onTapDown property

A pointer has contacted the screen at a particular location with a primary button, which might be the start of a tap.

This triggers after the down event, once a short timeout (deadline) has elapsed, or once the gestures has won the arena, whichever comes first.

If this recognizer doesn't win the arena, onTapCancel is called next. Otherwise, onTapUp is called next.

See also:

• kPrimaryButton, the button this callback responds to.
• onSecondaryTapDown, a similar callback but for a secondary button.
• onTertiaryTapDown, a similar callback but for a tertiary button.
• TapDownDetails, which is passed as an argument to this callback.
• GestureDetector.onTapDown, which exposes this callback.