java数组和jni数组对应关系

kotlin	jni
IntArray	jintArray
DoubleArray	jdoubleArray
LongArray	jlongArray
CharArray	jcharArray
ShortArray	jshortArray
Array	jobjectArray

  //kotlinexternal fun arrayInt(array: IntArray): Stringexternal fun arrayDouble(array: DoubleArray): Stringexternal fun arrayLong(array: LongArray): Stringexternal fun arrayChar(array: CharArray): Stringexternal fun arrayShort(array: ShortArray): Stringexternal fun arrayString(array: Array<String>): String

//jni
extern "C"
JNIEXPORT jstring JNICALL
Java_com_example_myapplication_MainActivity_arrayInt(JNIEnv *env, jobject thiz, jintArray array) {// TODO: implement arrayInt()
}extern "C"
JNIEXPORT jstring JNICALL
Java_com_example_myapplication_MainActivity_arrayDouble(JNIEnv *env, jobject thiz,jdoubleArray array) {// TODO: implement arrayDouble()
}extern "C"
JNIEXPORT jstring JNICALL
Java_com_example_myapplication_MainActivity_arrayLong(JNIEnv *env, jobject thiz, jlongArray array) {// TODO: implement arrayLong()
}extern "C"
JNIEXPORT jstring JNICALL
Java_com_example_myapplication_MainActivity_arrayChar(JNIEnv *env, jobject thiz, jcharArray array) {// TODO: implement arrayChar()
}extern "C"
JNIEXPORT jstring JNICALL
Java_com_example_myapplication_MainActivity_arrayShort(JNIEnv *env, jobject thiz,jshortArray array) {// TODO: implement arrayShort()
}extern "C"
JNIEXPORT jstring JNICALL
Java_com_example_myapplication_MainActivity_arrayString(JNIEnv *env, jobject thiz,jobjectArray array) {// TODO: implement arrayString()
}

jobjectArray 实战

获取数组长度

class MainActivity : AppCompatActivity() {private lateinit var binding: ActivityMainBindingoverride fun onCreate(savedInstanceState: Bundle?) {super.onCreate(savedInstanceState)binding = ActivityMainBinding.inflate(layoutInflater)setContentView(binding.root)val array = arrayOf("first", "two")binding.sampleText.text = "长度为：" + arrayLength(array)}/*** A native method that is implemented by the 'native-lib' native library,* which is packaged with this application.*/external fun arrayLength(array: Array<String>): Intcompanion object {// Used to load the 'native-lib' library on application startup.init {System.loadLibrary("native-lib")}}
}

native-lib.cpp

extern "C"
JNIEXPORT jint JNICALL
Java_com_example_myapplication_MainActivity_arrayLength(JNIEnv *env, jobject thiz,jobjectArray array) {//获取数组长度int length = env->GetArrayLength(array);return length;
}

获取数组第一个元素

lass MainActivity : AppCompatActivity() {private lateinit var binding: ActivityMainBindingoverride fun onCreate(savedInstanceState: Bundle?) {super.onCreate(savedInstanceState)binding = ActivityMainBinding.inflate(layoutInflater)setContentView(binding.root)val array = arrayOf("first", "two")binding.sampleText.text = "第一个元素：" + arrayFirst(array)}/*** A native method that is implemented by the 'native-lib' native library,* which is packaged with this application.*/external fun arrayFirst(array: Array<String>): Stringcompanion object {// Used to load the 'native-lib' library on application startup.init {System.loadLibrary("native-lib")}}
}

native-lib.cpp

extern "C"
JNIEXPORT jstring JNICALL
Java_com_example_myapplication_MainActivity_arrayFirst(JNIEnv *env, jobject thiz,jobjectArray array) {//获取array第一个元素jobject first = env->GetObjectArrayElement(array, 0);//把jobject强转成jstringreturn static_cast<jstring>(first);
}

jintArray 实战

获取第一个元素

class MainActivity : AppCompatActivity() {private lateinit var binding: ActivityMainBindingoverride fun onCreate(savedInstanceState: Bundle?) {super.onCreate(savedInstanceState)binding = ActivityMainBinding.inflate(layoutInflater)setContentView(binding.root)val array = intArrayOf(1, 2, 3)binding.sampleText.text = "第一个元素：" + arrayInt(array)}/*** A native method that is implemented by the 'native-lib' native library,* which is packaged with this application.*/external fun arrayInt(array: IntArray): Intcompanion object {// Used to load the 'native-lib' library on application startup.init {System.loadLibrary("native-lib")}}
}

native-lib.cpp


extern "C"
JNIEXPORT jint JNICALL
Java_com_example_myapplication_MainActivity_arrayInt(JNIEnv *env, jobject thiz, jintArray array) {jint *result = env->GetIntArrayElements(array, JNI_FALSE);//获取第一个元素return result[0];
}

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文章目录

java数组和jni数组对应关系

jobjectArray 实战

获取数组长度

获取数组第一个元素

jintArray 实战

获取第一个元素

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