Android AMS 架构之 ActivityManager

热度 ℃

ActivityManagerService架构中服务端AMS和客户端交互流程，通过Binder机制，上层App将请求发给AMS，AMS做出对应的请求处理。

IActivityManager.java

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/**
 * System private API for talking with the activity manager service.  This
 * provides calls from the application back to the activity manager.
 *
 * {@hide}
 */
public interface IActivityManager extends IInterface {
    public int startActivity(IApplicationThread caller, String callingPackage, Intent intent,
            String resolvedType, IBinder resultTo, String resultWho, int requestCode, int flags,
            ProfilerInfo profilerInfo, Bundle options) throws RemoteException;
    public int startActivityAsUser(IApplicationThread caller, String callingPackage, Intent intent,
            String resolvedType, IBinder resultTo, String resultWho, int requestCode, int flags,
            ProfilerInfo profilerInfo, Bundle options, int userId) throws RemoteException;
    public int startActivityAsCaller(IApplicationThread caller, String callingPackage,
            Intent intent, String resolvedType, IBinder resultTo, String resultWho, int requestCode,
            int flags, ProfilerInfo profilerInfo, Bundle options, boolean ignoreTargetSecurity,
            int userId) throws RemoteException;
    public WaitResult startActivityAndWait(IApplicationThread caller, String callingPackage,
            Intent intent, String resolvedType, IBinder resultTo, String resultWho,
            int requestCode, int flags, ProfilerInfo profilerInfo, Bundle options,
            int userId) throws RemoteException;
    public int startActivityWithConfig(IApplicationThread caller, String callingPackage,
            Intent intent, String resolvedType, IBinder resultTo, String resultWho,
            int requestCode, int startFlags, Configuration newConfig,
            Bundle options, int userId) throws RemoteException;
    public int startActivityFromRecents(int taskId, Bundle options) throws RemoteException;
    public boolean finishActivity(IBinder token, int code, Intent data, boolean finishTask)
            throws RemoteException;
    public void finishSubActivity(IBinder token, String resultWho, int requestCode) throws RemoteException;
    public boolean finishActivityAffinity(IBinder token) throws RemoteException;
    public void finishVoiceTask(IVoiceInteractionSession session) throws RemoteException;
    public boolean releaseActivityInstance(IBinder token) throws RemoteException;
    public void releaseSomeActivities(IApplicationThread app) throws RemoteException;
    public boolean willActivityBeVisible(IBinder token) throws RemoteException;
    public Intent registerReceiver(IApplicationThread caller, String callerPackage,
            IIntentReceiver receiver, IntentFilter filter,
            String requiredPermission, int userId) throws RemoteException;
    public void unregisterReceiver(IIntentReceiver receiver) throws RemoteException;
    public int broadcastIntent(IApplicationThread caller, Intent intent,
            String resolvedType, IIntentReceiver resultTo, int resultCode,
            String resultData, Bundle map, String[] requiredPermissions,
            int appOp, Bundle options, boolean serialized, boolean sticky, int userId) throws RemoteException;
    public void unbroadcastIntent(IApplicationThread caller, Intent intent, int userId) throws RemoteException;
    public void finishReceiver(IBinder who, int resultCode, String resultData, Bundle map,
            boolean abortBroadcast, int flags) throws RemoteException;
    public void attachApplication(IApplicationThread app) throws RemoteException;
    public void activityResumed(IBinder token) throws RemoteException;
    // ...
}

IActivityManager定义了一系列的Activity生命周期相关的方法，在Binder服务端和客户端，都有它的实现。

ActivityManagerNative.java

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/** {@hide} */
public abstract class ActivityManagerNative extends Binder implements IActivityManager
{
    /**
     * Cast a Binder object into an activity manager interface, generating
     * a proxy if needed.
     */
    static public IActivityManager asInterface(IBinder obj) {
        if (obj == null) {
            return null;
        }
        IActivityManager in =
            (IActivityManager)obj.queryLocalInterface(descriptor);
        if (in != null) {
            return in;
        }
        return new ActivityManagerProxy(obj);
    }
    /**
     * Retrieve the system's default/global activity manager.
     */
    static public IActivityManager getDefault() {
        return gDefault.get();
    }
    /**
     * Convenience for checking whether the system is ready.  For internal use only.
     */
    static public boolean isSystemReady() {
        if (!sSystemReady) {
            sSystemReady = getDefault().testIsSystemReady();
        }
        return sSystemReady;
    }
    static boolean sSystemReady = false;
    @Override
    public boolean onTransact(int code, Parcel data, Parcel reply, int flags)
            throws RemoteException {
        switch (code) {
        case START_ACTIVITY_TRANSACTION:
        {
            data.enforceInterface(IActivityManager.descriptor);
            IBinder b = data.readStrongBinder();
            IApplicationThread app = ApplicationThreadNative.asInterface(b);
            String callingPackage = data.readString();
            Intent intent = Intent.CREATOR.createFromParcel(data);
            String resolvedType = data.readString();
            IBinder resultTo = data.readStrongBinder();
            String resultWho = data.readString();
            int requestCode = data.readInt();
            int startFlags = data.readInt();
            ProfilerInfo profilerInfo = data.readInt() != 0
                    ? ProfilerInfo.CREATOR.createFromParcel(data) : null;
            Bundle options = data.readInt() != 0
                    ? Bundle.CREATOR.createFromParcel(data) : null;
            // SystemProcess层 调用 AMS#startActivity
            int result = startActivity(app, callingPackage, intent, resolvedType,
                    resultTo, resultWho, requestCode, startFlags, profilerInfo, options);
            reply.writeNoException();
            reply.writeInt(result);
            return true;
        }
        case FINISH_ACTIVITY_TRANSACTION: {
            data.enforceInterface(IActivityManager.descriptor);
            IBinder token = data.readStrongBinder();
            Intent resultData = null;
            int resultCode = data.readInt();
            if (data.readInt() != 0) {
                resultData = Intent.CREATOR.createFromParcel(data);
            }
            boolean finishTask = (data.readInt() != 0);
            // SystemProcess层 调用 AMS#finishActivity
            boolean res = finishActivity(token, resultCode, resultData, finishTask);
            reply.writeNoException();
            reply.writeInt(res ? 1 : 0);
            return true;
        }
        case ACTIVITY_RESUMED_TRANSACTION: {
            data.enforceInterface(IActivityManager.descriptor);
            IBinder token = data.readStrongBinder();
            activityResumed(token);
            reply.writeNoException();
            return true;
        }
        case ACTIVITY_PAUSED_TRANSACTION: {
            data.enforceInterface(IActivityManager.descriptor);
            IBinder token = data.readStrongBinder();
            activityPaused(token);
            reply.writeNoException();
            return true;
        }
        case ACTIVITY_STOPPED_TRANSACTION: {
            data.enforceInterface(IActivityManager.descriptor);
            IBinder token = data.readStrongBinder();
            Bundle map = data.readBundle();
            PersistableBundle persistentState = data.readPersistableBundle();
            CharSequence description = TextUtils.CHAR_SEQUENCE_CREATOR.createFromParcel(data);
            activityStopped(token, map, persistentState, description);
            reply.writeNoException();
            return true;
        }
        case ACTIVITY_DESTROYED_TRANSACTION: {
            data.enforceInterface(IActivityManager.descriptor);
            IBinder token = data.readStrongBinder();
            activityDestroyed(token);
            reply.writeNoException();
            return true;
        }
        // ...
    }
}

ActivityManagerService继承自ActivityManagerNative，并且实现了相关的方法，它是运行在SystemProcess中的。在收到App应用的请求之后，根据请求标识，调用相关的方法完成请求(onTransact)。

ActivityManagerService.java

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public final class ActivityManagerService extends ActivityManagerNative
        implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback {
    @Override
    public final int startActivity(IApplicationThread caller, String callingPackage,
            Intent intent, String resolvedType, IBinder resultTo, String resultWho, int requestCode,
            int startFlags, ProfilerInfo profilerInfo, Bundle options) {
        return startActivityAsUser(caller, callingPackage, intent, resolvedType, resultTo,
            resultWho, requestCode, startFlags, profilerInfo, options,
            UserHandle.getCallingUserId());
    }
    @Override
    public final int startActivityAsUser(IApplicationThread caller, String callingPackage,
            Intent intent, String resolvedType, IBinder resultTo, String resultWho, int requestCode,
            int startFlags, ProfilerInfo profilerInfo, Bundle options, int userId) {
        enforceNotIsolatedCaller("startActivity");
        userId = handleIncomingUser(Binder.getCallingPid(), Binder.getCallingUid(), userId,
                false, ALLOW_FULL_ONLY, "startActivity", null);
        // TODO: Switch to user app stacks here.
        return mStackSupervisor.startActivityMayWait(caller, -1, callingPackage, intent,
                resolvedType, null, null, resultTo, resultWho, requestCode, startFlags,
                profilerInfo, null, null, options, false, userId, null, null);
    }
    @Override
    public final boolean finishActivity(IBinder token, int resultCode, Intent resultData,
            boolean finishTask) {
        // ...
        boolean res;
        if (finishTask && r == rootR) {
            res = removeTaskByIdLocked(tr.taskId, false);
            if (!res) {
                Slog.i(TAG, "Removing task failed to finish activity");
            }
        } else {
            res = tr.stack.requestFinishActivityLocked(token, resultCode,
                    resultData, "app-request", true);
            if (!res) {
                Slog.i(TAG, "Failed to finish by app-request");
            }
        }
        return res;        
    }
    @Override
    public final void activityResumed(IBinder token) {
        final long origId = Binder.clearCallingIdentity();
        synchronized(this) {
            ActivityStack stack = ActivityRecord.getStackLocked(token);
            if (stack != null) {
                ActivityRecord.activityResumedLocked(token);
            }
        }
        Binder.restoreCallingIdentity(origId);
    }
    @Override
    public final void activityPaused(IBinder token) {
        final long origId = Binder.clearCallingIdentity();
        synchronized(this) {
            ActivityStack stack = ActivityRecord.getStackLocked(token);
            if (stack != null) {
                stack.activityPausedLocked(token, false);
            }
        }
        Binder.restoreCallingIdentity(origId);
    }
    @Override
    public final void activityStopped(IBinder token, Bundle icicle,
            PersistableBundle persistentState, CharSequence description) {
        if (DEBUG_ALL) Slog.v(TAG, "Activity stopped: token=" + token);
        // Refuse possible leaked file descriptors
        final long origId = Binder.clearCallingIdentity();
        synchronized (this) {
            ActivityRecord r = ActivityRecord.isInStackLocked(token);
            if (r != null) {
                r.task.stack.activityStoppedLocked(r, icicle, persistentState, description);
            }
        }
        trimApplications();
        Binder.restoreCallingIdentity(origId);
    }
    @Override
    public final void activityDestroyed(IBinder token) {
        if (DEBUG_SWITCH) Slog.v(TAG_SWITCH, "ACTIVITY DESTROYED: " + token);
        synchronized (this) {
            ActivityStack stack = ActivityRecord.getStackLocked(token);
            if (stack != null) {
                stack.activityDestroyedLocked(token, "activityDestroyed");
            }
        }
    }
    // ...
}

ActivityManagerService继承自ActivityManagerNative，运行在SystemProcess进程。在收到请求后，做出响应处理。

ActivityManagerProxy.java

ActivityManagerProxy运行在App进程内，通过它与AMS进行交互。

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class ActivityManagerProxy implements IActivityManager
{
    public ActivityManagerProxy(IBinder remote)
    {
        mRemote = remote;
    }
    public IBinder asBinder()
    {
        return mRemote;
    }
    public int startActivity(IApplicationThread caller, String callingPackage, Intent intent,
            String resolvedType, IBinder resultTo, String resultWho, int requestCode,
            int startFlags, ProfilerInfo profilerInfo, Bundle options) throws RemoteException {
        Parcel data = Parcel.obtain();
        Parcel reply = Parcel.obtain();
        data.writeInterfaceToken(IActivityManager.descriptor);
        data.writeStrongBinder(caller != null ? caller.asBinder() : null);
        data.writeString(callingPackage);
        intent.writeToParcel(data, 0);
        data.writeString(resolvedType);
        data.writeStrongBinder(resultTo);
        data.writeString(resultWho);
        data.writeInt(requestCode);
        data.writeInt(startFlags);
        if (profilerInfo != null) {
            data.writeInt(1);
            profilerInfo.writeToParcel(data, Parcelable.PARCELABLE_WRITE_RETURN_VALUE);
        } else {
            data.writeInt(0);
        }
        if (options != null) {
            data.writeInt(1);
            options.writeToParcel(data, 0);
        } else {
            data.writeInt(0);
        }
        // 发送消息给AMS
        mRemote.transact(START_ACTIVITY_TRANSACTION, data, reply, 0);
        reply.readException();
        int result = reply.readInt();
        reply.recycle();
        data.recycle();
        return result;
    }
    public boolean finishActivity(IBinder token, int resultCode, Intent resultData, boolean finishTask)
            throws RemoteException {
        Parcel data = Parcel.obtain();
        Parcel reply = Parcel.obtain();
        data.writeInterfaceToken(IActivityManager.descriptor);
        data.writeStrongBinder(token);
        data.writeInt(resultCode);
        if (resultData != null) {
            data.writeInt(1);
            resultData.writeToParcel(data, 0);
        } else {
            data.writeInt(0);
        }
        data.writeInt(finishTask ? 1 : 0);
        // 发送消息给AMS
        mRemote.transact(FINISH_ACTIVITY_TRANSACTION, data, reply, 0);
        reply.readException();
        boolean res = reply.readInt() != 0;
        data.recycle();
        reply.recycle();
        return res;
    }
    public void activityResumed(IBinder token) throws RemoteException
    {
        Parcel data = Parcel.obtain();
        Parcel reply = Parcel.obtain();
        data.writeInterfaceToken(IActivityManager.descriptor);
        data.writeStrongBinder(token);
        // 发送消息给AMS
        mRemote.transact(ACTIVITY_RESUMED_TRANSACTION, data, reply, 0);
        reply.readException();
        data.recycle();
        reply.recycle();
    }
    public void activityPaused(IBinder token) throws RemoteException
    {
        Parcel data = Parcel.obtain();
        Parcel reply = Parcel.obtain();
        data.writeInterfaceToken(IActivityManager.descriptor);
        data.writeStrongBinder(token);
        // 发送消息给AMS
        mRemote.transact(ACTIVITY_PAUSED_TRANSACTION, data, reply, 0);
        reply.readException();
        data.recycle();
        reply.recycle();
    }
    public void activityStopped(IBinder token, Bundle state,
            PersistableBundle persistentState, CharSequence description) throws RemoteException
    {
        Parcel data = Parcel.obtain();
        Parcel reply = Parcel.obtain();
        data.writeInterfaceToken(IActivityManager.descriptor);
        data.writeStrongBinder(token);
        data.writeBundle(state);
        data.writePersistableBundle(persistentState);
        TextUtils.writeToParcel(description, data, 0);
        // 发送消息给AMS
        mRemote.transact(ACTIVITY_STOPPED_TRANSACTION, data, reply, IBinder.FLAG_ONEWAY);
        reply.readException();
        data.recycle();
        reply.recycle();
    }
    public void activityDestroyed(IBinder token) throws RemoteException
    {
        Parcel data = Parcel.obtain();
        Parcel reply = Parcel.obtain();
        data.writeInterfaceToken(IActivityManager.descriptor);
        data.writeStrongBinder(token);
        // 发送消息给AMS
        mRemote.transact(ACTIVITY_DESTROYED_TRANSACTION, data, reply, IBinder.FLAG_ONEWAY);
        reply.readException();
        data.recycle();
        reply.recycle();
    }    
}

交互流程总结：

  1. App进程通过ActivityManagerProxy，给AMS发消息。
  2. AMS收到消息后，根据消息标识，做出响应，不同的消息类型处理方法不同，有的消息需要调用ApplicationThreadProxy与上层Application进行交互。

和生命周期相关的需要回调上层应用进程的方法

  • scheduleLaunchActivity
  • scheduleResumeActivity
  • schedulePauseActivity
  • scheduleStopActivity
  • scheduleDestroyActivity