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ViewDragHelper.Callback

public static abstract class ViewDragHelper.Callback
extends Object

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.

Summary

Public constructors
`ViewDragHelper.Callback()`

Public methods
`int`	`clampViewPositionHorizontal(View child, int left, int dx)` Restrict the motion of the dragged child view along the horizontal axis.
`int`	`clampViewPositionVertical(View child, int top, int dy)` Restrict the motion of the dragged child view along the vertical axis.
`int`	`getOrderedChildIndex(int index)` Called to determine the Z-order of child views.
`int`	`getViewHorizontalDragRange(View child)` Return the magnitude of a draggable child view's horizontal range of motion in pixels.
`int`	`getViewVerticalDragRange(View child)` Return the magnitude of a draggable child view's vertical range of motion in pixels.
`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.
`boolean`	`onEdgeLock(int edgeFlags)` Called when the given edge may become locked.
`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.
`void`	`onViewCaptured(View capturedChild, int activePointerId)` Called when a child view is captured for dragging or settling.
`void`	`onViewDragStateChanged(int state)` Called when the drag state changes.
`void`	`onViewPositionChanged(View changedView, int left, int top, int dx, int dy)` Called when the captured view's position changes as the result of a drag or settle.
`void`	`onViewReleased(View releasedChild, float xvel, float yvel)` Called when the child view is no longer being actively dragged.
`abstract boolean`	`tryCaptureView(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.

Inherited methods

From class


  
    java.lang.Object

`Object`	`clone()` Creates and returns a copy of this object.
`boolean`	`equals(Object obj)` Indicates whether some other object is "equal to" this one.
`void`	`finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
`final Class<?>`	`getClass()` Returns the runtime class of this `Object`.
`int`	`hashCode()` Returns a hash code value for the object.
`final void`	`notify()` Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()` Wakes up all threads that are waiting on this object's monitor.
`String`	`toString()` Returns a string representation of the object.
`final void`	`wait(long millis, int nanos)` Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object, or some other thread interrupts the current thread, or a certain amount of real time has elapsed.
`final void`	`wait(long millis)` Causes the current thread to wait until either another thread invokes the `notify()` method or the `notifyAll()` method for this object, or a specified amount of time has elapsed.
`final void`	`wait()` Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object.

Public constructors

ViewDragHelper.Callback

ViewDragHelper.Callback ()

Public methods

clampViewPositionHorizontal

int clampViewPositionHorizontal (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.

Parameters
`child`	`View`: Child view being dragged
`left`	`int`: Attempted motion along the X axis
`dx`	`int`: Proposed change in position for left

Returns
`int`	The new clamped position for left

clampViewPositionVertical

int clampViewPositionVertical (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.

Parameters
`child`	`View`: Child view being dragged
`top`	`int`: Attempted motion along the Y axis
`dy`	`int`: Proposed change in position for top

Returns
`int`	The new clamped position for top

getOrderedChildIndex

int getOrderedChildIndex (int index)

Called to determine the Z-order of child views.

Parameters
`index`	`int`: the ordered position to query for

Returns
`int`	index of the view that should be ordered at position `index`

getViewHorizontalDragRange

int getViewHorizontalDragRange (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.

Parameters
`child`	`View`: Child view to check

Returns
`int`	range of horizontal motion in pixels

getViewVerticalDragRange

int getViewVerticalDragRange (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.

Parameters
`child`	`View`: Child view to check

Returns
`int`	range of vertical motion in pixels

onEdgeDragStarted

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.

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

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(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

Returns
`boolean`	true to lock the edge, false to leave it unlocked

onEdgeTouched

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.

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

void onViewCaptured (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.

Parameters
`capturedChild`	`View`: Child view that was captured
`activePointerId`	`int`: Pointer id tracking the child capture

onViewDragStateChanged

void onViewDragStateChanged (int state)

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

Parameters
`state`	`int`: The new drag state

See also:

onViewPositionChanged

void onViewPositionChanged (View changedView, 
                int left, 
                int top, 
                int dx, 
                int dy)

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

void onViewReleased (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(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

boolean tryCaptureView (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(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

Returns
`boolean`	true if capture should be allowed, false otherwise

Interfaces

Classes

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ViewDragHelper.Callback

Summary

Public constructors

Public methods

Inherited methods

Public constructors

ViewDragHelper.Callback

Public methods

clampViewPositionHorizontal

clampViewPositionVertical

getOrderedChildIndex

getViewHorizontalDragRange

getViewVerticalDragRange

onEdgeDragStarted

onEdgeLock

onEdgeTouched

onViewCaptured

onViewDragStateChanged

onViewPositionChanged

onViewReleased

tryCaptureView