diff --git a/blogs/Android/Framework/Interview/其他应用组件相关/Provider 启动原理.md b/blogs/Android/Framework/Interview/其他应用组件相关/Provider 启动原理.md new file mode 100644 index 0000000..848165a --- /dev/null +++ b/blogs/Android/Framework/Interview/其他应用组件相关/Provider 启动原理.md @@ -0,0 +1,209 @@ +--- +Provider 的启动原理 +--- + +1. 了解 ContentProvider 的生命周期 +2. 熟悉 ContentProvider 的启动流程 +3. 熟悉 Provider 启动过程中各方通信原理 + +```java +ContextResolver resolver = context.getContentResolver(); +resolver.insert(uri, contentValues); +public ContextResolver getContextResolver(){ + return mContextResolver; +} +private ContextImpl(ConntextImpl container, ...) { + mContextResolver = new ApplicationContextResolver(this, ...); +} +public final Uri insert(Uri url, ContentValues values) { + IContentProvider provider = acquireProvider(url); + Uri createdRow = provider.insert(mPackageName, url, values); + return createdRow; +} +protected IContentProvider acquireProvider(Context context, String auth) { + return mMainThread.acquireProvider(context, ...); +} +IContentProvider acquireProvider(Context c, String auth, ...){ + IContentProvider provider = acquireExistingProvider(c, ...); + if(provider != null){ + return provider; + } + IActivityManager.ContentProviderHolder holder = null; + holder = ActivityManagerNative.getDefault().getContentProvider(getApplicationThread(), auth, userId, stable); + holder = installProvider(c, holder, holder.info, ...); + return holder.provider; +} +``` + +获取 ContentProvider 的过程小结： + +本地找 IContentProvider 对象 -> 找到直接返回，不然请求 AMS -> AMS 返回 holder，本地安装。 + +本地找： + +```java +IContentProvider acquireExistingProvider (Context c, ...) { + final ProviderKey key = new ProviderKey(auth, userId); + final ProviderClientRecord pr = mProviderMap.get(key); + if(pr == null){ + return null; + } + IContentProvider provider = pr.mProvider; + IBinder jBinder = provider.asBinder(); + if(!jBinder.isBinderAlive()) { + handleUnstableProvideDiedLocked(jBinder, true); + return null; + } + return provider; +} +``` + +远程找： + +```java +ContentProviderHolder getContentProvider(IApplicationThread caller, ...) { + return getContentProviderImpl(caller, name, null, ...); +} +ContentProviderHolder getContentProviderImpl(IApplicationThread caller, ...) { + // 如果 ContentProviderRecord 存在就直接返回 + // ContentProviderRecord 不存在，就创建一个 + // 如果 ContentProviderRecord 能跑在调用者进程，就直接返回，否则往下走 + // 如果 provider 所在进程没启动，就启动进程，然后等待发布，完成的时候返回 + // 如果 binder 对象还没发布就请求发布，然后等待，完成的时候返回 + + if(providerRunning){ + // provider 存在 + } + if(!providerRunning){ + // provider 不存在 + } + synchronized(cpr){ + while(cpr.provider == null){ + cpr.wait(); + } + } + return cpr!=null?cpr.newHolder(conn):null; +} +``` + +```java +if(providerRunning){ + cpi = cpr.info; + if(r!=null&&cpr.canRunHere(r)){ + ContentProviderHolder holder = cpr.newHolder(null); + holder.provider = null; + return holder; + } + conn = incProviderCountLocked(r, cpr, token, stable); + return cpr.newHolder(conn); +} +``` + +```java +// 应用端安装 provider +IActivityManager.ContentProviderHolder installProvider(Context context, ...) { + Context c = context.createPackageContext(ai.packageName, ...); + ContentProvider localProvider = cl.loadClass(info.name).newInstance(); + IContentProvider provider = localProvider.getIContentProvider(); + // 调用 provider#onCreate + localProvider.attachInfo(c, info); + + ProviderClientRecord pr = mLocalProvidersByName.get(cname); + holder = new IActivityManager.ContentProviderHolder(info); + holder.provider = provider; + pr = installProviderAuthoritiesLocked(provider, localProvider, holder); + mLocalProviders.put(jBinder, pr); + mLocalProvidersByName.put(cname, pr); + return pr.mHolder; +} +``` + +provider 不存在的情况： + +```java +if(!providerRunning) { + cpr = new ContentProviderRecord(this, cpi, ai, comp, singleton); + if(r!=null&&cpr.canRunHere(r)){ + return cpr.newHolder(null); + } + if(i>=N){ + ProcessRecord proc = getProcessRecordLocked(...); + if(proc!=null&&proc.thread!=null){ + proc.thread.scheduleInstallProvider(cpi); + }else{ + proc = startProcessLocked(cpi.processName, ...); + } + mLaunchingProviders.add(cpr); + } +} +``` + +应用启动时主动发布 provider 的 Binder 对象： + +```java +boolean attachApplicationLocked(IApplicationThread thread, ...){ + List providers = generateApplicationProvidersLocked(app); + if(providers != null && checkAppInLaunchingProvidersLocked(app)){ + Message msg = mHandler.obtainMessage(CONTENT_PROVIDER_PUBLISH_TIMEOUT_MSG); + msg.obj = app; + mHandler.sendMessageDelayed(msg, CONTENT_PROVIDER_PUBLISH_TIMEOUT); + } + // 让应用端初始化 provider + thread.bindApplication(processName, appInfo, providers, ...); + return true; +} +// 应用主线程执行 +private void handleBindApplication(AppBindData data){ + List provider = data.providers; + if(providers != null){ + installContentProviders(app, providers); + } +} +void installContentProviders(Context context, List providers){ + List results = new ArrayList(); + for(ProviderInfo cpi: providers){ + ContentProviderHolder cph = installProvider(context, ...); + results.add(cph); + } + AMP.publishContentProviders(getApplicationThread(), results); +} +void publishContentProviders(IApplicationThread caller, providers){ + final ProcessRecord r = getRecordForAppLocked(caller); + for(int i=0;i