Android 添加JNI文件到源码流程

1：添加cpp文件到\frameworks\base\core\jni

对应目录下的Android.mk中添加编译目标

LOCAL_SRC_FILES:= \ 标签下

LOCAL_SHARED_LIBRARIES := \ 标签下

对应目录下的AndroidRuntime.cpp文件中注册cpp文件

如extern int register_android_hardware_SerialPort(JNIEnv *env);

REG_JNI(register_android_hardware_SerialPort),

cpp文件中要添加注册函数，不然Java的本地调用找不到

namespace android

{

........

static JNINativeMethod method_table[] = {

{"native_open", "(Ljava/io/FileDescriptor;I)V",

(void *)android_hardware_SerialPort_open},

{"native_close", "()V", (void *)android_hardware_SerialPort_close},

{"native_read_array", "([BI)I",

(void *)android_hardware_SerialPort_read_array},

{"native_read_direct", "(Ljava/nio/ByteBuffer;I)I",

(void *)android_hardware_SerialPort_read_direct},

{"native_write_array", "([BI)V",

(void *)android_hardware_SerialPort_write_array},

{"native_write_direct", "(Ljava/nio/ByteBuffer;I)V",

(void *)android_hardware_SerialPort_write_direct},

{"native_send_break", "()V", (void *)android_hardware_SerialPort_send_break},

};

int register_android_hardware_SerialPort(JNIEnv *env)

{

jclass clazz = env->FindClass("android/hardware/SerialPort");

if (clazz == NULL) {

ALOGE("Can't find android/hardware/SerialPort");

return -1;

}

field_context = env->GetFieldID(clazz, "mNativeContext", "I");

if (field_context == NULL) {

ALOGE("Can't find SerialPort.mNativeContext");

return -1;

}

return AndroidRuntime::registerNativeMethods(env, "android/hardware/SerialPort",

method_table, NELEM(method_table));

}

}

2：或者添加cpp文件到\frameworks\base\services\jni

对应目录下的Android.mk中添加编译目标

LOCAL_SRC_FILES:= \ 标签下

LOCAL_SHARED_LIBRARIES := \ 标签下

对应目录下onload.cpp文件中注册cpp文件

此目录下的JNI文件主要是用来注册系统服务时使用的的如上一张讲到的需要调用本地方法时使用。

如：int register_android_server_SerialService(JNIEnv* env);

register_android_server_SerialService(env);

cpp文件中要添加注册函数，不然java的本地调用找不到

namespace android

{

........

static JNINativeMethod method_table[] = {

{ "native_open", "(Ljava/lang/String;)Landroid/os/ParcelFileDescriptor;",

(void*)android_server_SerialService_open },

};

int register_android_server_SerialService(JNIEnv *env)

{

jclass clazz = env->FindClass("com/android/server/SerialService");

if (clazz == NULL) {

ALOGE("Can't find com/android/server/SerialService");

return -1;

}

clazz = env->FindClass("android/os/ParcelFileDescriptor");

LOG_FATAL_IF(clazz == NULL, "Unable to find class android.os.ParcelFileDescriptor");

gParcelFileDescriptorOffsets.mClass = (jclass) env->NewGlobalRef(clazz);

gParcelFileDescriptorOffsets.mConstructor = env->GetMethodID(clazz, "<init>", "(Ljava/io/FileDescriptor;)V");

LOG_FATAL_IF(gParcelFileDescriptorOffsets.mConstructor == NULL,

"Unable to find constructor for android.os.ParcelFileDescriptor");

return jniRegisterNativeMethods(env, "com/android/server/SerialService",

method_table, NELEM(method_table));

}

}