Android浏览器开发 WebView setBlockNetworkImage来龙去脉

本身含义阻止图片网络数据
webSettings.setBlockNetworkImage(true);
解除数据阻止
webSettings.setBlockNetworkImage(false);

实际上简单的一句话为什么会造成这么强大的功力
我们来看下具体的实现
WebSettingsClassic.java
/**
* @see android.webkit.WebSettings#setBlockNetworkImage(boolean)
*/
@Override
public synchronized void setBlockNetworkImage(boolean flag) {
if (mBlockNetworkImage != flag) {
mBlockNetworkImage = flag;
postSync();
}
}
关键代码看上去只有
mBlockNetworkImage = flag;
但是不要忽略了
postSync();
这个就是通知c++层去读取mBlockNetworkImage数值
我们看下具体的postSync函数实现
/* Post a SYNC message to handle syncing the native settings. */
private synchronized void postSync() {
// Only post if a sync is not pending
if (!mSyncPending) {
mSyncPending = mEventHandler.sendMessage(
Message.obtain(null, EventHandler.SYNC));
}
}

通知给
// create a new handler
mHandler = new Handler() {
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case SYNC:
synchronized (WebSettingsClassic.this) {
if (mBrowserFrame.mNativeFrame != 0) {
nativeSync(mBrowserFrame.mNativeFrame);
}
mSyncPending = false;
}
break;

// Synchronize the native and java settings.
private native void nativeSync(int nativeFrame);
最后调用的函数

c++底层函数实现
WebKit/android/jni/WebSettings.cpp
//-------------------------------------------------------------
// JNI registration
//-------------------------------------------------------------
static JNINativeMethod gWebSettingsMethods[] = {
{ "nativeSync", "(I)V",
(void*) WebSettings::Sync }
};
static void Sync(JNIEnv* env, jobject obj, jint frame)
{
WebCore::Frame* pFrame = (WebCore::Frame*)frame;
ALOG_ASSERT(pFrame, "%s must take a valid frame pointer!", __FUNCTION__);
WebCore::Settings* s = pFrame->settings();
if (!s)
return;
WebCore::CachedResourceLoader* cachedResourceLoader = pFrame->document()->cachedResourceLoader();

flag = env->GetBooleanField(obj, gFieldIds->mBlockNetworkImage);
s->setBlockNetworkImage(flag);
if(!flag)
cachedResourceLoader->setBlockNetworkImage(false);
}

具体实现
CachedResourceLoader.cpp里面
void CachedResourceLoader::setBlockNetworkImage(bool block)
{
if (block == m_blockNetworkImage)
return;

m_blockNetworkImage = block;

if (!m_autoLoadImages || m_blockNetworkImage)
return;

DocumentResourceMap::iterator end = m_documentResources.end();
for (DocumentResourceMap::iterator it = m_documentResources.begin(); it != end; ++it) {
CachedResource* resource = it->second.get();
if (resource->type() == CachedResource::ImageResource) {
CachedImage* image = const_cast<CachedImage*>(static_cast<const CachedImage*>(resource));
image->setAutoLoadWasPreventedBySettings(false);
if (image->stillNeedsLoad()) {
image->setLoading(true);
load(image, true);
}
}
}
}

终于找到这个家伙了，原来搞了一个循环在呼呼的执行，发送一个个的网络请求
整体执行流程现在来看基本清晰了。

上面代码是针对android4.1.1版本代码的分析

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