Use the android* x86 NDK for eclipse* and porting the NDK Demo sample application

Goal

The Android plugin for Eclipse (ADT) now supports NDK-based application development.

It can proactively generate project and artifact files, as well as code stubs, and can be integrated into the entire Android application development (building native libraries, copying libraries to the corresponding JNI directory within the project, packaging the app, and generating a finally APK with NDK code). This article will discuss how to configure Eclipse to take advantage of this feature. and demonstrate examples of porting NDK applications.

Configuring the Eclipse ADT plugin to work with the NDK

You must first configure the Eclipse ADT plugin to point to the location of the NDK installation path. To use this new feature. Be sure to update the ADT plugin in Eclipse to get the latest changes and download the latest NDK from the following sites:

Http://developer.android.com/tools/sdk/ndk/index.html

In Eclipse, open the Preferences->android->ndk form. For example, the following see the input NDK installation path (here we assume you have downloaded the NDK to C:\SW\ANDROID-NDK on Windows *), click Apply, and then click OK.

Figure 1:eclipse NDK configuration in the Android ADT plugin

We should now enable and activate the NDK-related features in Eclipse ADT. Let's open one of the NDK JNI demo samples and build them.

Open the Hello-jni Demo sample NDK app in Eclipse. and add NDK build support to the project

To build an NDK JNI native demo sample in Eclipse, we need to let Eclipse ADT know that the demo sample uses native/NDK code.

Let's first import the Hellojni demo sample into Eclipse.

Open Android project from existing code, new, project, files, file, in Eclipse.

In the next screen, enter the path to the Hello-jni Demo sample project (available in the NDK installation directory). and select the "Copy to Workspace" check box. Then click "Finish".

Use the Hellojni path from your NDK installation directory to replace the root directory path.

Figure 2: Importing the Demo sample Hellojni project into Eclipse

Because the x86 Android NDK supports gingerbread* and a higher Android platform. We want to make sure to update the minimum and target SDK configurations in the application descriptive narrative file. In Eclipse, open the Hellojni Demo sample under Androidmanifest.xml. Click Use SDK in the Androidmanifest editor and check to see if the minimum SDK is set to ten (API 10).

Descriptive narrative file editor in Figure 3:eclipse

We are now ready to join NDK build support for this project in Eclipse.

In Eclipse. Right-click Hello-jni Project (COM.EXAMPLE.HELLOJNI.HELLOJNI), Android tools, ADD Native support, complete.

Figure 4: Adding NDK support to projects in Eclipse

This will update the project configuration with the settings related to the NDK widget.

As we build the project again. It will compile and build the NDK code first and copy the built library to the corresponding project directory. Then continue with the regular APK build process.

Build and execute apps in the simulator

Continue building apps today. and execute it in the Android emulator.

We assume that the gingerbread x86 AVD has been executed on the HAXM-based Android emulator.

In Eclipse, right-click the Hello-jni Project (Com.example.hellojni.HelloJni), execute AS-a Android app. Eclipse should proactively rebuild the project itself and try to deploy/execute the APK on the emulator.

However, when the emulator executes, we see the following error message. This is because the default NDK project settings do not support x86.

Figure 5: Performing a demo sample application in the simulator

In Eclipse, you can see Logcat display error "Unable to load Hello-jni"

Figure 6:logcat shows that the native library could not be loaded

By default, the NDK build does not build itself for the x86 ABI itself. We will need to create the artifact file "Application.mk" to understand the designation of our build target, or to pass the command line parameters to the NDK build command.

Porting apps to use the x86 ABI and NDK build files

We can change the project to support the x86 ABI.

In Eclipse, right-click the JNI directory in the HELLO-JNI project and select New, file, enter APPLICATION.MK as the file name, and then click Finish.

Figure 7: Adding the new NDK build file "Application.mk" to the Demo sample project

Edit the file "Application.mk", such as the following to see the join line "App_abi: = All". Then save the file.

Figure 8: Edit the Application.mk file to target the "all" schema

Build the app to verify that it builds the x86 library. and test the application in the x86 simulator

Currently, when we build the app again, it will be built for all the supported ABI in the NDK. Right-click "Hello-jni" in the Android app, Eclipse---. Eclipse will itself invoke the NDK build itself and generate all the native libraries.

You can verify it in the library directory, for example, as seen below.

Figure 9:eclipse Project Explorer shows the generated native library

Eclipse will deploy the app in the emulator. At this point we should see the app execute successfully, as seen in the screenshot:

Figure 10: Demo sample app successfully executed within the x86 Android emulator

We hope this article will help you understand how to configure Eclipse ADT to use it in NDK code development. And how to use the NDK build file "Application.mk" to build the desired target ABI.

Related articles and resources:

• Intel Hardware Acceleration Run Manager (Intel? HAXM)
• Intel? Graphics Performance Analyzer 2014 (Intel? GPA)

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Use the android* x86 NDK for eclipse* and porting the NDK Demo sample application