ViewDragHelper.Callback

public int clampViewPositionHorizontal(@NonNull View child, int left, int dx)

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.

public int clampViewPositionVertical(@NonNull View child, int top, int dy)

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.

public int getOrderedChildIndex(int index)

Called to determine the Z-order of child views.

public int getViewHorizontalDragRange(@NonNull View child)

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.

public int getViewVerticalDragRange(@NonNull View child)

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.

public void onEdgeDragStarted(int edgeFlags, int pointerId)

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.

public boolean onEdgeLock(int edgeFlags)

Called when the given edge may become locked. This can happen if an edge drag was preliminarily rejected before beginning, but after onEdgeTouched 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.

public void onEdgeTouched(int edgeFlags, int pointerId)

Called when one of the subscribed edges in the parent view has been touched by the user while no child view is currently captured.

public void onViewCaptured(@NonNull View capturedChild, int activePointerId)

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.

public void onViewDragStateChanged(int state)

Called when the drag state changes. See the STATE_* constants for more information.

public void onViewPositionChanged(
    @NonNull View changedView,
    int left,
    int top,
    @Px int dx,
    @Px int dy
)

Called when the captured view's position changes as the result of a drag or settle.

public void onViewReleased(@NonNull View releasedChild, float xvel, float yvel)

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 or flingCapturedView. 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.

public abstract boolean tryCaptureView(@NonNull View child, int pointerId)

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 will follow if the capture is successful.