init.rc檔案中面啟動c++程式，通過jni調用java實現

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</pre><p>註：假設是自己的myself.jar包，還要修改例如以下：</p><p>target/product/core_base.mk PRODUCT_BOOT_JARS := core:myself</p><p></p><p>功能：手機開機後要寫個標誌位。
已有實現。就是收到開機廣播後，啟動服務讀取bp中的標誌位（java代碼須要等待ril準備好）。並把這個標誌位寫入到ap中（java代碼調用c++）。
後來遇到的問題：實際應用中發現，接收開機廣播等待的時間更長，須要提前寫入ap時間。
解決方式：在init.rc檔案中面啟動c++程式，通過jni調用java實現。精簡代碼例如以下：C++程式碼:</p><p></p><pre code_snippet_id="517675" snippet_file_name="blog_20141113_2_8082170" name="code" class="plain">#define LOG_TAG "testmain"#define LOG_NDEBUG 0#include <dlfcn.h>#include <cutils/log.h>#include <utils/Log.h>#include <jni.h>using namespace android;void wirtePsCaliValToKernel();int main (int argc, char * argv[]){    ALOGI("start c");    wirtePsCaliValToKernel();    ALOGI("start c end");    return 0;}void wirtePsCaliValToKernel() {    JavaVM* vm;    JNIEnv* env;    // start a VM    JavaVMInitArgs args;    JavaVMOption opt;    opt.optionString =        "-agentlib:jdwp=transport=dt_android_adb,suspend=n,server=y";    args.version = JNI_VERSION_1_4;    args.options = &opt;    args.nOptions = 1;    args.ignoreUnrecognized = JNI_FALSE;    void* libdvm_dso = dlopen("libdvm.so", RTLD_NOW);    ALOGE_IF(!libdvm_dso, "DdmConnection: %s", dlerror());    void* libandroid_runtime_dso = dlopen("libandroid_runtime.so", RTLD_NOW);    ALOGE_IF(!libandroid_runtime_dso, "DdmConnection: %s", dlerror());    if (!libdvm_dso || !libandroid_runtime_dso) {        goto error;    }    jint (*JNI_CreateJavaVM)(JavaVM** p_vm, JNIEnv** p_env, void* vm_args);    JNI_CreateJavaVM = (typeof JNI_CreateJavaVM)dlsym(libdvm_dso, "JNI_CreateJavaVM");    ALOGE_IF(!JNI_CreateJavaVM, "DdmConnection: %s", dlerror());    jint (*registerNatives)(JNIEnv* env, jclass clazz);    registerNatives = (typeof registerNatives)dlsym(libandroid_runtime_dso,        "Java_com_android_internal_util_WithFramework_registerNatives");    ALOGE_IF(!registerNatives, "DdmConnection: %s", dlerror());    if (!JNI_CreateJavaVM || !registerNatives) {        goto error;    }    if (JNI_CreateJavaVM(&vm, &env, &args) == 0) {        jclass startClass;        jmethodID readPsMeth;        // register native code        if (registerNatives(env, 0) == 0) {            startClass = env->FindClass("android/hardware/Camera");            if (startClass) {                ALOGI(" startclass is ok");                //readPsMeth = env->GetStaticMethodID(startClass, "getCurrentFocusPosition", "(I)V");                readPsMeth = env->GetMethodID(startClass, "getCurrentFocusPosition", "()I");                int result = -1;                if (readPsMeth) {                    ALOGI("readPsMeth is ok, result = %d ",  result);                    result = env->CallStaticIntMethod(startClass, readPsMeth);                    ALOGI("readPsMeth is ok end, result = %d ",  result);                }else{                    ALOGE("-->> readPsMeth is fail");                }            }else{                ALOGE("startclass is fail");            }        }    }    return;error:    if (libandroid_runtime_dso) {        dlclose(libandroid_runtime_dso);    }    if (libdvm_dso) {        dlclose(libdvm_dso);    }}

Android.mk:

LOCAL_PATH:= $(call my-dir)include $(CLEAR_VARS)LOCAL_MODULE:= testmainLOCAL_SRC_FILES:=         testmain.cppLOCAL_C_INCLUDES :=LOCAL_MODULE_TAGS := optional engLOCAL_SHARED_LIBRARIES += libcutils                             libutils                              liblog                              libandroid_runtime                           libnativehelper                           libdl include $(BUILD_EXECUTABLE)

init.rc改動:

class 值為main時才幹開機自己主動啟動

service testmain /system/bin/testmainclass mainuser rootoneshot

end

init.rc檔案中面啟動c++程式，通過jni調用java實現