11 Using Lifecycle Listeners in MAF Applications

This chapter describes the lifecycle listeners that MAF provides for you to write code that can execute in response to events in your MAF application or application features.

This chapter includes the following sections:

11.1 Introduction to Lifecycle Listeners in MAF Applications

Lifecycle listeners are useful locations to write code that executes in response to specific events in your application. MAF provides lifecycle listeners where you can write code in response to application or application feature events. A typical implementation of an application lifecycle listener method may be to write code that initializes your application's database when the application starts, as described in Using the Local SQLite Database, or to update a security configuration from URL parameters, as described in How to Update Connection Attributes of a Named Connection at Runtime.

MAF provides the following two interfaces that you can implement to communicate with event notifications:

oracle.adfmf.application.LifeCycleListener

This interface specifies the following methods that an application lifecycle listener must implement:
- activate()
- deactivate()
- start()
- stop()
oracle.adfmf.feature.LifeCycleListener

This interface specifies the following methods that a feature lifecycle listener must implement:
- activate()
- deactivate()

You create a lifecycle listener by creating a Java class that implements the appropriate interface and registering the implementation in your MAF application, as described in Registering a Lifecycle Listener for a MAF Application or an Application Feature.

A new MAF application that you create implements the oracle.adfmf.application.LifeCycleListener interface through the default creation of the application.LifeCycleListenerImpl.java class in your application's ApplicationController project, as shown in Figure 11-1.

Figure 11-1 Implementation of Application Lifecycle Listener

The surrounding text describes this image.

Note that the application lifecycle listener is executed with an anonymous user (that is, there is no user associated with any of its methods and no secure web service is called).

Table 11-1 describes the specific times that MAF invokes application lifecycle methods during an application's startup, shutdown, and hibernation.

Table 11-1 Timing of MAF's Invocation of Application Lifecycle Methods

Method	Timing	When Called	Usage
`start`	Called after the MAF application has completely loaded the application features and immediately before presenting the user with the initial application feature or the springboard. This is a blocking call.	When the application process starts.	Uses include: Determining if there are updates to the MAF application. Requesting a remote server to download data to the local database.
`stop`	Called as the MAF application begins its shutdown.	When the application process terminates.	Uses include: Logging off from any remote services. Uploading any data change to the server before the application is closed.
`activate`	Called as the MAF application activates from being situated in the background (hibernating). This is a blocking call.	After the `start` method is called.	Uses include: Reading and re-populating cache stores. Processing web service requests. Obtaining required resources.
`deactivate`	Called as the MAF application deactivates and moves into the background (hibernating). This is a blocking call.	Before the `stop` method is called.	Uses include: Writing the restorable state. Closing the database cursor and the database connection.

Table 11-2 describes the specific times that MAF invokes feature lifecycle methods during a feature's activation and deactivation.

Table 11-2 Timing of MAF's Invocation of Feature Lifecycle Methods

Method Timing When Called Usage

Method	Timing	When Called	Usage
`activate`	Called before the current application feature is activated.	Called when a user selects the application feature for the first time after launching a MAF application, or when the application has been re-selected (that is, brought back to the foreground).	Uses include: Reading the `applicationScope` variable. Setting the current row on the first MAF AMX view.
`deactivate`	Called before the next application feature is activated, or before the application feature exits.	Called when the user selects another application feature.	You can, for example, use the `deactivate` event to write the `applicationScope` variable, or any other state information, for the next application feature to consume.

activate

Called before the current application feature is activated.

Called when a user selects the application feature for the first time after launching a MAF application, or when the application has been re-selected (that is, brought back to the foreground).

Uses include:

Reading the applicationScope variable.
Setting the current row on the first MAF AMX view.

deactivate

Called before the next application feature is activated, or before the application feature exits.

Called when the user selects another application feature.

You can, for example, use the deactivate event to write the applicationScope variable, or any other state information, for the next application feature to consume.

For more information about the oracle.adfmf.application.LifeCycleListener and oracle.adfmf.feature.LifeCycleListener interfaces, see the Java API Reference for Oracle Mobile Application Framework.

The LifecycleEvents sample application demonstrates declaring listener classes that implement both the application and feature interfaces. It registers these listener classes in the MAF application's maf-application.xml and maf-feature.xml files. For more information about this and other sample applications, see MAF Sample Applications.

11.2 Registering a Lifecycle Listener for a MAF Application or an Application Feature

You register an application lifecycle listener using the overview editor for the maf-application.xml file and a feature lifecycle listener using the overview editor for the maf-features.xml file.

To register an application lifecycle listener:

In the Applications window, expand the Application Resources panel.
In the Application Resources panel, expand Descriptors and then ADF META-INF.
Double-click maf-application.xml.
In the Application navigation tab, specify the Java class that implements the oracle.adfmf.application.LifeCycleListener interface in the Lifecycle Event Listener field. By default, this is set to application.LifeCycleListenerImpl.

A scenario where you might use a custom class different to the default implementation provided by MAF is if you want to package the application lifecycle listener in a JAR library that will be distributed for use elsewhere.

To register an application feature lifecycle listener:

In the Applications window, expand the ViewController project and then Application Sources and META-INF.
Double-click the maf-feature.xml file.
Select the feature in the Features list for which you want to register a feature lifecycle listener.
In the Lifecycle Event Listener field, specify the Java class that implements the oracle.adfmf.feature.LifeCycleListener interface.

11.3 What Happens When You Register a Lifecycle Listener

By default, a MAF application that you create implements an application lifecycle listener through the creation of the application.LifeCycleListenerImpl.java class in your application's ApplicationController project. The listener-class attribute in the maf-application.xml file registers this class, as shown in the following example.

<adfmf:application xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"                    xmlns:adfmf="http://xmlns.oracle.com/adf/mf"
                   version="1.0" name="NewMAFapp" id="com.company.NewMAFapp"
    appControllerFolder="ApplicationController" listener-class="application.LifeCycleListenerImpl">
...
</adfmf:application>

JDeveloper writes an entry to the maf-feature.xml file for the listener-class attribute when you register a feature lifecycle listener. The following example shows an entry in the LifecycleEvents sample application described in MAF Sample Applications.

<?xml version="1.0" encoding="UTF-8" ?>
<adfmf:features xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:adfmf="http://xmlns.oracle.com/adf/mf">
  <adfmf:feature id="Feature1" name="Feature1" listener-class="mobile.Feature1Handler">
    <adfmf:description>This is a sample feature to show the feature lifecycle handlers.
    </adfmf:description>
    <adfmf:content id="Feature1.1">
      <adfmf:amx file="Feature1/feature1.amx"/>
    </adfmf:content>
  </adfmf:feature>
...
</adfmf:features>