New three soft key layout for K850, W910 and Z750 phones

The new Sony Ericsson K850, W910 and Z750 Java™ Platform 8 (JP-8) phones introduce a new three soft key layout. This change affects how Java ME applications and games interact with the phone, and therefore the end-user experience, and here you'll find an overview of the two layouts and ten of the most common use cases when an application displays command labels.

Comparison of two soft key and three soft key layouts
Previous Sony Ericsson mobile phones have a two soft key layout. The left soft key should be used for the "most likely action", i.e. what the end-user usually wants to do. Additional actions or commands should be handled by the right soft key. In addition to these keys, the phones have a designated key for back action called the physical back key.

The K850, W910, Z750 and subsequent JP-8 phones will use a three soft key layout: left soft key, middle soft key and right soft key. These phones also include the new "Send" and "End" keys where pressing the "End" key prompts the end-user to end or minimize the application (a direct response now with no long press on the physical back key as before). The physical back key has been removed. The middle soft key should now be used for the "most likely action" and the right soft key for the back action. Other actions or commands will be handled with the left soft key.

The following overview will give you some guidance when designing applications and games for new JP-8 phones, including recommendations and examples of common cases then an application displays command labels.

Explanation of terminology
The phrase "most likely action" is used to indicate the most probable thing an end-user will do on a particular screen. Examples of such actions are:
- Select action
- Mark-an-item action
- OK action

"Back action" refers to the Back, Cancel and Exit actions, which are defined as:
- Back action should always be a safe thing to do. The application should not change internal state when a Back command is performed.
- Cancel action should be used to cancel or abort an action which may take some time to complete.
- Exit action should be used to close the application.

Application requirements and recommendations
Here are some requirements and recommendations for applications using the three soft keys. A preloaded application must comply with these requirements at all times. For all other applications, we strongly recommend that you use the following guidelines to maximize the end-user experience.

Requirements on the command labels in the application:
1. Most likely action on the middle soft key
2. Back, Cancel or Exit action always on the right soft key
3. The commands must be consistent (in their placement and usage) throughout the application

We recommend that an application should also follow these requirements:
- Emphasize the label for the middle soft key, e.g. by using a bold and bigger font
- A back icon should look similar to these: or depending on the screen size the application is optimized for.

If the application uses the high-level UI and adds Command objects to the current Screen, the platform places the commands on the correct soft key (as long as a logical type for the command is used). The platform also emphasizes the label of the middle soft key.

Common use cases
Here are ten of the most common cases when an application displays command labels.
Use cases when Back action existsWhen a Back action is visible on the screen the command should always be displayed on the right soft key.

1. Only a Back Action
Screens which only have a Back action must display the label to the right

2. Screen has 1 Command and Back Action
If a screen has one action command and also a Back command, the one action should be displayed on the middle soft key and the Back command displayed on the right soft key.

3. Screen has 2 Commands and Back Action
The "most likely action" should be displayed on the middle soft key and the other action should be displayed on the left soft key. The Back command should be displayed on the right soft key.

4. Screen has 3 or more Commands and Back Action
As in the previous use case, the "most likely action" should be displayed on the middle soft key and the Back key on the right soft key. The second, third and other actions have to be gathered at the Options menu on the left soft key.

Use cases when Back action doesn't exist
If a screen does not have a Back action there will be some more space to display soft key labels on.
5. Screen has only 1 Command
Screens which only have a one action must display the label on the middle soft key.

6. Screen has 2 Commands
When a screen has exactly two commands, the "most likely action" should be displayed on the middle soft key and the other action should be displayed on the left soft key.

7. Screen has 3 Commands
If a screen has exactly three commands, the "most likely action" should be displayed on the middle soft key, the second action should be displayed on the left soft key and the third on the right soft key.

8. Screen has 4 or more Commands
When a screen needs four or more actions, the first action should be displayed on the middle soft key and the second one on the right soft key. All other actions have to be gathered on an options menu on the left soft key.

Yes/No dialogs
It is common for applications to have questions where the user needs to answer "Yes" or "No". The simple rule to follow is that Yes (or confirmation action) should be displayed on the middle soft key. No (or not-confirm action) will be displayed either on the left soft key or on the right soft key depending on if there is a Back action on the screen or not. Back action should be interpreted as cancel and don't change the state of the application.

9. Yes/No question and Back
Use case where the application also has a Back action.

10.Yes/No question without Back
A simple Yes/No dialog without any Back action. Compare this use case with the use case example 6. No should be considered a Cancel action and is therefore placed on the right soft key.