services/core/java/com/android/server/ServiceWatcher.java - platform/frameworks/base - Gitiles

 /*
  * Copyright (C) 2012 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 package com.android.server;

 import android.annotation.Nullable;
 import android.app.ActivityManager;
 import android.content.BroadcastReceiver;
 import android.content.ComponentName;
 import android.content.Context;
 import android.content.Intent;
 import android.content.IntentFilter;
 import android.content.ServiceConnection;
 import android.content.pm.PackageInfo;
 import android.content.pm.PackageManager;
 import android.content.pm.PackageManager.NameNotFoundException;
 import android.content.pm.ResolveInfo;
 import android.content.pm.Signature;
 import android.content.res.Resources;
 import android.os.Bundle;
 import android.os.Handler;
 import android.os.IBinder;
 import android.os.Looper;
 import android.os.UserHandle;
 import android.util.Log;
 import android.util.Slog;

 import com.android.internal.annotations.GuardedBy;
 import com.android.internal.content.PackageMonitor;
 import com.android.internal.util.Preconditions;

 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Objects;

 /**
  * Find the best Service, and bind to it.
  * Handles run-time package changes.
  */
 public class ServiceWatcher implements ServiceConnection {

     private static final String TAG = "ServiceWatcher";
     private static final boolean D = false;

     public static final String EXTRA_SERVICE_VERSION = "serviceVersion";
     public static final String EXTRA_SERVICE_IS_MULTIUSER = "serviceIsMultiuser";

     /**
      * The runner that runs on the binder retrieved from {@link ServiceWatcher}.
      */
     public interface BinderRunner {
         /**
          * Runs on the retrieved binder.
          *
          * @param binder the binder retrieved from the {@link ServiceWatcher}.
          */
         void run(IBinder binder);
     }

     public static ArrayList<HashSet<Signature>> getSignatureSets(Context context,
             String... packageNames) {
         PackageManager pm = context.getPackageManager();

         ArrayList<HashSet<Signature>> signatureSets = new ArrayList<>(packageNames.length);
         for (String packageName : packageNames) {
             try {
                 Signature[] signatures = pm.getPackageInfo(packageName,
                         PackageManager.MATCH_SYSTEM_ONLY
                                 | PackageManager.GET_SIGNATURES).signatures;

                 HashSet<Signature> set = new HashSet<>();
                 Collections.addAll(set, signatures);
                 signatureSets.add(set);
             } catch (NameNotFoundException e) {
                 Log.w(TAG, packageName + " not found");
             }
         }
         return signatureSets;
     }

     /** Checks if signatures match. */
     public static boolean isSignatureMatch(Signature[] signatures,
             List<HashSet<Signature>> sigSets) {
         if (signatures == null) return false;

         // build hashset of input to test against
         HashSet<Signature> inputSet = new HashSet<>();
         Collections.addAll(inputSet, signatures);

         // test input against each of the signature sets
         for (HashSet<Signature> referenceSet : sigSets) {
             if (referenceSet.equals(inputSet)) {
                 return true;
             }
         }
         return false;
     }

     private final Context mContext;
     private final String mTag;
     private final String mAction;
     private final String mServicePackageName;
     private final List<HashSet<Signature>> mSignatureSets;

     private final Handler mHandler;

     // this lock is held to ensure the service binder is not exposed (via runOnBinder) until after
     // the new service initialization work has completed
     private final Object mBindLock = new Object();

     // read/write from handler thread
     private int mCurrentUserId;

     // read from any thread, write from handler thread
     private volatile ComponentName mBestComponent;
     private volatile int mBestVersion;
     private volatile int mBestUserId;
     private volatile IBinder mBestService;

     public ServiceWatcher(Context context, String logTag, String action,
             int overlaySwitchResId, int defaultServicePackageNameResId,
             int initialPackageNamesResId, Handler handler) {
         Resources resources = context.getResources();

         mContext = context;
         mTag = logTag;
         mAction = action;

         boolean enableOverlay = resources.getBoolean(overlaySwitchResId);
         if (enableOverlay) {
             String[] pkgs = resources.getStringArray(initialPackageNamesResId);
             mServicePackageName = null;
             mSignatureSets = getSignatureSets(context, pkgs);
             if (D) Log.d(mTag, "Overlay enabled, packages=" + Arrays.toString(pkgs));
         } else {
             mServicePackageName = resources.getString(defaultServicePackageNameResId);
             mSignatureSets = getSignatureSets(context, mServicePackageName);
             if (D) Log.d(mTag, "Overlay disabled, default package=" + mServicePackageName);
         }

         mHandler = handler;

         mBestComponent = null;
         mBestVersion = Integer.MIN_VALUE;
         mBestUserId = UserHandle.USER_NULL;

         mBestService = null;
     }

     // called on handler thread
     @GuardedBy("mBindLock")
     protected void onBind() {
         Preconditions.checkState(Looper.myLooper() == mHandler.getLooper());
     }

     // called on handler thread
     @GuardedBy("mBindLock")
     protected void onUnbind() {
         Preconditions.checkState(Looper.myLooper() == mHandler.getLooper());
     }

     /**
      * Start this watcher, including binding to the current best match and
      * re-binding to any better matches down the road.
      * <p>
      * Note that if there are no matching encryption-aware services, we may not
      * bind to a real service until after the current user is unlocked.
      *
      * @return {@code true} if a potential service implementation was found.
      */
     public final boolean start() {
         // if we have to return false, do it before registering anything
         if (isServiceMissing()) return false;

         // listen for relevant package changes if service overlay is enabled on handler
         if (mServicePackageName == null) {
             new PackageMonitor() {
                 @Override
                 public void onPackageUpdateFinished(String packageName, int uid) {
                     bindBestPackage(Objects.equals(packageName, getCurrentPackageName()));
                 }

                 @Override
                 public void onPackageAdded(String packageName, int uid) {
                     bindBestPackage(Objects.equals(packageName, getCurrentPackageName()));
                 }

                 @Override
                 public void onPackageRemoved(String packageName, int uid) {
                     bindBestPackage(Objects.equals(packageName, getCurrentPackageName()));
                 }

                 @Override
                 public boolean onPackageChanged(String packageName, int uid, String[] components) {
                     bindBestPackage(Objects.equals(packageName, getCurrentPackageName()));
                     return super.onPackageChanged(packageName, uid, components);
                 }
             }.register(mContext, UserHandle.ALL, true, mHandler);
         }

         // listen for user change on handler
         IntentFilter intentFilter = new IntentFilter();
         intentFilter.addAction(Intent.ACTION_USER_SWITCHED);
         intentFilter.addAction(Intent.ACTION_USER_UNLOCKED);
         mContext.registerReceiverAsUser(new BroadcastReceiver() {
             @Override
             public void onReceive(Context context, Intent intent) {
                 final String action = intent.getAction();
                 final int userId = intent.getIntExtra(Intent.EXTRA_USER_HANDLE,
                         UserHandle.USER_NULL);
                 if (Intent.ACTION_USER_SWITCHED.equals(action)) {
                     mCurrentUserId = userId;
                     bindBestPackage(false);
                 } else if (Intent.ACTION_USER_UNLOCKED.equals(action)) {
                     if (userId == mCurrentUserId) {
                         bindBestPackage(false);
                     }
                 }
             }
         }, UserHandle.ALL, intentFilter, null, mHandler);

         mCurrentUserId = ActivityManager.getCurrentUser();

         mHandler.post(() -> bindBestPackage(false));
         return true;
     }

     /** Returns the name of the currently connected package or null. */
     @Nullable
     public String getCurrentPackageName() {
         ComponentName bestComponent = mBestComponent;
         return bestComponent == null ? null : bestComponent.getPackageName();
     }

     /**
      * Runs the given BinderRunner if currently connected. All invocations to runOnBinder are run
      * serially.
      */
     public final void runOnBinder(BinderRunner runner) {
         synchronized (mBindLock) {
             IBinder service = mBestService;
             if (service != null) {
                 try {
                     runner.run(service);
                 } catch (Exception e) {
                     // remote exceptions cannot be allowed to crash system server
                     Log.e(TAG, "exception while while running " + runner + " on " + service
                             + " from " + this, e);
                 }
             }
         }
     }

     private boolean isServiceMissing() {
         return mContext.getPackageManager().queryIntentServicesAsUser(new Intent(mAction),
                 PackageManager.MATCH_DIRECT_BOOT_AWARE
                         | PackageManager.MATCH_DIRECT_BOOT_UNAWARE,
                 UserHandle.USER_SYSTEM).isEmpty();
     }

     private void bindBestPackage(boolean forceRebind) {
         Preconditions.checkState(Looper.myLooper() == mHandler.getLooper());

         Intent intent = new Intent(mAction);
         if (mServicePackageName != null) {
             intent.setPackage(mServicePackageName);
         }

         List<ResolveInfo> rInfos = mContext.getPackageManager().queryIntentServicesAsUser(intent,
                 PackageManager.GET_META_DATA | PackageManager.MATCH_DIRECT_BOOT_AUTO,
                 mCurrentUserId);
         if (rInfos == null) {
             rInfos = Collections.emptyList();
         }

         ComponentName bestComponent = null;
         int bestVersion = Integer.MIN_VALUE;
         boolean bestIsMultiuser = false;

         for (ResolveInfo rInfo : rInfos) {
             ComponentName component = rInfo.serviceInfo.getComponentName();
             String packageName = component.getPackageName();

             // check signature
             try {
                 PackageInfo pInfo = mContext.getPackageManager().getPackageInfo(packageName,
                         PackageManager.GET_SIGNATURES
                                 | PackageManager.MATCH_DIRECT_BOOT_AUTO);
                 if (!isSignatureMatch(pInfo.signatures, mSignatureSets)) {
                     Log.w(mTag, packageName + " resolves service " + mAction
                             + ", but has wrong signature, ignoring");
                     continue;
                 }
             } catch (NameNotFoundException e) {
                 Log.wtf(mTag, e);
                 continue;
             }

             // check metadata
             Bundle metadata = rInfo.serviceInfo.metaData;
             int version = Integer.MIN_VALUE;
             boolean isMultiuser = false;
             if (metadata != null) {
                 version = metadata.getInt(EXTRA_SERVICE_VERSION, Integer.MIN_VALUE);
                 isMultiuser = metadata.getBoolean(EXTRA_SERVICE_IS_MULTIUSER, false);
             }

             if (version > bestVersion) {
                 bestComponent = component;
                 bestVersion = version;
                 bestIsMultiuser = isMultiuser;
             }
         }

         if (D) {
             Log.d(mTag, String.format("bindBestPackage for %s : %s found %d, %s", mAction,
                     (mServicePackageName == null ? ""
                             : "(" + mServicePackageName + ") "), rInfos.size(),
                     (bestComponent == null ? "no new best component"
                             : "new best component: " + bestComponent)));
         }

         if (bestComponent == null) {
             Slog.w(mTag, "Odd, no component found for service " + mAction);
             unbind();
             return;
         }

         int userId = bestIsMultiuser ? UserHandle.USER_SYSTEM : mCurrentUserId;
         boolean alreadyBound = Objects.equals(bestComponent, mBestComponent)
                 && bestVersion == mBestVersion && userId == mBestUserId;
         if (forceRebind || !alreadyBound) {
             unbind();
             bind(bestComponent, bestVersion, userId);
         }
     }

     private void bind(ComponentName component, int version, int userId) {
         Preconditions.checkState(Looper.myLooper() == mHandler.getLooper());

         Intent intent = new Intent(mAction);
         intent.setComponent(component);

         mBestComponent = component;
         mBestVersion = version;
         mBestUserId = userId;

         if (D) Log.d(mTag, "binding " + component + " (v" + version + ") (u" + userId + ")");
         mContext.bindServiceAsUser(intent, this,
                 Context.BIND_AUTO_CREATE | Context.BIND_NOT_FOREGROUND | Context.BIND_NOT_VISIBLE,
                 UserHandle.of(userId));
     }

     private void unbind() {
         Preconditions.checkState(Looper.myLooper() == mHandler.getLooper());

         if (mBestComponent != null) {
             if (D) Log.d(mTag, "unbinding " + mBestComponent);
             mContext.unbindService(this);
         }

         mBestComponent = null;
         mBestVersion = Integer.MIN_VALUE;
         mBestUserId = UserHandle.USER_NULL;
     }

     @Override
     public final void onServiceConnected(ComponentName component, IBinder binder) {
         mHandler.post(() -> {
             if (D) Log.d(mTag, component + " connected");

             // hold the lock so that mBestService cannot be used by runOnBinder until complete
             synchronized (mBindLock) {
                 mBestService = binder;
                 onBind();
             }
         });
     }

     @Override
     public final void onServiceDisconnected(ComponentName component) {
         mHandler.post(() -> {
             if (D) Log.d(mTag, component + " disconnected");

             mBestService = null;
             synchronized (mBindLock) {
                 onUnbind();
             }
         });
     }

     @Override
     public String toString() {
         ComponentName bestComponent = mBestComponent;
         return bestComponent == null ? "null" : bestComponent.toShortString() + "@" + mBestVersion;
     }
 }
	/*
	* Copyright (C) 2012 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	package com.android.server;

	import android.annotation.Nullable;
	import android.app.ActivityManager;
	import android.content.BroadcastReceiver;
	import android.content.ComponentName;
	import android.content.Context;
	import android.content.Intent;
	import android.content.IntentFilter;
	import android.content.ServiceConnection;
	import android.content.pm.PackageInfo;
	import android.content.pm.PackageManager;
	import android.content.pm.PackageManager.NameNotFoundException;
	import android.content.pm.ResolveInfo;
	import android.content.pm.Signature;
	import android.content.res.Resources;
	import android.os.Bundle;
	import android.os.Handler;
	import android.os.IBinder;
	import android.os.Looper;
	import android.os.UserHandle;
	import android.util.Log;
	import android.util.Slog;

	import com.android.internal.annotations.GuardedBy;
	import com.android.internal.content.PackageMonitor;
	import com.android.internal.util.Preconditions;

	import java.util.ArrayList;
	import java.util.Arrays;
	import java.util.Collections;
	import java.util.HashSet;
	import java.util.List;
	import java.util.Objects;

	/**
	* Find the best Service, and bind to it.
	* Handles run-time package changes.
	*/
	public class ServiceWatcher implements ServiceConnection {

	private static final String TAG = "ServiceWatcher";
	private static final boolean D = false;

	public static final String EXTRA_SERVICE_VERSION = "serviceVersion";
	public static final String EXTRA_SERVICE_IS_MULTIUSER = "serviceIsMultiuser";

	/**
	* The runner that runs on the binder retrieved from {@link ServiceWatcher}.
	*/
	public interface BinderRunner {
	/**
	* Runs on the retrieved binder.
	*
	* @param binder the binder retrieved from the {@link ServiceWatcher}.
	*/
	void run(IBinder binder);
	}

	public static ArrayList<HashSet<Signature>> getSignatureSets(Context context,
	String... packageNames) {
	PackageManager pm = context.getPackageManager();

	ArrayList<HashSet<Signature>> signatureSets = new ArrayList<>(packageNames.length);
	for (String packageName : packageNames) {
	try {
	Signature[] signatures = pm.getPackageInfo(packageName,
	PackageManager.MATCH_SYSTEM_ONLY
	\| PackageManager.GET_SIGNATURES).signatures;

	HashSet<Signature> set = new HashSet<>();
	Collections.addAll(set, signatures);
	signatureSets.add(set);
	} catch (NameNotFoundException e) {
	Log.w(TAG, packageName + " not found");
	}
	}
	return signatureSets;
	}

	/** Checks if signatures match. */
	public static boolean isSignatureMatch(Signature[] signatures,
	List<HashSet<Signature>> sigSets) {
	if (signatures == null) return false;

	// build hashset of input to test against
	HashSet<Signature> inputSet = new HashSet<>();
	Collections.addAll(inputSet, signatures);

	// test input against each of the signature sets
	for (HashSet<Signature> referenceSet : sigSets) {
	if (referenceSet.equals(inputSet)) {
	return true;
	}
	}
	return false;
	}

	private final Context mContext;
	private final String mTag;
	private final String mAction;
	private final String mServicePackageName;
	private final List<HashSet<Signature>> mSignatureSets;

	private final Handler mHandler;

	// this lock is held to ensure the service binder is not exposed (via runOnBinder) until after
	// the new service initialization work has completed
	private final Object mBindLock = new Object();

	// read/write from handler thread
	private int mCurrentUserId;

	// read from any thread, write from handler thread
	private volatile ComponentName mBestComponent;
	private volatile int mBestVersion;
	private volatile int mBestUserId;
	private volatile IBinder mBestService;

	public ServiceWatcher(Context context, String logTag, String action,
	int overlaySwitchResId, int defaultServicePackageNameResId,
	int initialPackageNamesResId, Handler handler) {
	Resources resources = context.getResources();

	mContext = context;
	mTag = logTag;
	mAction = action;

	boolean enableOverlay = resources.getBoolean(overlaySwitchResId);
	if (enableOverlay) {
	String[] pkgs = resources.getStringArray(initialPackageNamesResId);
	mServicePackageName = null;
	mSignatureSets = getSignatureSets(context, pkgs);
	if (D) Log.d(mTag, "Overlay enabled, packages=" + Arrays.toString(pkgs));
	} else {
	mServicePackageName = resources.getString(defaultServicePackageNameResId);
	mSignatureSets = getSignatureSets(context, mServicePackageName);
	if (D) Log.d(mTag, "Overlay disabled, default package=" + mServicePackageName);
	}

	mHandler = handler;

	mBestComponent = null;
	mBestVersion = Integer.MIN_VALUE;
	mBestUserId = UserHandle.USER_NULL;

	mBestService = null;
	}

	// called on handler thread
	@GuardedBy("mBindLock")
	protected void onBind() {
	Preconditions.checkState(Looper.myLooper() == mHandler.getLooper());
	}

	// called on handler thread
	@GuardedBy("mBindLock")
	protected void onUnbind() {
	Preconditions.checkState(Looper.myLooper() == mHandler.getLooper());
	}

	/**
	* Start this watcher, including binding to the current best match and
	* re-binding to any better matches down the road.
	* <p>
	* Note that if there are no matching encryption-aware services, we may not
	* bind to a real service until after the current user is unlocked.
	*
	* @return {@code true} if a potential service implementation was found.
	*/
	public final boolean start() {
	// if we have to return false, do it before registering anything
	if (isServiceMissing()) return false;

	// listen for relevant package changes if service overlay is enabled on handler
	if (mServicePackageName == null) {
	new PackageMonitor() {
	@Override
	public void onPackageUpdateFinished(String packageName, int uid) {
	bindBestPackage(Objects.equals(packageName, getCurrentPackageName()));
	}

	@Override
	public void onPackageAdded(String packageName, int uid) {
	bindBestPackage(Objects.equals(packageName, getCurrentPackageName()));
	}

	@Override
	public void onPackageRemoved(String packageName, int uid) {
	bindBestPackage(Objects.equals(packageName, getCurrentPackageName()));
	}

	@Override
	public boolean onPackageChanged(String packageName, int uid, String[] components) {
	bindBestPackage(Objects.equals(packageName, getCurrentPackageName()));
	return super.onPackageChanged(packageName, uid, components);
	}
	}.register(mContext, UserHandle.ALL, true, mHandler);
	}

	// listen for user change on handler
	IntentFilter intentFilter = new IntentFilter();
	intentFilter.addAction(Intent.ACTION_USER_SWITCHED);
	intentFilter.addAction(Intent.ACTION_USER_UNLOCKED);
	mContext.registerReceiverAsUser(new BroadcastReceiver() {
	@Override
	public void onReceive(Context context, Intent intent) {
	final String action = intent.getAction();
	final int userId = intent.getIntExtra(Intent.EXTRA_USER_HANDLE,
	UserHandle.USER_NULL);
	if (Intent.ACTION_USER_SWITCHED.equals(action)) {
	mCurrentUserId = userId;
	bindBestPackage(false);
	} else if (Intent.ACTION_USER_UNLOCKED.equals(action)) {
	if (userId == mCurrentUserId) {
	bindBestPackage(false);
	}
	}
	}
	}, UserHandle.ALL, intentFilter, null, mHandler);

	mCurrentUserId = ActivityManager.getCurrentUser();

	mHandler.post(() -> bindBestPackage(false));
	return true;
	}

	/** Returns the name of the currently connected package or null. */
	@Nullable
	public String getCurrentPackageName() {
	ComponentName bestComponent = mBestComponent;
	return bestComponent == null ? null : bestComponent.getPackageName();
	}

	/**
	* Runs the given BinderRunner if currently connected. All invocations to runOnBinder are run
	* serially.
	*/
	public final void runOnBinder(BinderRunner runner) {
	synchronized (mBindLock) {
	IBinder service = mBestService;
	if (service != null) {
	try {
	runner.run(service);
	} catch (Exception e) {
	// remote exceptions cannot be allowed to crash system server
	Log.e(TAG, "exception while while running " + runner + " on " + service
	+ " from " + this, e);
	}
	}
	}
	}

	private boolean isServiceMissing() {
	return mContext.getPackageManager().queryIntentServicesAsUser(new Intent(mAction),
	PackageManager.MATCH_DIRECT_BOOT_AWARE
	\| PackageManager.MATCH_DIRECT_BOOT_UNAWARE,
	UserHandle.USER_SYSTEM).isEmpty();
	}

	private void bindBestPackage(boolean forceRebind) {
	Preconditions.checkState(Looper.myLooper() == mHandler.getLooper());

	Intent intent = new Intent(mAction);
	if (mServicePackageName != null) {
	intent.setPackage(mServicePackageName);
	}

	List<ResolveInfo> rInfos = mContext.getPackageManager().queryIntentServicesAsUser(intent,
	PackageManager.GET_META_DATA \| PackageManager.MATCH_DIRECT_BOOT_AUTO,
	mCurrentUserId);
	if (rInfos == null) {
	rInfos = Collections.emptyList();
	}

	ComponentName bestComponent = null;
	int bestVersion = Integer.MIN_VALUE;
	boolean bestIsMultiuser = false;

	for (ResolveInfo rInfo : rInfos) {
	ComponentName component = rInfo.serviceInfo.getComponentName();
	String packageName = component.getPackageName();

	// check signature
	try {
	PackageInfo pInfo = mContext.getPackageManager().getPackageInfo(packageName,
	PackageManager.GET_SIGNATURES
	\| PackageManager.MATCH_DIRECT_BOOT_AUTO);
	if (!isSignatureMatch(pInfo.signatures, mSignatureSets)) {
	Log.w(mTag, packageName + " resolves service " + mAction
	+ ", but has wrong signature, ignoring");
	continue;
	}
	} catch (NameNotFoundException e) {
	Log.wtf(mTag, e);
	continue;
	}

	// check metadata
	Bundle metadata = rInfo.serviceInfo.metaData;
	int version = Integer.MIN_VALUE;
	boolean isMultiuser = false;
	if (metadata != null) {
	version = metadata.getInt(EXTRA_SERVICE_VERSION, Integer.MIN_VALUE);
	isMultiuser = metadata.getBoolean(EXTRA_SERVICE_IS_MULTIUSER, false);
	}

	if (version > bestVersion) {
	bestComponent = component;
	bestVersion = version;
	bestIsMultiuser = isMultiuser;
	}
	}

	if (D) {
	Log.d(mTag, String.format("bindBestPackage for %s : %s found %d, %s", mAction,
	(mServicePackageName == null ? ""
	: "(" + mServicePackageName + ") "), rInfos.size(),
	(bestComponent == null ? "no new best component"
	: "new best component: " + bestComponent)));
	}

	if (bestComponent == null) {
	Slog.w(mTag, "Odd, no component found for service " + mAction);
	unbind();
	return;
	}

	int userId = bestIsMultiuser ? UserHandle.USER_SYSTEM : mCurrentUserId;
	boolean alreadyBound = Objects.equals(bestComponent, mBestComponent)
	&& bestVersion == mBestVersion && userId == mBestUserId;
	if (forceRebind \|\| !alreadyBound) {
	unbind();
	bind(bestComponent, bestVersion, userId);
	}
	}

	private void bind(ComponentName component, int version, int userId) {
	Preconditions.checkState(Looper.myLooper() == mHandler.getLooper());

	Intent intent = new Intent(mAction);
	intent.setComponent(component);

	mBestComponent = component;
	mBestVersion = version;
	mBestUserId = userId;

	if (D) Log.d(mTag, "binding " + component + " (v" + version + ") (u" + userId + ")");
	mContext.bindServiceAsUser(intent, this,
	Context.BIND_AUTO_CREATE \| Context.BIND_NOT_FOREGROUND \| Context.BIND_NOT_VISIBLE,
	UserHandle.of(userId));
	}

	private void unbind() {
	Preconditions.checkState(Looper.myLooper() == mHandler.getLooper());

	if (mBestComponent != null) {
	if (D) Log.d(mTag, "unbinding " + mBestComponent);
	mContext.unbindService(this);
	}

	mBestComponent = null;
	mBestVersion = Integer.MIN_VALUE;
	mBestUserId = UserHandle.USER_NULL;
	}

	@Override
	public final void onServiceConnected(ComponentName component, IBinder binder) {
	mHandler.post(() -> {
	if (D) Log.d(mTag, component + " connected");

	// hold the lock so that mBestService cannot be used by runOnBinder until complete
	synchronized (mBindLock) {
	mBestService = binder;
	onBind();
	}
	});
	}

	@Override
	public final void onServiceDisconnected(ComponentName component) {
	mHandler.post(() -> {
	if (D) Log.d(mTag, component + " disconnected");

	mBestService = null;
	synchronized (mBindLock) {
	onUnbind();
	}
	});
	}

	@Override
	public String toString() {
	ComponentName bestComponent = mBestComponent;
	return bestComponent == null ? "null" : bestComponent.toShortString() + "@" + mBestVersion;
	}
	}