webview的android片段中的onBackpressed和ProgressDialog问题

Question

在我的 android 应用程序中，我使用片段创建了 4 个选项卡，每个选项卡加载不同的 URL，效果很好，但是，

1) 我如何将 onBackpressed 添加到每个 webview 以在返回单击时加载上一页？我知道如何在 java 类中做到这一点，但 Override 在 Fragment 中不起作用。

2) 我的第二个问题是我已经为每个 webview 添加了一个 ProgressDialog，它工作正常，但覆盖整个布局，直到加载完整的网页，我如何让它只显示在像浏览器一样的顶部，同时能够查看和滚动加载的网页? 以下是我的片段代码。

GoogleFragment.java

Public class GoogleFragment extends Fragment {

    WebView myWebView;
    ProgressDialog pd;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        View v = inflater.inflate(R.layout.fragment_webview, container, false);
        final ProgressDialog pd = ProgressDialog.show(getContext(), "", "Loading Please wait...", true);


        myWebView = (WebView) v.findViewById(R.id.WebView);
        myWebView.getSettings().setJavaScriptEnabled(true);
        myWebView.loadUrl("http://www.google.com/");
        WebSettings webSettings = myWebView.getSettings();
        webSettings.setJavaScriptEnabled(true);
        //improve webView performance
        myWebView.getSettings().setRenderPriority(WebSettings.RenderPriority.HIGH);
        myWebView.getSettings().setCacheMode(WebSettings.LOAD_DEFAULT);
        myWebView.getSettings().setAppCacheEnabled(true);
        myWebView.setScrollBarStyle(View.SCROLLBARS_INSIDE_OVERLAY);
        webSettings.setDomStorageEnabled(true);
        webSettings.setLayoutAlgorithm(WebSettings.LayoutAlgorithm.NARROW_COLUMNS);
        webSettings.setUseWideViewPort(true);
        webSettings.setSavePassword(true);
        webSettings.setSaveFormData(true);
        webSettings.setEnableSmoothTransition(true);
        myWebView.setWebViewClient(new WebViewClient() {
            public void onReceivedError(WebView view, int errorCode, String description, String failingUrl) {

            }

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


            @Override
            public void onPageFinished(WebView view, String url) {
                pd.dismiss();

                String webUrl = myWebView.getUrl();

            }

        });
        return v;
    }


}

MainActivity.java

import android.content.SharedPreferences;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.support.design.widget.NavigationView;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.widget.Toast;

import com.google.android.gms.ads.InterstitialAd;
import com.google.android.gms.analytics.GoogleAnalytics;
import com.nav.R;
import com.nav.fragments.TabFragment;
import java.util.Timer;


public class MainActivity extends AppCompatActivity {

    Toolbar toolbar;
    DrawerLayout mDrawerLayout;
    NavigationView mNavigationView;
    FragmentManager mFragmentManager;
    FragmentTransaction mFragmentTransaction;
    private InterstitialAd interstitial;
    public Timer AdTimer;

    SharedPreferences preferences;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);


        setContentView(R.layout.activity_main);

        preferences = PreferenceManager.getDefaultSharedPreferences(getBaseContext());

        toolbar = (Toolbar) findViewById(R.id.toolbar);
        if (toolbar != null) {
            setSupportActionBar(toolbar);
        }


        mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
        mNavigationView = (NavigationView) findViewById(R.id.main_drawer) ;

        int width = getResources().getDisplayMetrics().widthPixels/2;
        DrawerLayout.LayoutParams params = (android.support.v4.widget.DrawerLayout.LayoutParams) mNavigationView.getLayoutParams();
        params.width = width;
        mNavigationView.setLayoutParams(params);

        mFragmentManager = getSupportFragmentManager();
        mFragmentTransaction = mFragmentManager.beginTransaction();
        mFragmentTransaction.replace(R.id.frame_container, new TabFragment()).commit();

        mNavigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(MenuItem menuItem) {

                menuItem.setChecked(true);
                mDrawerLayout.closeDrawers();
                //setTitle(menuItem.getTitle());

                if (menuItem.getItemId() == R.id.drawer_home) {
                    FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();
                    fragmentTransaction.replace(R.id.frame_container, new TabFragment()).commit();
                }

                if (menuItem.getItemId() == R.id.drawer_facebook){
                    Toast.makeText(MainActivity.this,
                            "Replace with your own function", Toast.LENGTH_LONG).show();
                }

                if (menuItem.getItemId() == R.id.drawer_gPlus){
                    Toast.makeText(MainActivity.this,
                            "Replace with your own function", Toast.LENGTH_LONG).show();
                }

                if (menuItem.getItemId() == R.id.drawer_rate) {
                    Toast.makeText(MainActivity.this,
                            "Replace with your own function", Toast.LENGTH_LONG).show();
                }

                if (menuItem.getItemId() == R.id.drawer_more) {
                    Toast.makeText(MainActivity.this,
                            "Replace with your own function", Toast.LENGTH_LONG).show();
                }

                if (menuItem.getItemId() == R.id.drawer_profile) {
                    Toast.makeText(MainActivity.this,
                            "Replace with your own function", Toast.LENGTH_LONG).show();
                }

                if (menuItem.getItemId() == R.id.drawer_share) {
                    Toast.makeText(MainActivity.this,
                            "Replace with your own function", Toast.LENGTH_LONG).show();
                }
                if (menuItem.getItemId() == R.id.drawer_youtube) {
                    Toast.makeText(MainActivity.this,
                            "Replace with your own function", Toast.LENGTH_LONG).show();
                }

                if (menuItem.getItemId() == R.id.drawer_exit) {
                    Toast.makeText(MainActivity.this,
                            "Replace with your own function", Toast.LENGTH_LONG).show();
                }

                return false;
            }

        });

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        ActionBarDrawerToggle mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout, toolbar, R.string.drawer_open, R.string.drawer_close);

        mDrawerLayout.setDrawerListener(mDrawerToggle);

        mDrawerToggle.syncState();



    }






    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.main, menu);

        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem menuItem) {
        switch (menuItem.getItemId()) {

            case android.R.id.home:
                onBackPressed();
                return true;

            default:
                return super.onOptionsItemSelected(menuItem);
        }
    }

    @Override
    public void onBackPressed() {
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        if (drawer.isDrawerOpen(GravityCompat.START)) {
            drawer.closeDrawer(GravityCompat.START);
        }
        else {
            super.onBackPressed();

        }

    }

    @Override
    public void onStart() {
        super.onStart();
        // analytics
        GoogleAnalytics.getInstance(this).reportActivityStart(this);
  }  }

TabFragment.java

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.design.widget.TabLayout;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.nav.R;

public class TabFragment extends Fragment {

    public static TabLayout tabLayout;
    public static ViewPager viewPager;
    public static int int_items = 6 ;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        View v =  inflater.inflate(R.layout.tab_layout, container, false);
        tabLayout = (TabLayout) v.findViewById(R.id.tabs);
        viewPager = (ViewPager) v.findViewById(R.id.viewpager);

        viewPager.setAdapter(new MyAdapter(getChildFragmentManager()));

        tabLayout.post(new Runnable() {
            @Override
            public void run() {
                tabLayout.setupWithViewPager(viewPager);
            }
        });

        return v;

    }

    class MyAdapter extends FragmentPagerAdapter {

        public MyAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int position)
        {
            switch (position){
                case 0 : return new GoogleFragment();
                case 1 : return new SportsFragment();
                case 2 : return new GamesFragment();
                case 3 : return new PhotographyFragment();
                case 4 : return new WildFragment();
                case 5 : return new TravelFragment();
            }
            return null;
        }

        @Override
        public int getCount() {

            return int_items;

        }

        @Override
        public CharSequence getPageTitle(int position) {

            switch (position){
                case 0 :
                    return getResources().getString(R.string.tab1);
                case 1 :
                    return getResources().getString(R.string.tab2);
                case 2 :
                    return getResources().getString(R.string.tab3);
                case 3 :
                    return getResources().getString(R.string.tab4);
                case 4 :
                    return getResources().getString(R.string.tab5);
                case 5 :
                    return getResources().getString(R.string.tab6);
            }
            return null;
        }
    }

}

Answer 1

1. 您可以在活动中更改 onBackPressed：

http://pastebin.com/3DR4nDWM

在你的片段类中：

public boolean goBack()
{
    if(webView.canGoBack())
    {
        webView.goBack();
        return true;
    }
    return false;
}

1. 尝试在 WebView 顶部添加 ProgressBar。