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Jni API:https://docs.oracle.com/javase/8/docs/technotes/guides/jni/spec/jniTOC.html
JNIEnv、jobject和jclass这三种基本类型
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操作API都在JNIEnv中，JNIEnv为Java与C/C++通信桥梁
jobject：Java层传递的对象（普通native方法传递）
jclass:Java层对应的Class类（静态native方法传递）
native普通方法与静态方法区别：Jni传递参数是jobject和jclass区别
android studio ndk api自动补齐
安装插件：
Android NDK Support
NDK WorkspaceManager Support
属性，方法，数组例子：
Java层
public class MainActivity extends AppCompatActivity {
private static final String TAG = "MainActivity";
//测试属性
public String strName ="test";
//排序数组
private int[] array = {89,2,4,34,88,100,1};
// Used to load the 'native-lib' library on application startup.
static {
System.loadLibrary("native-lib");
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Example of a call to a native method
TextView tv = (TextView) findViewById(R.id.sample_text);
//测试属性操作
tv.setText(updateStringFromC());
//测试方法调用
tv.setText(getJavaMethod());
//测试数组操作
this.operateArraySort(array);
for (int i = 0; i < array.length; i++){
Log.e(TAG, "onCreate: " + array[i]);
}
//异常处理 C++的异常 JAVA是无法try catch的，如果jni层出现了异常，那么Java的代码调用中止
try {
exception();
}catch (Exception e){
Log.e(TAG, "onCreate: " + e.getMessage());
}
Log.e(TAG, "onCreate: " + "end");
}
//测试方法
public String getMethod(int a){
return "method" + a;
}
/**
* A native method that is implemented by the 'native-lib' native library,
* which is packaged with this application.
*/
public native String stringFromJNI();
//从C返回字符串
public native String updateStringFromC();
//调用Java方法
public native String getJavaMethod();
//对array数组进行排序操作
public native void operateArraySort(int[] array);
//异常处理
public native void exception();}
Jni层：
#include
#include
#include "stdlib.h"
//C C++混编
int compare(const void* lhs, const void* rhs){
return (*(int*)lhs - *(int*)rhs);
}
//异常处理
extern "C"
JNIEXPORT void JNICALL
Java_com_home_adproj_androidndktest_MainActivity_exception(JNIEnv *env, jobject instance) {
jclass _jclass = env->GetObjectClass(instance);
jfieldID _jfieldID = env->GetFieldID(_jclass,"strName2","Ljava/lang/String;");//strName2不存在有异常
if(env->ExceptionCheck()){//检测异常
env->ExceptionClear();//清除异常 不会使Java层崩溃
//抛异常给Java层
jclass exceptionClass = env->FindClass("java/lang/IllegalArgumentException");
env->ThrowNew(exceptionClass,"strName2 不存在");//抛异常到Java层，Java层进行捕获
}
}
//对Java数组进行操作
extern "C"
JNIEXPORT void JNICALL
Java_com_home_adproj_androidndktest_MainActivity_operateArraySort(JNIEnv *env, jobject instance,
jintArray array_) {
jint *arrays = env->GetIntArrayElements(array_, NULL);
int _len = env->GetArrayLength(array_);//获取数组长度
//qsort(void* __base, size_t __nmemb, size_t __size, int (*__comparator)(const void* __lhs, const void* __rhs));
qsort(arrays,_len, sizeof(int),compare);//数组排序
env->ReleaseIntArrayElements(array_, arrays, 0);//释放
}
//调用Java层方法
extern "C"
JNIEXPORT jstring JNICALL
Java_com_home_adproj_androidndktest_MainActivity_getJavaMethod(JNIEnv *env, jobject instance) {
jclass _jclass =env->GetObjectClass(instance);
//(jclass clazz, const char* name, const char* sig)
jmethodID _jmethodID = env->GetMethodID(_jclass,"getMethod","(I)Ljava/lang/String;");//(参数类型)Ljava/lang/String返回值类型
jstring result = (jstring) env->CallObjectMethod(instance, _jmethodID,100);
char* str = (char *) env->GetStringUTFChars(result, NULL);//string 转char
return env->NewStringUTF(str);
}
//测试Java属性操作
extern "C"
JNIEXPORT jstring JNICALL
Java_com_home_adproj_androidndktest_MainActivity_updateStringFromC(JNIEnv *env, jobject instance) {
// TODO
jclass _jclass = env->GetObjectClass(instance);
//(jclass clazz, const char* name, const char* sig)
//name:属性名 sig:属性类型
jfieldID _jfieldID = env->GetFieldID(_jclass,"strName","Ljava/lang/String;");
jstring _result = (jstring) env->GetObjectField(instance, _jfieldID);
//如何转化成java string
char* str = (char *) env->GetStringUTFChars(_result, NULL);
char text[20] = "success";
return env->NewStringUTF(strcat(str,text));
}
extern "C"
JNIEXPORT jstring JNICALL
Java_com_home_adproj_androidndktest_MainActivity_stringFromJNI(
JNIEnv* env,
jobject /* this */) {
std::string hello = "Hello from C++";
return env->NewStringUTF(hello.c_str());
} lldb：jni调试工具
官网：http://lldb.llvm.org/tutorial.html