Android SystemServer 中 Service 的创建和启动流程

// frameworks/base/services/java/com/android/server/SystemServer.java
private void run() {
    // 1. 启动引导服务 (Bootstrap Services)
    startBootstrapServices();
    // 2. 启动核心服务 (Core Services)
    startCoreServices();
    // 3. 启动其他服务 (Other Services)
    startOtherServices();
    // 4. 系统就绪后的回调
    startSystemUi(context);
    systemReady();
}

// frameworks/base/services/java/com/android/server/SystemServer.java
private void startBootstrapServices() {
    // 启动 ActivityManagerService
    mActivityManagerService = ActivityManagerService.Lifecycle.startService(
        mSystemServiceManager, atm);
    mActivityManagerService.setSystemProcess();
    // 启动 PowerManagerService
    mPowerManagerService = mSystemServiceManager.startService(PowerManagerService.class);
    // 启动 PackageManagerService
    mPackageManagerService = PackageManagerService.main(mSystemContext, installer,
        mFactoryTestMode != FactoryTest.FACTORY_TEST_OFF, mOnlyCore);
    // 更多引导服务...
}

private void startCoreServices() {
    // 启动 BatteryService
    mSystemServiceManager.startService(BatteryService.class);
    // 启动 UsageStatsService
    mSystemServiceManager.startService(UsageStatsService.class);
    mActivityManagerService.setUsageStatsManager(
        LocalServices.getService(UsageStatsManagerInternal.class));
    // 启动 WebViewUpdateService
    mWebViewUpdateService = mSystemServiceManager.startService(WebViewUpdateService.class);
    // 更多核心服务...
}

private void startOtherServices() {
    // 启动 WindowManagerService
    wm = WindowManagerService.main(context, inputManager, !mFirstBoot, mOnlyCore,
            new PhoneWindowManager(), mActivityManagerService.mActivityTaskManager);
    ServiceManager.addService(Context.WINDOW_SERVICE, wm, /* allowIsolated= */ false);
    ServiceManager.addService(Context.INPUT_SERVICE, inputManager);
    // 启动 NotificationManagerService
    mSystemServiceManager.startService(NotificationManagerService.class);
    // 启动自定义服务（如你的 MDM 服务）
    try {
        traceBeginAndSlog("StartMdmPolicyManager");
        mdmPolicyManager = new MdmPolicyManagerService(context);
        ServiceManager.addService(Context.MDM_POLICY_SERVICE, mdmPolicyManager);
        traceEnd();
    } catch (Throwable e) {
        reportWtf("starting Mdm Policy Manager", e);
    }
    // 更多其他服务...
}

// 在 SystemServer 中
mSystemServiceManager.startService(YourService.class);
// 服务类定义
public class YourService extends SystemService {
    public YourService(Context context) {
        super(context);
    }
    @Override
    public void onStart() {
        // 服务启动逻辑
        publishBinderService(Context.YOUR_SERVICE, new YourBinder());
    }
    @Override
    public void onBootPhase(int phase) {
        if (phase == SystemService.PHASE_BOOT_COMPLETED) {
            // 启动完成后的操作
        }
    }
}

// 创建服务实例
YourService yourService = new YourService(context);
// 添加到 ServiceManager
ServiceManager.addService(Context.YOUR_SERVICE, yourService);
// 或者使用带权限的添加方式
ServiceManager.addService(Context.YOUR_SERVICE, yourService, 
    false, ServiceManager.DUMP_FLAG_PRIORITY_DEFAULT);

// 服务类中的静态方法
public static YourService main(Context context) {
    YourService service = new YourService(context);
    ServiceManager.addService(Context.YOUR_SERVICE, service);
    return service;
}
// 在 SystemServer 中调用
YourService.main(mSystemContext);

public class YourService extends SystemService {
    // ...
    @Override
    public void onBootPhase(int phase) {
        if (phase == PHASE_THIRD_PARTY_APPS_CAN_START) {
            // 第三方应用可以启动时的初始化
        } else if (phase == PHASE_BOOT_COMPLETED) {
            // 系统启动完成后的操作
        }
    }
}

private void systemReady() {
    // 通知所有服务系统已就绪
    mActivityManagerService.systemReady(() -> {
        // 系统就绪后的操作
    }, BOOT_TIMINGS_TRACE_LOG);
}

// frameworks/base/core/java/android/app/IMyCustomService.aidl
package android.app;
interface IMyCustomService {
    void doSomething(int param);
    int getSomething();
}

// frameworks/base/services/core/java/com/android/server/MyCustomService.java
package com.android.server;
import android.app.IMyCustomService;
import android.content.Context;
import android.os.IBinder;
import android.util.Slog;
public class MyCustomService extends IMyCustomService.Stub {
    private static final String TAG = "MyCustomService";
    private final Context mContext;
    public MyCustomService(Context context) {
        mContext = context;
        Slog.i(TAG, "MyCustomService created");
    }
    @Override
    public void doSomething(int param) {
        Slog.d(TAG, "doSomething called with param: " + param);
        // 实现具体功能
    }
    @Override
    public int getSomething() {
        Slog.d(TAG, "getSomething called");
        return 42; // 示例返回值
    }
}

// frameworks/base/services/java/com/android/server/SystemServer.java
public final class SystemServer {
    // ...
    private void startOtherServices() {
        // ...
        // 启动自定义服务
        try {
            traceBeginAndSlog("StartMyCustomService");
            MyCustomService myCustomService = new MyCustomService(context);
            ServiceManager.addService(Context.MY_CUSTOM_SERVICE, myCustomService);
            traceEnd();
        } catch (Throwable e) {
            reportWtf("starting My Custom Service", e);
        }
        // ...
    }
}

// frameworks/base/core/java/android/content/Context.java
public abstract class Context {
    // ...
    public static final String MY_CUSTOM_SERVICE = "my_custom_service";
    // ...
}

adb shell dumpsys my_custom_service

adb shell service list

adb logcat -s SystemServer