我想在我的Android项目中使用用C编写的exiv2库.为此,我尝试使用Android NDK交叉编译库.
对于交叉编译,我遵循以下步骤：
>将ndk路径添加到变量PATH
$PATH="/home/patrycja/android-packages/ndk:${PATH}"
$export PATH
>安装标准工具链,以便为Android交叉编译C/C++.
./make-standalone-toolchain.sh --platform=android-21 --install-dir=/tmp/my-android-toolchain --ndk-dir='/home/patrycja/android-packages/ndk/' --toolchain=arm-linux-androideabi-4.9 --system=linux-x86_64
Copying prebuilt binaries...
Copying sysroot headers and libraries...
Copying c++ runtime headers and libraries...
Copying files to: /tmp/my-android-toolchain
Cleaning up...
Done.
>设置一些环境变量,以便配置和构建过程将使用正确的编译器.
$export PATH=/tmp/my-android-toolchain/bin:$PATH
$export CC="arm-linux-androideabi-gcc"
$export CXX="arm-linux-androideabi-g++"
$export CFLAGS='-mthumb -O2'
$export CXXFLAGS='-mthumb -O2'
$export LDFLAGS='-Wl,--fix-cortex-a8'
$export LIBS='-lstdc++ -lsupc++'
> Bulid静态库和足够的标头
./configure --prefix=$(pwd)/build --host=arm-linux-androideabi --disable-shared --disable-xmp --disable-nls
结果我创建了’build’类别文件：
├── bin
│ └── exiv2
├── include
│ └── exiv2
│ ├── *.hpp
│
├── lib
│ ├── libexiv2.a
│ ├── libexiv2.la
│ └── pkgconfig
│ └── exiv2.pc
└── share
└── man
└── man1
└── exiv2.1
我在appName / src / main / jni / prebuild中复制了创建的静态库libexiv2.a并将文件夹包含到我的Android项目中.
Android.mk看起来像：
LOCAL_PATH := $(call my-dir)
#static library info
LOCAL_MODULE := exiv2
LOCAL_SRC_FILES := ../prebuild/libexiv2.a
LOCAL_EXPORT_C_INCLUDES := ../prebuild/include/
LOCAL_EXPORT_LDLIBS := -lz
include $(PREBUILT_STATIC_LIBRARY)
#wrapper info
include $(CLEAR_VARS)
LOCAL_C_INCLUDES += $(LOCAL_PATH)/../prebuild/include/
LOCAL_MODULE := helloJNI
LOCAL_SRC_FILES := helloJNI.cpp
LOCAL_STATIC_LIBRARIES := exiv2
include $(BUILD_SHARED_LIBRARY)
在Android的包装器中,我尝试使用该库.它看起来如下：
#include 但是ndk-build输出它无法找到它.
[arm64-v8a] Compile++ : helloJNI <= helloJNI.cpp
[arm64-v8a] SharedLibrary : libhelloJNI.so
jni/../prebuild/libexiv2.a: error adding symbols: File in wrong format
collect2: error: ld returned 1 exit status
make: *** [obj/local/arm64-v8a/libhelloJNI.so] Error 1
我相信交叉编译中的标志有问题.我尝试了几种选择,但仍有问题.
我遵循了这些说明：https://groups.google.com/forum/#!topic/android-ndk/mYh1LzMu_0U
不使用ndk-build进行交叉编译很难在Android上正确使用,特别是因为你不仅应该支持armv5,而且还应该支持armv7,x86,x86_64,arm64-v8a ……
您应该首先将–platform选项设置为与最低SDK级别相同的级别.然后重建您的lib并将其放在../prebuild/armeabi下.
然后交叉编译你的lib也用于x86架构：
./make-standalone-toolchain.sh --platform=android-9 --install-dir=/tmp/my-android-toolchain-x86 --ndk-dir='/home/patrycja/android-packages/ndk/' --arch=x86 --toolchain=x86-4.8 --system=linux-x86_64
$export PATH=/tmp/my-android-toolchain-x86/bin:$PATH
$export CC="i686-linux-android-gcc"
$export CXX="i686-linux-android-g++"
$export CFLAGS='-O2 -mtune=atom -mssse3 -mfpmath=sse'
$export CXXFLAGS='-O2 -mtune=atom -mssse3 -mfpmath=sse'
$export LDFLAGS=''
$export LIBS='-lstdc++ -lsupc++'
./configure --prefix=$(pwd)/build-x86 --host=x86 --disable-shared --disable-xmp --disable-nls
并将创建的.a移动到../prebuild/x86.
理想情况下,您应该对armeabi-v7a,mips,mips64,arm64-v8a重复相同的过程.
最后,您可以使用TARGET_ARCH_ABI变量在Android.mk中包含正确的.a,如下所示：
LOCAL_PATH := $(call my-dir)
#static library info
LOCAL_MODULE := exiv2
LOCAL_SRC_FILES := ../prebuild/$(TARGET_ARCH_ABI)/libexiv2.a
LOCAL_EXPORT_C_INCLUDES := ../prebuild/include/
LOCAL_EXPORT_LDLIBS := -lz
include $(PREBUILT_STATIC_LIBRARY)
#wrapper info
include $(CLEAR_VARS)
LOCAL_C_INCLUDES += $(LOCAL_PATH)/../prebuild/include/
LOCAL_MODULE := helloJNI
LOCAL_SRC_FILES := helloJNI.cpp
LOCAL_STATIC_LIBRARIES := exiv2
include $(BUILD_SHARED_LIBRARY)
在Application.mk(创建一个新文件,如果它不存在)中,指定您支持的体系结构和您要定位的最小平台：
APP_ABI := armeabi x86 # ideally,this should be set to "all"
APP_PLATFORM := android-14 # should the same as -platform and your minSdkVersion.
