Android 网络bind流程

        在国内无法使用谷歌GMS包，我们选择NLP（network location provider）有提供商有： 百度、高德、腾讯等可以选择，那这一块初始化流程是怎样的呢？我们代码梳理下：

我们知道，LocationManagerService 是由 SystemServer 启动的，然后在 SystemServer 里面执行：locationF.systemRunning()，locationF 就是 LocationManagerService，那看下具体代码：

http://androidxref.com/9.0.0_r3/xref/frameworks/base/services/core/java/com/android/server/LocationManagerService.java#systemRunning

    public void systemRunning() {
        synchronized (mLock) {
            if (D) Log.d(TAG, "systemRunning()");

…………

            // prepare providers
            loadProvidersLocked();  ---> 主要看下这个

在 loadProvidersLocked 方法中，我们仅看和网络相关的，重点是下面的这个bind

        // bind to network provider
        LocationProviderProxy networkProvider = LocationProviderProxy.createAndBind(
                mContext,
                LocationManager.NETWORK_PROVIDER,
                NETWORK_LOCATION_SERVICE_ACTION,
                com.android.internal.R.bool.config_enableNetworkLocationOverlay,   ---> 这几个都是在这里配置：/frameworks/base/core/res/res/values/config.xml
                com.android.internal.R.string.config_networkLocationProviderPackageName,  ---> 三方包名，比如百度Nlp：com.baidu.map.location
                com.android.internal.R.array.config_locationProviderPackageNames, ---> 添加三方包名，比如百度Nlp：com.baidu.map.location
                mLocationHandler);
        if (networkProvider != null) {
            mRealProviders.put(LocationManager.NETWORK_PROVIDER, networkProvider);
            mProxyProviders.add(networkProvider);
            addProviderLocked(networkProvider);
        } else {
            Slog.w(TAG, "no network location provider found");
        }

http://androidxref.com/9.0.0_r3/xref/frameworks/base/services/core/java/com/android/server/location/LocationProviderProxy.java#createAndBind

    public static LocationProviderProxy createAndBind(   ---> 先去根据config去启动初始包
            Context context, String name, String action,
            int overlaySwitchResId, int defaultServicePackageNameResId,
            int initialPackageNamesResId, Handler handler) {
        LocationProviderProxy proxy = new LocationProviderProxy(context, name, action,
                overlaySwitchResId, defaultServicePackageNameResId, initialPackageNamesResId,
                handler);
        if (proxy.bind()) {   ---> 然后才去bind
            return proxy;
        } else {
            return null;
        }

看下对应参数：

        name：NETWORK_PROVIDER

        action："com.android.location.service.v3.NetworkLocationProvider"

        overlaySwitchResId：config_enableNetworkLocationOverlay     ---> 一般是 false

        ​defaultServicePackageNameResId​：三方包名

        ​initialPackageNamesResId​：配置的包含三方包名

    private LocationProviderProxy(Context context, String name, String action,
            int overlaySwitchResId, int defaultServicePackageNameResId,
            int initialPackageNamesResId, Handler handler) {
        mContext = context;
        mName = name;
        mServiceWatcher = new ServiceWatcher(mContext, TAG + "-" + name, action, overlaySwitchResId,
                defaultServicePackageNameResId, initialPackageNamesResId,
                mNewServiceWork, handler);
    }

    public ServiceWatcher(Context context, String logTag, String action,
            int overlaySwitchResId, int defaultServicePackageNameResId,
            int initialPackageNamesResId, Runnable newServiceWork,
            Handler handler) {
        mContext = context;
        mTag = logTag;
        mAction = action;
        mPm = mContext.getPackageManager();
        mNewServiceWork = newServiceWork;
        mHandler = handler;
        Resources resources = context.getResources();

        // Whether to enable service overlay.
        boolean enableOverlay = resources.getBoolean(overlaySwitchResId);
        ArrayList<String> initialPackageNames = new ArrayList<String>();
        if (enableOverlay) {  ---> 一般是false，所以走 else 的逻辑
            // A list of package names used to create the signatures.
            String[] pkgs = resources.getStringArray(initialPackageNamesResId);
            if (pkgs != null) initialPackageNames.addAll(Arrays.asList(pkgs));
            mServicePackageName = null;
            if (D) Log.d(mTag, "Overlay enabled, packages=" + Arrays.toString(pkgs));
        } else {
            // The default package name that is searched for service implementation when overlay is
            // disabled.
            String servicePackageName = resources.getString(defaultServicePackageNameResId);
            if (servicePackageName != null) initialPackageNames.add(servicePackageName);
            mServicePackageName = servicePackageName;
            if (D) Log.d(mTag, "Overlay disabled, default package=" + servicePackageName);  --->配置的三方包名
        }
        mSignatureSets = getSignatureSets(context, initialPackageNames);
    }

走完后，我们再看上面提到的 proxy.bind 方法：

    private boolean bind () {
        return mServiceWatcher.start();
    }

http://androidxref.com/9.0.0_r3/xref/frameworks/base/services/core/java/com/android/server/ServiceWatcher.java#start

    public boolean start() {
        if (isServiceMissing()) return false;

        synchronized (mLock) {
            bindBestPackageLocked(mServicePackageName, false);  ---> 注意这个方法，false 传下去，会用到
        }

        // listen for user change
        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)) {
                    switchUser(userId);
                } else if (Intent.ACTION_USER_UNLOCKED.equals(action)) {
                    unlockUser(userId);
                }
            }
        }, UserHandle.ALL, intentFilter, null, mHandler);

        // listen for relevant package changes if service overlay is enabled.
        if (mServicePackageName == null) {
            mPackageMonitor.register(mContext, null, UserHandle.ALL, true);
        }

        return true;
    }

    /**
     * Searches and binds to the best package, or do nothing if the best package
     * is already bound, unless force rebinding is requested.
     *
     * @param justCheckThisPackage Only consider this package, or consider all
     *            packages if it is {@code null}.
     * @param forceRebind Force a rebinding to the best package if it's already
     *            bound.
     * @returns {@code true} if a valid package was found to bind to.
     */
    @GuardedBy("mLock")
    private boolean bindBestPackageLocked(String justCheckThisPackage, boolean forceRebind) {
        Intent intent = new Intent(mAction);
        if (justCheckThisPackage != null) {
            intent.setPackage(justCheckThisPackage);
        }
        final List<ResolveInfo> rInfos = mPm.queryIntentServicesAsUser(intent,
                PackageManager.GET_META_DATA | PackageManager.MATCH_DEBUG_TRIAGED_MISSING,
                mCurrentUserId);   ---> 查找
        int bestVersion = Integer.MIN_VALUE;
        ComponentName bestComponent = null;
        boolean bestIsMultiuser = false;
        if (rInfos != null) {
            for (ResolveInfo rInfo : rInfos) {
                final ComponentName component = rInfo.serviceInfo.getComponentName();
                final String packageName = component.getPackageName();

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

                // check metadata  --> NLP中service需要配置metadata属性，因为下面会和默认最小值比对
                int version = Integer.MIN_VALUE;
                boolean isMultiuser = false;
                if (rInfo.serviceInfo.metaData != null) {
                    version = rInfo.serviceInfo.metaData.getInt(
                            EXTRA_SERVICE_VERSION, Integer.MIN_VALUE);
                    isMultiuser = rInfo.serviceInfo.metaData.getBoolean(EXTRA_SERVICE_IS_MULTIUSER);
                }

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

            if (D) {
                Log.d(mTag, String.format("bindBestPackage for %s : %s found %d, %s", mAction,
                        (justCheckThisPackage == null ? ""
                                : "(" + justCheckThisPackage + ") "), rInfos.size(),
                        (bestComponent == null ? "no new best component"
                                : "new best component: " + bestComponent)));
            }
        } else {
            if (D) Log.d(mTag, "Unable to query intent services for action: " + mAction);
        }

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

        final int userId = bestIsMultiuser ? UserHandle.USER_SYSTEM : mCurrentUserId;
        final boolean alreadyBound = Objects.equals(bestComponent, mBoundComponent)
                && bestVersion == mBoundVersion && userId == mBoundUserId;
        if (forceRebind || !alreadyBound) {   ---> forceRebind 传下来的参数是 false，第一次，alreadyBound 也为false
            unbindLocked();  --> 执行
            bindToPackageLocked(bestComponent, bestVersion, userId);
        }
        return true;
    }

    @GuardedBy("mLock")
    private void bindToPackageLocked(ComponentName component, int version, int userId) {
        Intent intent = new Intent(mAction);
        intent.setComponent(component);
        mBoundComponent = component;
        mBoundPackageName = component.getPackageName();
        mBoundVersion = version;
        mBoundUserId = userId;
        if (D) Log.d(mTag, "binding " + component + " (v" + version + ") (u" + userId + ")");
        mContext.bindServiceAsUser(intent, this,        ---> bind，成功后回调该 onServiceConnected 方法，失败回调 onServiceDisconnected
                Context.BIND_AUTO_CREATE | Context.BIND_NOT_FOREGROUND | Context.BIND_NOT_VISIBLE,
                new UserHandle(userId));
    }

绑定成功后回调：

    @Override
    public void onServiceConnected(ComponentName component, IBinder binder) {
        synchronized (mLock) {
            if (component.equals(mBoundComponent)) {
                if (D) Log.d(mTag, component + " connected");
                mBoundService = binder;
                if (mHandler !=null && mNewServiceWork != null) {
                    mHandler.post(mNewServiceWork);    ---> 这个是之前传下来的，现在执行这个
                }
            } else {
                Log.w(mTag, "unexpected onServiceConnected: " + component);
            }
        }
    }

http://androidxref.com/9.0.0_r3/xref/frameworks/base/services/core/java/com/android/server/location/LocationProviderProxy.java#mNewServiceWork

    private Runnable mNewServiceWork = new Runnable() {
        @Override
        public void run() {
            if (D) Log.d(TAG, "applying state to connected service");

            boolean enabled;
            final ProviderProperties[] properties = new ProviderProperties[1];
            ProviderRequest request;
            WorkSource source;
            synchronized (mLock) {
                enabled = mEnabled;
                request = mRequest;
107                source = mWorksource;
108            }
109
110
111            mServiceWatcher.runOnBinder(new ServiceWatcher.BinderRunner() {
112                @Override
113                public void run(IBinder binder) {
114                    ILocationProvider service = ILocationProvider.Stub.asInterface(binder);  ---> 这个service实际上就是bind三方的NLP
115                    try {
116                        // load properties from provider
117                        properties[0] = service.getProperties();
118                        if (properties[0] == null) {
119                            Log.e(TAG, mServiceWatcher.getBestPackageName() +
120                                    " has invalid location provider properties");
121                        }
122
123                        // apply current state to new service
124                        if (enabled) {
125                            service.enable();
126                            if (request != null) {
127                                service.setRequest(request, source);
128                            }
129                        }
130                    } catch (RemoteException e) {
131                        Log.w(TAG, e);
132                    } catch (Exception e) {
133                        // never let remote service crash system server
134                        Log.e(TAG, "Exception from " + mServiceWatcher.getBestPackageName(), e);
135                    }
136                }
137            });

            synchronized (mLock) {
                mProperties = properties[0];
            }
        }
    };

至此，整个bind流程记录完毕，另外如何集成三方NLP呢？这个我们可以参考公众号：蘑菇君先生

Android R 集成 百度NLP