This document provides instructions for Windows developers to get started with native Android development. It outlines how to install Eclipse, the Android SDK, USB drivers, the NDK, and Cygwin. It then walks through running a sample native application in Eclipse. The code is reviewed, explaining the Java code calls the native C code, and the Android.mk and Application.mk files configure the native application build. Contact information is provided for additional Android programming help.

1. Native Android
for
Windows Developers
Yossi Cohen

2. INSTALLATIONS
Install Eclipse + CDT
Install SDK
Install ADT
Install USB Driver
Install NDK
Install Cygwin ….

3. Eclipse Installation
• Download & Install Eclipse
▫ Select the classic version from
http://www.eclipse.org/downloads/
▫ CDT for C/C++ development is recommended
 Select “Install New Software” from Eclipse’ Help menu
 Select available software sites
 Check CDT
 Install CDT components

4. SDK Installation
• Download & Install SDK (select windows option)
▫ http://developer.android.com/sdk/index.html
• Install the ADT (Android Developer Tools) for Eclipse
▫ Instructions:
▫ http://developer.android.com/sdk/eclipse-adt.html#installing
▫ Press Add in available software menu
▫ Add ADT with the link below
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5. USB Driver / NDK Installations
• Install USB Driver
▫ If you don’t have a nexus phone download driver
from vendor. Instructions:
http://developer.android.com/sdk/oem-usb.html#InstallingDriver
• Install NDK
▫ http://developer.android.com/sdk/ndk/index.html
• Preferably do all Installations in D:Android
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6. Cygwin Installation
• Goo to http://cygwin.com/ and download setup
• Install Cygwin.
• Select default install options
• After installation, add the following Dirs to
Cygwin Path:
▫ C:Androidandroid-sdktools
▫ C:Androidandroid-ndk-r7buildtools
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7. THE FIRST NDK SAMPLE

8. Running a native sample app
• In Eclipse, Select:
▫ File->New->Project->Android
Project
• Select “Create Project From
Existing Source”
• change the directory to the
Installed NDK samples:
• D:Androidandroid-ndk-
r7samplesHello-Jni
• Select target and finish

9. Compile & Run
• Compile the Java application
• Run it on your phone target
• Crash?
• Open Cygwin window
• Compile the native code in:
D:Androidandroid-ndk-r7samplesHello-Jni
JNI using ndk-build command
• Compile the Java application
• Run it on your target
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10. CODE REVIEW
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11. Java Code Review
• Java part of the application is simple:
• On create, the application prints to the screen a
string it receives from stringFromJNI() declared
as a Native function
• Native library hello-jni is loaded
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12. Java to C calling convention
/* sample method where the Java call passed no parameters */
void Java_ClassName_MethodName (JNIEnv *env, jobject obj)
{/* do something */ }
/* another sample method with two parameters passed, returning
a double */
jdouble Java_ClassName_MethodName ( JNIEnv* env, jobject obj,
jdouble x, jdouble y)
{ return x + y; }
• Note: Android Java identifies the native functions according to their
C type signature. If the call is for CPP functions, the Java program
will not recognize them. The solution to this problem is to use
extern “C” { } around the CPP functions

13. Make Files
• Android native applications must could have two
make files:
▫ Android.mk – details the source header and
libraries used to create the application (library)
▫ Application.mk – details the target platform,
processor (ARM 7) and API level (API 10). The
application.mk file is not mandatory

14. Android.mk Sample
Example, the HelloJNI NDK sample make File
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := hello-jni
LOCAL_SRC_FILES := hello-jni.c
include $(BUILD_SHARED_LIBRARY)

15. Android.mk Review
• LOCAL_PATH := $(call my-dir)
▫ first understand where we are since include paths
are usually RELATIVE to our current location.
This must be the first command in the mk file
• CLEAR_VARS - clears special GNU Makefile
LOCAL_XXX variables like LOCAL_SRC_FILES
• LOCAL_MODULE := hello-jni
The LOCAL_MODULE variable must be defined
to identify each module you describe in your
Android.mk. The name must be *unique*
without spaces.

16. Application.mk Review
• The hello-jni sample does not include
application.mk file.
• Application.mk can define the target platform as
9 (Android 2.2) APP_PLATFORM := android-9
• Application file can also define the processor
version:
# Build both ARMv5TE and ARMv7-A machine code.
APP_ABI := armeabi armeabi-v7a

17. Refrences
• Review of Android Make file
• Native android development
• Cygwin Install for Android

18. DSP-IP Contact information
For courses & programming services contact
Yossi Cohen
yossi@dsp-ip.com
+972-545-313092