middle_softkey_notes.txt

一个简单的资源管理器

Middle softkey labelling (MSK)
==============================

The middle softkey concept was introduced in S60 3rd Edition, Feature Pack 2. 
It provides support for labelling the selection key. It is recommended that all 
S60 applications from S60 3rd Edition, Feature Pack 2 onwards provide labelling 
for the middle softkey.

The label is displayed only when the display is in portrait mode and softkey 
labels are at the bottom of the display. The label is not displayed on a touch 
screen. In standard UI applications, once the application has enabled and 
defined the middle softkey, the framework takes care of displaying it when 
needed. 

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ENABLING THE MIDDLE SOFTKEY LABEL IN STANDARD UI APPLICATIONS

1. Update the application resources. Choose one of the following:

  * Use predefined softkey layouts from Avkon that 
    have the middle softkey, such as R_AVKON_SOFTKEYS_OPTIONS_BACK__SELECT

   or

  * Create a new resource for softkeys using CBA struct and 
    define the three softkeys there. The first one is the left softkey, 
    the second is the right softkey, and the third is the middle softkey.


2. Enable the middle softkey in the application by giving the EAknEnableMSK 
   flag for BaseConstructL.


3. Handle the command for the middle softkey in the same way as any other 
   command that has been assigned to other softkeys.


Providing multi-release support
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
It is possible to develop applications for multiple releases that display 
the middle softkey correctly on different S60 3rd Edition releases. To achieve 
this, developers can compile their application using S60 3rd Edition, Feature 
Pack 1 SDK or S60 3rd Edition, Feature Pack 2 SDK.


Note that the EAknEnableMSK flag is already provided in the S60 3rd Edition, 
Feature Pack 1 SDK; however, the label is not displayed in the application 
until S60 3rd Edition, Feature Pack 2.

In the FileList example, the SIS file is compiled using the S60 3rd Edition, 
Feature Pack 2 SDK. It has been tested to install and run on various S60 3rd 
Edition devices (see the release notes of the example for further information). 
However, as the Scalable Vector Graphics Tiny (SVGT) icon does not show in S60 
3rd Edition devices, a separate version for it is provided.


S60 3rd Edition-specific issues:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Note that SDKs before S60 3rd Edition, FP1 do not support the EAknEnableMSK 
flag. To be able to compile an application on, for example, the S60 3rd 
Edition, MR SDK, the EAknEnableMSK flag and all references to the middle 
softkey need to be removed from the source code or bypassed using the 
__SERIES60_30__ macro (used in the example application).

In applications compiled with S60 3rd Edition, FP1 or newer SDKs, the SVGT 
application icons do not show on S60 3rd Edition devices. The solution is 
to compile a separate version using the S60 3rd Edition SDK or to implement 
application icons as bitmaps.

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USING MIDDLE SOFTKEY LABELLING IN CUSTOM UI APPLICATIONS

Note that custom UI applications draw their own softkey labels. They are also 
responsible for displaying the middle softkey label. It is technically possible 
to display the middle softkey label in any S60 release. However, it is 
recommended that they also follow the S60 UI Style Guide and display the middle 
softkey label only in certain screen layouts in devices supporting S60 3rd 
Edition, Feature Pack 2 or later.

S60 Platform: Scalable Screen-Drawing Example demonstrates how to implement the 
middle softkey label for custom UI applications:
http://www.forum.nokia.com/info/sw.nokia.com/id/e4835ec0-e891-4cdf-94fd-9b57476c6d0c/S60_Platform_Scalable_Screen_Drawing_Example.html