How does WebView interact with native applications? What are the implementation methods?

WebView interaction with native applications can be implemented through the following methods:

1. JavaScriptInterface (Android):

   • In Android, expose Java objects to JavaScript through addJavascriptInterface method
   • JavaScript can directly call methods of this object
   • Note: Need to use @JavascriptInterface annotation to avoid security vulnerabilities

2. WKScriptMessageHandler (iOS):

   • In iOS, use addScriptMessageHandler method of WKUserContentController
   • JavaScript sends messages via webkit.messageHandlers.xxx.postMessage()
   • Native receives messages by implementing userContentController:didReceiveScriptMessage: method

3. URL Scheme:

   • JavaScript initiates URLs with specific formats through window.location.href or iframe.src
   • Native intercepts via shouldOverrideUrlLoading (Android) or decidePolicyForNavigationAction (iOS)
   • Advantage: Good cross-platform compatibility; Disadvantage: URL length limitation

4. WebMessagePort:

   • Message channel API supported by modern WebView
   • Provides bidirectional communication capability, supports sending complex data
   • More efficient and secure than URL Scheme

5. File sharing:

   • Implement data exchange through shared files
   • Suitable for large data transmission

6. Third-party frameworks:

   • Such as React Native's WebView component
   • Cordova/PhoneGap's bridging mechanism
   • Advantage: Encapsulates complex interaction logic, easier to use

The choice of interaction method should be based on comprehensive consideration of specific scenarios, data volume, performance requirements and other factors.