Constructing +views in traditional architecture

diff -r 43e37759235e -r 51a74ef9ed63 Symbian3/SDK/Source/GUID-BE871265-147B-45F3-8772-A4E091223EDB.dita --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/Symbian3/SDK/Source/GUID-BE871265-147B-45F3-8772-A4E091223EDB.dita Wed Mar 31 11:11:55 2010 +0100 @@ -0,0 +1,112 @@ + + + + + +Constructing +views in traditional architecture +

The call on the first phase constructor method of the view occurs in UI controller. The +view serves as the top-level window under the UI controller.

The methods you need to implement for your CCoeControl-derived +view are as follows:

C++ default constructor, which cannot contain code that leaves. +A common implementation is:
+ + +CMyAppView::CMyAppView() + { + // No implementation required + } +
Comment to reviewers: We will +link these Cleanup stack and new (ELeave) methods to the Symbian Developer +Library API Reference.
+ +
two-phase constructor, a common implementation is:
+ +CMyAppView* CMyAppView::NewL( const TRect& aRect ) + { + CMyAppView* self = CMyAppView::NewLC( aRect ); + CleanupStack::Pop( self ); + return self; + } + +CMyAppView* CMyAppView::NewLC( const TRect& aRect ) + { + CMyAppView* self = new ( ELeave ) CMyAppView; + CleanupStack::PushL( self ); + self->ConstructL( aRect ); + return self; + } + +
The declarations for CMyAppView::NewL() and CMyAppView::NewLC in +the class header file needs to be public to support the construction method +required. CMyAppView is the default constructor for the CMyAppView class +and it is private.
+
In this approach, CMyAppView::NewL() is called +from the UI controller. It creates a view object by calling CMyAppView::NewLC(). CMyAppView::NewLC() calls +new (ELeave) on the C++ default constructor CMyAppView to +create the object (and leave if it cannot), pushes a pointer to the clean-up stack in case the second phase construction method +leaves, and then calls the second phase construction method of the object. +When it returns to CMyAppView::NewL(), the pointer pushed +to the cleanup stack is removed.
+ +
Symbian 2nd phase constructor with code that might leave. +A common implementation is:
+ +void CMyAppView::ConstructL( const TRect& aRect ) + { + // Create a window for this application view + CreateWindowL(); + + //add construction for other controls if required + + // Set the windows size + SetRect( aRect ); + + // Activate the window, which makes it ready to be drawn + ActivateL(); + } +
CMyAppView::ConstructL() is a private class providing +the second phase construction that accepts the rectangle the view is drawn +to.
+
CCoeControl::CreateWindowL() creates a window for +the control. Note that this window is a child of the UI controller. This method +makes the control a window-owning +control. While the use of window-owning controls is generally discouraged +to prevent the taxing of run-time resources, this is the top-level window +for the UI controller.
+
This is a simple control that does not contain other controls; other +controls could be added to the control between CCoeControl::CreateWindowL() and CCoeControl::SetRect(aRect). +For more information, see Compound +controls in traditional architecture.
+
CCoeControl::SetRect(aRect) sets the window size +according to the requirements of the mobile device. The top-level control +rectangle is set to the area that the framework provides for the application. +Calling CCoeControl::SetRect(aRect) calls the CCoeControl::SizeChanged() method, +where the control should set the position and size for any child controls +and thus adjust the control layout to the UI.
+
CCoeControl::ActivateL() sets the control as ready +to be drawn.
+ +

If required for your application, you may need to implement other methods +for your control. For top-level windows, you would need to implement CCoeControl::SizeChanged() +to respond to changes to the size and position of the contents of this control. +This is called by the platform when a change occurs. A typical implementation +for a compound control is:

+void CMyAppView::SizeChanged() + { + // Control resize code + iControl->SetExtent( const TPoint &aPosition, const TSize &aSize); + } + \ No newline at end of file