其中一种在Android系统的解决方案是：
把c/c++中所有线程的创建，由pthread_create函数替换为由Java层的创建线程的函数AndroidRuntime::createJavaThread。
假设有c++函数:
[cpp] view plaincopy
void *thread_entry(void *args)
{
while(1)
{
printf("thread running...\n")
sleep(1)
}
}
void init()
{
pthread_t thread
pthread_create(&thread,NULL,thread_entry,(void *)NULL)
}
init()函数创建一个线程，需要在该线程中调用java类Test的回调函数Receive:
[cpp] view plaincopy
public void Receive(char buffer[],int length){
String msg = new String(buffer)
msg = "received from jni callback:" + msg
Log.d("Test", msg)
}
首先在c++中定义回调函数指针：
[cpp] view plaincopy
//test.h
#include <pthread.h>
//function type for receiving data from native
typedef void (*ReceiveCallback)(unsigned char *buf, int len)
/** Callback for creating a thread that can call into the Java framework code.
* This must be used to create any threads that report events up to the framework.
*/
typedef pthread_t (* CreateThreadCallback)(const char* name, void (*start)(void *), void* arg)
typedef struct{
ReceiveCallback recv_cb
CreateThreadCallback create_thread_cb
}Callback
再修改c++中的init和thread_entry函数：
[cpp] view plaincopy
//test.c
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <sys/wait.h>
#include <unistd.h>
#include "test.h"
void *thread_entry(void *args)
{
char *str = "i'm happy now"
Callback cb = NULL
int len
if(args != NULL){
cb = (Callback *)args
}
len = strlen(str)
while(1)
{
printf("thread running...\n")
//invoke callback method to java
if(cb != NULL &&cb->recv_cb != NULL){
cb->recv_cb((unsigned char*)str, len)
}
sleep(1)
}
}
void init(Callback *cb)
{
pthread_t thread
//pthread_create(&thread,NULL,thread_entry,(void *)NULL)
if(cb != NULL &&cb->create_thread_cb != NULL)
{
cb->create_thread_cb("thread",thread_entry,(void *)cb)
}
}
然后在jni中实现回调函数，以及其他实现：
[cpp] view plaincopy
//jni_test.c
#include <stdlib.h>
#include <malloc.h>
#include <jni.h>
#include <JNIHelp.h>
#include "android_runtime/AndroidRuntime.h"
#include "test.h"
#define RADIO_PROVIDER_CLASS_NAME "com/tonny/Test"
using namespace android
static jobject mCallbacksObj = NULL
static jmethodID method_receive
static void checkAndClearExceptionFromCallback(JNIEnv* env, const char* methodName) {
if (env->ExceptionCheck()) {
LOGE("An exception was thrown by callback '%s'.", methodName)
LOGE_EX(env)
env->ExceptionClear()
}
}
static void receive_callback(unsigned char *buf, int len)
{
int i
JNIEnv* env = AndroidRuntime::getJNIEnv()
jcharArray array = env->NewCharArray(len)
jchar *pArray
if(array == NULL){
LOGE("receive_callback: NewCharArray error.")
return
}
pArray = (jchar*)calloc(len, sizeof(jchar))
if(pArray == NULL){
LOGE("receive_callback: calloc error.")
return
}
//copy buffer to jchar array
for(i = 0i <leni++)
{
*(pArray + i) = *(buf + i)
}
//copy buffer to jcharArray
env->SetCharArrayRegion(array,0,len,pArray)
//invoke java callback method
env->CallVoidMethod(mCallbacksObj, method_receive,array,len)
//release resource
env->DeleteLocalRef(array)
free(pArray)
pArray = NULL
checkAndClearExceptionFromCallback(env, __FUNCTION__)
}
static pthread_t create_thread_callback(const char* name, void (*start)(void *), void* arg)
{
return (pthread_t)AndroidRuntime::createJavaThread(name, start, arg)
}
static Callback mCallbacks = {
receive_callback,
create_thread_callback
}
static void jni_class_init_native
(JNIEnv* env, jclass clazz)
{
method_receive = env->GetMethodID(clazz, "Receive", "([CI)V")
}
static int jni_init
(JNIEnv *env, jobject obj)
{
if (!mCallbacksObj)
mCallbacksObj = env->NewGlobalRef(obj)
return init(&mCallbacks)
}
static const JNINativeMethod gMethods[] = {
{ "class_init_native", "()V", (void *)jni_class_init_native },
{ "native_init","()I", (void *)jni_init },
}
static int registerMethods(JNIEnv* env) {
const char* const kClassName = RADIO_PROVIDER_CLASS_NAME
jclass clazz
/* look up the class */
clazz = env->FindClass(kClassName)
if (clazz == NULL) {
LOGE("Can't find class %s/n", kClassName)
return -1
}
/* register all the methods */
if (env->RegisterNatives(clazz,gMethods,sizeof(gMethods)/sizeof(gMethods[0])) != JNI_OK)
{
LOGE("Failed registering methods for %s/n", kClassName)
return -1
}
/* fill out the rest of the ID cache */
return 0
}
jint JNI_OnLoad(JavaVM* vm, void* reserved) {
JNIEnv* env = NULL
jint result = -1
LOGI("Radio JNI_OnLoad")
if (vm->GetEnv((void**) &env, JNI_VERSION_1_4) != JNI_OK) {
LOGE("ERROR: GetEnv failed/n")
goto fail
}
if(env == NULL){
goto fail
}
if (registerMethods(env) != 0) {
LOGE("ERROR: PlatformLibrary native registration failed/n")
goto fail
}
/* success -- return valid version number */
result = JNI_VERSION_1_4
fail:
return result
}
jni的Android.mk文件中共享库设置为：
[cpp] view plaincopy
LOCAL_SHARED_LIBRARIES := liblog libcutils libandroid_runtime libnativehelper
最后再实现Java中的Test类：
[java] view plaincopy
//com.tonny.Test.java
public class Test {
static{
try {
System.loadLibrary("test")
class_init_native()
} catch(UnsatisfiedLinkError ule){
System.err.println("WARNING: Could not load library libtest.so!")
}
}
public int initialize() {
return native_radio_init()
}
public void Receive(char buffer[],int length){
String msg = new String(buffer)
msg = "received from jni callback" + msg
Log.d("Test", msg)
}
protected static native void class_init_native()
protected native int native_init()
}
一、alps/packages/apps/Bluetooth/src/com/android/bluetooth/hfp/HeadsetStateMachine.java
processAnswerCall
这个方法就是接听电话 我们来往上走 还是
alps/packages/apps/Bluetooth/src/com/android/bluetooth/hfp/HeadsetStateMachine.java
原来是jni回调java。
alps/packages/apps/Bluetooth/jni/com_android_bluetooth_hfp.cpp
alps/packages/apps/Bluetooth/jni/com_android_bluetooth_hfp.cpp
alps/packages/apps/Bluetooth/jni/com_android_bluetooth_hfp.cpp
alps/packages/apps/Bluetooth/jni/com_android_bluetooth_hfp.cpp
alps/packages/apps/Bluetooth/jni/com_android_bluetooth_hfp.cpp
alps/system/bt/btif/src/btif_hf.c
alps/system/bt/btif/src/btif_hf.c
alps/system/bt/btif/src/btif_hf.c
alps/hardware/libhardware/include/hardware/bt_hf.h
好了 跟踪完了
logcat | grep "AT cmd"
第一个是接听 第二个是挂断
再往下跟
p_cmd_cback
alps/system/bt/bta/ag/bta_ag_at.c
bta_ag_process_at
alps/system/bt/bta/ag/bta_ag_at.c
system/bt/bta/ag/bta_ag_act.c
