Android ContentProvider Unknown authority 问题

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java.lang.IllegalArgumentException: Unknown authority com.example.myprovider

从字面意思理解是没有找到特定的 ContentProvider。

一般定义 ContentProvider 如下：

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<provider
    android:name=".MyProvider"
    android:authorities="com.example.myprovider"
    android:exported="true" />

当调用如下代码时出错：

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private fun callMethodInstaller(context: Context, extras: Bundle?): Bundle? {
    val uri = Uri.parse("content://com.example.provider")
    return context.contentResolver.call(uri, "myMethod", null, extras)
}

源码分析，以 Android 11.0(R/api-30) 为例：

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@Override
public final Bundle call(String authority, String method,
        String arg, Bundle extras) {
    IContentProvider provider = acquireProvider(authority);
    if (provider == null) {
        throw new IllegalArgumentException("Unknown authority " + authority);
    }
    try {
        final Bundle res = provider.call(mPackageName, authority, ...);
        Bundle.setDefusable(res, true);
        return res;
    } catch (RemoteException e) {
        return null;
    } finally {
        releaseProvider(provider);
    }
}
  1. 如果获取不到 provider 就会抛出异常；
  2. 调用 provider 的方法，返回结果；
  3. 最后释放 provider；

acquireProvider 会调用到 ContextImpl.ApplicationContentResolver#acquireProvider() 方法：

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protected IContentProvider acquireProvider(Context context, String auth) {
    return mMainThread.acquireProvider(context,
            ContentProvider.getAuthorityWithoutUserId(auth),
            resolveUserIdFromAuthority(auth), true);
}

再调用 ActivityThread#acquireProvider() 方法：

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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.
    ContentProviderHolder holder = null;
    try {
        synchronized (getGetProviderLock(auth, userId)) {
            holder = ActivityManager.getService().getContentProvider(
                    getApplicationThread(), c.getOpPackageName(), auth, userId, stable);
        }
    } catch (RemoteException ex) {
        throw ex.rethrowFromSystemServer();
    }
    if (holder == null) {
        if (UserManager.get(c).isUserUnlocked(userId)) {
            Slog.e(TAG, "Failed to find provider info for " + auth);
        } else {
            Slog.w(TAG, "Failed to find provider info for " + auth + " (user not unlocked)");
        }
        return null;
    }

    // Install provider will increment the reference count for us, and break
    // any ties in the race.
    holder = installProvider(c, holder, holder.info,...);
    return holder.provider;
}

public final IContentProvider acquireExistingProvider(
        Context c, String auth,...) {
    synchronized (mProviderMap) {
        final ProviderKey key = new ProviderKey(auth, userId);
        final ProviderClientRecord pr = mProviderMap.get(key);
        if (pr == null) {
            return null;
        }

        // ...

        ProviderRefCount prc = mProviderRefCountMap.get(jBinder);
        if (prc != null) {
            incProviderRefLocked(prc, stable);
        }
        return provider;
    }
}
  1. 查找 provider 是否存在，如果已存在直接返回；
  2. 如果不存在，则通过 AMS 查找符合条件的 provider；
  3. AMS 没找到返回 null；否则安装 provider；