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209 lines
6.4 KiB
209 lines
6.4 KiB
---
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Provider 的启动原理
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---
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1. 了解 ContentProvider 的生命周期
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2. 熟悉 ContentProvider 的启动流程
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3. 熟悉 Provider 启动过程中各方通信原理
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```java
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ContextResolver resolver = context.getContentResolver();
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resolver.insert(uri, contentValues);
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public ContextResolver getContextResolver(){
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return mContextResolver;
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}
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private ContextImpl(ConntextImpl container, ...) {
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mContextResolver = new ApplicationContextResolver(this, ...);
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}
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public final Uri insert(Uri url, ContentValues values) {
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IContentProvider provider = acquireProvider(url);
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Uri createdRow = provider.insert(mPackageName, url, values);
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return createdRow;
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}
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protected IContentProvider acquireProvider(Context context, String auth) {
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return mMainThread.acquireProvider(context, ...);
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}
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IContentProvider acquireProvider(Context c, String auth, ...){
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IContentProvider provider = acquireExistingProvider(c, ...);
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if(provider != null){
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return provider;
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}
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IActivityManager.ContentProviderHolder holder = null;
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holder = ActivityManagerNative.getDefault().getContentProvider(getApplicationThread(), auth, userId, stable);
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holder = installProvider(c, holder, holder.info, ...);
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return holder.provider;
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}
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```
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获取 ContentProvider 的过程小结：
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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。
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本地找：
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```java
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IContentProvider acquireExistingProvider (Context c, ...) {
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final ProviderKey key = new ProviderKey(auth, userId);
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final ProviderClientRecord pr = mProviderMap.get(key);
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if(pr == null){
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return null;
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}
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IContentProvider provider = pr.mProvider;
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IBinder jBinder = provider.asBinder();
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if(!jBinder.isBinderAlive()) {
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handleUnstableProvideDiedLocked(jBinder, true);
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return null;
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}
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return provider;
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}
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```
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远程找：
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```java
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ContentProviderHolder getContentProvider(IApplicationThread caller, ...) {
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return getContentProviderImpl(caller, name, null, ...);
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}
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ContentProviderHolder getContentProviderImpl(IApplicationThread caller, ...) {
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// 如果 ContentProviderRecord 存在就直接返回
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// ContentProviderRecord 不存在，就创建一个
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// 如果 ContentProviderRecord 能跑在调用者进程，就直接返回，否则往下走
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// 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
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// 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
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if(providerRunning){
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// provider 存在
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}
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if(!providerRunning){
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// provider 不存在
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}
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synchronized(cpr){
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while(cpr.provider == null){
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cpr.wait();
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}
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}
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return cpr!=null?cpr.newHolder(conn):null;
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}
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```
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```java
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if(providerRunning){
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cpi = cpr.info;
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if(r!=null&&cpr.canRunHere(r)){
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ContentProviderHolder holder = cpr.newHolder(null);
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holder.provider = null;
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return holder;
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}
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conn = incProviderCountLocked(r, cpr, token, stable);
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return cpr.newHolder(conn);
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}
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```
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```java
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// 应用端安装 provider
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IActivityManager.ContentProviderHolder installProvider(Context context, ...) {
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Context c = context.createPackageContext(ai.packageName, ...);
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ContentProvider localProvider = cl.loadClass(info.name).newInstance();
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IContentProvider provider = localProvider.getIContentProvider();
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// 调用 provider#onCreate
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localProvider.attachInfo(c, info);
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ProviderClientRecord pr = mLocalProvidersByName.get(cname);
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holder = new IActivityManager.ContentProviderHolder(info);
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holder.provider = provider;
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pr = installProviderAuthoritiesLocked(provider, localProvider, holder);
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mLocalProviders.put(jBinder, pr);
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mLocalProvidersByName.put(cname, pr);
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return pr.mHolder;
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}
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```
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provider 不存在的情况：
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```java
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if(!providerRunning) {
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cpr = new ContentProviderRecord(this, cpi, ai, comp, singleton);
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if(r!=null&&cpr.canRunHere(r)){
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return cpr.newHolder(null);
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}
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if(i>=N){
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ProcessRecord proc = getProcessRecordLocked(...);
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if(proc!=null&&proc.thread!=null){
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proc.thread.scheduleInstallProvider(cpi);
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}else{
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proc = startProcessLocked(cpi.processName, ...);
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}
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mLaunchingProviders.add(cpr);
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}
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}
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```
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应用启动时主动发布 provider 的 Binder 对象：
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```java
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boolean attachApplicationLocked(IApplicationThread thread, ...){
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List<ProviderInfo> providers = generateApplicationProvidersLocked(app);
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if(providers != null && checkAppInLaunchingProvidersLocked(app)){
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Message msg = mHandler.obtainMessage(CONTENT_PROVIDER_PUBLISH_TIMEOUT_MSG);
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msg.obj = app;
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mHandler.sendMessageDelayed(msg, CONTENT_PROVIDER_PUBLISH_TIMEOUT);
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}
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// 让应用端初始化 provider
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thread.bindApplication(processName, appInfo, providers, ...);
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return true;
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}
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// 应用主线程执行
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private void handleBindApplication(AppBindData data){
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List<ProviderInfo> provider = data.providers;
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if(providers != null){
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installContentProviders(app, providers);
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}
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}
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void installContentProviders(Context context, List<ProviderInfo> providers){
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List<ContentProviderHolder> results = new ArrayList<ContentProviderHolder>();
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for(ProviderInfo cpi: providers){
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ContentProviderHolder cph = installProvider(context, ...);
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results.add(cph);
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}
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AMP.publishContentProviders(getApplicationThread(), results);
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}
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void publishContentProviders(IApplicationThread caller, providers){
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final ProcessRecord r = getRecordForAppLocked(caller);
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for(int i=0;i<N;i++){
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ContentProviderHolder src = providers.get(i);
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ContentProviderRecord dst = r.pubProviders.get(src.info.name);
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// 更新 provider 缓存
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// 更新 mLaunchingProviders
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// 删除超时计时的消息
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synchronized(dst){
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dst.provider = src.provider;
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dst.proc = r;
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dst.notifyAll();
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}
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}
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}
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```
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AMS 主动向应用请求发布 provider：
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```java
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public void scheduleInstallProvider(ProviderInfo provider){
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sendMessage(H.INSTALL_PROVIDER, provider);
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}
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public void handleInstallProvider(ProviderInfo info){
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installContentProviders(mInitialApplication, Lists.newArrayList(info));
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}
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```
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#### 总结
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Provider 进程未启动：
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Provider 进程已经启动：
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