实现自己的HAL-4 JNI层的代码编写

Posted 2021-07-27 杨斌并

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JNI层的代码

jni层代码的编写

首先找到系统中onload.cpp 所在的目录
我的是在Z:\\itop-3399_8.1\\frameworks\\base\\services\\core\\jni 这个路径
在这个路径下创建com_android_server_HelloWorldService.cpp的cpp文件

代码

#include <nativehelper/JNIHelp.h>
#include <jni.h>
#include <android_runtime/AndroidRuntime.h>
#include <utils/misc.h>
#include <utils/Log.h>
#include <hardware/hardware.h>
#include <hardware/helloworld.h>
#include <stdio.h>
#include <android_runtime/Log.h>

namespace android {

    struct helloworld_device_t * helloworld_device = NULL;

    static jboolean helloworld_init(JNIEnv* env, jobject clazz){

        helloworld_module_t *module;
        ALOGI("hello jni init");
        if(hw_get_module(HELLOWORLD_HARDWARE_MODULE_ID, (const struct hw_module_t**)&module)== 0){

            ALOGI("hw_get_module success");

            if(module->common.methods->open(&(module->common),HELLOWORLD_HARDWARE_MODULE_ID, (struct hw_device_t **)&helloworld_device) == 0){
                 ALOGI("open success");
                return JNI_TRUE;
            }

            ALOGI("open error");
            return JNI_FALSE;

        }
        ALOGI("hw_get_module error");
        return JNI_FALSE;

    }



    static jint helloworld_AddVal(JNIEnv* env, jobject clazz, jint a, jint b){

        int result;
        if(!helloworld_device){
            ALOGI("hello jni device is not open");
            return  JNI_FALSE;
        }

        helloworld_device->helloworld_add(helloworld_device, a, b, &result);
        return result;

    }
    static JNINativeMethod sMethods[] = {
        {"init", "()Z", (void*)helloworld_init},
        {"addValue", "(II)I", (void*)helloworld_AddVal},
    };

    int request_android_server_HelloWorldService(JNIEnv* env){
        return jniRegisterNativeMethods(env, "com/android/server/HelloWorldService", sMethods, NELEM(sMethods));
    }
}

"Z:/itop-3399_8.1/hardware/libhardware/include/",
"Z:/itop-3399_8.1/system/core/include",
"Z:/itop-3399_8.1/libnativehelper/include",
"Z:/itop-3399_8.1/libnativehelper/include_jni",
"Z:/itop-3399_8.1/frameworks/base/core/jni/include",
"Z:/itop-3399_8.1/frameworks/native/libs/binder/include"

Android.mk 的修改

在LOCAL_SRC_FILES 下添加自己的com_android_server_HelloWorldService.cpp 文件

LOCAL_SRC_FILES += \\
    $(LOCAL_REL_DIR)/BroadcastRadio/JavaRef.cpp \\
    $(LOCAL_REL_DIR)/BroadcastRadio/NativeCallbackThread.cpp \\
    $(LOCAL_REL_DIR)/BroadcastRadio/BroadcastRadioservice.cpp \\
    $(LOCAL_REL_DIR)/BroadcastRadio/Tuner.cpp \\
    $(LOCAL_REL_DIR)/BroadcastRadio/TunerCallback.cpp \\
    $(LOCAL_REL_DIR)/BroadcastRadio/convert.cpp \\
    $(LOCAL_REL_DIR)/BroadcastRadio/regions.cpp \\
    $(LOCAL_REL_DIR)/com_android_server_AlarmManagerService.cpp \\
    $(LOCAL_REL_DIR)/com_android_server_am_BatteryStatsService.cpp \\
    $(LOCAL_REL_DIR)/com_android_server_connectivity_Vpn.cpp \\
    $(LOCAL_REL_DIR)/com_android_server_connectivity_tethering_OffloadHardwareInterface.cpp \\
    $(LOCAL_REL_DIR)/com_android_server_ConsumerIrService.cpp \\
    $(LOCAL_REL_DIR)/com_android_server_HardwarePropertiesManagerService.cpp \\
    $(LOCAL_REL_DIR)/com_android_server_hdmi_HdmiCecController.cpp \\
    $(LOCAL_REL_DIR)/com_android_server_input_InputApplicationHandle.cpp \\
    $(LOCAL_REL_DIR)/com_android_server_input_InputManagerService.cpp \\
    $(LOCAL_REL_DIR)/com_android_server_input_InputWindowHandle.cpp \\
    $(LOCAL_REL_DIR)/com_android_server_lights_LightsService.cpp \\
    $(LOCAL_REL_DIR)/com_android_server_location_ContextHubService.cpp \\
    $(LOCAL_REL_DIR)/com_android_server_location_GnssLocationProvider.cpp \\
    $(LOCAL_REL_DIR)/com_android_server_locksettings_SyntheticPasswordManager.cpp \\
    $(LOCAL_REL_DIR)/com_android_server_power_PowerManagerService.cpp \\
    $(LOCAL_REL_DIR)/com_android_server_SerialService.cpp \\
    $(LOCAL_REL_DIR)/com_android_server_storage_AppFuseBridge.cpp \\
    $(LOCAL_REL_DIR)/com_android_server_SystemServer.cpp \\
    $(LOCAL_REL_DIR)/com_android_server_tv_TvUinputBridge.cpp \\
    $(LOCAL_REL_DIR)/com_android_server_tv_TvInputHal.cpp \\
    $(LOCAL_REL_DIR)/com_android_server_vr_VrManagerService.cpp \\
    $(LOCAL_REL_DIR)/com_android_server_UsbDeviceManager.cpp \\
    $(LOCAL_REL_DIR)/com_android_server_UsbDescriptorParser.cpp \\
    $(LOCAL_REL_DIR)/com_android_server_UsbMidiDevice.cpp \\
    $(LOCAL_REL_DIR)/com_android_server_UsbHostManager.cpp \\
    $(LOCAL_REL_DIR)/com_android_server_VibratorService.cpp \\
    $(LOCAL_REL_DIR)/com_android_server_PersistentDataBlockService.cpp \\
    $(LOCAL_REL_DIR)/com_android_server_GraphicsStatsService.cpp \\
    ############################################################
	$(LOCAL_REL_DIR)/com_android_server_HelloWorldService.cpp \\
    ############################################################
    $(LOCAL_REL_DIR)/onload.cpp

onload.cpp修改

在namespace android 中声明自己在com_android_server_HelloWorldService.cpp 中编写的 request_android_server_HelloWorldService(JNIEnv* env) 这个函数

namespace android {
	int request_android_server_HelloWorldService(JNIEnv* env);
}

然后在JNI_OnLoad 函数中将request_android_server_HelloWorldService(JNIEnv* env) 添加进入

extern "C" jint JNI_OnLoad(JavaVM* vm, void* /* reserved */)
{
    JNIEnv* env = NULL;
    jint result = -1;

    if (vm->GetEnv((void**) &env, JNI_VERSION_1_4) != JNI_OK) {
        ALOGE("GetEnv failed!");
        return result;
    }
    ALOG_ASSERT(env, "Could not retrieve the env!");
    register_com_android_server_rkdisplay_RkDisplayModes(env);
    request_android_server_HelloWorldService(env);
    return JNI_VERSION_1_4;
}