- 发布ContentProvider
发布ContentProvider
拉起进程
创建ContentProvider是随着进程启动时进行的，在进程启动后，进入到进程的main方法，相关方法调用如下。
ActivityThread.main() ->
ActivityThread.attach() ->
AMS.attachApplication() ->
AMS.attachApplicationLocked() {
Message msg = mHandler.obtainMessage(CONTENT_PROVIDER_PUBLISH_TIMEOUT_MSG);
msg.obj = app;
mHandler.sendMessageDelayed(msg,
ContentResolver.CONTENT_PROVIDER_PUBLISH_TIMEOUT_MILLIS);
} ->
AMS.attachApplicationLocked() ->
ApplicationThread.bindApplication() ->
ActivityThread.handleBindApplication() ->
AT.handleBindApplication()
AMS.attachApplicationLocked()
主要是通过bindApplication()创建Application和启动其它三大组件（如果需要的话），对Provider拉起的进程来说，主要看bindApplication()过程。
获取当前APP的所有ProviderInfo信息：
List<ProviderInfo> providers = normalMode
? mCpHelper.generateApplicationProvidersLocked(app)
: null;
final ProviderInfoList providerList = ProviderInfoList.fromList(providers);
ContentProviderHelper.generateApplicationProvidersLocked()如下：
List<ProviderInfo> generateApplicationProvidersLocked(ProcessRecord app) {
final List<ProviderInfo> providers;
try {
providers = AppGlobals.getPackageManager().queryContentProviders(
app.processName, app.uid, ActivityManagerService.STOCK_PM_FLAGS
| PackageManager.GET_URI_PERMISSION_PATTERNS
| PackageManager.MATCH_DIRECT_BOOT_AUTO, /*metaDataKey=*/ null)
.getList();
} catch (RemoteException ex) {
return null;
}
传入到后续创建进程流程中：
thread.bindApplication(processName, appInfo,
app.sdkSandboxClientAppVolumeUuid, app.sdkSandboxClientAppPackage,
providerList, null, profilerInfo, null, null, null, testMode,
mBinderTransactionTrackingEnabled, enableTrackAllocation,
isRestrictedBackupMode || !normalMode, app.isPersistent(),
new Configuration(app.getWindowProcessController().getConfiguration()),
app.getCompat(), getCommonServicesLocked(app.isolated),
mCoreSettingsObserver.getCoreSettingsLocked(),
buildSerial, autofillOptions, contentCaptureOptions,
app.getDisabledCompatChanges(), serializedSystemFontMap,
app.getStartElapsedTime(), app.getStartUptime());
ApplicationThread.bindApplication()
在这里将相关参数封装到AppBindData对象中，然后通过H.BIND_APPLICATION消息发送到ActivityThread。
data.providers = providerList.getList();
sendMessage(H.BIND_APPLICATION, data);
AT.handleBindApplication()
private void handleBindApplication(AppBindData data) {...}
安装Provider：
// don't bring up providers in restricted mode; they may depend on the
// app's custom Application class
if (!data.restrictedBackupMode) {
if (!ArrayUtils.isEmpty(data.providers)) {
installContentProviders(app, data.providers);
}
}
AT.installContentProviders()
这里主要进行两步。
(1) installProvider()：将进程中的所有Provider安装到本进程中
List
(2) publishContentProviders()：将Provider信息发布到AMS中
其它APP访问Provider时通过AMS查询。
private void installContentProviders(
Context context, List<ProviderInfo> providers) {
final ArrayList<ContentProviderHolder> results = new ArrayList<>();
for (ProviderInfo cpi : providers) {
if (DEBUG_PROVIDER) {
StringBuilder buf = new StringBuilder(128);
buf.append("Pub ");
buf.append(cpi.authority);
buf.append(": ");
buf.append(cpi.name);
Log.i(TAG, buf.toString());
}
ContentProviderHolder cph = installProvider(context, null, cpi,
false /*noisy*/, true /*noReleaseNeeded*/, true /*stable*/);
if (cph != null) {
cph.noReleaseNeeded = true;
results.add(cph);
}
}
try {
ActivityManager.getService().publishContentProviders(
getApplicationThread(), results);
} catch (RemoteException ex) {
throw ex.rethrowFromSystemServer();
}
}
Provider的install及onCreate()过程
与发布过程在installContentProviders()前是一样的。
ActivityThread.installContentProviders() ->
ActivityThread.installProvider() ->
ContentProvider.attachInfo() ->
ContentProvider.onCreate()
在ActivityThread.installProvider()方法中，调用attachInfo()的作用是将新创建的ContentProvider的ProviderInfo和Context关联起来，最后调用该Provider的onCreate()方法初始化ContentProvider。
通常会在onCreate()中完成对数据库的创建和升级等操作，返回true表示内容提供器初始化成功，返回false则表示失败。
AT.installProvider()
private ContentProviderHolder installProvider(Context context,
ContentProviderHolder holder, ProviderInfo info,
boolean noisy, boolean noReleaseNeeded, boolean stable) {...}
AT.installProvider()中的主要作用为将跨进程的Provider相关数据保存到本进程中，执行以下流程：
- 通过ProviderInfo info获取Provider所在进程的Context
- 通过Context获取到Provider对象及Binder引用
- 将Provider相关信息封装到ContentProviderHolder对象中
- 更新该Provider的引用计数
private ContentProviderHolder installProvider(Context context,
ContentProviderHolder holder, ProviderInfo info,
boolean noisy, boolean noReleaseNeeded, boolean stable) {
ContentProvider localProvider = null;
IContentProvider provider;
// holder为null表示还没有install过
if (holder == null || holder.provider == null) {
if (DEBUG_PROVIDER || noisy) {
Slog.d(TAG, "Loading provider " + info.authority + ": "
+ info.name);
}
Context c = null;
ApplicationInfo ai = info.applicationInfo;
//...
//获取Provider所在进程的Context
try {
final java.lang.ClassLoader cl = c.getClassLoader();
LoadedApk packageInfo = peekPackageInfo(ai.packageName, true);
if (packageInfo == null) {
// System startup case.
packageInfo = getSystemContext().mPackageInfo;
}
// 创建provider对象
localProvider = packageInfo.getAppFactory()
.instantiateProvider(cl, info.name);
// 获取IContentProvider对象，用于跨进程binder引用
provider = localProvider.getIContentProvider();
//...
// provider的attach，其中最重要的是会执行provider的onCreate
localProvider.attachInfo(c, info);
} catch (java.lang.Exception e) {
//...
}
} else {
provider = holder.provider;
if (DEBUG_PROVIDER) Slog.v(TAG, "Installing external provider " + info.authority + ": "
+ info.name);
}
// provider的对象创建好了，那么接下来需要做的就是数据结构的封装
// 把provider相关信息保存到ContentProviderHolder对象中
ContentProviderHolder retHolder;
synchronized (mProviderMap) {
if (DEBUG_PROVIDER) Slog.v(TAG, "Checking to add " + provider
+ " / " + info.name);
IBinder jBinder = provider.asBinder();
if (localProvider != null) {
ComponentName cname = new ComponentName(info.packageName, info.name);
// mLocalProvidersByName的key是component信息，value是对应的ProviderClientReocrd
ProviderClientRecord pr = mLocalProvidersByName.get(cname);
if (pr != null) {
// 不为空代表install过
provider = pr.mProvider;
} else {
// 对于新创建的provider，创建其对应的ContentProviderHolder对象
holder = new ContentProviderHolder(info);
holder.provider = provider;
holder.noReleaseNeeded = true;
pr = installProviderAuthoritiesLocked(provider, localProvider, holder);
// mLocalProviders的key是IContentProvider的binder对象，value是ProviderClientRecord
// 将封装好的provider放入map中
mLocalProviders.put(jBinder, pr);
mLocalProvidersByName.put(cname, pr);
}
retHolder = pr.mHolder;
} else { // 接下来更新引用计数
// mProviderRefCountMap的key是binder对象，value是ProviderRefCount
// ProviderRefCount中记录了这个provider的stable和unstable的数量
ProviderRefCount prc = mProviderRefCountMap.get(jBinder);
if (prc != null) {
if (DEBUG_PROVIDER) {
Slog.v(TAG, "installProvider: lost the race, updating ref count");
}
// We need to transfer our new reference to the existing
// ref count, releasing the old one... but only if
// release is needed (that is, it is not running in the
// system process).
if (!noReleaseNeeded) {
incProviderRefLocked(prc, stable);
try {
ActivityManager.getService().removeContentProvider(
holder.connection, stable);
} catch (RemoteException e) {
//do nothing content provider object is dead any way
}
}
} else {
ProviderClientRecord client = installProviderAuthoritiesLocked(
provider, localProvider, holder);
if (noReleaseNeeded) {
prc = new ProviderRefCount(holder, client, 1000, 1000);
} else {
prc = stable
? new ProviderRefCount(holder, client, 1, 0)
: new ProviderRefCount(holder, client, 0, 1);
}
mProviderRefCountMap.put(jBinder, prc);
}
retHolder = prc.holder;
}
}
return retHolder;
}
ContentProvider.attachInfo()
调用到目标Provider中，授予读写权限并执行onCreate()。
public void attachInfo(Context context, ProviderInfo info) {
attachInfo(context, info, false);
}
private void attachInfo(Context context, ProviderInfo info, boolean testing) {
mNoPerms = testing;
mCallingAttributionSource = new ThreadLocal<>();
/*
* Only allow it to be set once, so after the content service gives
* this to us clients can't change it.
*/
if (mContext == null) {
mContext = context;
if (context != null && mTransport != null) {
mTransport.mAppOpsManager = (AppOpsManager) context.getSystemService(
Context.APP_OPS_SERVICE);
}
mMyUid = Process.myUid();
if (info != null) {
setReadPermission(info.readPermission);
setWritePermission(info.writePermission);
setPathPermissions(info.pathPermissions);
mExported = info.exported;
mSingleUser = (info.flags & ProviderInfo.FLAG_SINGLE_USER) != 0;
setAuthorities(info.authority);
}
if (Build.IS_DEBUGGABLE) {
setTransportLoggingEnabled(Log.isLoggable(getClass().getSimpleName(),
Log.VERBOSE));
}
ContentProvider.this.onCreate();
}
}
MyContentProvider.onCreate()
执行自定义Provider对象的onCreate()。
Provider的publish过程
Provider进程端安装Provider过程：
ActivityThread.installContentProviders() ->
AMS.publishContentProviders() ->
ContentProviderHelper.publishContentProviders(){
removeMessage(CONTENT_PROVIDER_PUBLISH_TIMEOUT_MSG) }
AMS.publishContentProviders()的工作主要就是将ContentProvider的信息保存到AMS服务中去。AMS服务保存ContentProvider的信息主要是在类ProviderMap中，它里边有两种保存的Provider信息的集合：
- ProviderByClass：以ComponentName为key保存了ContentProviderRecord的信息；
- ProviderByName：以authority为key保存了ContentProviderRecord的信息。
AMS.publishContentProviders()
实际上的发布过程是在CPH.publishContentProviders()中完成的。
public final void publishContentProviders(IApplicationThread caller,
List<ContentProviderHolder> providers) {
if (Trace.isTagEnabled(Trace.TRACE_TAG_ACTIVITY_MANAGER)) {
final int maxLength = 256;
final StringBuilder sb = new StringBuilder(maxLength);
sb.append("publishContentProviders: ");
if (providers != null) {
boolean first = true;
for (int i = 0, size = providers.size(); i < size; i++) {
final ContentProviderHolder holder = providers.get(i);
if (holder != null && holder.info != null && holder.info.authority != null) {
final int len = holder.info.authority.length();
if (sb.length() + len > maxLength) {
sb.append("[[TRUNCATED]]");
break;
}
if (!first) {
sb.append(';');
} else {
first = false;
}
sb.append(holder.info.authority);
}
}
}
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, sb.toString());
}
try {
mCpHelper.publishContentProviders(caller, providers);
} finally {
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
}
}
CPH.publishContentProviders()
在这里将Provider的信息添加到system_server进程中，实际上就是CPH的mProviderMap数据中，以后如果有其它进程访问，则不再执行onCreate()，而是直接通过AMS返回对象。
本步骤主要进行以下流程：
- 遍历Provider所在进程下所有已经安装的provider，将新的Provider保存到mProviderMap中；
- 从正在启动列表mLaunchingProviders中移除该Provider信息，因为已成功启动；
- 移除该Provider的超时消息；
- 唤醒正在等待该Provider的线程
void publishContentProviders(IApplicationThread caller, List<ContentProviderHolder> providers) {
if (providers == null) {
return;
}
mService.enforceNotIsolatedOrSdkSandboxCaller("publishContentProviders");
synchronized (mService) {
// 获取Provider所在进程对象
final ProcessRecord r = mService.getRecordForAppLOSP(caller);
if (r == null) {
throw new SecurityException("Unable to find app for caller " + caller
+ " (pid=" + Binder.getCallingPid()
+ ") when publishing content providers");
}
final long origId = Binder.clearCallingIdentity();
boolean providersPublished = false;
// 遍历该进程下所有已经安装的provider
for (int i = 0, size = providers.size(); i < size; i++) {
ContentProviderHolder src = providers.get(i);
if (src == null || src.info == null || src.provider == null) {
continue;
}
ContentProviderRecord dst = r.mProviders.getProvider(src.info.name);
if (dst == null) {
continue;
}
if (DEBUG_MU) {
Slog.v(TAG_MU, "ContentProviderRecord uid = " + dst.uid);
}
providersPublished = true;
// 将这个providerRecord放入到mProviderMap中
ComponentName comp = new ComponentName(dst.info.packageName, dst.info.name);
mProviderMap.putProviderByClass(comp, dst);
String[] names = dst.info.authority.split(";");
for (int j = 0; j < names.length; j++) {
mProviderMap.putProviderByName(names[j], dst);
}
// 如果该Provider在正在启动的列表中，则移除
boolean wasInLaunchingProviders = false;
for (int j = 0, numLaunching = mLaunchingProviders.size(); j < numLaunching; j++) {
if (mLaunchingProviders.get(j) == dst) {
mLaunchingProviders.remove(j);
wasInLaunchingProviders = true;
j--;
numLaunching--;
}
}
// 移除超时消息
if (wasInLaunchingProviders) {
mService.mHandler.removeMessages(
ActivityManagerService.WAIT_FOR_CONTENT_PROVIDER_TIMEOUT_MSG, dst);
mService.mHandler.removeMessages(
ActivityManagerService.CONTENT_PROVIDER_PUBLISH_TIMEOUT_MSG, r);
}
// Make sure the package is associated with the process.
// XXX We shouldn't need to do this, since we have added the package
// when we generated the providers in generateApplicationProvidersLocked().
// But for some reason in some cases we get here with the package no longer
// added... for now just patch it in to make things happy.
r.addPackage(dst.info.applicationInfo.packageName,
dst.info.applicationInfo.longVersionCode, mService.mProcessStats);
// 唤醒正在等待该Provider的线程
synchronized (dst) {
dst.provider = src.provider;
dst.setProcess(r);
dst.notifyAll();
dst.onProviderPublishStatusLocked(true);
}
dst.mRestartCount = 0;
if (hasProviderConnectionLocked(r)) {
r.mProfile.addHostingComponentType(HOSTING_COMPONENT_TYPE_PROVIDER);
}
}
// update the app's oom adj value and each provider's usage stats
if (providersPublished) {
mService.updateOomAdjLocked(r, OomAdjuster.OOM_ADJ_REASON_GET_PROVIDER);
for (int i = 0, size = providers.size(); i < size; i++) {
ContentProviderHolder src = providers.get(i);
if (src == null || src.info == null || src.provider == null) {
continue;
}
maybeUpdateProviderUsageStatsLocked(r,
src.info.packageName, src.info.authority);
}
}
Binder.restoreCallingIdentity(origId);
}
}