Android下的JNI创建多线程的方法
16lz
2021-01-24
本文参考了http://www.cnblogs.com/lknlfy/archive/2012/03/16/2400786.html这篇博文,加了点自己的东西
废话不多说,贴代码上来
java的代码:
package com.example.jni_thread_demo;import android.os.Bundle;import android.app.Activity;import android.util.Log;import android.view.Menu;import android.view.View;import android.widget.Button;public class JNI_ThreadActivity extends Activity {private Button mButton = null;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_jni__thread);mButton = (Button)findViewById(R.id.button);mButton.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {// 调用JNI中的函数来启动JNI中的线程mainThread();}});// 初始化JNI环境setJNIEnv();}//由JNI中的线程回调类方法private static void fromJNI(int i){Log.v("Java---------->", ""+i);} //自己定义的线程回调成员方法private void From_JNI_Again (int i){Log.v("Java_object------------>", ""+i);}// 本地方法private native void mainThread();private native void setJNIEnv();static{System.loadLibrary("JNIThread");}}
jni中的代码:
#include<stdio.h>#include<stdlib.h>#include<unistd.h>#include<pthread.h>#include<string.h>#include<assert.h>#include<jni.h>#include<android/log.h>#define LOGI(...) ((void)__android_log_print(ANDROID_LOG_INFO, "jni_thread", __VA_ARGS__))#define LOGW(...) ((void)__android_log_print(ANDROID_LOG_WARN, "jni_thread", __VA_ARGS__))#define LOGE(...) ((void)__android_log_print(ANDROID_LOG_ERROR, "jni_thread", __VA_ARGS__))// 线程数#define NUMTHREADS 5// 指定要注册的类#define JNIREG_CLASS "com/example/jni_thread_demo/JNI_ThreadActivity"// 全局变量JavaVM* g_jvm = NULL;jobject g_obj = NULL;void* thread_fun(void* arg){JNIEnv *env;jclass cls;jmethodID mid, mid1;// Attach主线程if((*g_jvm)->AttachCurrentThread(g_jvm, &env, NULL) != JNI_OK){LOGE("%s: AttachCurrentThread() failed", __FUNCTION__);return NULL;}// 找到对应的类cls = (*env)->GetObjectClass(env, g_obj);if(cls == NULL){LOGE("FindClass() Error ......");goto error;}// 再获得类中的方法mid = (*env)->GetStaticMethodID(env, cls, "fromJNI", "(I)V");if(mid == NULL){LOGE("GetStaticMethodID() Error ......");goto error;}// 最后调用java中的静态方法(*env)->CallStaticVoidMethod(env, cls, mid, (int)arg);//获得类中的“成员”方法mid1 = (*env)->GetMethodID(env, cls, "From_JNI_Again", "(I)V");if(mid == NULL){LOGE("GetMethodID() Error ......");goto error;}// 最后调用类中“成员”方法(*env)->CallVoidMethod(env, g_obj, mid1, (int)arg);//错误处理代码error://Detach主线程if((*g_jvm)->DetachCurrentThread(g_jvm) != JNI_OK){LOGE("%s: DetachCurrentThread() failed", __FUNCTION__);}pthread_exit(0);}/* * Class: com_example_jni_thread_demo_JNI_ThreadActivity * Method: mainThread * Signature: ()V *//*不用JNI_OnLoad时的复杂命名方式JNIEXPORT void JNICALL Java_com_example_jni_1thread_1demo_JNI_1ThreadActivity_mainThread (JNIEnv *env, jobject obj){int i;pthread_t pt[NUMTHREADS];for(i=0; i<NUMTHREADS; i++){// 创建线程,并指明调用的函数pthread_create(&pt[i], NULL, &thread_fun, (void*)i);}}*//* * Class: com_example_jni_thread_demo_JNI_ThreadActivity * Method: setJNIEnv * Signature: ()V *//*不用JNI_OnLoad时的复杂命名方式JNIEXPORT void JNICALL Java_com_example_jni_1thread_1demo_JNI_1ThreadActivity_setJNIEnv (JNIEnv *env, jobject obj){// 保存全局JVM以便在子线程中使用(*env)->GetJavaVM(env, &g_jvm);// 不能直接赋值(g_obj = ojb)g_obj = (*env)->NewGlobalRef(env, obj);}*/JNIEXPORT void JNICALL native_mainThread(JNIEnv *env, /*jclass clazz*/ jobject obj)// 使用jclass和jobject都可以{LOGI("native_mainThread");int i;pthread_t pt[NUMTHREADS];for(i=0; i<NUMTHREADS; i++){// 创建线程,并指明调用的函数,注意只接收一个参数i作为thread_fun的参数,后面会介绍怎么传多个参数pthread_create(&pt[i], NULL, &thread_fun, (void*)i);}}JNIEXPORT void JNICALL native_setJNIEnv(JNIEnv *env, /*jclass obj*/ jobject obj)// 使用jclass和jobject都可以{LOGI("native_setJNIEnv");// 保存全局JVM以便在子线程中使用(*env)->GetJavaVM(env, &g_jvm);// 不能直接赋值(g_obj = ojb)g_obj = (*env)->NewGlobalRef(env, obj);}/*** Table of methods associated with a single class.*/static JNINativeMethod gMethods[] ={{"mainThread", "()V", (void*)native_mainThread },// 绑定:注意千万签名结尾不能加分号!!!!!!{"setJNIEnv", "()V", (void*)native_setJNIEnv },};/** Register several native methods for one class.*/static int registerNativeMethods(JNIEnv* env, const char* className,JNINativeMethod* gMethods, int numMethods){jclass clazz;clazz = (*env)->FindClass(env, className);if (clazz == NULL){return JNI_FALSE;}if ((*env)->RegisterNatives(env, clazz, gMethods, numMethods) < 0){return JNI_FALSE;}return JNI_TRUE;}/** Register native methods for all classes we know about.*/static int registerNatives(JNIEnv* env){if (!registerNativeMethods(env, JNIREG_CLASS, gMethods,sizeof(gMethods) / sizeof(gMethods[0])))return JNI_FALSE;return JNI_TRUE;}/** Set some test stuff up.** Returns the JNI version on success, -1 on failure.*/JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM* vm, void* reserved){JNIEnv* env = NULL;jint result = -1;if ((*vm)->GetEnv(vm, (void**) &env, JNI_VERSION_1_4) != JNI_OK) {LOGE("GetEnv failed!");return -1;}//===========================================assert(env != NULL);if (!registerNatives(env)){// 注册本地方法return -1;}//===========================================/* success -- return valid version number */result = JNI_VERSION_1_4;return result;}
Android.mk文件中的代码:
LOCAL_PATH :=$(call my-dir)include $(CLEAR_VAR)LOCAL_MODULE := JNIThreadLOCAL_SRC_FILES := JNI_Thread.cLOCAL_MODULE_FILENAME := libJNIThread//如果报LOCAL_MODULE_FILENAME的错的话,需要加上这句话LOCAL_LDLIBS := -lloginclude $(BUILD_SHARED_LIBRARY)
如何给线程函数传递多个参数:
涉及多参数传递给线程的,都需要使用结构体将参数封装后,将结构体指针传给线程
定义一个结构体
struct mypara{ var para1;//参数1 var para2;//参数2}
将这个结构体指针,作为void *形参的实际参数传递
struct mypara pstru;pthread_create(&ntid, NULL, thr_fn,& (pstru));
函数中需要定义一个mypara类型的结构指针来引用这个参数
void *thr_fn(void *arg){ mypara *pstru; pstru = (* struct mypara) arg; pstru->para1;//参数1 pstru->para2;//参数2}
如何多线程同步通信:
至于多个线程是怎么进行同步通信的,可以参考这篇博文
http://blog.csdn.net/chenghongyue/article/details/8124976
更多相关文章
- Android实现关机重启的方法
- android屏幕和view的截图
- Android(安卓)JNI入门第六篇――C调用Java
- android fragment show hide回调
- Android(安卓)lifecycle 实战及使用进阶
- android scrollview的所有touchevent的顺序
- 理解杀进程的实现原理
- 转发:bitmap 设置图片尺寸,避免 内存溢出 OutOfMemoryError的优化
- Android(安卓)UI 学习 自定义的布局 平滑移动 VelocityTracker()