java - 如何使用从一个 Android 应用程序生成的 .so 文件,并在另一个应用程序中使用它?
问题描述
我是 NDK 开发的新手,我创建了支持 C++ 的项目。但是我刚刚添加了 1 个 cpp 类并生成了 .SO 文件。并尝试在另一个项目中访问该 so 文件。我参考了许多stackoverflow 链接、博客和 Google 开发者网站。但无法解决它。这是我的代码。
本地属性
ndk.dir=/home/android/Android/Sdk/ndk/20.1.5948944
sdk.dir=/home/android/Android/Sdk
src/main/cpp/CMakeLists.txt
# For more information about using CMake with Android Studio, read the
# documentation: https://d.android.com/studio/projects/add-native-code.html
# Sets the minimum version of CMake required to build the native library.
cmake_minimum_required(VERSION 3.4.1)
# Creates and names a library, sets it as either STATIC
# or SHARED, and provides the relative paths to its source code.
# You can define multiple libraries, and CMake builds them for you.
# Gradle automatically packages shared libraries with your APK.
add_library( # Sets the name of the library.
hello_world_lib
# Sets the library as a shared library.
SHARED
# Provides a relative path to your source file(s).
hello_world_lib.cpp
HelloWorld.cpp
)
# Searches for a specified prebuilt library and stores the path as a
# variable. Because CMake includes system libraries in the search path by
# default, you only need to specify the name of the public NDK library
# you want to add. CMake verifies that the library exists before
# completing its build.
find_library( # Sets the name of the path variable.
log-lib
# Specifies the name of the NDK library that
# you want CMake to locate.
log)
# Specifies libraries CMake should link to your target library. You
# can link multiple libraries, such as libraries you define in this
# build script, prebuilt third-party libraries, or system libraries.
target_link_libraries( # Specifies the target library.
hello_world_lib
# Links the target library to the log library
# included in the NDK.
${log-lib})
src/main/cpp/hello_world_lib.cpp
#include <jni.h>
#include <string>
#include <bitset>
#include "HelloWorld.h"
extern "C" JNIEXPORT jstring JNICALL
Java_com_dc_testapplication_MainActivity_stringFromJNI(
JNIEnv *env,
jobject /* this */) {
std::string hello = "Hello from C++";
return env->NewStringUTF(hello.c_str());
}
extern "C" JNIEXPORT jint JNICALL
Java_com_dc_testapplication_MainActivity_getSumOfValues(JNIEnv *env,
jobject,jint a ,jint b,jstring sign){
// working Solution
const char *nativeString = env->GetStringUTFChars(sign, 0);
HelloWorld helloWorld;
helloWorld.setValues((int)a,(int)b);
helloWorld.setOperationType(*nativeString);
jint mData = (jint)helloWorld.getSumOf2Values();
return mData;
}
在构建/运行应用程序后,我从这里得到了这些文件。app/build/intermediates/cmake/debug/obj/{abis}/{nameoflib}.so
现在我需要在另一个项目中访问这些 .so 文件。它的包名是com.dc.usendklib。现在这是我的新项目代码。
app/libs/{abi 文件夹名称}/.so 文件。src/main/jniLibs/{abi 文件夹名称}/.so
src/main/jniLibs/Android.mk
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := hello_world_lib-prebuilt
LOCAL_SRC_FILES := $(TARGET_ARCH_ABI)/libhello_world_lib.so
LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/include
include $(PREBUILT_SHARED_LIBRARY)
src/main/jniLibs/Application.mk
APP_ABI := armeabi-v7a arm64-v8a x86
应用程序的gradle
apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply plugin: 'kotlin-android-extensions'
android {
compileSdkVersion 29
buildToolsVersion "29.0.2"
sourceSets.main {
jniLibs.srcDir 'src/main/jniLibs' //set .so files location to libs
jni.srcDirs = [] //disable automatic ndk-build call
}
defaultConfig {
applicationId "com.dc.usendklib"
minSdkVersion 21
targetSdkVersion 29
versionCode 1
versionName "1.0"
testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
ndk {
moduleName "hello_world_lib"
}
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
}
}
// sourceSets {
// main {
// // let gradle pack the shared library into apk
// jniLibs.srcDirs = ['src/main/jniLibs','src/main/CPP']
// }
// }
// sourceSets.main {
// jniLibs.srcDir 'src/main/jniLibs'
// }
// externalNativeBuild {
// cmake {
// path "src/main/cpp/CMakeLists.txt"
// version "3.10.2"
// }
// }
}
dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation"org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
implementation 'androidx.appcompat:appcompat:1.1.0'
implementation 'androidx.core:core-ktx:1.1.0'
implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
testImplementation 'junit:junit:4.12'
androidTestImplementation 'androidx.test.ext:junit:1.1.1'
androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
}
当我运行它时,我收到了这个错误。
2020-01-03 11:44:54.946 17235-17235/com.dc.usendklib E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.dc.usendklib, PID: 17235
java.lang.UnsatisfiedLinkError: No implementation found for java.lang.String com.dc.usendklib.MainActivity.stringFromJNI() (tried Java_com_dc_usendklib_MainActivity_stringFromJNI and Java_com_dc_usendklib_MainActivity_stringFromJNI__)
at com.dc.usendklib.MainActivity.stringFromJNI(Native Method)
at com.dc.usendklib.MainActivity.onCreate(MainActivity.kt:14)
at android.app.Activity.performCreate(Activity.java:7136)
at android.app.Activity.performCreate(Activity.java:7127)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2893)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6669)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
MainActivity.kt
package com.dc.usendklib
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import kotlinx.android.synthetic.main.activity_main.*
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
// Example of a call to a native method
sample_text.text = stringFromJNI()
}
/**
* A native method that is implemented by the 'native-lib' native library,
* which is packaged with this application.
*/
external fun stringFromJNI(): String
companion object {
// Used to load the 'native-lib' library on application startup.
init {
System.loadLibrary("hello_world_lib")
}
}
}
现在我的问题是,
我生成和选择 .so 文件的方式是正确的方式吗?
JNI 类方法使用 Java_{package}_method,所以在生成 .so 之后,是否可以在另一个项目中使用该文件?
如果是,请告诉我如何。任何帮助将不胜感激。提前致谢。
解决方案
是的,您可以将您的 so 文件访问到其他项目。但您的项目目录必须与旧项目相同。在您的情况下,项目目录必须是这样的:
com/dc/testapplication/MainActivity.class
你MainActivity.class
必须有getSumOfValues
方法。
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