在 android 中使用 cpp 和 java 时，任务 ':app:externalNativeBuildDebug' 执行失败

Question

我的 android studio 项目在使用 jni

将 c++ 链接到 java 时无法构建并出现此错误

Build command failed.
Error while executing process C:\Users\conno\AppData\Local\Android\Sdk\cmake.10.2.4988404\bin\ninja.exe with arguments {-C D:\Connor\DMA\Pipes\Android\Smart_Pipes\app\.cxx\cmake\debug\arm64-v8a native-lib}
ninja: Entering directory `D:\Connor\DMA\Pipes\Android\Smart_Pipes\app\.cxx\cmake\debug\arm64-v8a'
[1/1] Linking CXX shared library D:\Connor\DMA\Pipes\Android\Smart_Pipes\app\build\intermediates\cmake\debug\obj\arm64-v8a\libnative-lib.so
FAILED: D:/Connor/DMA/Pipes/Android/Smart_Pipes/app/build/intermediates/cmake/debug/obj/arm64-v8a/libnative-lib.so 
cmd.exe /C "cd . && C:\Users\conno\AppData\Local\Android\Sdk\ndk.4.7075529\toolchains\llvm\prebuilt\windows-x86_64\bin\clang++.exe --target=aarch64-none-linux-android21 --gcc-toolchain=C:/Users/conno/AppData/Local/Android/Sdk/ndk/21.4.7075529/toolchains/llvm/prebuilt/windows-x86_64 --sysroot=C:/Users/conno/AppData/Local/Android/Sdk/ndk/21.4.7075529/toolchains/llvm/prebuilt/windows-x86_64/sysroot -fPIC -g -DANDROID -fdata-sections -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -D_FORTIFY_SOURCE=2 -Wformat -Werror=format-security   -O0 -fno-limit-debug-info  -Wl,--exclude-libs,libgcc.a -Wl,--exclude-libs,libgcc_real.a -Wl,--exclude-libs,libatomic.a -static-libstdc++ -Wl,--build-id -Wl,--fatal-warnings -Wl,--no-undefined -Qunused-arguments -shared -Wl,-soname,libnative-lib.so -o D:\Connor\DMA\Pipes\Android\Smart_Pipes\app\build\intermediates\cmake\debug\obj\arm64-v8a\libnative-lib.so CMakeFiles/native-lib.dir/oboe/samples/debug-utils/trace.cpp.o CMakeFiles/native-lib.dir/jni_bridge.cpp.o CMakeFiles/native-lib.dir/AudioEngine.cpp.o CMakeFiles/native-lib.dir/LatencyTuningCallback.cpp.o CMakeFiles/native-lib.dir/SoundGenerator.cpp.o  -llog oboe/liboboe.a -llog -lOpenSLES -latomic -lm && cd ."
CMakeFiles/native-lib.dir/jni_bridge.cpp.o: In function `Java_com_android_smartpipes_PlaybackEngine_native_1setNote':
D:/Connor/DMA/Pipes/Android/Smart_Pipes/app/src/main/cpp/jni_bridge.cpp:189: undefined reference to `SoundGenerator::_Frequency'
D:/Connor/DMA/Pipes/Android/Smart_Pipes/app/src/main/cpp/jni_bridge.cpp:189: undefined reference to `SoundGenerator::_Frequency'
CMakeFiles/native-lib.dir/SoundGenerator.cpp.o: In function `SoundGenerator::tap(bool)':
D:/Connor/DMA/Pipes/Android/Smart_Pipes/app/src/main/cpp/SoundGenerator.cpp:(.text._ZN14SoundGenerator3tapEb+0x58): undefined reference to `SoundGenerator::_Frequency'
D:/Connor/DMA/Pipes/Android/Smart_Pipes/app/src/main/cpp/SoundGenerator.cpp:(.text._ZN14SoundGenerator3tapEb+0x5c): undefined reference to `SoundGenerator::_Frequency'
clang++: error: linker command failed with exit code 1 (use -v to see invocation)
ninja: build stopped: subcommand failed.

jni_bridge.cpp

中的方法

JNIEXPORT void JNICALL
Java_com_android_smartpipes_PlaybackEngine_native_1setNote(JNIEnv *env, jclass clazz, int note) {
    double freqScale[] = {419.98,   //LG
                          480.00,   //LA
                          540.03,   //B
                          599.88,   //C
                          644.42,   //D
                          720.02,   //E
                          802.60,   //F
                          839.96,   //HG
                          960.00    //HA
    };

    SoundGenerator::_Frequency = freqScale[note];
}

我的java代码PlaybackEngine.java

    static void setNote(ENote note){
        switch (note){
            case ELG:
                native_setNote(0);
            case ELA:
                native_setNote(1);
            case EB:
                native_setNote(2);
            case EC:
                native_setNote(3);
            case ED:
                native_setNote(4);
            case EE:
                native_setNote(5);
            case EF:
                native_setNote(6);
            case EHG:
                native_setNote(7);
            case EHA:
                native_setNote(8);
            default:
                native_setNote(8);
        }
    }

    private static native void native_setNote(int note);

SoundGenerator.cpp

void SoundGenerator::tap(bool isOn) {

    for (int i = 0; i < mChannelCount; ++i) {
        mOscillators[i].setFrequency(SoundGenerator::_Frequency);
        mOscillators[i].setWaveOn(isOn);
    }
}

SoundGenerator.h

class SoundGenerator{
   static double _Frequency;
}

我正在尝试将 java 枚举注释作为 int 传递给 cpp，然后将其转换为 c++ 的双精度数。

感谢您的帮助

Answer 1

可能，您需要在.cpp 文件中为静态class-成员SoundGenerator::_Frequency 单独定义实际变量，如下所示。

SoundGenerator.cpp

double SoundGenerator::_Frequency = 440.0; // A

在 android 中使用 cpp 和 java 时，任务 ':app:externalNativeBuildDebug' 执行失败

Execution failed for task ':app:externalNativeBuildDebug' when using cpp and java in android

java

android

c++

java-native-interface