Changes between Version 1 and Version 2 of BuildingForAndroid

Timestamp:

02/08/11 15:45:43 (2 years ago)

Author:

rolker

Comment:

--

BuildingForAndroid

@@ -1 @@
-== Building GDAL using Android NDK on Linux ==
+= Building GDAL using Android NDK on Linux =
 
 ''' Warning! this is still a work in progress! '''
 
 
-This procedure was developed on a Linux system using Android NDK r5b.
+This procedure was developed on a Linux system using Android NDK r5b and is based on
+information from this thread: http://groups.google.com/group/android-ndk/browse_thread/thread/9988752f332eff45
+
+== Cross compiling GDAL ==
 
 First, a standalone toolchain is created to make the configure script easier to use. (See android-ndk-r5b/docs/STANDALONE-TOOLCHAIN.html for more details)
@@ -18 +21 @@
 }}}
 
-From the GDAL source directory, configure for cross compiling and make.
+From the GDAL source directory, configure for cross compiling and make. (This assumes config.guess and config.sub
+where updated. Latest versions can be found here: http://git.savannah.gnu.org/cgit/config.git/tree/)
 
 {{{
-gdal$ CC="arm-linux-androideabi-gcc" CXX="arm-linux-androideabi-g++" \
-CFLAGS="-mthumb" CXXFLAGS="-mthumb" LIBS="-lsupc++ -lstdc++"  ./configure --host=arm-linux-eabi --without-grib
+gdal$ CFLAGS="-mthumb" CXXFLAGS="-mthumb" LIBS="-lsupc++ -lstdc++" \
+      ./configure --host=arm-linux-androideabi --without-grib --prefix=$PROJECT/external/gdal
 gdal$ make
+gdal$ make install
+}}}
+
+The $PROJECT variable contains the path to where you want your Android NDK modules to live.
+
+In $PROJECT/external/gdal, an Android.mk file is created  with the following contents:
+
+{{{
+LOCAL_PATH := $(call my-dir)
+include $(CLEAR_VARS)
+LOCAL_MODULE := gdal
+LOCAL_SRC_FILES := lib/libgdal.a
+LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/include
+LOCAL_EXPORT_LDLIBS := -lz
+include $(PREBUILT_STATIC_LIBRARY)
+}}}
+
+== Using in a JNI library ==
+
+Here's a !HelloGdal app to test the use of the library as part of a JNI component
+of an Android project.
+
+In the project's jni directory, hello-jdal.cpp was create with the following contents:
+
+{{{
+#include <jni.h>
+#include <ogr_api.h>
+#include <sstream>
+
+extern "C" {
+    JNIEXPORT jstring
+    JNICALL Java_org_gdal_HelloGdal_stringFromGDAL(JNIEnv*env, jobject thiz);
+}
+
+JNIEXPORT jstring
+JNICALL Java_org_gdal_HelloGdal_stringFromGDAL(JNIEnv* env, jobject thiz)
+{
+    OGRRegisterAll();
+    std::ostringstream drivers;
+    drivers << "OGR Drivers:\n";
+    for (int i = 0; i < OGRGetDriverCount(); ++i)
+        drivers << "\t" << OGR_Dr_GetName(OGRGetDriver(i)) << "\n";
+
+    return env->NewStringUTF(drivers.str().c_str());
+}
+}}}
+
+(Yes, I know, it's called !HelloGdal, yet it lists the OGR drivers. I'll leave it as
+an exercise to have the GDAL drivers listed) 
+
+Here's the corresponding Android.mk file:
+
+{{{
+LOCAL_PATH := $(call my-dir)
+include $(CLEAR_VARS)
+LOCAL_MODULE := hello-gdal
+LOCAL_SRC_FILES := hello-gdal.cpp
+LOCAL_STATIC_LIBRARIES := gdal
+include $(BUILD_SHARED_LIBRARY)
+$(call import-module,gdal)
+}}}
+
+The path to the external GDAL module is set and the library is built using the NDK's build process.
+
+{{{
+jni$ export NDK_MODULE_PATH=$PROJECT/external
+jni$ $NDK_ROOT/ndk-build
+}}}
+
+Finally, the Java portion that uses the JNI library.
+
+{{{
+package org.gdal;
+
+import android.app.Activity;
+import android.os.Bundle;
+import android.widget.TextView;
+
+
+public class HelloGdal extends Activity {
+        
+        public void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        TextView  tv = new TextView(this);
+        tv.setText( stringFromGDAL() );
+        setContentView(tv);
+    }
+        
+        public native String stringFromGDAL();
+        
+        static {
+        System.loadLibrary("hello-gdal");
+    }
+        
+}
 }}}
 
 == Next steps ==
 
- * check if resulting libs are usable.
  * build and adapt the Java swig bindings to expose GDAL to the Java portion of an Android application.