Android原生代码编译

admin 提交于 周五, 05/14/2021 - 08:03

从Android Studio 2.2以后,原生代码更倾向于使用CMake(CMakeLists.txt)来编译,而不是Android.mk(但也一直支持,不过不允许混用)。参考:Android.mk转换成CMakeLists.txt

Android的工程可以在命令行下编译:

工程目录> ./gradlew assembleDebug

CMake的基本用法 

调试基础

默认环境已内置LLDB,可以直接对C++文件进行断点调试。需要先以Debug App模式启动,然后在应用等待调试进程连接的时候,点击Attch Debuger to Android Process.

在Android Studio里打开apk文件,可以看到里面的内容,可以查看某些资源文件是否被正确打包进去了。

a. 编译libsndfile库

源代码:https://github.com/libsndfile/libsndfile(这个交叉编译有错,对mp3lame有依赖,不能用),要用以前官网的稳定版1.0.28:http://www.mega-nerd.com/libsndfile/

a.1 构建toolchain

ndk自带了toolchain:~/Library/Android/sdk/ndk/21.2.6472646/toolchains/arm-linux-androideabi-4.9/prebuilt/darwin-x86_64/bin

NDKr19之前需要自己编译toolchain:

~/code/ndk-21.2.6472646$ build/tools/make-standalone-toolchain.sh --toolchain=arm-linux-androideabi-4.9 --platform=android-30 --install-dir=../ndk-toolchain-21.2.6472646

HOST_OS=darwin

HOST_EXE=

HOST_ARCH=x86_64

HOST_TAG=darwin-x86_64

HOST_NUM_CPUS=4

BUILD_NUM_CPUS=8

Auto-config: --arch=arm

Toolchain installed to ../ndk-toolchain-21.2.6472646.

a.2 编译

libsndfile里有个Android编译说明,但是已经过时不能用了。

 

export NDK=~/Library/Android/sdk/ndk/21.2.6472646

export TOOLCHAIN=$NDK/toolchains/llvm/prebuilt/darwin-x86_64

export TARGET=armv7a-linux-androideabi

 export API=21

export AR=$TOOLCHAIN/bin/llvm-ar

export CC=$TOOLCHAIN/bin/$TARGET$API-clang

export AS=$CC

export CXX=$TOOLCHAIN/bin/$TARGET$API-clang++

export LD=$TOOLCHAIN/bin/ld

 export RANLIB=$TOOLCHAIN/bin/llvm-ranlib

export STRIP=$TOOLCHAIN/bin/llvm-strip

export TOOLCHAIN=$NDK/toolchains/llvm/prebuilt/darwin-x86_64

brew install autogen

./autogen.sh

./configure --prefix=/opt/android --host=$TARGET --enable-static --enable-shared=no --disable-mpeg

make

cp src/.libs/libsndfile.a libs/armeabi-v7a/

不同芯片架构交叉编译参数映射如下:

  • armeabi-v7a => export TARGET=armv7a-linux-androideabi
  • arm64-v8a => export TARGET=aarch64-linux-android
  • x86 => export TARGET=i686-linux-android
  • x86_64 => export TARGET=x86_64-linux-android

参考:

将 NDK 与其他构建系统配合使用

HOWTO Cross compiling on Android

b. Android文件权限问题(这个问题浪费了我半天时间!)

Google has a new feature on Android Q: filtered view for external storage. A quick fix for that is to add this code in the AndroidManifest.xml file:

<manifest ... >
    <!-- This attribute is "false" by default on apps targeting Android Q. -->
    <application android:requestLegacyExternalStorage="true" ... >
     ...
    </application>
</manifest>

You can read more about it here: https://developer.android.com/training/data-storage/compatibility

参考:https://stackoverflow.com/questions/8854359/exception-open-failed-eacces-permission-denied-on-android

c. JNI编程

教程

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