WebContents是content模块核心，是呈现 Web 内容（通常为 HTML）位于矩形区域中。
最直观的是一个浏览器标签对应一个WebContents，里面加载一个网页等。
二、看下WebContents定义：
content\public\browser\web_contents.h
{
WebContents具体实现在：
content\browser\web_contents\web_contents_impl.cc
content\browser\web_contents\web_contents_impl.h
}
WebContents继承自base::SupportsUserData
cpp复制代码
// WebContents is the core class in content/. A WebContents renders web content
// (usually HTML) in a rectangular area.
//
// Instantiating one is simple:
// std::unique_ptr<content::WebContents> web_contents(
// content::WebContents::Create(
// content::WebContents::CreateParams(browser_context)));
// gfx::NativeView view = web_contents->GetNativeView();
// // |view| is an HWND, NSView*, etc.; insert it into the view hierarchy
// // wherever it needs to go.
//
// That's it; go to your kitchen, grab a scone, and chill. WebContents will do
// all the multi-process stuff behind the scenes. More details are at
// https://www.chromium.org/developers/design-documents/multi-process-architecture
// .
//
// The owner of `std::unique_ptr<content::WebContents> web_contents` is
// responsible for ensuring that `web_contents` are destroyed (e.g. closed)
// *before* the corresponding `browser_context` is destroyed.
//
// Each WebContents has a `NavigationController`, which can be obtained from
// `GetController()`, and is used to load URLs into the WebContents, navigate
// it backwards/forwards, etc.
// See navigation_controller.h for more details.
class WebContents : public PageNavigator,
public base::SupportsUserData {
// Do not remove this macro!
// The macro is maintained by the memory safety team.
ADVANCED_MEMORY_SAFETY_CHECKS();
public:
struct CONTENT_EXPORT CreateParams {
explicit CreateParams(
BrowserContext* context,
base::Location creator_location = base::Location::Current());
CreateParams(BrowserContext* context,
scoped_refptr<SiteInstance> site,
base::Location creator_location = base::Location::Current());
CreateParams(const CreateParams& other);
~CreateParams();
..................................
};
三、base::SupportsUserData定义：
base\supports_user_data.h
注意：看下这几个方法：
Data* GetUserData(const void* key) const;
\[nodiscard\]\] std::unique_ptr\ TakeUserData(const void\* key);
void SetUserData(const void\* key, std::unique_ptr\ data);
void RemoveUserData(const void\* key);
```cpp
namespace base {
// This is a helper for classes that want to allow users to stash random data by
// key. At destruction all the objects will be destructed.
class BASE_EXPORT SupportsUserData {
public:
SupportsUserData();
SupportsUserData(SupportsUserData&&);
SupportsUserData& operator=(SupportsUserData&&);
SupportsUserData(const SupportsUserData&) = delete;
SupportsUserData& operator=(const SupportsUserData&) = delete;
// Derive from this class and add your own data members to associate extra
// information with this object. Alternatively, add this as a public base
// class to any class with a virtual destructor.
class BASE_EXPORT Data {
public:
virtual ~Data() = default;
// Returns a copy of |this|; null if copy is not supported.
virtual std::unique_ptr Clone();
};
// The user data allows the clients to associate data with this object.
// |key| must not be null--that value is too vulnerable for collision.
// NOTE: SetUserData() with an empty unique_ptr behaves the same as
// RemoveUserData().
Data* GetUserData(const void* key) const;
[[nodiscard]] std::unique_ptr TakeUserData(const void* key);
void SetUserData(const void* key, std::unique_ptr data);
void RemoveUserData(const void* key);
// Adds all data from |other|, that is clonable, to |this|. That is, this
// iterates over the data in |other|, and any data that returns non-null from
// Clone() is added to |this|.
void CloneDataFrom(const SupportsUserData& other);
// SupportsUserData is not thread-safe, and on debug build will assert it is
// only used on one execution sequence. Calling this method allows the caller
// to hand the SupportsUserData instance across execution sequences. Use only
// if you are taking full control of the synchronization of that hand over.
void DetachFromSequence();
protected:
virtual ~SupportsUserData();
// Clear all user data from this object. This can be used if the subclass
// needs to provide reset functionality.
void ClearAllUserData();
private:
// Externally-defined data accessible by key.
absl::flat_hash_map> user_data_;
bool in_destructor_ = false;
// Guards usage of |user_data_|
SEQUENCE_CHECKER(sequence_checker_);
};
// Adapter class that releases a refcounted object when the
// SupportsUserData::Data object is deleted.
template
class UserDataAdapter : public SupportsUserData::Data {
public:
static T* Get(const SupportsUserData* supports_user_data, const void* key) {
UserDataAdapter* data =
static_cast(supports_user_data->GetUserData(key));
return data ? static_cast(data->object_.get()) : nullptr;
}
explicit UserDataAdapter(T* object) : object_(object) {}
UserDataAdapter(const UserDataAdapter&) = delete;
UserDataAdapter& operator=(const UserDataAdapter&) = delete;
~UserDataAdapter() override = default;
T* release() { return object_.release(); }
private:
scoped_refptr const object_;
};
} // namespace base
```
### 四、在WebContents添加数据定义：
由于WebContents继承自base::SupportsUserData，所以只需要调用
base::SupportsUserData::SetUserData 方法即可。
#### 1、需要定义一个类AwSettingsUserData 继承自base::SupportsUserData::Data
```cpp
class AwSettingsUserData : public base::SupportsUserData::Data {
public:
//添加自己的数据
private:
};
```
#### 2、base::SupportsUserData::SetUserData设置数据：
web_contents-\>SetUserData(kAwSettingsUserDataKey,
std::make_unique\(this));
#### 3、base::SupportsUserData::GetUserData获取数据：
AwSettingsUserData\* data = static_cast\(
web_contents-\>GetUserData(kAwSettingsUserDataKey));
### 总结：至此在WebContents添加自定义数据方法介绍完毕。
添加自定义数据主要是为了标记WebContents 可以根据此标记对标签进行特殊处理。