Question

我有一个MainActivity和一些片段，我正在使用WebView在所有片段中加载一些网站。在我按下后退按钮之前无法进入上一页但现在我能够。我有一切正常，但我无法在启动时加载片段。如果我在MainActivity中添加此代码以自动加载片段，它可以正常工作，但它会破坏其他片段中的后退键导航，

getFragmentManager().beginTransaction()
                .replace(R.id.content_frame
                        , new aboutus())
                .addToBackStack(null).commit();

启动时默认情况下我是否可以通过其他方式加载片段？这是我的MainActivity（包括自动打开片段的代码），

package com.science.s11;

import android.os.Bundle;
import android.support.design.widget.NavigationView;
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.MenuItem;



public class MainActivity extends AppCompatActivity
    implements NavigationView.OnNavigationItemSelectedListener {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    getFragmentManager().beginTransaction()
            .replace(R.id.content_frame
                    , new aboutus())
            .addToBackStack(null).commit();
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
        this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
    drawer.setDrawerListener(toggle);
    toggle.syncState();

    NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
    navigationView.setNavigationItemSelectedListener(this);
}



@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}
@Override
public void onBackPressed() {

    if (aboutus.mWebView!= null) {
        if (aboutus.mWebView.canGoBack()) {
            aboutus.mWebView.goBack();
        } else {
            if (getFragmentManager().getBackStackEntryCount() > 1) {
                getFragmentManager().popBackStack();
            }else{
            finish();}
        }
    }

    else if(amp.mWebView!= null){
        if ( amp.mWebView.canGoBack()){
            amp.mWebView.goBack();
        }else {
            if (getFragmentManager().getBackStackEntryCount() > 1) {
                getFragmentManager().popBackStack();
            }else{
                finish();}

        }
    }
    else if(ask.mWebView!= null){
        if ( ask.mWebView.canGoBack()){
            ask.mWebView.goBack();
        }else {
            if (getFragmentManager().getBackStackEntryCount() > 1) {
                getFragmentManager().popBackStack();
            }else{
                finish();}

        }
    }
    else if(feedback.mWebView!= null){
        if ( feedback.mWebView.canGoBack()){
            feedback.mWebView.goBack();
        }else {
            if (getFragmentManager().getBackStackEntryCount() > 1) {
                getFragmentManager().popBackStack();
            }else{
                finish();}

        }
    }
    else if(subscribe.mWebView!= null){
        if ( subscribe.mWebView.canGoBack()){
            subscribe.mWebView.goBack();
        }else {
            if (getFragmentManager().getBackStackEntryCount() > 1) {
                getFragmentManager().popBackStack();
            }else{
                finish();}

        }
    }
    else{
        super.onBackPressed();
    }
}

@SuppressWarnings("StatementWithEmptyBody")
@Override

public boolean onNavigationItemSelected(MenuItem item) {
    // Handle navigation view item clicks here.
    int id = item.getItemId();
    android.app.FragmentManager fragmentManager = getFragmentManager();

    if (id == R.id.nav_aboutus) {
        fragmentManager.beginTransaction()
                .replace(R.id.content_frame
                        , new aboutus())
                .addToBackStack(null).commit();
        // Handle the camera action
    } else if (id == R.id.nav_amp) {
    fragmentManager.beginTransaction()
        .replace(R.id.content_frame
                , new amp())
            .addToBackStack(null).commit();
    } else if (id == R.id.nav_ask) {
        fragmentManager.beginTransaction()
                .replace(R.id.content_frame
                        , new ask())
                .addToBackStack(null).commit();
    } else if (id == R.id.nav_feedback) {
        fragmentManager.beginTransaction()
                .replace(R.id.content_frame
                        , new feedback())
                .addToBackStack(null).commit();
    } else if (id == R.id.nav_subscribe) {
        fragmentManager.beginTransaction()
                .replace(R.id.content_frame
                        , new subscribe())
                .addToBackStack(null).commit();
    }

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

以下是我所有片段中的示例代码

package com.science.s11;

import android.app.Fragment;
import android.content.Context;
import android.graphics.Bitmap;
import android.net.ConnectivityManager;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.LinearLayout;
import android.widget.ProgressBar;
import android.net.NetworkInfo;

public class aboutus extends Fragment {

public static WebView mWebView;

public ProgressBar progressBar;
public LinearLayout layoutProgress;

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

    View v = inflater.inflate(R.layout.aboutus, container, false);
    mWebView = (WebView) v.findViewById(R.id.aboutuswebView);
    progressBar = (ProgressBar) v.findViewById(R.id.progressBar);
    layoutProgress = (LinearLayout) v.findViewById(R.id.layoutProgress);
    mWebView.setVisibility(View.GONE);
    mWebView.getSettings().setCacheMode(WebSettings.LOAD_DEFAULT);
    WebSettings webSettings = mWebView.getSettings();
    webSettings.setJavaScriptEnabled(true);
    mWebView.getSettings().setCacheMode(WebSettings.LOAD_CACHE_ELSE_NETWORK);
    WebSettings settings = mWebView.getSettings();
    settings.setSupportMultipleWindows(true);
    settings.setBuiltInZoomControls(false);
    settings.setSupportZoom(false);
    settings.setDisplayZoomControls(false);

    mWebView.setWebViewClient(new WebViewClient() {

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


        @Override
        public void onPageFinished(WebView view, String url) {
            mWebView.setVisibility(View.VISIBLE);
            layoutProgress.setVisibility(View.GONE);
            progressBar.setIndeterminate(true);
            super.onPageFinished(view, url);

        }

        @Override
        public void onPageStarted(WebView view, String url, Bitmap favicon) {
            layoutProgress.setVisibility(View.VISIBLE);
            progressBar.setIndeterminate(false);
            super.onPageStarted(view, url, favicon);
        }


    });




    if (isOnline()) {
        mWebView.loadUrl("http://science19.com/index.php");
    } else {
        mWebView.loadUrl("file:///android_asset/cti.html");
    }
    return v;
}
public boolean onKeyDown(int keyCode, KeyEvent event) {
    if ((keyCode == KeyEvent.KEYCODE_BACK) && mWebView.canGoBack()) {
        mWebView.goBack();
        return true;
    }
    return onKeyDown(keyCode, event);
}
public static boolean canGoBack(){
    return mWebView.canGoBack();
}

public static void goBack(){
    mWebView.goBack();
}



public boolean isOnline() {
    ConnectivityManager cm = (ConnectivityManager)  getActivity().getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo netInfo = cm.getActiveNetworkInfo();
    return (netInfo != null && netInfo.isConnected());
}

}

编辑（补充说明）：我实际上想在app启动时显示片段，片段包含WebView。我可以使用此代码

来做到这一点

getFragmentManager().beginTransaction()
            .replace(R.id.content_frame
                    , new aboutus())
            .addToBackStack(null).commit();

但我甚至还有其他片段，每个人都有能力回到上一页。每当我使用这段代码时，我都无法在其他片段的背面按回到上一页，它只能在使用代码打开的片段中工作，这里是 aboutus 。那么，为什么这实际发生了，我该如何解决呢？

Answer 1

使用 AppCompatActivity

getSupportFragmentManager()

而不是

getFragmentManager()

后退按钮不能处理片段

1 个答案: