WKWebView 注册js和移除js
/*! @abstract Adds a script message handler to the main world used by page content itself.
@param scriptMessageHandler The script message handler to add.
@param name The name of the message handler.
@discussion Calling this method is equivalent to calling addScriptMessageHandler:contentWorld:name:
with [WKContentWorld pageWorld] as the contentWorld argument.
*/
- (void)addScriptMessageHandler:(id <WKScriptMessageHandler>)scriptMessageHandler name:(NSString *)name;
每调佣一次,webview被retain一次。
说明这里是强引用,
在退出的时候,必须remove掉。
才能彻底释放掉webview.