Compound +controls in traditional architecture

diff -r 000000000000 -r 89d6a7a84779 Symbian3/SDK/Source/GUID-97486385-88F7-4AF1-B880-D9A8AA4D7094.dita --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/Symbian3/SDK/Source/GUID-97486385-88F7-4AF1-B880-D9A8AA4D7094.dita Thu Jan 21 18:18:20 2010 +0000 @@ -0,0 +1,102 @@ + + + + + +Compound +controls in traditional architecture +

Compound controls are +controls that contain other controls. To create a compound control, you must +do the following:

construct the control in the parent control, which is the +control that owns the window in which the control appears. The control should +be constructed in the constructor for the window. An example of an implementation +is as follows:
+ +void CMyViewContainer::ConstructL(const TRect& aRect) + { + CreateWindowL(); + + iLabel = new (ELeave) CEikLabel; + iLabel->SetContainerWindowL( *this ); + iLabel->SetTextL( _L("MyView 1\n\nSelect local view\nswitching from menu") ); + + SetRect(aRect); + ActivateL(); + } +
, where
+
iLabel = new (ELeave) CEikLabel; creates a CEikLabel object, +which is a class that supports the display of text in the parent window.
+
CCoeControl::SetContainerWindowL makes +the non-window-owning +control a child of the window-owning control.
+
CEikLabel::SetTextL sets a text for the label
+
The other methods are the standard methods for creating a window for +the window-owning control.
+ +
add a method to the owning control that returns the number +of controls in the compound control. An example of an implementation is as +follows:
+ +TInt CMyViewAppContainer::CountComponentControls() const + { + return KNumberOfControls; // return nbr of controls inside this compound control + } +
, where
+
CMyViewAppContainer::CountComponentControls() overrides CCoeControl::CountComponentControls to +return the number of controls in the compound control
+
KNumberOfControls is a TInt constant +for the number of controls in the application. Other approaches could be used.
+ +
Add a method to the owning control that returns each of the +controls by a zero-based index. An example of an implementation is as follows:
+ +CCoeControl* CContainerContainer::ComponentControl( + TInt aIndex) const + { + switch ( aIndex ) + { + case 0: + return iLabel; // return a pointer to the + //iLabel + default: + return NULL; + } + } + +
, where
+
CCoeControl* CContainerContainer::ComponentControl(TInt aIndex) gets +an indexed component of a compound control. There are two ways to implement +a compound control. One way is to override this function. The other way is +to use the CCoeControlArray functionality (see the CCoeControl::InitComponentArrayL method). +
+ +
Within a compound control, each component control is identified by an +index.
+ +
All child controls should be accessible by CCoeControl::ComponentControl at any time, regardless +of whether they are visible or not. You can adjust the visibility of a control +using the CCoeControl::MakeVisible method.
+ +

CCoeControl* CContainerContainer::ComponentControl(TInt aIndex) and CCoeControl::CountComponentControls work +in conjunction with each other. The Symbian platform can query the control +as to how many components it has and then request a pointer to each of the +component's controls. Controls can be added or removed at run time using these +two methods. The framework uses this information to draw the container.

The compound control usually owns the child controls and therefore it +is responsible of their construction and destruction. The compound control +should also set the positions and sizes of its child controls; it must ensure +that all child controls are inside the compound control rectangle and visible +child rectangles do not overlap each other.

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