Android开发笔记: 3.6 Android NDK

3.6 Android NDK

Refer to ndk. Run <sdk_root>/tools/android to update app project file. Then under JNI subfolder run <ndk_root>/ndk-build to build native code. If build directly from Eclipse, use mouse right click Project=>Android Tools=>Add native Support, might see many not resolved error as Eclipse might not use the right include path. Also, Eclipse will auto delete all .so files under libs(jar files is ok) when building NDK code. So if have other prebuilt .so files, don't put them under libs. Either put them somewhere else, or follow this SO to treat as prebuilt. Refer Ndk guide for using prebuilt librarries. Refer to this SO and JNI tip for calling Java from native code. Eclipse ADK might have problem with NDK: it can build, but report Semantic Error with Method/Symbol could not be resolved. Refer to Android NDK build, Method could not be resolved and Eclipse compiles successfully but still gives semantic errors as it might be a bug with Eclipse plugin. For me, restart Eclipse may be ok.

Regarding armeabi/armeabi-v7a, refer to ABIs and application_mk guide. APP_ABI := armeabi armeabi-v7a x86 mips can only be set in Application.mk. By default, add NDK support from Eclipse ADT doesn't create this Application.mk. So if needs to generate other than the default armeabi binary, will need to add a Application.mk with the APP_ABI line. Use TARGET_ARCH_ABI in Android.mk won't do it.

Get Android NDK: WARNING: APP_PLATFORM android-16 is larger than android:minSdkVersion 14 in ./AndroidManifest.xml: Refer to this SO; need to add APP_PLATFORM := android-14 in jni/Application.mk, otherwise the setting is taken from project.properties file, which is the setting of compileSdkVersion.

Below is Android.mk and Application.mk for NagaSoft vjplayer prebuilt libs(armeabi-v7a only):

#Android.mk

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE := vjplayer

LOCAL_SRC_FILES := libvjplayer_jni.so

include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)

LOCAL_MODULE := p2pcore

LOCAL_SRC_FILES := libp2pcore.so

include $(PREBUILT_SHARED_LIBRARY)

#Application.mk

APP_ABI := armeabi-v7a

APP_PLATFORM := android-14

Problem with NDK r13: this NDK toolchain mostly are 4.9, but when I use this NDK to build OpenSSL-Vitamio, it always looks for 4.8 toolchain. The NDK CHANGELOG.MD mentioned `NDK_TOOLCHAIN_VERSION` now defaults to Clang. So I have to do build like:

ndk-build NDK_TOOLCHAIN_VERSION=4.9. Get problem fox x86_64: BN_ULONG redefined. As mentioned in check-all-builds.sh: The $HOST_OS-x86_64 is currently broken because the single <openssl/opensslconf.h> header is tailored for 32-bits. So just build for arm v7a: ndk-build NDK_TOOLCHAIN_VERSION=4.9 APP_ABI=armeabi-v7a