How to Enable/Disable Drag and Move Events in a Control
This snippet shows how to Enable or Disable Drag and Move Pointer events in a Symbian C++ UI Control.
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Overview
By default, pointer drag events and pointer move events are not delivered to controls. The default behaviour when a window is created is that move, drag, enter and exit events are filtered out and not delivered to the client. In order for the control to receive drag events occurring in its window, we need to call EnableDragEvents() in the control’s construction routine. Having done that, the control will receive drag events as calls to its HandlePointerEventL() virtual function.
Preconditions
Here we assume that we already have a working code for UI based Application.
MMP file
The following capabilities and libraries are required:
CAPABILITY None LIBRARY cone.lib include <COECNTRL.H>
Enabling Drag and Move Events
void CSomeAppView::ConstructL(const TRect& aRect)
{
// Create a window for the container
CreateWindowL();
.
. .
. . .
// Enable Drag Events.
EnableDragEvents();
// OR can also be done with
Window().PointerFilter(EPointerFilterDrag, 0);
.. ..
}
Handling Drag and Move Events
Control receive's drag and move events in its HandlePointerEventL() virtual function, hence whatever processing is required for Drag and Move events can be done inside this function.
void CSomeAppView::HandlePointerEventL(const TPointerEvent& aPointerEvent)
{
switch (aPointerEvent.iType)
{
.
. .
. . .
case TPointerEvent::EDrag:
{
// Handle drag event here.
break;
}
case TPointerEvent::EMove:
{
// Handle move event here.
break;
}
default:
{
// do something
break;
}
}
Disabling Drag and Move Events
The control framework does not provide a function to disable drag events at a later time, but this can be done via the Window Server API, by calling Window()->PointerFilter().
// A 1 bit causes the corresponding event to be filtered out, a 0 bit lets through the corresponding event.
Window().PointerFilter(EPointerFilterDrag, 1);
Postconditions
Drag and Move Pointer Events will be Enabled/Disabled.
30 Sep
2009
In some scenario we need to enable/disable drag and move event in control. This article demonstrates how to enable/disable drag and move event in control. Basically we need to call PointerFilter() method of class RWindowBase to enable/disable drag and move event, as explained in this article. The article is well explained and useful to beginners as well as experienced developer.