Android 驱动开发系列五

这一篇将说到 如何为JNI接口（Frameworks层）添加对应的service访问服务

 

在Android系统中，硬件服务一般是运行在一个独立的进程中为各种应用程序提供服务。因此，调用这些硬件服务的应用程序与这些硬件服务之间

的痛惜需要通过代理来进行。为此，我们需要先定义好通信的接口。

 

1、定义通信接口

进入到android-4.0.4_r1.2/frameworks/base/core/java/android/os目录，添加 ITTTService.aidl 文件：

root@brantyou-ubuntu:~/workspace/android-4.0.4_r1.2/frameworks/base/core/java/android/os# gedit ITTTService.aidl root@brantyou-ubuntu:~/workspace/android-4.0.4_r1.2/frameworks/base/core/java/android/os#

其内容如下：

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

 

2、添加接口文件编译配置

进入到 android-4.0.4_r1.2/frameworks/base 目录，打开 Android.mk 文件，在 LOCAL_SRC_FILES 变量中加入这么一行：

core/java/android/os/ITTTService.aidl \

 

3、实现service处理

进入到 android-4.0.4_r1.2/frameworks/base/services/java/com/android/server 目录，添加 TTTService.java 文件：

root@brantyou-ubuntu:~/workspace/android-4.0.4_r1.2/frameworks/base/services/java/com/android/server# gedit TTTService.java 

文件内容如下：

package com.android.server;import android.content.Context;import android.os.ITTTService;import android.util.Slog;public class TTTService extends ITTTService.Stub{private static final String TAG = "TTTService";TTTService(){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();};

TTTService 主要是通过调用 JNI 方法中的 init_native、setVal_native 和 getVal_native （这些接口我们在上一篇实现JNI里面提供出来的）来提供硬件服务。

 

4、配置开机启动TTTService服务

打开android-4.0.4_r1.2/frameworks/base/services/java/com/android/server 目录下的 SystemServer.java 文件，在其中的 run() 函数中找到
            try {
                Slog.i(TAG, "DiskStats Service");
                ServiceManager.addService("diskstats", new DiskStatsService(context));
            } catch (Throwable e) {
                reportWtf("starting DiskStats Service", e);
            }

这一段，在后面加上下面的代码：

            try {                Slog.i(TAG, "TTT Service");                ServiceManager.addService("ttt", new TTTService());            } catch (Throwable e) {                // TODO: handle exception                reportWtf("Failure starting TTTService", e);            }

在这个文件前面不用忘了加入引用：

import com.android.server.TTTService;

 

5、开始编译

我这里已经执行了 build/envsetup.sh ，就不执行了，没有执行这个的，需要先执行这个文件再进行源码编译。

执行下面的指令，编译生成ITTTService的stub接口： 

root@brantyou-ubuntu:~/workspace/android-4.0.4_r1.2# mmm frameworks/base============================================PLATFORM_VERSION_CODENAME=RELPLATFORM_VERSION=4.0.4TARGET_PRODUCT=fullTARGET_BUILD_VARIANT=engTARGET_BUILD_TYPE=releaseTARGET_BUILD_APPS=TARGET_ARCH=armTARGET_ARCH_VARIANT=armv7-aHOST_ARCH=x86HOST_OS=linuxHOST_BUILD_TYPE=releaseBUILD_ID=IMM76I============================================make:进入目录'/home/brantyou/workspace/android-4.0.4_r1.2'target Dex: frameworkCopying: out/target/common/obj/JAVA_LIBRARIES/framework_intermediates/noproguard.classes.dextarget Jar: framework (out/target/common/obj/JAVA_LIBRARIES/framework_intermediates/javalib.jar) 'out/target/common/obj/JAVA_LIBRARIES/framework_intermediates/classes.dex' as 'classes.dex'...Dexpreopt Boot Jar: out/target/product/generic/dex_bootjars/system/framework/framework.odexProcessing target/product/generic/dex_bootjars/system/framework/framework.jarDone!Install: out/target/product/generic/system/framework/framework.odexInstall: out/target/product/generic/system/framework/framework.jarmake:离开目录“/home/brantyou/workspace/android-4.0.4_r1.2”root@brantyou-ubuntu:~/workspace/android-4.0.4_r1.2# 

 

编译 TTTService 服务：

root@brantyou-ubuntu:~/workspace/android-4.0.4_r1.2# mmm frameworks/base/services/java============================================PLATFORM_VERSION_CODENAME=RELPLATFORM_VERSION=4.0.4TARGET_PRODUCT=fullTARGET_BUILD_VARIANT=engTARGET_BUILD_TYPE=releaseTARGET_BUILD_APPS=TARGET_ARCH=armTARGET_ARCH_VARIANT=armv7-aHOST_ARCH=x86HOST_OS=linuxHOST_BUILD_TYPE=releaseBUILD_ID=IMM76I============================================make:进入目录'/home/brantyou/workspace/android-4.0.4_r1.2'target Java: services (out/target/common/obj/JAVA_LIBRARIES/services_intermediates/classes)注意：某些输入文件使用或覆盖了已过时的 API。注意：要了解详细信息，请使用 -Xlint:deprecation 重新编译。注意：某些输入文件使用了未经检查或不安全的操作。注意：要了解详细信息，请使用 -Xlint:unchecked 重新编译。Copying: out/target/common/obj/JAVA_LIBRARIES/services_intermediates/classes-jarjar.jarCopying: out/target/common/obj/JAVA_LIBRARIES/services_intermediates/emma_out/lib/classes-jarjar.jarCopying: out/target/common/obj/JAVA_LIBRARIES/services_intermediates/classes.jarCopying: out/target/common/obj/JAVA_LIBRARIES/services_intermediates/noproguard.classes.jartarget Dex: servicesCopying: out/target/common/obj/JAVA_LIBRARIES/services_intermediates/noproguard.classes.dextarget Jar: services (out/target/common/obj/JAVA_LIBRARIES/services_intermediates/javalib.jar) 'out/target/common/obj/JAVA_LIBRARIES/services_intermediates/classes.dex' as 'classes.dex'...Dexpreopt Boot Jar: out/target/product/generic/dex_bootjars/system/framework/android.policy.odexProcessing target/product/generic/dex_bootjars/system/framework/android.policy.jarDone!Dexpreopt Boot Jar: out/target/product/generic/dex_bootjars/system/framework/services.odexProcessing target/product/generic/dex_bootjars/system/framework/services.jarDone!Install: out/target/product/generic/system/framework/services.odexInstall: out/target/product/generic/system/framework/services.jarmake:离开目录“/home/brantyou/workspace/android-4.0.4_r1.2”root@brantyou-ubuntu:~/workspace/android-4.0.4_r1.2# 

重新打包 system.img ：

root@brantyou-ubuntu:~/workspace/android-4.0.4_r1.2# make snod============================================PLATFORM_VERSION_CODENAME=RELPLATFORM_VERSION=4.0.4TARGET_PRODUCT=full_smdkv210TARGET_BUILD_VARIANT=engTARGET_BUILD_TYPE=releaseTARGET_BUILD_APPS=TARGET_ARCH=armTARGET_ARCH_VARIANT=armv7-a-neonHOST_ARCH=x86HOST_OS=linuxHOST_BUILD_TYPE=releaseBUILD_ID=IMM76I============================================build/core/Makefile:25: 警告：覆盖关于目标“out/target/product/smdkv210/system/bin/pppd”的命令build/core/base_rules.mk:523: 警告：忽略关于目标“out/target/product/smdkv210/system/bin/pppd”的旧命令make snod: ignoring dependenciesTarget system fs image: out/target/product/smdkv210/system.imgout/target/product/smdkv210/system.img total size is 150853824root@brantyou-ubuntu:~/workspace/android-4.0.4_r1.2# 

 

好，到此，添加Service访问JNI接口的已经完了。接下来将会是Android程序调用Service服务来调用底层接口读写。