JNI中的java接口使用
项目需求，需要在c++函数中监听相应的状态，并在java端进行一些列的处理。
这个需要在JNI中写一个subscriber，注册后在需要的地方进行引入使用。
目录结构
初始化是AS上的c++工程文件，这边先暂时实现简单的demo，CdemoActivity是NativeActivity的实现，我们暂时别管，因为实现是c++层控制的，有兴趣可以去百度下
主要涉及jnicallback等c文件和JNIUtil这java文件
JNIUtil
public class JNIUtil {
static {
System.loadLibrary("native-event");
}
// 注册函数
public static native void setJniCallBack(JniCallBack callBack);
// 解注册函数
public static native void unJniCallBack();
public interface JniCallBack{
void onReceiveCInfo();
}
}
jnicallback.h
//
// Created by 86130 on 2020/9/9.
//
#ifndef CDEMO_JNICALLBACK_H
#define CDEMO_JNICALLBACK_H
#ifdef __cplusplus
extern "C"{
#endif
//方法回调
void onReceiveMsg();
#ifdef __cplusplus
}
#endif
#endif //CDEMO_JNICALLBACK_H
jnicallback.cpp
#include <jni.h>
#include <malloc.h>
#include <cstring>
#include "jnicallback.h"
#ifdef __cplusplus
extern "C"{
#endif
JavaVM *g_VM;
jobject subscriber;
extern "C"
JNIEXPORT void JNICALL Java_com_demo_cdemo_JNIUtil_setJniCallBack(JNIEnv* env,jclass clazz, jobject call_back) {
env->GetJavaVM(&g_VM);
subscriber = env->NewGlobalRef(call_back);
}
extern "C"
JNIEXPORT void JNICALL Java_com_demo_cdemo_JNIUtil_unJniCallBack(JNIEnv* env, jclass clazz) {
if (subscriber != NULL)
{
env->DeleteGlobalRef(subscriber);
}
}
JNIEnv *getEnv()
{
JNIEnv *env;
if (g_VM ==NULL)
{
return NULL;
}
int envStat = g_VM->GetEnv((void **) &env, JNI_VERSION_1_6);
if (envStat == JNI_EDETACHED)
{
if (g_VM->AttachCurrentThread(&env, NULL) != 0)
{
return NULL;
}
}
return env;
}
jmethodID getMethodIdByNameAndSig(JNIEnv *env, const char *name, const char *sig)
{
if (env == NULL || subscriber == NULL)
{
return NULL;
}
jclass subscriberClass = env->GetObjectClass(subscriber);
if (subscriber == 0)
{
return NULL;
}
jmethodID methodId = env->GetMethodID(subscriberClass, name, sig);
if (methodId == 0)
{
return NULL;
}
return methodId;
}
// 头文件方法实现
void onReceiveMsg()
{
JNIEnv *env = getEnv();
jmethodID onReceiveMethodId = getMethodIdByNameAndSig(env, "onReceiveCInfo", "()V");
if (onReceiveMethodId == NULL)
{
return;
}
env->CallVoidMethod(subscriber, onReceiveMethodId);
}
#ifdef __cplusplus
}
#endif
在其他的cpp文件中引入jnicallback的头文件就可以使用相应的方法。
CMake文件
project(Native-Activity)
cmake_minimum_required(VERSION 3.4.1)
#引入native_app_glue头文件
include_directories(F:/AndroidSdk/Sdk/ndk-bundle/sources/android/native_app_glue)
add_library(native-activity SHARED
main.cpp
jnicallback.cpp)
add_library(native-event SHARED jnicallback.cpp)
find_library(log-lib log)
find_library(OPENGLES3_LIBRARY GLESv3 "OpenGL ES v3.0 library")
find_library(EGL_LIBRARY EGL "EGL 1.4 library")
find_library(android-lib android)
#编译为静态库
add_library(app_glue STATIC
android_native_app_glue.c)
target_link_libraries(native-event
${log-lib} #链接log库
${android-lib} #链接android库
)
target_link_libraries(native-activity
app_glue #链接静态库native_app_glue
${log-lib} #链接log库
${android-lib} #链接android库
${OPENGLES3_LIBRARY} #链接OpenGLES库
${EGL_LIBRARY} #链接EGL库
)
JNIUtil的使用
package com.demo.cdemo;
import android.app.NativeActivity;
import android.content.Intent;
import android.os.Bundle;
import android.os.Looper;
import android.util.Log;
public class CdemoActivity extends NativeActivity {
static {
System.loadLibrary("native-activity");
}
boolean isFirst = false;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
JNIUtil.setJniCallBack(new JNIUtil.JniCallBack() {
@Override
public void onReceiveCInfo() {
boolean isMain = isMainThread();
Log.d("zzkk",
"CdemoActivity onReceiveCInfo isMain = " + isMain);
if (!isFirst)
{
isFirst = true;
runOnUiThread(new Runnable() {
@Override public void run() {
Intent intent = new Intent(CdemoActivity.this
, MainActivity.class);
startActivity(intent);
}
});
}
}
});
}
private boolean isMainThread() {
return Looper.getMainLooper() == Looper.myLooper();
}
}
可以看见onReceiveCInfo这行日志的打印
综上
