android系统核心机制基础（09）Android 添加新模块-白红宇

android系统核心机制基础（09）Android 添加新模块

阅读量：522 次

发布时间：2019-03-07

本文共 24847 字，大约阅读时间需要 82 分钟。

该系列文章总纲链接：

本章关键点总结 & 说明：

这里主要关注➕右下角部分添加新模块即可。本章节详细解读了android新模块从驱动层、HAL层、framework层、APP层的流程。上面的图添加新模块部分可能会看不清，这里单独截取该部分，如下所示：

这样就清晰多了。本章节主要描述了android系统从上到下添加一个模块的流程，因为仅针对流程，所以关于其使用的原理本部分不会涉及，但在binder以及其他章节中会有所涉及。

1 添加驱动程序（源码见wds_hello_driver），添加流程如下：

1.1 添加代码

对应代码位置-->kernel/drivers/wds_hello，驱动层代码如下：

@1 wds_hello.h

#ifndef _WDS_HELLO_ANDROID_H_  #define _WDS_HELLO_ANDROID_H_  #include 
   
      #include 
    
       #define WDS_HELLO_DEVICE_NODE_NAME  "wds_hello"  #define WDS_HELLO_DEVICE_FILE_NAME  "wds_hello"  #define WDS_HELLO_DEVICE_PROC_NAME  "wds_hello"  #define WDS_HELLO_DEVICE_CLASS_NAME "wds_hello"  struct wds_hello_android_dev {  	int val;  	struct semaphore sem;  	struct cdev dev;  };  #endif

@2 wds_hello.c

#include 
   
      #include 
    
       #include 
     
        #include 
      
         #include 
       
          #include 
        
          #include 
         
           #include "wds_hello.h" /*主设备和从设备号变量*/ static int wds_hello_major = 0; static int wds_hello_minor = 0; /*设备类别和设备变量*/ static struct class* wds_hello_class = NULL; static struct wds_hello_android_dev* wds_hello_dev = NULL; /*传统的设备文件操作方法*/ static int wds_hello_open(struct inode* inode, struct file* filp); static int wds_hello_release(struct inode* inode, struct file* filp); static ssize_t wds_hello_read(struct file* filp, char __user *buf, size_t count, loff_t* f_pos); static ssize_t wds_hello_write(struct file* filp, const char __user *buf, size_t count, loff_t* f_pos); /*设备文件操作方法表*/ static struct file_operations wds_hello_fops = { .owner = THIS_MODULE, .open = wds_hello_open, .release = wds_hello_release, .read = wds_hello_read, .write = wds_hello_write, }; /*访问设置属性方法*/ static ssize_t wds_hello_val_show(struct device* dev, struct device_attribute* attr, char* buf); static ssize_t wds_hello_val_store(struct device* dev, struct device_attribute* attr, const char* buf, size_t count); /*定义设备属性*/ static DEVICE_ATTR(val, S_IRUGO | S_IWUSR, wds_hello_val_show, wds_hello_val_store); ////*打开设备方法*/ static int wds_hello_open(struct inode* inode, struct file* filp) { struct wds_hello_android_dev* dev; /*将自定义设备结构体保存在文件指针的私有数据域中，以便访问设备时拿来用*/ dev = container_of(inode->i_cdev, struct wds_hello_android_dev, dev); filp->private_data = dev; return 0; } /*设备文件释放时调用，空实现*/ static int wds_hello_release(struct inode* inode, struct file* filp) { return 0; } /*读取设备的寄存器val的值*/ static ssize_t wds_hello_read(struct file* filp, char __user *buf, size_t count, loff_t* f_pos) { ssize_t err = 0; struct wds_hello_android_dev* dev = filp->private_data; /*同步访问*/ if(down_interruptible(&(dev->sem))) { return -ERESTARTSYS; } if(count < sizeof(dev->val)) { goto out; } /*将寄存器val的值拷贝到用户提供的缓冲区*/ if(copy_to_user(buf, &(dev->val), sizeof(dev->val))) { err = -EFAULT; goto out; } err = sizeof(dev->val); out: up(&(dev->sem)); return err; } /*写设备的寄存器值val*/ static ssize_t wds_hello_write(struct file* filp, const char __user *buf, size_t count, loff_t* f_pos) { struct wds_hello_android_dev* dev = filp->private_data; ssize_t err = 0; /*同步访问*/ if(down_interruptible(&(dev->sem))) { return -ERESTARTSYS; } if(count != sizeof(dev->val)) { goto out; } /*将用户提供的缓冲区的值写到设备寄存器去*/ if(copy_from_user(&(dev->val), buf, count)) { err = -EFAULT; goto out; } err = sizeof(dev->val); out: up(&(dev->sem)); return err; }////*读取寄存器val的值到缓冲区buf中，内部使用*/ static ssize_t __wds_hello_get_val(struct wds_hello_android_dev* dev, char* buf) { int val = 0; /*同步访问*/ if(down_interruptible(&(dev->sem))) { return -ERESTARTSYS; } val = dev->val; up(&(dev->sem)); return snprintf(buf, PAGE_SIZE, "%d\n", val); } /*把缓冲区buf的值写到设备寄存器val中去，内部使用*/ static ssize_t __wds_hello_set_val(struct wds_hello_android_dev* dev, const char* buf, size_t count) { int val = 0; /*将字符串转换成数字*/ val = simple_strtol(buf, NULL, 10); /*同步访问*/ if(down_interruptible(&(dev->sem))) { return -ERESTARTSYS; } dev->val = val; up(&(dev->sem)); return count; } /*读取设备属性val*/ static ssize_t wds_hello_val_show(struct device* dev, struct device_attribute* attr, char* buf) { struct wds_hello_android_dev* hdev = (struct wds_hello_android_dev*)dev_get_drvdata(dev); return __wds_hello_get_val(hdev, buf); } /*写设备属性val*/ static ssize_t wds_hello_val_store(struct device* dev, struct device_attribute* attr, const char* buf, size_t count) { struct wds_hello_android_dev* hdev = (struct wds_hello_android_dev*)dev_get_drvdata(dev); return __wds_hello_set_val(hdev, buf, count); } ////*读取设备寄存器val的值，保存在page缓冲区中*/ static ssize_t wds_hello_proc_read(char* page, char** start, off_t off, int count, int* eof, void* data) { if(off > 0) { *eof = 1; return 0; } return __wds_hello_get_val(wds_hello_dev, page); } /*把缓冲区的值buff保存到设备寄存器val中去*/ static ssize_t wds_hello_proc_write(struct file* filp, const char __user *buff, unsigned long len, void* data) { int err = 0; char* page = NULL; if(len > PAGE_SIZE) { printk(KERN_ALERT"The buff is too large: %lu.\n", len); return -EFAULT; } page = (char*)__get_free_page(GFP_KERNEL); if(!page) { printk(KERN_ALERT"Failed to alloc page.\n"); return -ENOMEM; } /*先把用户提供的缓冲区值拷贝到内核缓冲区中去*/ if(copy_from_user(page, buff, len)) { printk(KERN_ALERT"Failed to copy buff from user.\n"); err = -EFAULT; goto out; } err = __wds_hello_set_val(wds_hello_dev, page, len); out: free_page((unsigned long)page); return err; } /*创建/proc/hello文件*/ static void wds_hello_create_proc(void) { struct proc_dir_entry* entry; entry = create_proc_entry(WDS_HELLO_DEVICE_PROC_NAME, 0, NULL); if(entry) { //entry->owner = THIS_MODULE; //wds modify entry->read_proc = wds_hello_proc_read; entry->write_proc = wds_hello_proc_write; } } /*删除/proc/hello文件*/ static void wds_hello_remove_proc(void) { remove_proc_entry(WDS_HELLO_DEVICE_PROC_NAME, NULL); } ////*初始化设备*/ static int __wds_hello_setup_dev(struct wds_hello_android_dev* dev) { int err; dev_t devno = MKDEV(wds_hello_major, wds_hello_minor); memset(dev, 0, sizeof(struct wds_hello_android_dev)); cdev_init(&(dev->dev), &wds_hello_fops); dev->dev.owner = THIS_MODULE; dev->dev.ops = &wds_hello_fops; /*注册字符设备*/ err = cdev_add(&(dev->dev),devno, 1); if(err) { return err; } /*初始化信号量和寄存器val的值*/ //init_MUTEX(&(dev->sem)); sema_init(&(dev->sem),1); //wds modify dev->val = 0; return 0; } /*模块加载方法*/ static int __init wds_hello_init(void){ int err = -1; dev_t dev = 0; struct device* temp = NULL; printk(KERN_ALERT"Initializing wds_hello device.\n"); /*动态分配主设备和从设备号*/ err = alloc_chrdev_region(&dev, 0, 1, WDS_HELLO_DEVICE_NODE_NAME); if(err < 0) { printk(KERN_ALERT"Failed to alloc char dev region.\n"); goto fail; } wds_hello_major = MAJOR(dev); wds_hello_minor = MINOR(dev); /*分配helo设备结构体变量*/ wds_hello_dev = kmalloc(sizeof(struct wds_hello_android_dev), GFP_KERNEL); if(!wds_hello_dev) { err = -ENOMEM; printk(KERN_ALERT"Failed to alloc hello_dev.\n"); goto unregister; } /*初始化设备*/ err = __wds_hello_setup_dev(wds_hello_dev); if(err) { printk(KERN_ALERT"Failed to setup dev: %d.\n", err); goto cleanup; } /*在/sys/class/目录下创建设备类别目录hello*/ wds_hello_class = class_create(THIS_MODULE, WDS_HELLO_DEVICE_CLASS_NAME); if(IS_ERR(wds_hello_class)) { err = PTR_ERR(wds_hello_class); printk(KERN_ALERT"Failed to create hello class.\n"); goto destroy_cdev; } /*在/dev/目录和/sys/class/hello目录下分别创建设备文件hello*/ temp = device_create(wds_hello_class, NULL, dev, "%s", WDS_HELLO_DEVICE_FILE_NAME); if(IS_ERR(temp)) { err = PTR_ERR(temp); printk(KERN_ALERT"Failed to create hello device."); goto destroy_class; } /*在/sys/class/hello/hello目录下创建属性文件val*/ err = device_create_file(temp, &dev_attr_val); if(err < 0) { printk(KERN_ALERT"Failed to create attribute val."); goto destroy_device; } dev_set_drvdata(temp, wds_hello_dev); /*创建/proc/hello文件*/ wds_hello_create_proc(); printk(KERN_ALERT"Succedded to initialize hello device.\n"); return 0; destroy_device: device_destroy(wds_hello_class, dev); destroy_class: class_destroy(wds_hello_class); destroy_cdev: cdev_del(&(wds_hello_dev->dev)); cleanup: kfree(wds_hello_dev); unregister: unregister_chrdev_region(MKDEV(wds_hello_major, wds_hello_minor), 1); fail: return err; } /*模块卸载方法*/ static void __exit wds_hello_exit(void) { dev_t devno = MKDEV(wds_hello_major, wds_hello_minor); printk(KERN_ALERT"Destroy hello device.\n"); /*删除/proc/hello文件*/ wds_hello_remove_proc(); /*销毁设备类别和设备*/ if(wds_hello_class) { device_destroy(wds_hello_class, MKDEV(wds_hello_major, wds_hello_minor)); class_destroy(wds_hello_class); } /*删除字符设备和释放设备内存*/ if(wds_hello_dev) { cdev_del(&(wds_hello_dev->dev)); kfree(wds_hello_dev); } /*释放设备号*/ unregister_chrdev_region(devno, 1); } MODULE_LICENSE("GPL"); MODULE_DESCRIPTION("First Android Driver"); module_init(wds_hello_init); module_exit(wds_hello_exit);

@3 创建Makefile文件并添加一行：

obj-$(CONFIG_WDS_HELLO) += wds_hello.o

@4 创建Kconfig配置文件并添加一行：

config WDS_HELLO           tristate "wds First Android Driver wds_hello"           default n           help           This is the first android driver

1.2 配置代码

同时，配置对应代码-->kernel/drivers/Kconfig 与 kernel/drivers/Makefile

@1 Kconfig代码添加如下：

menu "Device Drivers"source "drivers/base/Kconfig"#...source "drivers/sensors/Kconfig"#wds_addsource "drivers/wds_hello/Kconfig"endmenu

@2 Makefile代码配置添加如下：

## Makefile for the Linux kernel device drivers.## 15 Sep 2000, Christoph Hellwig 
   
    # Rewritten to use lists instead of if-statements.## GPIO must come after pinctrl as gpios may need to mux pins etcobj-y				+= pinctrl/obj-y				+= gpio/obj-$(CONFIG_PCI)		+= pci/obj-$(CONFIG_PARISC)		+= parisc/obj-$(CONFIG_RAPIDIO)		+= rapidio/#...obj-$(CONFIG_CORESIGHT)		+= coresight/obj-$(CONFIG_BIF)		+= bif/obj-$(CONFIG_SENSORS)		+= sensors/#wds addobj-$(CONFIG_WDS_HELLO)		+= wds_hello/

接下来的配置对应代码-->arch/arm/configs/msm8226-config 与 arch/arm/Kconfig

注：后面的配置主要跟平台有关，上面的是高通平台的修改方案，其余平台参照其内核的编译配置即可

@3 msm8226_defconfig的添加如下：

#...CONFIG_MSM_RDBG=m #carl add for touchpad gesture input 2014 7 18CONFIG_KEYBOARD_LOE=yCONFIG_FOR_EVT=y#CONFIG_FOR_EVB is not set#config the VGA display for watch strap connect the debug board#CONFIG_FOR_VGA=yCONFIG_AVERAGE=y#CONFIG_FOR_EVT3=y#wds addCONFIG_WDS_HELLO=y

Kconifg实现如下：

#...source "lib/Kconfig"#wds addsource "drivers/wds_hello/Kconfig"

这里的配置文件和平台关系很大，这里仅给出msm8226平台作为参考。

1.3 编译代码

make bootimage，确保这里无误后才可以继续写demo测试程序

2 编写驱动测试程序（源码见wds_hello_driver），添加流程如下：

2.1 添加代码

测试代码这里对应位置代码-->external/wds_test

代码实现如下：

#include 
   
      #include 
    
       #include 
     
        #define DEVICE_NAME "/dev/wds_hello"  int main(int argc, char** argv){  	int fd = -1;  	int val = 0;  	fd = open(DEVICE_NAME, O_RDWR);  	if(fd == -1) {  		printf("Failed to open device %s.\n", DEVICE_NAME);  		return -1;  	}  	printf("Read original value:\n");  	read(fd, &val, sizeof(val));  	printf("%d.\n\n", val);  	if(argc == 2){		val = atoi(argv[1]);  	}else{		val = 3;	}		printf("Write value %d to %s.\n\n", val, DEVICE_NAME);  	write(fd, &val, sizeof(val));  	printf("Read the value again:\n");  	read(fd, &val, sizeof(val));  	printf("%d.\n\n", val);  	close(fd);  	return 0;  }

同时Android.mk实现如下：

LOCAL_PATH := $(call my-dir)include $(CLEAR_VARS)LOCAL_MODULE_TAGS := optionalLOCAL_MODULE := wds_helloLOCAL_SRC_FILES := $(call all-subdir-c-files)include $(BUILD_EXECUTABLE)

2.2 编译代码

mmm external/wds_hello

3 编写HAL层代码（源码见wds_hello_hal）

3.1 添加代码

hal_include<--对应代码-->hardware/libhardware/include

代码实现如下：

#ifndef ANDROID_WDS_HELLO_INTERFACE_H  #define ANDROID_WDS_HELLO_INTERFACE_H  #include 
   
      __BEGIN_DECLS  /*定义模块ID*/  #define WDS_HELLO_HARDWARE_MODULE_ID "wds_hello"  /*硬件模块结构体*/  struct wds_hello_module_t {  	struct hw_module_t common;  };  /*硬件接口结构体*/  struct wds_hello_device_t {  	struct hw_device_t common;  	int fd;  	int (*set_val)(struct wds_hello_device_t* dev, int val);  	int (*get_val)(struct wds_hello_device_t* dev, int* val);  };  __END_DECLS  #endif

hal_module_wds_hello<--对应代码-->hardware/libhardware/modules/wds_hello/

wds_hello.c代码实现如下：

#define LOG_TAG "WDS_HelloStub"  #include 
   
      #include 
    
       #include 
     
        #include 
      
         #include 
       
          #include 
        
          #define DEVICE_NAME "/dev/wds_hello" #define MODULE_NAME "wds_hello" #define MODULE_AUTHOR "DS-AGS" /*设备打开和关闭接口*/ static int wds_hello_device_open(const struct hw_module_t* module, const char* name, struct hw_device_t** device); static int wds_hello_device_close(struct hw_device_t* device); /*设备访问接口*/ static int wds_hello_set_val(struct wds_hello_device_t* dev, int val); static int wds_hello_get_val(struct wds_hello_device_t* dev, int* val); /*模块方法表*/ static struct hw_module_methods_t wds_hello_module_methods = { open: wds_hello_device_open}; /*模块实例变量*/ struct wds_hello_module_t HAL_MODULE_INFO_SYM = { common: { tag: HARDWARE_MODULE_TAG, version_major: 1, version_minor: 0, id: WDS_HELLO_HARDWARE_MODULE_ID, name: MODULE_NAME, author: MODULE_AUTHOR, methods: &wds_hello_module_methods, } }; ///static int wds_hello_device_open(const struct hw_module_t* module, const char* name, struct hw_device_t** device) { struct wds_hello_device_t* dev; dev = (struct wds_hello_device_t*)malloc(sizeof(struct wds_hello_device_t)); if(!dev) { ALOGE("Hello Stub: failed to alloc space"); return -EFAULT; } memset(dev, 0, sizeof(struct wds_hello_device_t)); dev->common.tag = HARDWARE_DEVICE_TAG; dev->common.version = 0; dev->common.module = (hw_module_t*)module; dev->common.close = wds_hello_device_close; dev->set_val = wds_hello_set_val; dev->get_val = wds_hello_get_val; if((dev->fd = open(DEVICE_NAME, O_RDWR)) == -1) { ALOGE("Hello Stub: failed to open /dev/hello -- %s.", strerror(errno)); free(dev); return -EFAULT; } *device = &(dev->common); ALOGI("WDS_Hello Stub: open /dev/wds_hello successfully."); return 0; } ///static int wds_hello_device_close(struct hw_device_t* device) { struct wds_hello_device_t* wds_hello_device = (struct wds_hello_device_t*)device; if(wds_hello_device) { close(wds_hello_device->fd); free(wds_hello_device); } return 0; } static int wds_hello_set_val(struct wds_hello_device_t* dev, int val) { ALOGI("WDS_Hello Stub: set value %d to device.", val); write(dev->fd, &val, sizeof(val)); return 0;}static int wds_hello_get_val(struct wds_hello_device_t* dev, int* val) { if(!val) { ALOGE("WDS_Hello Stub: error val pointer"); return -EFAULT; } read(dev->fd, val, sizeof(*val)); ALOGI("WDS_Hello Stub: get value %d from device", *val); return 0; }

同时Android.mk 代码实现如下：

LOCAL_PATH := $(call my-dir)include $(CLEAR_VARS)LOCAL_MODULE_TAGS := optionalLOCAL_PRELINK_MODULE := falseLOCAL_MODULE_PATH := $(TARGET_OUT_SHARED_LIBRARIES)/hwLOCAL_SHARED_LIBRARIES := liblog libcutilsLOCAL_SRC_FILES := wds_hello.cLOCAL_MODULE := wds_hello.defaultinclude $(BUILD_SHARED_LIBRARY)

3.2 配置代码

system_core_rootdir_ueventd_rc<--对应代码--> system/core/rootdir/uevent.rc

uevent.rc代码添加如下：

/dev/null                 0666   root       root/dev/zero                 0666   root       root/dev/full                 0666   root       root/dev/ptmx                 0666   root       root/dev/tty                  0666   root       root/dev/random               0666   root       root/dev/urandom              0666   root       root/dev/ashmem               0666   root       root/dev/binder               0666   root       root/dev/wds_hello			  0666   root		root	//wds add/dev/touchpad_mode_switch                     0666   root       root // root permission/dev/touchpanel_switch                        0666   root       root  // permission//...

3.3 编译代码

mmm hardware/libhardware/modules/wds_hello/;

make snod;

4 编写framework层代码（源码见wds_hello_framework），添加流程如下：

4.1 添加与修改代码

framework_base_services_jni<--对应代码-->framework/base/services/jni

@1 com_android_server_WDS_HelloService.c代码实现如下：

#include "jni.h"  #include "JNIHelp.h"  #include "android_runtime/AndroidRuntime.h"  #include 
   
      #include 
    
       #include 
     
        #include 
      
         #include 
       
          #define LOG_TAG "wdsHelloService"  namespace android  {  	/*在硬件抽象层中定义的硬件访问结构体，参考
        
         */ struct wds_hello_device_t* wds_hello_device = NULL; /*通过硬件抽象层定义的硬件访问接口设置硬件寄存器val的值*/ static void wds_hello_setVal(JNIEnv* env, jobject clazz, jint value) { int val = value; ALOGI("Hello JNI: set value %d to device.", val); if(!wds_hello_device) { ALOGI("Hello JNI: device is not open."); return; } wds_hello_device->set_val(wds_hello_device, val); } /*通过硬件抽象层定义的硬件访问接口读取硬件寄存器val的值*/ static jint wds_hello_getVal(JNIEnv* env, jobject clazz) { int val = 0; if(!wds_hello_device) { ALOGI("Hello JNI: device is not open."); return val; } wds_hello_device->get_val(wds_hello_device, &val); ALOGI("Hello JNI: get value %d from device.", val); return val; } /*通过硬件抽象层定义的硬件模块打开接口打开硬件设备*/ static inline int wds_hello_device_open(const hw_module_t* module, struct wds_hello_device_t** device) { return module->methods->open(module, WDS_HELLO_HARDWARE_MODULE_ID, (struct hw_device_t**)device); } /*通过硬件模块ID来加载指定的硬件抽象层模块并打开硬件*/ static jboolean wds_hello_init(JNIEnv* env, jclass clazz) { wds_hello_module_t* module; ALOGI("WDS_Hello JNI: initializing......"); if(hw_get_module(WDS_HELLO_HARDWARE_MODULE_ID, (const struct hw_module_t**)&module) == 0) { ALOGI("WDS_Hello JNI: hello Stub found."); if(wds_hello_device_open(&(module->common), &wds_hello_device) == 0) { ALOGI("WDS_Hello JNI: hello device is open."); return 0; } ALOGE("WDS_Hello JNI: failed to open hello device."); return -1; } ALOGE("WDS_Hello JNI: failed to get hello stub module."); return -1; } /*JNI方法表*/ static const JNINativeMethod method_table[] = { {"init_native", "()Z", (void*)wds_hello_init}, {"setVal_native", "(I)V", (void*)wds_hello_setVal}, {"getVal_native", "()I", (void*)wds_hello_getVal}, }; /*注册JNI方法*/ int register_android_server_WDS_HelloService(JNIEnv *env) { return jniRegisterNativeMethods(env, "com/android/server/WDS_HelloService", method_table, NELEM(method_table)); } };

@2 onload.cpp代码添加如下：

#include "JNIHelp.h"#include "jni.h"#include "utils/Log.h"#include "utils/misc.h"namespace android {int register_android_server_AlarmManagerService(JNIEnv* env);int register_android_server_ConsumerIrService(JNIEnv *env);//...int register_android_server_WDS_HelloService(JNIEnv *env);//wds add};using namespace android;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_android_server_PowerManagerService(env);    register_android_server_SerialService(env);    //...    register_android_server_WDS_HelloService(env); //wds add    return JNI_VERSION_1_4;}

Android.mk代码添加如下：

LOCAL_PATH:= $(call my-dir)include $(CLEAR_VARS)LOCAL_SRC_FILES:= \    com_android_server_AlarmManagerService.cpp \    #...    com_android_server_WDSHelloService.cpp \    onload.cpp#...

framework_base_core_java_android_os<--对应代码-->framework/base/core/java/android/os

IWDSHelloService.aidl的实现如下所示：

package android.os;  interface IWDSHelloService {  	void setVal(int val);  	int getVal();  }

@3 framework_base<--对应代码-->framework/base/Android.mk

代码添加如下：

LOCAL_SRC_FILES += \	core/java/android/accessibilityservice/IAccessibilityServiceConnection.aidl \#...		core/java/android/os/IWDSHelloService.aidl \#...

4.2 编译代码生成stub类

mmm framework/base/services/jni;

mmm framework/base/core/java/android/os;

mmm framework/base;

make snod;

4.3 添加代码

framework_base_services_java<--对应代码-->framework/base/services/java

生成的service如下所示：

package com.android.server;  import android.content.Context;  import android.os.IWDSHelloService;  import android.util.Slog;  public class WDSHelloService extends IWDSHelloService.Stub {  	private static final String TAG = "WDSHelloService";  	WDSHelloService() {  		init_native();  	}  	public void setVal(int val) {  		setVal_native(val);  	}     	public int getVal() {  		return getVal_native();  	}  	private static native boolean init_native();  	private static native void setVal_native(int val);  	private static native int getVal_native();  };

同时，保证开机启动该服务，在SystemServer.java中添加代码：

//...			try {				Slog.i(TAG, "Print Service");				printManager = new PrintManagerService(context);				ServiceManager.addService(Context.PRINT_SERVICE, printManager);			} catch (Throwable e) {				reportWtf("starting Print Service", e);			}			if (!disableNonCoreServices) {				try {					Slog.i(TAG, "Media Router Service");					mediaRouter = new MediaRouterService(context);					ServiceManager.addService(Context.MEDIA_ROUTER_SERVICE, mediaRouter);				} catch (Throwable e) {					reportWtf("starting MediaRouterService", e);				}			}			try {				Slog.i(TAG, "WDS_Hello Service");				ServiceManager.addService("wds_hello", new WDSHelloService());			} catch (Throwable e) {				Slog.e(TAG, "Failure starting WDS Hello Service", e);			}		}//...

因为每个版本代码是不一样的，只要在服务启动项中添加即可。

4.4 整体编译

make snod

5 编写APP demo测试服务（源码见wds_hello_APP）

5.1 android studio中添加代码

wds_hello_APP<--对应代码-->packages/apps/wds_hello

package com.ags.wds;//import com.ags.wds.R;import android.app.Activity;import android.os.ServiceManager; import android.os.IWDSHelloService; import android.os.Bundle;import android.os.RemoteException;import android.util.Log;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.EditText;public class MainActivity extends Activity implements OnClickListener {	private final static String LOG_TAG = "com.ags.wds_Hello";	private IWDSHelloService wdshelloService = null;	private EditText valueText = null;	private Button readButton = null;	private Button writeButton = null;	private Button clearButton = null;	@Override	protected void onCreate(Bundle savedInstanceState) {		super.onCreate(savedInstanceState);		setContentView(R.layout.activity_main);		wdshelloService = IWDSHelloService.Stub.asInterface(ServiceManager.getService("wds_hello"));		valueText = (EditText) findViewById(R.id.edit_value);		readButton = (Button) findViewById(R.id.button_read);		writeButton = (Button) findViewById(R.id.button_write);		clearButton = (Button) findViewById(R.id.button_clear);		readButton.setOnClickListener(this);		writeButton.setOnClickListener(this);		clearButton.setOnClickListener(this);		Log.i(LOG_TAG, "WDS Hello Activity Created");	}	@Override	public void onClick(View v) {		if (v.equals(readButton)) {			try {				int val = wdshelloService.getVal();				String text = String.valueOf(val);				valueText.setText(text);			} catch (RemoteException e) {				Log.e(LOG_TAG,"Remote Exception while reading value from device.");			}		} else if (v.equals(writeButton)) {			try {				String text = valueText.getText().toString();				int val = Integer.parseInt(text);				wdshelloService.setVal(val);			} catch (RemoteException e) {				Log.e(LOG_TAG,"Remote Exception while writing value to device.");			}		} else if (v.equals(clearButton)) {			String text = "";			valueText.setText(text);		}	}}

同时activity_main.xml文件如下所示：

这里 Android.mk文件实现如下：

LOCAL_PATH:= $(call my-dir)include $(CLEAR_VARS)LOCAL_MODULE_TAGS := optionalLOCAL_SRC_FILES := $(call all-subdir-java-files)LOCAL_PACKAGE_NAME := wds_Helloinclude $(BUILD_PACKAGE)include $(call all-makefiles-under,$(LOCAL_PATH))

同时APP demo其他文件自动生成。

5.2 编译代码

mmm packages/apps/wds_hello

6 总结

工程整体框架如下所示：//wds_modules in android

├── wds_hello_APP

│ ├── AndroidManifest.xml

│ ├── Android.mk

│ ├── ic_launcher-web.png

│ ├── proguard-project.txt

│ ├── project.properties

│ ├── res