Callback
abstract class Callback
| kotlin.Any | |
| ↳ | androidx.customview.widget.ViewDragHelper.Callback |
A Callback is used as a communication channel with the ViewDragHelper back to the parent view using it. on*methods are invoked on siginficant events and several accessor methods are expected to provide the ViewDragHelper with more information about the state of the parent view upon request. The callback also makes decisions governing the range and draggability of child views.
Summary
Public constructors |
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|---|---|
<init>()A Callback is used as a communication channel with the ViewDragHelper back to the parent view using it. |
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Public methods |
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| open Int |
clampViewPositionHorizontal(@NonNull child: View, left: Int, dx: Int)Restrict the motion of the dragged child view along the horizontal axis. |
| open Int |
clampViewPositionVertical(@NonNull child: View, top: Int, dy: Int)Restrict the motion of the dragged child view along the vertical axis. |
| open Int |
getOrderedChildIndex(index: Int)Called to determine the Z-order of child views. |
| open Int |
getViewHorizontalDragRange(@NonNull child: View)Return the magnitude of a draggable child view's horizontal range of motion in pixels. |
| open Int |
getViewVerticalDragRange(@NonNull child: View)Return the magnitude of a draggable child view's vertical range of motion in pixels. |
| open Unit |
onEdgeDragStarted(edgeFlags: Int, pointerId: Int)Called when the user has started a deliberate drag away from one of the subscribed edges in the parent view while no child view is currently captured. |
| open Boolean |
onEdgeLock(edgeFlags: Int)Called when the given edge may become locked. |
| open Unit |
onEdgeTouched(edgeFlags: Int, pointerId: Int)Called when one of the subscribed edges in the parent view has been touched by the user while no child view is currently captured. |
| open Unit |
onViewCaptured(@NonNull capturedChild: View, activePointerId: Int)Called when a child view is captured for dragging or settling. |
| open Unit |
onViewDragStateChanged(state: Int)Called when the drag state changes. |
| open Unit |
Called when the captured view's position changes as the result of a drag or settle. |
| open Unit |
onViewReleased(@NonNull releasedChild: View, xvel: Float, yvel: Float)Called when the child view is no longer being actively dragged. |
| abstract Boolean |
tryCaptureView(@NonNull child: View, pointerId: Int)Called when the user's input indicates that they want to capture the given child view with the pointer indicated by pointerId. |
Public constructors
<init>
Callback()
A Callback is used as a communication channel with the ViewDragHelper back to the parent view using it. on*methods are invoked on siginficant events and several accessor methods are expected to provide the ViewDragHelper with more information about the state of the parent view upon request. The callback also makes decisions governing the range and draggability of child views.
Public methods
clampViewPositionHorizontal
open fun clampViewPositionHorizontal(
@NonNull child: View,
left: Int,
dx: Int
): Int
Restrict the motion of the dragged child view along the horizontal axis. The default implementation does not allow horizontal motion; the extending class must override this method and provide the desired clamping.
| Parameters | |
|---|---|
child |
View: Child view being dragged |
left |
Int: Attempted motion along the X axis |
dx |
Int: Proposed change in position for left |
| Return | |
|---|---|
Int |
The new clamped position for left |
clampViewPositionVertical
open fun clampViewPositionVertical(
@NonNull child: View,
top: Int,
dy: Int
): Int
Restrict the motion of the dragged child view along the vertical axis. The default implementation does not allow vertical motion; the extending class must override this method and provide the desired clamping.
| Parameters | |
|---|---|
child |
View: Child view being dragged |
top |
Int: Attempted motion along the Y axis |
dy |
Int: Proposed change in position for top |
| Return | |
|---|---|
Int |
The new clamped position for top |
getOrderedChildIndex
open fun getOrderedChildIndex(index: Int): Int
Called to determine the Z-order of child views.
| Parameters | |
|---|---|
index |
Int: the ordered position to query for |
| Return | |
|---|---|
Int |
index of the view that should be ordered at position index |
getViewHorizontalDragRange
open fun getViewHorizontalDragRange(@NonNull child: View): Int
Return the magnitude of a draggable child view's horizontal range of motion in pixels. This method should return 0 for views that cannot move horizontally.
| Parameters | |
|---|---|
child |
View: Child view to check |
| Return | |
|---|---|
Int |
range of horizontal motion in pixels |
getViewVerticalDragRange
open fun getViewVerticalDragRange(@NonNull child: View): Int
Return the magnitude of a draggable child view's vertical range of motion in pixels. This method should return 0 for views that cannot move vertically.
| Parameters | |
|---|---|
child |
View: Child view to check |
| Return | |
|---|---|
Int |
range of vertical motion in pixels |
onEdgeDragStarted
open fun onEdgeDragStarted(
edgeFlags: Int,
pointerId: Int
): Unit
Called when the user has started a deliberate drag away from one of the subscribed edges in the parent view while no child view is currently captured.
| Parameters | |
|---|---|
edgeFlags |
Int: A combination of edge flags describing the edge(s) dragged |
pointerId |
Int: ID of the pointer touching the described edge(s) |
See Also
onEdgeLock
open fun onEdgeLock(edgeFlags: Int): Boolean
Called when the given edge may become locked. This can happen if an edge drag was preliminarily rejected before beginning, but after onEdgeTouched(int, int) was called. This method should return true to lock this edge or false to leave it unlocked. The default behavior is to leave edges unlocked.
| Parameters | |
|---|---|
edgeFlags |
Int: A combination of edge flags describing the edge(s) locked |
| Return | |
|---|---|
Boolean |
true to lock the edge, false to leave it unlocked |
onEdgeTouched
open fun onEdgeTouched(
edgeFlags: Int,
pointerId: Int
): Unit
Called when one of the subscribed edges in the parent view has been touched by the user while no child view is currently captured.
| Parameters | |
|---|---|
edgeFlags |
Int: A combination of edge flags describing the edge(s) currently touched |
pointerId |
Int: ID of the pointer touching the described edge(s) |
See Also
onViewCaptured
open fun onViewCaptured(
@NonNull capturedChild: View,
activePointerId: Int
): Unit
Called when a child view is captured for dragging or settling. The ID of the pointer currently dragging the captured view is supplied. If activePointerId is identified as INVALID_POINTER the capture is programmatic instead of pointer-initiated.
| Parameters | |
|---|---|
capturedChild |
View: Child view that was captured |
activePointerId |
Int: Pointer id tracking the child capture |
onViewDragStateChanged
open fun onViewDragStateChanged(state: Int): Unit
Called when the drag state changes. See the STATE_* constants for more information.
| Parameters | |
|---|---|
state |
Int: The new drag state |
See Also
onViewPositionChanged
open fun onViewPositionChanged(
@NonNull changedView: View,
left: Int,
top: Int,
@Px dx: Int,
@Px dy: Int
): Unit
Called when the captured view's position changes as the result of a drag or settle.
| Parameters | |
|---|---|
changedView |
View: View whose position changed |
left |
Int: New X coordinate of the left edge of the view |
top |
Int: New Y coordinate of the top edge of the view |
dx |
Int: Change in X position from the last call |
dy |
Int: Change in Y position from the last call |
onViewReleased
open fun onViewReleased(
@NonNull releasedChild: View,
xvel: Float,
yvel: Float
): Unit
Called when the child view is no longer being actively dragged. The fling velocity is also supplied, if relevant. The velocity values may be clamped to system minimums or maximums.
Calling code may decide to fling or otherwise release the view to let it settle into place. It should do so using settleCapturedViewAt(int, int) or flingCapturedView(int, int, int, int). If the Callback invokes one of these methods, the ViewDragHelper will enter STATE_SETTLING and the view capture will not fully end until it comes to a complete stop. If neither of these methods is invoked before onViewReleased returns, the view will stop in place and the ViewDragHelper will return to STATE_IDLE.
| Parameters | |
|---|---|
releasedChild |
View: The captured child view now being released |
xvel |
Float: X velocity of the pointer as it left the screen in pixels per second. |
yvel |
Float: Y velocity of the pointer as it left the screen in pixels per second. |
tryCaptureView
abstract fun tryCaptureView(
@NonNull child: View,
pointerId: Int
): Boolean
Called when the user's input indicates that they want to capture the given child view with the pointer indicated by pointerId. The callback should return true if the user is permitted to drag the given view with the indicated pointer.
ViewDragHelper may call this method multiple times for the same view even if the view is already captured; this indicates that a new pointer is trying to take control of the view.
If this method returns true, a call to onViewCaptured(android.view.View, int) will follow if the capture is successful.
| Parameters | |
|---|---|
child |
View: Child the user is attempting to capture |
pointerId |
Int: ID of the pointer attempting the capture |
| Return | |
|---|---|
Boolean |
true if capture should be allowed, false otherwise |