RawScaleObserver
interface RawScaleObserver
| androidx.compose.ui.gesture.RawScaleObserver |
Observes various events sent by rawScaleGestureFilter. Implement and pass into rawScaleGestureFilter so that rawScaleGestureFilter may call the functions when events occur.
Summary
| Public methods | |
|---|---|
| open Unit |
onCancel()Override to be notified when the scale has been cancelled. |
| open Float |
Override to be notified when scaling has occurred. |
| open Unit |
onStart()Override to be notified when scaling has started. |
| open Unit |
onStop()Override to be notified when scaling has stopped. |
Public methods
onCancel
open fun onCancel(): Unit
Override to be notified when the scale has been cancelled.
This is called if onStart has ben called and then a cancellation event has occurs (for example, due to the gesture detector being removed from the tree) before onStop is called.
onScale
open fun onScale(scaleFactor: Float): Float
Override to be notified when scaling has occurred.
When overridden, return the amount of scaling, expressed as a scale factor, that should be consumed. For example, if the scaleFactor is 1.5 and the client wants to consume all of the scaling, it should return 1.5. If it wants to consume none of the scaling, it should return 1.
Always called just after onStart (and for every subsequent scale).
| Parameters | |
|---|---|
| scaleFactor: Float | The ratio of newSize / oldSize that the scaling gesture has expressed between pointers last position and current position (this value is not cumulative over the lifetime of of the gesture). For example, if 2 fingers are 10 pixel apart, and then move such that they are 20 pixels apart, the scaleFactor will be 2. If 2 fingers that are 20 pixels apart move such that they are 10 pixels apart, the scaleFactor will be .5. |
| Return | |
|---|---|
| The amount scaling that was actually used. | This value should also be a scaleFactor that is in the range of S to 1, where S is the value of scaleFactor. (If you are scaling an image, just return the scaleFactor that the image actually scaled. For example, if scaleFactor is 2, and the image can only scale to 1.5, return 1.5). If you don't want bother with "nested scaling" (you simply want to consume all of the pointer movement related to scaling), just return the value of scaleFactor. |
onStart
open fun onStart(): Unit
Override to be notified when scaling has started.
This will be called when scaling occurs (and when the associated rawScaleGestureFilter is allowed to start). Always called just before onScale and isn't called again until after onStop.
See Also