深入显出 - Android系统移植与平台开发（十） - led HAL案例分析

include $(call all-subdir-makefiles)

# 调用宏my-dir，这个宏返回当前Android.mk文件所在的路径

LOCAL_PATH:= $(call my-dir)                                    

# 包含CLEAR_VARS变量指向的mk文件build/core/clear_vars.mk，它主要用来清除编译时依赖的编译变量

include $(CLEAR_VARS)                                   

# 指定当前目标的TAG标签，关于其作用见前面Android编译系统章节

LOCAL_MODULE_TAGS := user

# 当前mk文件的编译目标模块

LOCAL_PACKAGE_NAME := LedDemo

# 编译目标时依赖的源码，它调用了一个宏all-java-files-under，该宏在build/core/definitions.mk中定义

# 表示在当前目录下查找所有的java文件，将查找到的java文件返回

LOCAL_SRC_FILES := $(callall-java-files-under, src)

# 在编译Android应用程序时都要指定API level，也就是当前程序的编译平台版本

# 这里表示使用当前源码的版本

LOCAL_SDK_VERSION := current

# 最重要的就是这句代码，它包含了一个文件build/core/package.mk，根据前面设置的编译变量，编译生成Android包文件，即：apk文件

include $(BUILD_PACKAGE)

package com.hello;

 import com.hello.LedService;

 import com.hello.R;

 importandroid.app.Activity;

 importandroid.os.Bundle;

 importandroid.util.Log;

 importandroid.view.View;

 import android.view.View.OnClickListener;

 importandroid.widget.Button;

 public classLedDemo extends Activity {

     privateLedService led_svc;

     private Buttonbtn;

     private booleaniflag = false;

     private Stringtitle;

     /** Calledwhen the activity is first created. */

     @Override

     public voidonCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.main);

        Log.i("Java App", "OnCreate");

         led_svc =new LedService();

         btn =(Button) this.findViewById(R.id.Button01);

        this.btn.setOnClickListener(new OnClickListener() {

            public void onClick(View v) {

                Log.i("Java App", "btnOnClicked");

                if (iflag) {

                    title = led_svc.set_off();

                    btn.setText("Turn On");

                    setTitle(title);

                    iflag = false;

                } else {

                     title = led_svc.set_on();

                    btn.setText("Turn Off");

                    setTitle(title);

                    iflag = true;

                }

             }

         });

     }

 }

package com.hello;

import android.util.Log;

public class LedService {

    /*

     * loadnative service.

     */

    static {         // 静态初始化语言块，仅在类被加载时被执行一次，通常用来加载库

        Log.i ("Java Service" , "Load Native Serivce LIB" );

       System.loadLibrary ( "led_runtime" );

    }

    // 构造方法

    publicLedService() {     

        int icount ;

        Log.i ("Java Service" , "do init Native Call" );

        _init ();        

        icount =_get_count ();

        Log.d ("Java Service" , "led count = " + icount );

        Log.d ("Java Service" , "Init OK " );

    }

    /*

     * LED nativemethods.

     */

    public Stringset_on() {

        Log.i ("com.hello.LedService" , "LED On" );

        _set_on();

        return"led on" ;

     }

     publicString set_off() {

         Log.i ("com.hello.LedService" , "LED Off" );

         _set_off();

         return"led off" ;

     }

     /*

     * declareall the native interface.

     */

     privatestatic native boolean _init();

     privatestatic native int _set_on();

     privatestatic native int _set_off();

     privatestatic native int _get_count();

 }

LOCAL_PATH:= $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE_TAGS := eng

LOCAL_MODULE:= libled_runtime                    # 编译目标模块

LOCAL_SRC_FILES:= \

       services/jni/com_farsight_LedService.cpp

LOCAL_SHARED_LIBRARIES := \                       # 编译时依赖的动态库

       libandroid_runtime \

       libnativehelper \

        libcutils\

        libutils\

       libhardware

LOCAL_C_INCLUDES += \                                  #编译时用到的头文件目录

       $(JNI_H_INCLUDE)

LOCAL_PRELINK_MODULE := false                            # 本目标为非预链接模块

include $(BUILD_SHARED_LIBRARY)                # 编译生成共享动态库

#define LOG_TAG "LedService"

#include "utils/Log.h"

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

#include <assert.h>

#include <jni.h>

#include "../../../hardware/led.h"

static led_control_device_t *sLedDevice = 0;

static led_module_t* sLedModule=0;

static jint get_count(void)

{

    LOGI("%sE", __func__);

   if(sLedDevice)

        returnsLedDevice->get_led_count(sLedDevice);

    else

       LOGI("sLedDevice is null");

    return 0;

}

static jint led_setOn(JNIEnv* env, jobject thiz) {

    LOGI("%sE", __func__);

    if(sLedDevice) {

       sLedDevice->set_on(sLedDevice);

    }else{

       LOGI("sLedDevice is null");

     }

     return 0;

 }

 static jintled_setOff(JNIEnv* env, jobject thiz) {

    LOGI("%s E", __func__);

     if(sLedDevice) {

        sLedDevice->set_off(sLedDevice);

     }else{

         LOGI("sLedDevice is null");

     }

     return 0;

 }

static inline int led_control_open(const structhw_module_t* module,

     structled_control_device_t** device) {

    LOGI("%s E ", __func__);

     returnmodule->methods->open(module,

        LED_HARDWARE_MODULE_ID, (struct hw_device_t**)device);

 }

 static jintled_init(JNIEnv *env, jclass clazz)

 {

     led_module_tconst * module;

    LOGI("%s E ", __func__);

     if(hw_get_module(LED_HARDWARE_MODULE_ID, (const hw_module_t**)&module) == 0){

        LOGI("get Module OK");

        sLedModule = (led_module_t *) module;

         if(led_control_open(&module->common, &sLedDevice) != 0) {

            LOGI("led_init error");

             return-1;

         }

     }

    LOGI("led_init success");

     return 0;

 }

 /*

  *

  * Array ofmethods.

  * Each entryhas three fields: the name of the method, the method

  * signature,and a pointer to the native implementation.

  */

 static constJNINativeMethod gMethods[] = {

    {"_init",    "()Z",(void*)led_init},

     {"_set_on",   "()I",(void*)led_setOn },

     {"_set_off", "()I",(void*)led_setOff },

     {"_get_count", "()I",(void*)get_count },

 };

 static intregisterMethods(JNIEnv* env) {

     static constchar* const kClassName = "com/hello/LedService";

     jclassclazz;

     /* look upthe class */

     clazz =env->FindClass(kClassName);

     if (clazz ==NULL) {

        LOGE("Can't find class %s\n", kClassName);

         return-1;

     }

     /* registerall 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 outthe rest of the ID cache */

     return 0;

 }

 /*

  * This iscalled by the VM when the shared library is first loaded.

  */

 jintJNI_OnLoad(JavaVM* vm, void* reserved) {

     JNIEnv* env= NULL;

     jint result= -1;

    LOGI("JNI_OnLoad");

     if(vm->GetEnv((void**) &env, JNI_VERSION_1_4) != JNI_OK) {

        LOGE("ERROR: GetEnv failed\n");

         gotofail;

     }

     assert(env!= NULL);

     if(registerMethods(env) != 0) {

         LOGE("ERROR: PlatformLibrary nativeregistration failed\n");

         gotofail;

     }

     /* success-- return valid version number */

     result =JNI_VERSION_1_4;

 fail:

     returnresult;

 }

typedef struct {

         constchar* name;

         constchar* signature;

         void*fnPtr;

} JNINativeMethod;

// 构造方法

    publicLedService() {     

        int icount ;

        Log.i ("Java Service" , "do init Native Call" );

        _init ();        

        icount =_get_count ();

        Log.d ("Java Service" , "led count = " + icount );

        Log.d ("Java Service" , "Init OK " );

    }

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_C_INCLUDES += \

         include/

LOCAL_PRELINK_MODULE := false

LOCAL_MODULE_PATH := $(TARGET_OUT_SHARED_LIBRARIES)/hw

LOCAL_SHARED_LIBRARIES := liblog

LOCAL_SRC_FILES := led.c

LOCAL_MODULE := led.default

include $(BUILD_SHARED_LIBRARY)