The App Inventor Java Bridge

[Fiifi Baidoo]

If you are a newbie with Android development and want something to start quickly then App Inventor would be a great start. This is like the Designer view of Dreamweaver whiles the SDK is like the Code view. You can start with App inventor whiles you switch your code to the SDK using the Java Bridge. Enjoy the Java Bridge from the App inventor team below:

The App Inventor Java Bridge

The App Inventor Java Bridge helps make a transition from developing Android applications with App Inventor for Android, to developing with Java and the Android SDK.  It lets you incorporate App Inventor components into apps that you create in Java with the standard Android SDK tools.  If you’ve been using App Inventor and know some Java, then the Java Bridge is a good way to get started with the SDK, because building with App Inventor components hides many of the complexities of the Android framework.   As you gain experience, you can switch over to regular SDK development and create apps that harness the full power of Android.

For entry-level computing courses that use App Inventor, introducing the Bridge in conjunction with a first look at Java, can give students a preview of more advanced material.  The Bridge can also be valuable in advanced courses, where students are already experienced with programming:  Begin with App Inventor to illustrate the basic ideas of mobile app development, and let students start building apps right away.   Then introduce the Bridge and have students build apps in Java with the App Inventor components.  Later, ease in to the details of the Android framework and advanced topics in mobile development.

The Bridge consists of three parts:

1. A sample project, BridgeToJava, that implements a tiny app using a few components.   The comments in the source code for BridgeSample.java provide rudimentary documentation for coding using the Bridge.
2. A compiled jar file, libSimpleAndroidRuntime.jar, which contains all the App Inventor component classes.   Include this as a library with your Java projects in order to use the components.
3. The source code for all the App Inventor components.  You don’t need this to build apps with the Bridge, but you can consult it as a reference to see how to call the component classes from Java code.  And you can also use the code as a model for building your own components.

Using the Bridge

To use the Bridge, you’ll need to install the Android SDK, set up a development environment and verify that you can build and run Android projects.  You can do this by going through the Hello World setup process and tutorial example on the Android Developer site.

To get started with the Bridge, download the sample project from the App-Inventor-for-Android project at code.google.com.   You can download the project source code with svn (subversion):  Connect to a directory where you typically keep Java projects and issue the command:

svn co http://app-inventor-for-android.googlecode.com/svn/trunk/samples/BridgeToJava

This should create a BridgeToJava folder on your computer, with all the files required to build the app.

To build the BridgeToJava sample project using Eclipse, use the New / Android Project, select “Create project from existing source” and enter the location of the BridgeToJava directory.  Verify that you can build run the BridgeSample  project.  

To build the BridgeToJava sample at a command line using Ant, first cd to the BridgeToJava directory.  Then run

android update project -p .

where android is a command found in the tools directory of your install Android sdk.  Then you should be able to run:

ant debug

or “ant release”, if your prefer.

Notice that the project folder has a libs/ subfolder that contains the libSimpleAndroidRuntime.jar library. If you create your own project that uses the Bridge you’ll want to create a similar libs directory and put libSimpleAndroidRuntime.jar in there. You should always be able to get the latest version of in http://code.google.com/p/app-inventor-for-android/source/browse/trunk/jars/

For documentation, see the BridgeSample.java source file.   Try changing the code to build some variants of the app.  To see how to use other App Inventor components, see the java source code the components, which is in the App-Inventor-for-Android project at http://code.google.com/p/app-inventor-for-android/source/browse/trunk/src/components.

Fiifi Baidoo
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