试着做一个简单的浏览器，但是不能设置一个显示当前webview的url的字段。试着覆盖函数，但是总是说“函数名”什么都不覆盖。也可以添加webview在fragment中。也许我可以从mainactivity调用这个，但是idk怎么做。webview_fragment.kt

package com.example.webviewapp

import android.content.ContentValues.TAG
import android.graphics.Bitmap
import android.os.Bundle
import android.util.Log
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.webkit.WebView
import android.webkit.WebViewClient
import android.widget.TextView
import android.widget.Toast
import androidx.activity.OnBackPressedCallback
import androidx.fragment.app.Fragment

class webview_fragment : Fragment(){

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?

    ): View? {
        val view : View = inflater.inflate(R.layout.layout_webview_fragment, container, false)
        val  mWebView : WebView = view.findViewById(R.id.webViewMain)
        mWebView.loadUrl("https://google.com")
        val webSettings = mWebView.getSettings()
        webSettings.setJavaScriptEnabled(true)
        mWebView.setWebViewClient(WebViewClient())
        requireActivity()
            .onBackPressedDispatcher
            .addCallback(viewLifecycleOwner, object : OnBackPressedCallback(true) {
                override fun handleOnBackPressed() {
                    Log.d(TAG, "Fragment back pressed invoked")
                    if (mWebView.canGoBack()){
                        mWebView.goBack()
                    } else {
                        requireActivity().finishAndRemoveTask()
                    }
                }
            }
            )
        mWebView.webViewClient = object : WebViewClient(){
            override fun onPageFinished(view: WebView?, url: String?) {
                super.onPageFinished(view, url)
                val urlText: TextView? = view?.findViewById(R.id.urlText)
                val  mWebView : WebView? = view?.findViewById(R.id.webViewMain)
                urlText?.setText(mWebView?.getUrl())
            }
        }
        return view
    }
}

mainactivity.kt

package com.example.webviewapp

import android.content.ContentValues.TAG
import android.content.Context
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.util.Log

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        
        if (getSharedPreferences("app", Context.MODE_PRIVATE).getBoolean("Boolean", false) == false) {
            supportFragmentManager
                .beginTransaction()
                .replace(R.id.fullcreen_holder, start_fragment())
                .commit()
        } else {
            supportFragmentManager
                .beginTransaction()
                .replace(R.id.fullcreen_holder, webview_fragment())
                .commit()
        }
    }
}