ios框架wkwebview
H5使用vue作為框架
現(xiàn)象：
一個聊天框，跳其他頁面后再反回去內(nèi)容被刷了
嘗試打印pageshow-》e.persisted顯示false券勺。說明bfcahe失效
在看問題之前先了解下MessageChannel
然后看下webkit相關(guān)源碼
首先是PageCache文件描述了頁面緩存相關(guān)的信息
static bool canCacheFrame(Frame& frame, DiagnosticLoggingClient& diagnosticLoggingClient, unsigned indentLevel)
{
.....
Vector<ActiveDOMObject*> unsuspendableObjects;
if (frame.document() && !frame.document()->canSuspendActiveDOMObjectsForDocumentSuspension(&unsuspendableObjects)) {
PCLOG(" -The document cannot suspend its active DOM Objects");
for (auto* activeDOMObject : unsuspendableObjects) {
PCLOG(" - Unsuspendable: ", activeDOMObject->activeDOMObjectName());
diagnosticLoggingClient.logDiagnosticMessage(DiagnosticLoggingKeys::unsuspendableDOMObjectKey(), activeDOMObject->activeDOMObjectName(), ShouldSample::Yes);
UNUSED_PARAM(activeDOMObject);
}
logPageCacheFailureDiagnosticMessage(diagnosticLoggingClient, DiagnosticLoggingKeys::cannotSuspendActiveDOMObjectsKey());
isCacheable = false;
}
.......
}
//canSuspendActiveDOMObjectsForDocumentSuspension()主要處理是否可緩存信息
然后看下對應(yīng)ScriptExecutionContext文件
有個canSuspendForDocumentSuspension方法
bool ScriptExecutionContext::canSuspendActiveDOMObjectsForDocumentSuspension(Vector<ActiveDOMObject*>* unsuspendableObjects)
{
checkConsistency();
bool canSuspend = true;
forEachActiveDOMObject([&](auto& activeDOMObject) {
if (!activeDOMObject.canSuspendForDocumentSuspension()) {
canSuspend = false;
if (unsuspendableObjects)
unsuspendableObjects->append(&activeDOMObject);
else
return ShouldContinue::No;
}
return ShouldContinue::Yes;
});
if (unsuspendableObjects) {
// Remove activeDOMObjects that have been destroyed while we were iterating above.
unsuspendableObjects->removeAllMatching([&](auto* activeDOMObject) {
return !m_activeDOMObjects.contains(activeDOMObject);
});
}
return canSuspend;
}
那有哪些activeDOMObject對象呢,在webcore下搜了下 53個
可以看下worker
bool Worker::canSuspendForDocumentSuspension() const
{
// FIXME: It is not currently possible to suspend a worker, so pages with workers can not go into page cache.
return false;
}
//canSuspendForDocumentSuspension 直接返回false 用了 new Worker也不會生效了
//
//idb操作的
bool IDBObjectStore::canSuspendForDocumentSuspension() const
{
return false;
}
//indexedDB.open('test')
//eventsource操作的
bool EventSource::canSuspendForDocumentSuspension() const
{
// FIXME: We should return true here when we can because this object is not actually currently active.
return false;
}
//new EventSource
再看(MessagePort文件)[https://github.com/WebKit/webkit/blob/master/Source/WebCore/dom/MessagePort.cpp]
bool MessagePort::canSuspendForDocumentSuspension() const
{
return !hasPendingActivity() || (!m_started || m_closed);
}
//canSuspendForDocumentSuspension拿到false（由于條件限制無法開調(diào)試看具體原因）
實際現(xiàn)象是使用
var nmc= new MessageChannel();
//必須有下面這句
nmc.port1.onmessage =function(){}
//vue2.6之前版本用了MessageChannel
//解決辦法
//1. MessageChannel=null
//2.ios多開webview
