OfferKeyEventL()

virtual TKeyResponse OfferKeyEventL(const TKeyEvent& aKeyEvent,TEventCode aType);

Description

Handles key events.

If a control wishes to process key events, it should implement this function. The implementation must ensure that the function returns EKeyWasNotConsumed if it does not do anything in response to a key event — otherwise, other controls or dialogs may be prevented from receiving the key event. If it is able to process the event it should return EKeyWasConsumed.

注释:

      如果一个控件希望处理按键事件,那么它就应该实现这个函数。如果对一个按键事件,控件并没做任何事情,那么函数的实现中必须确保函数返回EKeyWasNotConsumed。否则,(控件栈中的)其它控件或对话框可能会接收不到按键事件。如果此控件能够处理按键事件,那么它应该返回EKeyWasConsumed。

When a key event occurs, the control framework calls this function for each control on the control stack, until one of them can process the key event (and returns EKeyWasConsumed).

注释:

      当一个按键事件发生时,控件框架调用控件栈上的每个控件的OfferKeyEventL方法,直到它们中的一个能够处理这个按键事件(并且返回EKeyWasConsumed)。

Parameters

Return value

Notes:

• Each keyboard key press results in three separate events: EEventKeyDown, EEventKey, and EEventKeyUp, in that order.

每个键被按下时会顺序产生三个独立的事件:EEventKeyDown、EEventKey、EEventKeyUp。

• To receive key events, which can be processed by this function, the application should call CCoeAppUi::AddToStackL() to add the control to the stack. This only applies, however, to controls which are not components of a compound control. Compound controls should pass key events to their components as necessary: the components themselves do not go on the stack.

为了接收到按键事件,应用程序应该调用CCoeAppUi::AddToStackL() 方法把控件增加到栈上。尽管这个规则仅仅用在非混合控件。混合控件应该传递按键事件给其组件:组件自己并不在控件栈上。

• Classes that override CCoeControl::OfferKeyEventL() should also override the InputCapabilities() virtual function, returning a TCoeInputCapabilities object whose attributes correspond to the behaviour of the OfferKeyEventL() function. Note that it is not necessary to call InputCapabilities() on any component controls from inside a class' InputCapabilities() function — this is done automatically by the UI Control Framework.

重载CCoeControl::OfferKeyEventL()的类也应该重载虚函数InputCapabilities() ,它会返回一个TCoeInputCapabilities 对象,这个对象的属性和OfferKeyEventL()方法的行为吻合。注意,在控件中并不是必须要调用InputCapabilities() 方法,因为这个过程自动被UI Control Framework完成了。