android c打日志回调java方法（非静态方法）

最新推荐文章于 2021-08-10 22:35:59 发布

SoLucky2017

最新推荐文章于 2021-08-10 22:35:59 发布

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分类专栏： android 文章标签： android

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本文介绍如何从本地C/C++代码通过JNI接口调用Java层的方法，包括无返回值的方法、返回整型的方法及返回字符串的方法。通过具体实例展示了如何在Android环境下实现跨语言调用。

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#include <jni.h>
#include <stdlib.h>
#include <android/log.h>
#define LOG_TAG "jni-test"
#define LOGD(...) __android_log_print(ANDROID_LOG_DEBUG, LOG_TAG, __VA_ARGS__)
/**
* 把一个jstring转换成一个c语言的char* 类型.
*/
char* _JString2CStr(JNIEnv* env, jstring jstr) {
char* rtn = NULL;
jclass clsstring = (*env)->FindClass(env, "java/lang/String");
jstring strencode = (*env)->NewStringUTF(env,"GB2312");
jmethodID mid = (*env)->GetMethodID(env, clsstring, "getBytes", "(Ljava/lang/String;)[B");
jbyteArray barr = (jbyteArray)(*env)->CallObjectMethod(env, jstr, mid, strencode); // String .getByte("GB2312");
jsize alen = (*env)->GetArrayLength(env, barr);
jbyte* ba = (*env)->GetByteArrayElements(env, barr, JNI_FALSE);
if(alen > 0) {
rtn = (char*)malloc(alen+1); //"\0"
memcpy(rtn, ba, alen);
rtn[alen]=0;
}
(*env)->ReleaseByteArrayElements(env, barr, ba,0);
return rtn;
}
JNIEXPORT void JNICALL Java_com_itheima_callbackjava_JNI_callbackvoidmethod
(JNIEnv * env, jobject clazz){
//jclass (*FindClass)(JNIEnv*, const char*);
//① 获取字节码对象
jclass claz = (*env)->FindClass(env,"com/itheima/callbackjava/JNI");
//②获取Method对象
//jmethodID (*GetMethodID)(JNIEnv*, jclass, const char*, const char*);
jmethodID methodID =(*env)->GetMethodID(env,claz,"helloFromJava","()V");
//③通过字节码对象创建一个Object
//④通过对象调用方法
//void (*CallVoidMethod)(JNIEnv*, jobject, jmethodID, ...);
(*env)->CallVoidMethod(env,clazz,methodID);

}

JNIEXPORT void JNICALL Java_com_itheima_callbackjava_JNI_callbackintmethod
(JNIEnv * env, jobject clazz){
//① 获取字节码对象
jclass claz =(*env)->FindClass(env,"com/itheima/callbackjava/JNI");
//②获取Method对象
jmethodID methodID = (*env)->GetMethodID(env,claz,"add","(II)I");
//jint (*CallIntMethod)(JNIEnv*, jobject, jmethodID, ...);
int result =(*env)->CallIntMethod(env,clazz,methodID,3,4);
LOGD("result = %d",result);
}

JNIEXPORT void JNICALL Java_com_itheima_callbackjava_JNI_callbackStringmethod
(JNIEnv * env, jobject clazz){
//① 获取字节码对象
jclass claz =(*env)->FindClass(env,"com/itheima/callbackjava/JNI");
//② 获取Method对象
jmethodID methodid =(*env)->GetMethodID(env,claz,"printString","(Ljava/lang/String;)V");
//
jstring result =(*env)->NewStringUTF(env,"hello from c");
(*env)->CallVoidMethod(env,clazz,methodid,result);
}
JNIEXPORT void JNICALL Java_com_itheima_callbackjava_JNI_callbackShowToast
(JNIEnv * env, jobject clazz){
jclass claz =(*env)->FindClass(env,"com/itheima/callbackjava/JNI");
jmethodID methodid =(*env)->GetMethodID(env,claz,"showToast","(Ljava/lang/String;)V");
//jobject (*AllocObject)(JNIEnv*, jclass);
//通过字节码对象创建 java对象在这儿就是创建了mainactivity的对象
//jobject obj =(*env)->AllocObject(env,claz);
jstring result =(*env)->NewStringUTF(env,"hello from c");
//void (*CallVoidMethod)(JNIEnv*, jobject, jmethodID, ...);
(*env)->CallVoidMethod(env,clazz,methodid,result);
}