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[Android][Framework] 添加系统服务

做系统开发,有时候需要自己定义一些接口供App使用, 同时为了方便维护管理,就会需要自己建立一个服务,把新的功能集中在一起。下面就是新建一个系统服务的基本步骤。

  1. 添加接口

    frameworks/base/core/java/android/app/IDemoManager.aidl

    package android.app;

    interface IDemoManager
    {
    int getCpuTemperature();
    }
  2. 添加服务,实现aidl文件定义的接口

    frameworks/base/services/core/java/com/android/server/DemoManagerService.java

    package com.android.server;

    import android.app.IDemoManager;
    import android.content.Context;
    import android.util.Slog;

    public class DemoManagerService extends IDemoManager.Stub {
    private Context mContext;

    public DemoManagerService(Context context) {
    mContext = context;
    Slog.d("Demo", "Construct");
    }

    @Override
    public int getCpuTemperature() {
    return 100; // Test code
    }
    }
  3. 添加对应的Manager

    frameworks/base/core/java/android/app/DemoManager.java

    package android.app;

    import android.content.Context;
    import android.os.RemoteException;
    import android.util.Slog;

    public class DemoManager {
    Context mContext;
    IDemoManager mService;

    public DemoManager(Context context, IDemoManager service) {
    mContext = context;
    mService = service;
    }

    public int getCpuTemperature() {
    if (mService != null) {
    try {
    return mService.getCpuTemperature();
    } catch (RemoteException e) {
    Slog.e("Demo", "RemoteException " + e);
    }
    }
    return -1;
    }
    }
  4. 添加aidl到Makefile src

    frameworks/base/Android.mk

    LOCAL_SRC_FILES += \
    core/java/android/app/IDemoManager.aidl \
  5. 添加DEMO_SERVICE常量

    frameworks/base/core/java/android/content/Context.java

    public static final String DEMO_SERVICE = "demo";
  6. 注册系统服务

    frameworks/base/core/java/android/app/SystemServiceRegistry.java

    registerService(Context.ORISLINK_SERVICE, DemoManager.class,
    new CachedServiceFetcher<DemoManager>() {
    @Override
    public DemoManager createService(ContextImpl ctx) {
    IBinder b = ServiceManager.getService(Context.DEMO_SERVICE);
    return new DemoManager(ctx, IDemoManager.Stub.asInterface(b));
    }});
  7. 开机启动服务

    frameworks/base/services/java/com/android/server/SystemServer.java

    try {
    ServiceManager.addService(Context.DEMO_SERVICE, new DemoManagerService(context));
    } catch (Throwable e) {
    Slog.e("Demo", "Failed to start Demo Service " + e);
    }
  8. 编译源码,因为添加了接口,所以需要

    make update-api

    更新接口。然后再整编刷机。

  9. service list 查看服务,不存在,这是因为selinux权限没加。

  10. 添加sepolicy权限

    device/qcom/sepolicy/msm8937/service.te

    type demo_service, system_api_service, system_server_service, service_manager_type;

    device/qcom/sepolicy/msm8937/service_contexts

    demo  u:object_r:demo_service:s0
  11. 重新编译代码,使用下面测试代码验证

    import android.app.DemoManager;

    DemoManager om = (DemoManager) getSystemService(Context.DEMO_SERVICE);
    Log.d(TAG, "Current temperature is " + om.getCpuTemperature());

    最终log打印出100,服务添加完成。

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