State and Notifications Broker Properties and Notification Types (Windows Embedded CE 6.0)
1/6/2010
State and Notifications Broker supports one type of state property: persistent state property. This type of state property has the same value both before and after device reset or shutdown.
All system state properties exposed by Windows Mobile software are stored in the registry at HKEY_CURRENT_USER\System\State and HKEY_LOCAL_MACHINE\System\State registry keys. These are protected registry locations. Normal applications have read-only access to these locations.
You can create subkeys in HKEY_CURRENT_USER\Software\State or HKEY_LOCAL_MACHINE\Software\State to store non-system properties.
Conditional Notification
You can configure notifications to be sent only when the requested state property has changed to a desired value. This kind of comparison can be used to reduce the need to code conditional comparisons over a number of notifications into the client, and reduce message traffic.
Batch Mode Registration
You can configure notifications to work in batch mode for state properties that frequently change. State and Notifications Broker allows you to set a period of time for a state property value to stabilize before the State and Notifications Broker sends a change notification. The default time period is 200 milliseconds (ms) and there is no maximum time limit. You can set this time period in the registry. For more information, see RegistryBatchNotification.
Notification Types
The following table shows the notification types.
| Type | Description |
|---|---|
Transient |
Notification requests that are only valid while the client application is running. The request is lost when the device is reset or when the application is closed. |
Persistent |
Notification requests that remain valid after the device is reset or after the application is closed. |
Notification Modes
The following table shows the notification modes.
| Mode | Description |
|---|---|
Application activation |
State and Notifications Broker starts a client application when a notification is sent. If the client is already running, State and Notifications Broker sends a message to the process window. For more information, see RegistryNotifyApp. This mode applies only to persistent notifications. |
Message Queue |
State and Notifications Broker signals a registered client, by using a message queue, that a state property change has occurred. For more information, see RegistryNotifyMsgQueue. This mode applies only to transient notifications. |
Window message |
State and Notifications Broker signals a registered client, by using a window message, that a state property change has occurred. For more information, see RegistryNotifyWindow. This mode applies only to transient notifications. |
Callback |
State and Notifications Broker signals a registered client, by using a callback, that a state property change has occurred. For more information, see RegistryNotifyCallback. This mode applies only to transient notifications. |
See Also
Reference
State and Notifications Broker Reference
Concepts
State and Notifications Broker Usage Model
Using the State and Notifications Broker in Native Code