其实一看也没做什么事情，主要就是将provider信息保存到了mProviderMap里面。到这里加载provider的过程就完了。下面继续看看第二个大问题：ContentProvider的调用。

大家都知道是contentprovider是这么用的

getContentResolver().query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder);对了，那我们就从getContentResolver()说起

简单给大家列一下这里边的方法堆栈调用，然后就其他几个重要的点特别说明一下。

getContentResolver()获取到的就是ContextImpl中的mContentResolver，它是一个ApplicationContentResolver继承于ContentResolver。看看执行query发生了什么事情，ContentResolver又是如何与对应的ContentProvider发生关系的呢，要说清楚这个还得先说说ContentProvider是如何具备跨进程通信能力的。这里有三个类功不可没，IContentProvider、ContentProviderNative和ContentProviderProxy。这几个名字有木有很熟悉，还是一个代理模式还是Binder机制。获取到的IContentProvider接口实际上是一个在ContentProvider类的内部所创建的一个Transport对象的远程接口。这个Transport类继承了ContentProviderNative类，是一个Binder对象的Stub类，因此，接下来就会进入到这个Binder对象的Proxy类ContentProviderProxy中执行对应操作。

    public final Cursor query(final Uri uri, String[] projection,            String selection, String[] selectionArgs, String sortOrder,            CancellationSignal cancellationSignal) {        IContentProvider unstableProvider = acquireUnstableProvider(uri);        if (unstableProvider == null) {            return null;        }        IContentProvider stableProvider = null;        try {            long startTime = SystemClock.uptimeMillis();            ICancellationSignal remoteCancellationSignal = null;            if (cancellationSignal != null) {                cancellationSignal.throwIfCanceled();                remoteCancellationSignal = unstableProvider.createCancellationSignal();                cancellationSignal.setRemote(remoteCancellationSignal);            }            Cursor qCursor;            try {                qCursor = unstableProvider.query(uri, projection,                        selection, selectionArgs, sortOrder, remoteCancellationSignal);            } catch (DeadObjectException e) {                 // The remote process has died...  but we only hold an unstable                // reference though, so we might recover!!!  Let's try!!!!                // This is exciting!!1!!1!!!!1                unstableProviderDied(unstableProvider);                stableProvider = acquireProvider(uri);                if (stableProvider == null) {                    return null;                }                qCursor = stableProvider.query(uri, projection,                        selection, selectionArgs, sortOrder, remoteCancellationSignal);            }            if (qCursor == null) {                return null;            }            // force query execution            qCursor.getCount();            long durationMillis = SystemClock.uptimeMillis() - startTime;            maybeLogQueryToEventLog(durationMillis, uri, projection, selection, sortOrder);            // Wrap the cursor object into CursorWrapperInner object            CursorWrapperInner wrapper = new CursorWrapperInner(qCursor,                    stableProvider != null ? stableProvider : acquireProvider(uri));            stableProvider = null;            return wrapper;        } catch (RemoteException e) {            // Arbitrary and not worth documenting, as Activity            // Manager will kill this process shortly anyway.            return null;        } finally {             if (unstableProvider != null) {                releaseUnstableProvider(unstableProvider);            }            if (stableProvider != null) {                releaseProvider(stableProvider);            }        }    }

这就是ContentResolver的query方法，这里最核心就是几个acquireProvider的方法，也就是获取ContentProvider的地方。它们最后都会调到ActivityThread的acquireProvider方法

    public final IContentProvider acquireProvider(            Context c, String auth, int userId, boolean stable) {        final IContentProvider provider = acquireExistingProvider(c, auth, userId, stable);        if (provider != null) {            return provider;        }        // There is a possible race here.  Another thread may try to acquire        // the same provider at the same time.  When this happens, we want to ensure        // that the first one wins.        // Note that we cannot hold the lock while acquiring and installing the        // provider since it might take a long time to run and it could also potentially        // be re-entrant in the case where the provider is in the same process.        IActivityManager.ContentProviderHolder holder = null;        try {            holder = ActivityManagerNative.getDefault().getContentProvider(                    getApplicationThread(), auth, userId, stable);        } catch (RemoteException ex) {        }        if (holder == null) {            Slog.e(TAG, "Failed to find provider info for " + auth);            return null;         }        // Install provider will increment the reference count for us, and break        // any ties in the race.        holder = installProvider(c, holder, holder.info,                true /*noisy*/, holder.noReleaseNeeded, stable);        return holder.provider;}

这里有三步，首先会调用acquireExistingProvider在本进程中去查找其实就是在前面提到的mProviderMap去找，如果没有就会执行第二步去ActivityManagerService中去getContentProvider，找到之后继续第三不将这个对象保存到当前进程中。SO，同一个进程中使用的是同一个ContentProvider对象。如果要去服务中找这个过程就是进程间的问题咯，下面继续分析

    public final ContentProviderHolder getContentProvider(            IApplicationThread caller, String name, int userId, boolean stable) {        enforceNotIsolatedCaller("getContentProvider");        if (caller == null) {            String msg = "null IApplicationThread when getting content provider "                    + name;            Slog.w(TAG, msg);            throw new SecurityException(msg);        }        userId = handleIncomingUser(Binder.getCallingPid(), Binder.getCallingUid(), userId,                false, true, "getContentProvider", null);        return getContentProviderImpl(caller, name, null, stable, userId);    }

    private final ContentProviderHolder getContentProviderImpl(IApplicationThread caller,            String name, IBinder token, boolean stable, int userId) {        ContentProviderRecord cpr;        ContentProviderConnection conn = null;        ProviderInfo cpi = null;        synchronized(this) {            ProcessRecord r = null;            if (caller != null) {                r = getRecordForAppLocked(caller);                if (r == null) {                    throw new SecurityException(                            "Unable to find app for caller " + caller                          + " (pid=" + Binder.getCallingPid()                          + ") when getting content provider " + name);                }            }            // First check if this content provider has been published...            cpr = mProviderMap.getProviderByName(name, userId);            boolean providerRunning = cpr != null;            if (providerRunning) {                cpi = cpr.info;                String msg;                 if ((msg=checkContentProviderPermissionLocked(cpi, r)) != null) {                    throw new SecurityException(msg);                }                if (r != null && cpr.canRunHere(r)) {                    // This provider has been published or is in the process                    // of being published...  but it is also allowed to run                    // in the caller's process, so don't make a connection                    // and just let the caller instantiate its own instance.                    ContentProviderHolder holder = cpr.newHolder(null);                    // don't give caller the provider object, it needs                    // to make its own.                    holder.provider = null;                    return holder;                }                final long origId = Binder.clearCallingIdentity();                // In this case the provider instance already exists, so we can                // return it right away.                conn = incProviderCountLocked(r, cpr, token, stable);                 if (conn != null && (conn.stableCount+conn.unstableCount) == 1) {                    if (cpr.proc != null && r.setAdj <= ProcessList.PERCEPTIBLE_APP_ADJ) {                        // If this is a perceptible app accessing the provider,                        // make sure to count it as being accessed and thus                        // back up on the LRU list.  This is good because                        // content providers are often expensive to start.                        updateLruProcessLocked(cpr.proc, false);                    }                }                if (cpr.proc != null) {                    if (false) {                        if (cpr.name.flattenToShortString().equals(                                "com.android.providers.calendar/.CalendarProvider2")) {                            Slog.v(TAG, "****************** KILLING "                                + cpr.name.flattenToShortString());                            Process.killProcess(cpr.proc.pid);                        }                    }                    boolean success = updateOomAdjLocked(cpr.proc);                    if (DEBUG_PROVIDER) Slog.i(TAG, "Adjust success: " + success);                     // NOTE: there is still a race here where a signal could be                    // pending on the process even though we managed to update its                    // adj level.  Not sure what to do about this, but at least                    // the race is now smaller.                    if (!success) {                        // Uh oh...  it looks like the provider's process                        // has been killed on us.  We need to wait for a new                        // process to be started, and make sure its death                        // doesn't kill our process.                        Slog.i(TAG,                                "Existing provider " + cpr.name.flattenToShortString()                                + " is crashing; detaching " + r);                        boolean lastRef = decProviderCountLocked(conn, cpr, token, stable);                        appDiedLocked(cpr.proc, cpr.proc.pid, cpr.proc.thread);                        if (!lastRef) {                            // This wasn't the last ref our process had on                            // the provider...  we have now been killed, bail.                            return null;                        }                        providerRunning = false;                         conn = null;                    }                }                Binder.restoreCallingIdentity(origId);            }            boolean singleton;            if (!providerRunning) {                try {                    cpi = AppGlobals.getPackageManager().                        resolveContentProvider(name,                            STOCK_PM_FLAGS | PackageManager.GET_URI_PERMISSION_PATTERNS, userId);                } catch (RemoteException ex) {                }                if (cpi == null) {                    return null;                }                singleton = isSingleton(cpi.processName, cpi.applicationInfo,                        cpi.name, cpi.flags);                 if (singleton) {                    userId = 0;                }                 cpi.applicationInfo = getAppInfoForUser(cpi.applicationInfo, userId);                String msg;                if ((msg=checkContentProviderPermissionLocked(cpi, r)) != null) {                    throw new SecurityException(msg);                }                if (!mProcessesReady && !mDidUpdate && !mWaitingUpdate                        && !cpi.processName.equals("system")) {                    // If this content provider does not run in the system                    // process, and the system is not yet ready to run other                    // processes, then fail fast instead of hanging.                    throw new IllegalArgumentException(                            "Attempt to launch content provider before system ready");                }                // Make sure that the user who owns this provider is started.  If not,                // we don't want to allow it to run.                 if (mStartedUsers.get(userId) == null) {                    Slog.w(TAG, "Unable to launch app "                            + cpi.applicationInfo.packageName + "/"                            + cpi.applicationInfo.uid + " for provider "                            + name + ": user " + userId + " is stopped");                    return null;                }                ComponentName comp = new ComponentName(cpi.packageName, cpi.name);                cpr = mProviderMap.getProviderByClass(comp, userId);                final boolean firstClass = cpr == null;                if (firstClass) {                    try {                        ApplicationInfo ai =                            AppGlobals.getPackageManager().                                getApplicationInfo(                                        cpi.applicationInfo.packageName,                                        STOCK_PM_FLAGS, userId);                         if (ai == null) {                            Slog.w(TAG, "No package info for content provider "                                    + cpi.name);                            return null;                        }                        ai = getAppInfoForUser(ai, userId);                        cpr = new ContentProviderRecord(this, cpi, ai, comp, singleton);                    } catch (RemoteException ex) {                        // pm is in same process, this will never happen.                    }                }                if (r != null && cpr.canRunHere(r)) {                     // If this is a multiprocess provider, then just return its                    // info and allow the caller to instantiate it.  Only do                    // this if the provider is the same user as the caller's                    // process, or can run as root (so can be in any process).                    return cpr.newHolder(null);                }                if (DEBUG_PROVIDER) {                    RuntimeException e = new RuntimeException("here");                    Slog.w(TAG, "LAUNCHING REMOTE PROVIDER (myuid " + r.uid                          + " pruid " + cpr.appInfo.uid + "): " + cpr.info.name, e);                }                // This is single process, and our app is now connecting to it.                // See if we are already in the process of launching this                // provider.                final int N = mLaunchingProviders.size();                int i;                 for (i=0; i= N) {                    final long origId = Binder.clearCallingIdentity();                    try {                        // Content provider is now in use, its package can't be stopped.                        try {                            AppGlobals.getPackageManager().setPackageStoppedState(                                    cpr.appInfo.packageName, false, userId);                        } catch (RemoteException e) {                        } catch (IllegalArgumentException e) {                            Slog.w(TAG, "Failed trying to unstop package "                                    + cpr.appInfo.packageName + ": " + e);                        }                         ProcessRecord proc = startProcessLocked(cpi.processName,                                cpr.appInfo, false, 0, "content provider",                                new ComponentName(cpi.applicationInfo.packageName,                                        cpi.name), false, false);                        if (proc == null) {                            Slog.w(TAG, "Unable to launch app "                                    + cpi.applicationInfo.packageName + "/"                                    + cpi.applicationInfo.uid + " for provider "                                    + name + ": process is bad");                            return null;                        }                        cpr.launchingApp = proc;                        mLaunchingProviders.add(cpr);                    } finally {                        Binder.restoreCallingIdentity(origId);                    }                }                 // Make sure the provider is published (the same provider class                // may be published under multiple names).                if (firstClass) {                    mProviderMap.putProviderByClass(comp, cpr);                }                mProviderMap.putProviderByName(name, cpr);                conn = incProviderCountLocked(r, cpr, token, stable);                if (conn != null) {                    conn.waiting = true;                }            }        }         // Wait for the provider to be published...        synchronized (cpr) {            while (cpr.provider == null) {                if (cpr.launchingApp == null) {                    Slog.w(TAG, "Unable to launch app "                            + cpi.applicationInfo.packageName + "/"                            + cpi.applicationInfo.uid + " for provider "                            + name + ": launching app became null");                    EventLog.writeEvent(EventLogTags.AM_PROVIDER_LOST_PROCESS,                            UserHandle.getUserId(cpi.applicationInfo.uid),                            cpi.applicationInfo.packageName,                            cpi.applicationInfo.uid, name);                    return null;                }                try {                    if (DEBUG_MU) {                        Slog.v(TAG_MU, "Waiting to start provider " + cpr + " launchingApp="                                + cpr.launchingApp);                    }                    if (conn != null) {                        conn.waiting = true;                    }                    cpr.wait();                } catch (InterruptedException ex) {                 } finally {                    if (conn != null) {                        conn.waiting = false;                    }                }            }        }        return cpr != null ? cpr.newHolder(conn) : null;    }

上面这个方法需要大家细细的看一下，里面有一些需要注意的地方我已经将原有注释标红了。在AndroidManifest中注册ContentProvider时可以设置一个android:multiprocess="true"，意思是说配置当前Provider组件对象是否可以运行在多个进程（配置进程之间是否是单例）。同时这里还可以很明显的看到关于进程优先级的概念，在某些生命周期时设置不运行结束当前进程等维护LRU的操作。

大家注意到了上面的方法中还有一个ContentProviderConnection的东东，这个作用还没有说到，另外还有第三个问题，内容监听机制也会在后文中说明。

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