered this control.

Event handler argument is an instance of HoverEvent class with the following properties:

  • local_x - x component of the local position of the pointer.
  • local_y - y component of the local position of the pointer.
  • global_x - x component of the global position of the pointer.
  • global_y - y component of the global position of the pointer.
  • delta_x - x component of the distance in logical pixels that the pointer moved since the last hover event.
  • delta_x - y component of the distance in logical pixels that the pointer moved since the last hover event.
  • timestamp - event's timestamp.

on_long_press_end

A pointer that has triggered a long-press with a primary button has stopped contacting the screen.

Event handler argument is an instance of LongPressEndEvent class with the following properties:

  • local_x - x component of the local position at which the pointer contacted the screen.
  • local_y - y component of the local position at which the pointer contacted the screen.
  • global_x - x component of the global position at which the pointer contacted the screen.
  • global_y - y component of the global position at which the pointer contacted the screen.
  • velocity_x - x component of the pointer's velocity when it stopped contacting the screen.
  • velocity_y - y component of the pointer's velocity when it stopped contacting the screen.

on_long_press_start

Called when a long press gesture with a primary button has been recognized.

Triggered when a pointer has remained in contact with the screen at the same location for a long period of time.

Event handler argument is an instance of LongPressStartEvent class with the following properties:

  • local_x - x component of the local position at which the pointer contacted the screen.
  • local_y - y component of the local position at which the pointer contacted the screen.
  • global_x - x component of the global position at which the pointer contacted the screen.
  • global_y - y component of the global position at which the pointer contacted the screen.

on_pan_end

A pointer that was previously in contact with the screen with a primary button and moving is no longer in contact with the screen and was moving at a specific velocity when it stopped contacting the screen.

Event handler argument is an instance of DragEndEvent class.

on_pan_start

A pointer has contacted the screen with a primary button and has begun to move.

Event handler argument is an instance of DragStartEvent class.

on_pan_update

A pointer that is in contact with the screen with a primary button and moving has moved again.

Event handler argument is an instance of DragUpdateEvent class.

on_scale_end

Event handler argument is an instance of ScaleEndEvent class with the following properties:

  • pointer_count - the number of pointers being tracked by the gesture recognizer.
  • velocity_x - x component of the velocity of the last pointer to be lifted off of the screen.
  • velocity_y - y component of the velocity of the last pointer to be lifted off of the screen.

on_scale_start

The pointers in contact with the screen have established a focal point and initial scale of 1.0.

Event handler argument is an instance of ScaleStartEvent class with the following properties:

  • focal_point_x - x component of the initial focal point of the pointers in contact with the screen.
  • focal_point_y - y component of the initial focal point of the pointers in contact with the screen.
  • local_focal_point_x - x component of the initial focal point of the pointers in contact with the screen.
  • local_focal_point_y - y component of the initial focal point of the pointers in contact with the screen.
  • pointer_count - the number of pointers being tracked by the gesture recognizer.

on_scale_update

Event handler argument is an instance of ScaleUpdateEvent class with the following properties:

  • focal_point_x - x component of the focal point of the pointers in contact with the screen.
  • focal_point_y - y component of the focal point of the pointers in contact with the screen.
  • focal_point_delta_x - x component of the amount the gesture's focal point has moved in the coordinate space of the event receiver since the previous update.
  • focal_point_delta_y - y component of the amount the gesture's focal point has moved in the coordinate space of the event receiver since the previous update.
  • local_focal_point_x - x component of the focal point of the pointers in contact with the screen.
  • local_focal_point_y - y component of the focal point of the pointers in contact with the screen.
  • pointer_count - the number of pointers being tracked by the gesture recognizer.
  • horizontal_scale - the scale implied by the average distance along the horizontal axis between the pointers in contact with the screen.
  • vertical_scale - the scale implied by the average distance along the vertical axis between the pointers in contact with the screen.
  • scale - the scale implied by the average distance between the pointers in contact with the screen.

on_secondary_long_press_end

A pointer that has triggered a long-press with a secondary button has stopped contacting the screen.

Event handler argument is an instance of LongPressEndEvent class.

on_secondary_long_press_start

Called when a long press gesture with a secondary button has been recognized.

Triggered when a pointer has remained in contact with the screen at the same location for a long period of time.

Event handler argument is an instance of LongPressStartEvent class.

on_secondary_tap

A tap with a secondary button has occurred.

on_secondary_tap_down

A pointer that might cause a tap with a secondary button has contacted the screen at a particular location.

Event handler argument is an instance of TapEvent class.

on_secondary_tap_up

A pointer that will trigger a tap with a secondary button has stopped contacting the screen at a particular location.

Event handler argument is an instance of TapEvent class.

on_tap

A tap with a primary button has occurred.

on_tap_down

A pointer that might cause a tap with a primary button has contacted the screen at a particular location.

Event handler argument is an instance of TapEvent class with the following properties:

  • local_x - x component of the local position at which the pointer contacted the screen.
  • local_y - y component of the local position at which the pointer contacted the screen.
  • global_x - x component of the global position at which the pointer contacted the screen.
  • global_y - y component of the global position at which the pointer contacted the screen.
  • kind - The kind of the device that initiated the event.

on_tap_up

A pointer that will trigger a tap with a primary button has stopped contacting the screen at a particular location.

Event handler argument is an instance of TapEvent class.

on_vertical_drag_end

A pointer that was previously in contact with the screen with a primary button and moving vertically is no longer in contact with the screen and was moving at a specific velocity when it stopped contacting the screen.

Event handler argument is an instance of DragEndEvent class.

on_vertical_drag_start

A pointer has contacted the screen with a primary button and has begun to move vertically.

Event handler argument is an instance of DragStartEvent class.

on_vertical_drag_update

A pointer that is in contact with the screen with a primary button and moving vertically has moved in the vertical direction.

Event handler argument is an instance of DragUpdateEvent class.

on_multi_long_press

Called when a long press gesture with multiple pointers has been recognized.

on_multi_tap

Triggered when multiple pointers contacted the screen.

Event handler argument is an instance of MultiTapEvent class with the following properties:

  • correct_touches - True a multi_tap_touches number of pointers touched the screen; otherwise False.

on_scroll

Event handler argument is an instance of ScrollEvent class with the following properties:

  • local_x - x component of the local position of the pointer.
  • local_y - y component of the local position of the pointer.
  • global_x - x component of the global position of the pointer.
  • global_y - y component of the global position of the pointer.
  • scroll_delta_x - x component of the the amount to scroll, in logical pixels.
  • scroll_delta_x - y component of the the amount to scroll, in logical pixels.