错误：(128, 31) 错误：不兼容的类型：第一个片段无法转换为片段

Question

我是 android studio 的新手。我在运行应用程序时遇到了这个问题。android studio 显示以下错误 - Error:(128, 31) error: incompatible types: first fragment cannot be convert to Fragment 所以请建议我如何解决此错误。

我的第一个片段.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);
    }
}

我的 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

你可能想在那里扩展Fragment。