| java.lang.Object | |
| ↳ | android.support.v4.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.
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| Public Methods | |||||||||||
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Restrict the motion of the dragged child view along the horizontal axis.
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Restrict the motion of the dragged child view along the vertical axis.
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Called to determine the Z-order of child views.
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Return the magnitude of a draggable child view's horizontal range of motion in pixels.
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Return the magnitude of a draggable child view's vertical range of motion in pixels.
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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.
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Called when the given edge may become locked.
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Called when one of the subscribed edges in the parent view has been touched
by the user while no child view is currently captured.
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Called when a child view is captured for dragging or settling.
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Called when the drag state changes.
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Called when the captured view's position changes as the result of a drag or settle.
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Called when the child view is no longer being actively dragged.
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Called when the user's input indicates that they want to capture the given child view
with the pointer indicated by pointerId.
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[Expand]
Inherited Methods | |||||||||||
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From class
java.lang.Object
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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.
| child | Child view being dragged |
|---|---|
| left | Attempted motion along the X axis |
| dx | Proposed change in position for left |
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.
| child | Child view being dragged |
|---|---|
| top | Attempted motion along the Y axis |
| dy | Proposed change in position for top |
Called to determine the Z-order of child views.
| index | the ordered position to query for |
|---|
Developers
index
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.
| child | Child view to check |
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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.
| child | Child view to check |
|---|
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.
| edgeFlags | A combination of edge flags describing the edge(s) dragged |
|---|---|
| pointerId | ID of the pointer touching the described edge(s) |
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.
| edgeFlags | A combination of edge flags describing the edge(s) locked |
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Called when one of the subscribed edges in the parent view has been touched by the user while no child view is currently captured.
| edgeFlags | A combination of edge flags describing the edge(s) currently touched |
|---|---|
| pointerId | ID of the pointer touching the described edge(s) |
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.
| capturedChild | Child view that was captured |
|---|---|
| activePointerId | Pointer id tracking the child capture |
Called when the drag state changes. See the STATE_* constants
for more information.
| state | The new drag state |
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Called when the captured view's position changes as the result of a drag or settle.
| changedView | View whose position changed |
|---|---|
| left | New X coordinate of the left edge of the view |
| top | New Y coordinate of the top edge of the view |
| dx | Change in X position from the last call |
| dy | Change in Y position from the last call |
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.
| releasedChild | The captured child view now being released |
|---|---|
| xvel | X velocity of the pointer as it left the screen in pixels per second. |
| yvel | Y velocity of the pointer as it left the screen in pixels per second. |
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.
| child | Child the user is attempting to capture |
|---|---|
| pointerId | ID of the pointer attempting the capture |