涉及的类
android.app.ContextImpl
public ContentResolver getContentResolver()
android.app.ContextImpl.ApplicationContentResolver
protected IContentProvider acquireProvider(Context context, String auth)
一般我们这么使用 contentProvider
getContentResolver().insert(Uri.parse("http://wwww.baidu.com/q/"),null);
getConentProvider 方法是 Context 的，Context 实现类是 ContextImpl
ContextImpl 中方法返回的是一个 成员变量：
@Override
public ContentResolver getContentResolver() {
return mContentResolver;
}
这个成员变量是一个 ApplicationContentResolver 对象，赋值是在 ContextImpl 的 构造函数中传参赋值：
private ContextImpl(@Nullable ContextImpl container, @NonNull ActivityThread mainThread,
@NonNull LoadedApk packageInfo, @Nullable String splitName,
@Nullable IBinder activityToken, @Nullable UserHandle user, int flags,
@Nullable ClassLoader classLoader, @Nullable String overrideOpPackageName){
....
mContentResolver = new ApplicationContentResolver(this, mainThread);
...
}
这里 ContextImpl 的初始化和 Activity 的启动相关，可以看 Activity 启动流程相关的内容
这里ContentProvider 的实现已经清晰，继续进入 insert() 方法的调用
IContentProvider provider = acquireProvider(url);
进入 ApplicationContentResolver 的 acquireProvider 方法
@Override
@UnsupportedAppUsage
protected IContentProvider acquireProvider(Context context, String auth) {
return mMainThread.acquireProvider(context,
ContentProvider.getAuthorityWithoutUserId(auth),
resolveUserIdFromAuthority(auth), true);
}
又是调用了 ActivityThread 的同名方法：
@UnsupportedAppUsage
public final IContentProvider acquireProvider(
Context c, String auth, int userId, boolean stable) {
/**
这里是 首先查看是否已经有缓存的 cp
*/
final IContentProvider provider = acquireExistingProvider(c, auth, userId, stable);
if (provider != null) {
return provider;
}
ContentProviderHolder holder = null;
try {
//远程调用
synchronized (getGetProviderLock(auth, userId)) {
holder = ActivityManager.getService().getContentProvider(
getApplicationThread(), c.getOpPackageName(), auth, userId, stable);
}
} catch (RemoteException ex) {
throw ex.rethrowFromSystemServer();
}
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;
}
发起远程调用 拿到一个 ContentProviderHolder
holder = ActivityManager.getService().getContentProvider(
getApplicationThread(), c.getOpPackageName(), auth, userId, stable);
```java
Android api 26 以后已经弃用了 ActivityManagerNative（就是手写了实现了一遍 aidl ） ，可以直接看 IActivityManager.aidl 中的定义
然后进入 ActivityManagerService
```java
public class ActivityManagerService extends IActivityManager.Stub implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback
getContentProvider 方法最后调用了 getContentProviderImpl 方法
private ContentProviderHolder getContentProviderImpl(IApplicationThread caller,
String name, IBinder token, int callingUid, String callingPackage, String callingTag,
boolean stable, int userId) {
ContentProviderRecord cpr;
ContentProviderConnection conn = null;
ProviderInfo cpi = null;
boolean providerRunning = false;
synchronized(this) {
long startTime = SystemClock.uptimeMillis();
ProcessRecord r = null;
if (caller != null) {
//首先拿到调用者的进程记录
r = getRecordForAppLocked(caller);
if (r == null) {
throw new SecurityException(
"Unable to find app for caller " + caller
+ " (pid=" + Binder.getCallingPid()
+ ") when getting content provider " + name);
}
}
boolean checkCrossUser = true;
checkTime(startTime, "getContentProviderImpl: getProviderByName");
// First check if this content provider has been published...
cpr = mProviderMap.getProviderByName(name, userId);
if (providerRunning) {
cpi = cpr.info;
String msg;
//检查 provider的属性，配置了 multiprocess = true 会直接实例化一个实例运行在调用者的进程，也就是说并不会启动 contentProvider
//所在的进程。后续直接返回到
if (r != null && cpr.canRunHere(r)) {
if ((msg = checkContentProviderAssociation(r, callingUid, cpi)) != null) {
throw new SecurityException("Content provider lookup "
+ cpr.name.flattenToShortString()
+ " failed: association not allowed with package " + msg);
}
ContentProviderHolder holder = cpr.newHolder(null);
holder.provider = null;
return holder;
}
// Don't expose providers between normal apps and instant apps
try {
if (AppGlobals.getPackageManager()
.resolveContentProvider(name, 0 /*flags*/, userId) == null) {
return null;
}
} catch (RemoteException e) {
}
if ((msg = checkContentProviderAssociation(r, callingUid, cpi)) != null) {
throw new SecurityException("Content provider lookup "
+ cpr.name.flattenToShortString()
+ " failed: association not allowed with package " + msg);
}
checkTime(startTime,
"getContentProviderImpl: before checkContentProviderPermission");
if ((msg = checkContentProviderPermissionLocked(cpi, r, userId, checkCrossUser))
!= null) {
throw new SecurityException(msg);
}
checkTime(startTime,
"getContentProviderImpl: after checkContentProviderPermission");
final long origId = Binder.clearCallingIdentity();
checkTime(startTime, "getContentProviderImpl: incProviderCountLocked");
// In this case the provider instance already exists, so we can
// return it right away.
conn = incProviderCountLocked(r, cpr, token, callingUid, callingPackage, callingTag,
stable);
if (conn != null && (conn.stableCount+conn.unstableCount) == 1) {
if (cpr.proc != null && r.setAdj <= ProcessList.PERCEPTIBLE_LOW_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.
checkTime(startTime, "getContentProviderImpl: before updateLruProcess");
mProcessList.updateLruProcessLocked(cpr.proc, false, null);
checkTime(startTime, "getContentProviderImpl: after updateLruProcess");
}
}
checkTime(startTime, "getContentProviderImpl: before updateOomAdj");
if (!providerRunning) {
try {
checkTime(startTime, "getContentProviderImpl: before resolveContentProvider");
cpi = AppGlobals.getPackageManager().
resolveContentProvider(name,
STOCK_PM_FLAGS | PackageManager.GET_URI_PERMISSION_PATTERNS, userId);
checkTime(startTime, "getContentProviderImpl: after resolveContentProvider");
} catch (RemoteException ex) {
}
if (cpi == null) {
return null;
}
final boolean firstClass = cpr == null;
if (firstClass) {
final long ident = Binder.clearCallingIdentity();
// If permissions need a review before any of the app components can run,
// we return no provider and launch a review activity if the calling app
// is in the foreground.
if (!requestTargetProviderPermissionsReviewIfNeededLocked(cpi, r, userId)) {
return null;
}
try {
checkTime(startTime, "getContentProviderImpl: before getApplicationInfo");
ApplicationInfo ai =
AppGlobals.getPackageManager().
getApplicationInfo(
cpi.applicationInfo.packageName,
STOCK_PM_FLAGS, userId);
checkTime(startTime, "getContentProviderImpl: after getApplicationInfo");
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.
} finally {
Binder.restoreCallingIdentity(ident);
}
}
checkTime(startTime, "getContentProviderImpl: now have ContentProviderRecord");
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) Slog.w(TAG_PROVIDER, "LAUNCHING REMOTE PROVIDER (myuid "
+ (r != null ? r.uid : null) + " pruid " + cpr.appInfo.uid + "): "
+ cpr.info.name + " callers=" + Debug.getCallers(6));
// 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; i++) {
if (mLaunchingProviders.get(i) == cpr) {
break;
}
}
// If the provider is not already being launched, then get it
// started.
if (i >= N) {
final long origId = Binder.clearCallingIdentity();
try {
// Content provider is now in use, its package can't be stopped.
try {
checkTime(startTime, "getContentProviderImpl: before set stopped state");
AppGlobals.getPackageManager().setPackageStoppedState(
cpr.appInfo.packageName, false, userId);
checkTime(startTime, "getContentProviderImpl: after set stopped state");
} catch (RemoteException e) {
} catch (IllegalArgumentException e) {
Slog.w(TAG, "Failed trying to unstop package "
+ cpr.appInfo.packageName + ": " + e);
}
// Use existing process if already started
checkTime(startTime, "getContentProviderImpl: looking for process record");
ProcessRecord proc = getProcessRecordLocked(
cpi.processName, cpr.appInfo.uid, false);
if (proc != null && proc.thread != null && !proc.killed) {
if (DEBUG_PROVIDER) Slog.d(TAG_PROVIDER,
"Installing in existing process " + proc);
if (!proc.pubProviders.containsKey(cpi.name)) {
checkTime(startTime, "getContentProviderImpl: scheduling install");
proc.pubProviders.put(cpi.name, cpr);
try {
//这里让 目标进程初始话 ContentProvider，这里进入 到ActivityThread 的 scheduleInstallProvider 方
//法，provider 初始化以后，回调 publishContentproviders
proc.thread.scheduleInstallProvider(cpi);
} catch (RemoteException e) {
}
}
} else {
checkTime(startTime, "getContentProviderImpl: before start process");
proc = startProcessLocked(cpi.processName,
cpr.appInfo, false, 0,
new HostingRecord("content provider",
new ComponentName(cpi.applicationInfo.packageName,
cpi.name)), false, false, false);
checkTime(startTime, "getContentProviderImpl: after start process");
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);
}
}
checkTime(startTime, "getContentProviderImpl: updating data structures");
// 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, callingUid, callingPackage, callingTag,
stable);
if (conn != null) {
conn.waiting = true;
}
}
checkTime(startTime, "getContentProviderImpl: done!");
grantEphemeralAccessLocked(userId, null /*intent*/,
UserHandle.getAppId(cpi.applicationInfo.uid),
UserHandle.getAppId(Binder.getCallingUid()));
}
//等待 ContentProvider 发布
// Wait for the provider to be published...
final long timeout = SystemClock.uptimeMillis() + CONTENT_PROVIDER_WAIT_TIMEOUT;
boolean timedOut = false;
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 {
final long wait = Math.max(0L, timeout - SystemClock.uptimeMillis());
if (DEBUG_MU) Slog.v(TAG_MU,
"Waiting to start provider " + cpr
+ " launchingApp=" + cpr.launchingApp + " for " + wait + " ms");
if (conn != null) {
conn.waiting = true;
}
cpr.wait(wait);
if (cpr.provider == null) {
timedOut = true;
break;
}
} catch (InterruptedException ex) {
} finally {
if (conn != null) {
conn.waiting = false;
}
}
}
}
if (timedOut) {
// Note we do it afer releasing the lock.
String callerName = "unknown";
synchronized (this) {
final ProcessRecord record = mProcessList.getLRURecordForAppLocked(caller);
if (record != null) {
callerName = record.processName;
}
}
Slog.wtf(TAG, "Timeout waiting for provider "
+ cpi.applicationInfo.packageName + "/"
+ cpi.applicationInfo.uid + " for provider "
+ name
+ " providerRunning=" + providerRunning
+ " caller=" + callerName + "/" + Binder.getCallingUid());
return null;
}
return cpr.newHolder(conn);
}
注意两个方法
canRunHere 这个方法用于检查 provider 的配置属性，一般我们可能会这么配置provider
<provider
android:name="com.hiray.androidlottie.TestContentProvider"
android:authorities="com.hiray.androidlottie"
android:exported="true"
android:multiprocess="true"
android:process=":testprovider" />
配置了 multiprocess 属性值等于 true ，那么就符合 canRunHere 的条件，直接在调用者的进程 初始化 provider ，这里 newHolder 方法的 conn 参数 是null,因为不需要后续通过 conn 来进行加减计数
后续注意 scheduleInstallProvider 方法，这里会回到客户端，看ActivityThread 的 同名方法， 利用 Handler 发送了一个 what = INSTALL_PROVIDER 的消息，来到 handleInstallProvider 方法
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();
}
}
这里是安装好 ContentProvider 后，调用了服务端的 publishContentProviders 方法，使得服务端的 getContentProviderImpl 方法不再阻塞，也就是我们的 调用端的 insert 方法 不被阻塞 ，即 getContentResolver().insert(Uri.parse(“http://wwww.baidu.com/q/"),null); 这句代码执行
继续看 installContentProviders 方法里面调用的 installProvider 方法
private ContentProviderHolder installProvider(Context context,
ContentProviderHolder holder, ProviderInfo info,
boolean noisy, boolean noReleaseNeeded, boolean stable) {
ContentProvider localProvider = null;
IContentProvider provider;
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;
if (context.getPackageName().equals(ai.packageName)) {
c = context;
} else if (mInitialApplication != null &&
mInitialApplication.getPackageName().equals(ai.packageName)) {
c = mInitialApplication;
} else {
try {
c = context.createPackageContext(ai.packageName,
Context.CONTEXT_INCLUDE_CODE);
} catch (PackageManager.NameNotFoundException e) {
// Ignore
}
}
if (c == null) {
Slog.w(TAG, "Unable to get context for package " +
ai.packageName +
" while loading content provider " +
info.name);
return null;
}
if (info.splitName != null) {
try {
c = c.createContextForSplit(info.splitName);
} catch (NameNotFoundException e) {
throw new RuntimeException(e);
}
}
try {
final java.lang.ClassLoader cl = c.getClassLoader();
LoadedApk packageInfo = peekPackageInfo(ai.packageName, true);
if (packageInfo == null) {
// System startup case.
packageInfo = getSystemContext().mPackageInfo;
}
localProvider = packageInfo.getAppFactory()
.instantiateProvider(cl, info.name);
provider = localProvider.getIContentProvider();
if (provider == null) {
Slog.e(TAG, "Failed to instantiate class " +
info.name + " from sourceDir " +
info.applicationInfo.sourceDir);
return null;
}
if (DEBUG_PROVIDER) Slog.v(
TAG, "Instantiating local provider " + info.name);
// XXX Need to create the correct context for this provider.
localProvider.attachInfo(c, info);
} catch (java.lang.Exception e) {
if (!mInstrumentation.onException(null, e)) {
throw new RuntimeException(
"Unable to get provider " + info.name
+ ": " + e.toString(), e);
}
return null;
}
} else {
provider = holder.provider;
if (DEBUG_PROVIDER) Slog.v(TAG, "Installing external provider " + info.authority + ": "
+ info.name);
}
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);
ProviderClientRecord pr = mLocalProvidersByName.get(cname);
if (pr != null) {
if (DEBUG_PROVIDER) {
Slog.v(TAG, "installProvider: lost the race, "
+ "using existing local provider");
}
provider = pr.mProvider;
} else {
holder = new ContentProviderHolder(info);
holder.provider = provider;
holder.noReleaseNeeded = true;
pr = installProviderAuthoritiesLocked(provider, localProvider, holder);
mLocalProviders.put(jBinder, pr);
mLocalProvidersByName.put(cname, pr);
}
retHolder = pr.mHolder;
} else {
ProviderRefCount prc = mProviderRefCountMap.get(jBinder);
if (prc != null) {
if (DEBUG_PROVIDER) {
Slog.v(TAG, "installProvider: lost the race, updating ref count");
}
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;
}
方法内部反射初始化了 ContentProvider ，调用 attachInfo 方法 ，给 provider 传入 context 上下文，并调用 ContentProvider 的onCreate 方法。
目前为止，我们可以知道，整个调用过程初始化了很多东西，客户端服务端来回调用，才能初始化一个ContentProvider ，所以 provider 的初始化是一件非常耗时的过程。
客户端创建完成后，继续回到 AMS 的 getContentProviderImpl 方法的后半段。此时 客户端的 provider 已经安装完成，调用了服务端的 publishContentProviders . 这时候关注一下 getContentProviderImpl 最后等待 provider 安装完成阻塞的代码
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;
}
}
}
}
publishContentProviders 方法 部分代码
//取出 cpr ，并且给 provider 赋值,并且唤醒线程。并且做了缓存
ContentProviderRecord dst = r.pubProviders.get(src.info.name);
if (DEBUG_MU) Slog.v(TAG_MU, "ContentProviderRecord uid = " + dst.uid);
if (dst != null) {
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++) {
//缓存起来，后续 如果在此请求 此provider ，可以直接返回
mProviderMap.putProviderByName(names[j], dst);
}
int launchingCount = mLaunchingProviders.size();
int j;
boolean wasInLaunchingProviders = false;
for (j = 0; j < launchingCount; j++) {
if (mLaunchingProviders.get(j) == dst) {
mLaunchingProviders.remove(j);
wasInLaunchingProviders = true;
j--;
launchingCount--;
}
}
if (wasInLaunchingProviders) {
mHandler.removeMessages(CONTENT_PROVIDER_PUBLISH_TIMEOUT_MSG, r);
}
synchronized (dst) {
dst.provider = src.provider;
dst.proc = r;
dst.notifyAll();
}
由此整个 ContentProvider 的初始化流程结束。