錯誤：（128,31）錯誤：不兼容的類型：第一個片段無法轉換爲片段

Question

我是android studio的新手。我正在面臨這個問題，當我運行該應用程序。安卓工作室顯示以下錯誤 - 錯誤：（128,31）錯誤：不兼容的類型：第一個片段不能轉換爲片段所以請建議我，如何解決此錯誤。

我firstfragment.java

package com.hanumanbeniwal.www.hanumanbeniwal; 

import android.app.Fragment; 
import android.graphics.Bitmap; 
import android.support.v7.app.AppCompatActivity; 
import android.os.Bundle; 
import android.view.KeyEvent; 
import android.view.View; 
import android.webkit.WebView; 
import android.webkit.WebViewClient; 
import android.widget.ProgressBar; 

public class firstfragment extends AppCompatActivity { 
    WebView webView; 
    ProgressBar bar; 


    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.first_layout); 
     webView = (WebView) findViewById(R.id.WebView); 
     bar=(ProgressBar) findViewById(R.id.progressBar2); 
     webView.setWebViewClient(new myWebclient()); 
     webView.getSettings().setJavaScriptEnabled(true); 
     webView.loadUrl("http://www.google.com"); 


    } 

    public class myWebclient extends WebViewClient{ 
     @Override 
     public void onPageFinished(WebView view, String url) { 
      super.onPageFinished(view, url); 
      bar.setVisibility(View.GONE); 
     } 

     @Override 
     public void onPageStarted(WebView view, String url, Bitmap favicon) { 
      super.onPageStarted(view, url, favicon); 
     } 

     @Override 
     public boolean shouldOverrideUrlLoading(WebView view, String url) { 
      view.loadUrl(url); 
      return super.shouldOverrideUrlLoading(view, url); 
     } 
    } 

    @Override 
    public boolean onKeyDown(int keyCode, KeyEvent event) { 
     if((keyCode==KeyEvent.KEYCODE_BACK) && webView.canGoBack()){ 
      webView.goBack(); 
      return true; 
     } 

     return super.onKeyDown(keyCode, event); 
    } 
} 

我MainActivity.java

@Override 
    public boolean onNavigationItemSelected(MenuItem item) { 
     // Handle navigation view item clicks here. 
     int id = item.getItemId(); 
     FragmentManager fragmentManager = getFragmentManager(); 
     if (id == R.id.nav_activity_main) { 
      fragmentManager.beginTransaction() 
        .replace(R.id.content_frame 
         , new homefragment()) 
        .commit(); 
     } 

     if (id == R.id.nav_first_layout) { 
      fragmentManager.beginTransaction() 
        .replace(R.id.content_frame 
          , new firstfragment()) 
        .commit(); 

     } else if (id == R.id.nav_second_layout) { 
      fragmentManager.beginTransaction() 
        .replace(R.id.content_frame 
          , new secondfragment()) 
        .commit(); 

     } else if (id == R.id.nav_third_layout) { 
      fragmentManager.beginTransaction() 
        .replace(R.id.content_frame 
          , new thirdfragment()) 
        .commit(); 

     } else if (id == R.id.nav_share) { 

     } else if (id == R.id.nav_send) { 

     } 

     DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); 
     drawer.closeDrawer(GravityCompat.START); 
     return true; 
    } 

Answer 1

firstfragment extends AppCompatActivity 

你可能要延長Fragment那裏。