ContentProvider内容提供者
内容提供者是Android四大组件之一主要提供给其他app自己app内部的内容
获取ContentResolver对象
content.getContentResolver()
核心功能:增删改查
insert
query
delete
update
1.注册
通过PMS解析清单文件注册到PackageParse内部静态类Package的providers集合
public final ArrayList<Provider> providers = new ArrayList<Provider>(0);
2.content.getContentResolver().query()
//创建ApplicationContentResolver对象
mContentResolver = new ApplicationContentResolver(this, mainThread, user);
public ContentResolver getContentResolver() {
return mContentResolver;
}
//query()调用的
public final @Nullable Cursor query(final @NonNull Uri uri, @Nullable String[] projection,
@Nullable String selection, @Nullable String[] selectionArgs,
@Nullable String sortOrder, @Nullable CancellationSignal cancellationSignal) {
Preconditions.checkNotNull(uri, "uri");
//2.1通过传递的uri获取IContentProvider对象
IContentProvider unstableProvider = acquireUnstableProvider(uri);
if (unstableProvider == null) {
return null;
}
IContentProvider stableProvider = null;
Cursor qCursor = null;
try {
long startTime = SystemClock.uptimeMillis();
ICancellationSignal remoteCancellationSignal = null;
if (cancellationSignal != null) {
cancellationSignal.throwIfCanceled();
remoteCancellationSignal = unstableProvider.createCancellationSignal();
cancellationSignal.setRemote(remoteCancellationSignal);
}
try {
qCursor = unstableProvider.query(mPackageName, uri, projection,
selection, selectionArgs, sortOrder, remoteCancellationSignal);
} catch (DeadObjectException e) {
// The remote process has died... but we only hold an unstable
// reference though, so we might recover!!! Let's try!!!!
// This is exciting!!1!!1!!!!1
unstableProviderDied(unstableProvider);
stableProvider = acquireProvider(uri);
if (stableProvider == null) {
return null;
}
qCursor = stableProvider.query(mPackageName, uri, projection,
selection, selectionArgs, sortOrder, remoteCancellationSignal);
}
if (qCursor == null) {
return null;
}
// Force query execution. Might fail and throw a runtime exception here.
qCursor.getCount();
long durationMillis = SystemClock.uptimeMillis() - startTime;
maybeLogQueryToEventLog(durationMillis, uri, projection, selection, sortOrder);
// Wrap the cursor object into CursorWrapperInner object.
CursorWrapperInner wrapper = new CursorWrapperInner(qCursor,
stableProvider != null ? stableProvider : acquireProvider(uri));
stableProvider = null;
qCursor = null;
return wrapper;
} catch (RemoteException e) {
// Arbitrary and not worth documenting, as Activity
// Manager will kill this process shortly anyway.
return null;
} finally {
if (qCursor != null) {
qCursor.close();
}
if (cancellationSignal != null) {
cancellationSignal.setRemote(null);
}
if (unstableProvider != null) {
releaseUnstableProvider(unstableProvider);
}
if (stableProvider != null) {
releaseProvider(stableProvider);
}
}
}
2.1 acquireUnstableProvider(uri)
public final IContentProvider acquireUnstableProvider(Uri uri) {
if (!SCHEME_CONTENT.equals(uri.getScheme())) {
return null;
}
String auth = uri.getAuthority();
if (auth != null) {
//2.2ContentResover的抽象方法找子类实现
return acquireUnstableProvider(mContext, uri.getAuthority());
}
return null;
}
2.2 acquireUnstableProvider
protected IContentProvider acquireUnstableProvider(Context c, String auth) {
//2.3 调用ActivityThread的acuireProvider方法
return mMainThread.acquireProvider(c,
ContentProvider.getAuthorityWithoutUserId(auth),
resolveUserIdFromAuthority(auth), false);
}
2.3 acquireProvider
public final IContentProvider acquireProvider(
Context c, String auth, int userId, boolean stable) {
//2.4通过获取获取IContentProvider对象
final IContentProvider provider = acquireExistingProvider(c, auth, userId, stable);
if (provider != null) {
return provider;
}
IActivityManager.ContentProviderHolder holder = null;
try {
//2.5 没有缓存区AMS获取
holder = ActivityManagerNative.getDefault().getContentProvider(
getApplicationThread(), auth, userId, stable);
} catch (RemoteException ex) {
}
holder = installProvider(c, holder, holder.info,
true /*noisy*/, holder.noReleaseNeeded, stable);
return holder.provider;
}
2.4 acquireExistingProvider
public final IContentProvider acquireExistingProvider(
Context c, String auth, int userId, boolean stable) {
synchronized (mProviderMap) {
final ProviderKey key = new ProviderKey(auth, userId);
//通过mProviderMap集合获取ProviderClientRecord对象(缓存机制)
final ProviderClientRecord pr = mProviderMap.get(key);
if (pr == null) {
return null;
}
IContentProvider provider = pr.mProvider;
IBinder jBinder = provider.asBinder();
//jBinder的进程是否存活
if (!jBinder.isBinderAlive()) {
//清除缓存对象
handleUnstableProviderDiedLocked(jBinder, true);
//返回null
return null;
}
//获取跨进程的缓存对象 ProviderRefCount
ProviderRefCount prc = mProviderRefCountMap.get(jBinder);
if (prc != null) {
incProviderRefLocked(prc, stable);
}
return provider;
}
}
2.5 getContentProvider
public final ContentProviderHolder getContentProvider(
IApplicationThread caller, String name, int userId, boolean stable) {
enforceNotIsolatedCaller("getContentProvider");
//调用线程的caller对象空抛异常
if (caller == null) {
String msg = "null IApplicationThread when getting content provider "
+ name;
Slog.w(TAG, msg);
throw new SecurityException(msg);
}
return getContentProviderImpl(caller, name, null, stable, userId);
}
private final ContentProviderHolder getContentProviderImpl(IApplicationThread caller,
String name, IBinder token, boolean stable, int userId) {
ContentProviderRecord cpr;
ContentProviderConnection conn = null;
ProviderInfo cpi = null;
synchronized(this) {
long startTime = SystemClock.elapsedRealtime();
//获取调用者进程
ProcessRecord r = null;
if (caller != null) {
r = getRecordForAppLocked(caller);
}
boolean checkCrossUser = true;
checkTime(startTime, "getContentProviderImpl: getProviderByName");
//通过mPriverMap缓存获取cpr
cpr = mProviderMap.getProviderByName(name, userId);
//如果有缓存并且userid不等于USER_OWNER
if (cpr == null && userId != UserHandle.USER_OWNER) {
//替换cpr内容提供者包装对象
cpr = mProviderMap.getProviderByName(name, UserHandle.USER_OWNER);
if (cpr != null) {
cpi = cpr.info;
if (isSingleton(cpi.processName, cpi.applicationInfo,
cpi.name, cpi.flags)
&& isValidSingletonCall(r.uid, cpi.applicationInfo.uid)) {
userId = UserHandle.USER_OWNER;
checkCrossUser = false;
} else {
cpr = null;
cpi = null;
}
}
}
boolean providerRunning = cpr != null;
//cpr存活
if (providerRunning) {
cpi = cpr.info;
String msg;
checkTime(startTime, "getContentProviderImpl: before checkContentProviderPermission");
checkTime(startTime, "getContentProviderImpl: after checkContentProviderPermission");
//2.5.1设置provider参数multiprocess设置true或者同一进程
if (r != null && cpr.canRunHere(r)) {
ContentProviderHolder holder = cpr.newHolder(null);
holder.provider = null;
//直接返回holder
return holder;
}
final long origId = Binder.clearCallingIdentity();
checkTime(startTime, "getContentProviderImpl: incProviderCountLocked");
//2.5.2非统一进程创建conn可跨进程的对象
conn = incProviderCountLocked(r, cpr, token, stable);
if (conn != null && (conn.stableCount+conn.unstableCount) == 1) {
if (cpr.proc != null && r.setAdj <= ProcessList.PERCEPTIBLE_APP_ADJ) {
checkTime(startTime, "getContentProviderImpl: before updatLruProcess");
updateLruProcessLocked(cpr.proc, false, null);
checkTime(startTime, "getContentProviderImpl: after updateLruProcess");
}
}
if (cpr.proc != null) {
if (false) {
if (cpr.name.flattenToShortString().equals(
"com.android.providers.calendar/.CalendarProvider2")) {
Slog.v(TAG, "****************** KILLING "
+ cpr.name.flattenToShortString());
Process.killProcess(cpr.proc.pid);
}
}
checkTime(startTime, "getContentProviderImpl: before updateOomAdj");
boolean success = updateOomAdjLocked(cpr.proc);
maybeUpdateProviderUsageStatsLocked(r, cpr.info.packageName, name);
checkTime(startTime, "getContentProviderImpl: after updateOomAdj");
if (!success) {
Slog.i(TAG, "Existing provider " + cpr.name.flattenToShortString()
+ " is crashing; detaching " + r);
boolean lastRef = decProviderCountLocked(conn, cpr, token, stable);
checkTime(startTime, "getContentProviderImpl: before appDied");
appDiedLocked(cpr.proc);
checkTime(startTime, "getContentProviderImpl: after appDied");
if (!lastRef) {
return null;
}
providerRunning = false;
conn = null;
}
}
Binder.restoreCallingIdentity(origId);
}
boolean singleton;
//没有运行第一次
if (!providerRunning) {
try {
checkTime(startTime, "getContentProviderImpl: before resolveContentProvider");
//通过ams查询注册的provider
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;
}
//实例化singleton
singleton = isSingleton(cpi.processName, cpi.applicationInfo,
cpi.name, cpi.flags)
&& isValidSingletonCall(r.uid, cpi.applicationInfo.uid);
if (singleton) {
userId = UserHandle.USER_OWNER;
}
cpi.applicationInfo = getAppInfoForUser(cpi.applicationInfo, userId);
checkTime(startTime, "getContentProviderImpl: got app info for user");
checkTime(startTime, "getContentProviderImpl: after checkContentProviderPermission");
//分装componentName
ComponentName comp = new ComponentName(cpi.packageName, cpi.name);
checkTime(startTime, "getContentProviderImpl: before getProviderByClass");
//从mProviderMap查询cpr
cpr = mProviderMap.getProviderByClass(comp, userId);
checkTime(startTime, "getContentProviderImpl: after getProviderByClass");
final boolean firstClass = cpr == null;
// 第一次false
if (firstClass) {
final long ident = Binder.clearCallingIdentity();
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");
//如果不需要跨进程直接返回
if (r != null && cpr.canRunHere(r)) {
//不需要跨进程不需要conn对象
return cpr.newHolder(null);
}
//启动的providers
final int N = mLaunchingProviders.size();
int i;
for (i = 0; i < N; i++) {
if (mLaunchingProviders.get(i) == cpr) {
break;
}
}
//如果没有provider
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);
}
checkTime(startTime, "getContentProviderImpl: looking for process record");
//查询cpi对应进程
ProcessRecord proc = getProcessRecordLocked(
cpi.processName, cpr.appInfo.uid, false);
//判断是否启动的进程
if (proc != null && proc.thread != null) {
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 {
proc.thread.scheduleInstallProvider(cpi);
} catch (RemoteException e) {
}
}
} else {
checkTime(startTime, "getContentProviderImpl: before start process");
//启动进程 内部会遍历清单文件查询需要启动的四大组件
proc = startProcessLocked(cpi.processName,
cpr.appInfo, false, 0, "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");
if (firstClass) {
mProviderMap.putProviderByClass(comp, cpr);
}
//添加缓存
mProviderMap.putProviderByName(name, cpr);
conn = incProviderCountLocked(r, cpr, token, stable);
if (conn != null) {
conn.waiting = true;
}
}
checkTime(startTime, "getContentProviderImpl: done!");
}
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;
}
//等待进程里面的对象创建
cpr.wait();
} catch (InterruptedException ex) {
} finally {
if (conn != null) {
conn.waiting = false;
}
}
}
}
//返回
return cpr != null ? cpr.newHolder(conn) : null;
}
2.5.1 canRunHere
public boolean canRunHere(ProcessRecord app) {
return (info.multiprocess || info.processName.equals(app.processName))
&& uid == app.info.uid;
}
2.5.2 incProviderCountLocked
//可跨进程的对象
public final class ContentProviderConnection extends Binder {
//provider封装对象
public final ContentProviderRecord provider;
//进程
public final ProcessRecord client;
public final long createTime;
public int stableCount;
public int unstableCount;
// The client of this connection is currently waiting for the provider to appear.
// Protected by the provider lock.
public boolean waiting;
// The provider of this connection is now dead.
public boolean dead;
// For debugging.
public int numStableIncs;
public int numUnstableIncs;
public ContentProviderConnection(ContentProviderRecord _provider, ProcessRecord _client) {
provider = _provider;
client = _client;
createTime = SystemClock.elapsedRealtime();
}
}
总结:
注册:
内容提供者是通过PMS解析xml读取信息封装成prvider对象
查询:
通过ContextImpl实现类查询getContentResolver,ContentResolver对象获取先通过binder到AMS服务中去查询对应provider是否缓存如果有缓存直接返回
没有缓存判断清单文件是否设置了multiprocess=true参数 如果设置了就创建对应Context对象就可以通过类加载机制去获取Provider相关代码，
如果设置process参数需要跨进程就会创建进程然后再创建provider，
这个过程会调用wait等待，等待创建完成后ntoityAll进行通知创建完成在返回
如果不需要跨进程直接返回conn跨进程对象为null
