This article describes an add-on for Spring Roo that can be used to accelerate development of Android applications. The add-on extends the Roo shell with an apk Maven module packaing type and commands for common tasks including:

• Creating activities and fragments,
• Creating layouts and adding views to them,
• Adding resources, system services and permissions and
• Binding views, resources and system services to fields.

The add-on provides annotations that are used by Roo to generate AspectJ Inter-Type Declarations (ITDs). These separate the concern of initialising views, resources, services etc. from adding functionality to an application. The technique resembles that used in the AndroidAnnotations project. The Roo annotations can be removed and the ITD code pushed into the standard .java files if preferred.

The add-on is provided as two JARs. They are standard OSGI bundles and can be dropped into the bundle sub-directory of a Roo installation.

The ànnotations JAR does not have any dependencies upon the Spring Framework. It can be added as a dependency to an existing Android project to provide the annotations used by Roo.

An Android project can be created using the normal project command with apk packaging specified:

    roo> project --topLevelPackage org.roodroid --projectName roodroid --packaging APK

Alternatively, the add-on provides a configuration of the tailor add-on. If activated apk packaging is used by default.

    roo> tailor activate --name android
    roo> project --topLevelPackage org.roodroid --projectName roodroid

Additionally, when the tailor configuration is activated the commands provided by the add-on need not begin with android.

The activity command creates a new sub-class of Activity and adds an <activity/> element to the AndroidManifest.xml file.

    roo> activity --class ~.MainActivity --launcher --layout main --fullscreen

If specified, the launcher option designates the activity as being the main entry point to the app's user interface. The layout option can be used to specify the name of a layout resource. If the resource does not exist a simple layout will be created. Roo will generate an ITD implementing the onCreate method and pass the id of the resource to setContentView. The noTitle option makes requesting a window feature with no title convenient. Similarly, the fullscreen option sets flags that configure the window to use the entire screen.

    roo> fragment --class ~.MyFragment --layout fragment_layout --support

The fragment command creates a new sub-class of Fragment. The support option makes Roo use the Fragment class from the Android Support Library and adds a dependency to the Maven POM if necessary. The layout option can specify a layout resource to be bound to a contentView field in the generated onCreateView method.

The view command creates a View and binds it to a field on the specified type. If the type has a layout the view will be added to it. The view option can be either the fully-qualified type name or the simple name, where the package is assumed to be android.widget.

    roo> view --type ~.MainActivity --fieldName textView --view TextView

The resource command can be used to add resources and bind them to field values.

    roo> resource string --fieldName message --value "foo bar"

The service command binds a system service the a field on the given type.

    roo> system service --name LAYOUT_INFLATER --fieldName inflater

    roo> permission --name FLASHLIGHT

In the keynote speech at Google I/O 2010 SpringSource's Ben Alex presented Spring Roo its new Google WebToolkit (GWT) add-on. This article describes a fork of the GWT add-on that provides Android client side scaffolding that also uses the RequestFactory protocol. The templates for the GWT client side scaffolding have been modified to use GWT Bootstrap and mgwt.

The add-on provides a configuration for Roo's tailor add-on. This customizes the shell for use with projects created using the add-on.

    roo> tailor activate --name requestfactory

With the tailor configuration activated the project command will create a multi-module Maven project with the structure:

• client
  • android
  • gwt
• shared
• server

The shared module has no runtime dependencies upon the server or the client module. The server module will be focused for all JPA and MongoDB commands. The shared module is focussed for all enum commands. All commands beginning web requestfactory no longer require that prefix when the requestfactory tailoring is active.

Active Record-style entities may be used with JPA. Service and repository layers are required for Mongo and may also be used with JPA. An entity can be identified for use with the RequestFactory add-on using the scaffold entity command. The primary and secondary options can be used to indicate the fields that best describe the entity (this metadata may be used when generating user interfaces).

    roo> scaffold entity

Since Roo can not remove of modify fields directly once they have been added to an entity the tailored add-on effectively overrides the field commands to provide these options:

• exclude - field is to be excluded from the proxy
• readOnly - field is to be read only in the proxy
• invisible - field is not to be included in views of the proxy
• uneditable - field is not to be included when editing the proxy
• helpText - a short string describing the field (used in tooltips etc.)

The field string command is extended to provide password and textArea options that add an annotation that can influrnce the type of widget used on the client-side.

    roo> field string --fieldName password --password --invisible

The reference command has an unowned option that marks the field with the Unowned annotation from Google AppEngine (GAE) to support unowned one-to-one and many-to-one relationships. The add-on also provides a field list command that closely resembles the existing field set command and provides support for owned one-to-many relationships when using GAE.

Some classes are required by both the client module and the server module and some classes are used by multiple client-side implementations. As in the GWT add-on, RequestFactory Proxy and Request classes can be generated for each of the entities.

    roo> proxy request all

The application scaffold that may be shared between the clients can be generated using this command:

    roo> scaffold all

Until ROO-2988 is resolved a dependency on the server module will have to be removed from the shared module to ensure decoupling.

    roo> dependency remove --groupId com.example.drooid.server --artifactId drooid-server --version 0.1.0.BUILD-SNAPSHOT

To generate scaffolding for a GWT client application use the command:

    roo> gwt scaffold all

To generate scaffolding for an Android client application use the command:

    roo> android scaffold all