ViewPager内的Master Detail转到横向模式时提供空异常

Question

我使用的场景是我需要在本机android应用程序的ViewPager中查看主详细信息（列表详细信息）。请在下面找到我要遵循的方法。

TabBarActivity.java

import android.content.Intent;
import android.content.res.Configuration;
import android.os.Bundle;
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.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;

import java.util.ArrayList;
import java.util.List;

public class TabBarActivity extends AppCompatActivity implements 
LaunchDialogFragmentListener, HandleCallBack {
    private static final String TAG = TabBarActivity.class.getSimpleName();

    private SectionsPagerAdapter mSectionsPagerAdapter;

    private static final String STATE_IS_FIRST_RUN = "STATE_IS_FIRST_RUN";
    private boolean isFirstRun = true;

    private ViewPager mViewPager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_tab_bar);

        if (savedInstanceState != null) {
            isFirstRun = savedInstanceState.getBoolean(STATE_IS_FIRST_RUN);
        }

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);


        mSectionsPagerAdapter = new 
        SectionsPagerAdapter(getSupportFragmentManager());

        mSectionsPagerAdapter.addFragment(new MasterProfileFragment(), 
        Integer.valueOf(NavSectionProvider.POS_PROFILE));
        mSectionsPagerAdapter.addFragment(new PestidFragment(), 
        Integer.valueOf(NavSectionProvider.POS_PEST_ID));
        mSectionsPagerAdapter.addFragment(new AboutFragment(), 
        Integer.valueOf(NavSectionProvider.POS_ABOUT));


        mViewPager = (ViewPager) findViewById(R.id.tab_bar_vp_container);
        mViewPager.setAdapter(mSectionsPagerAdapter);
        mViewPager.addOnPageChangeListener(new 
        ViewPager.OnPageChangeListener() {

            @Override
            public void onPageScrolled(int position, float positionOffset, 
            int positionOffsetPixels) {

            }

            @Override
            public void onPageSelected(int position) {
                manageHomeButton(position);
                manageTitle(position);
            }

            @Override
            public void onPageScrollStateChanged(int state) {
            }

        });

        TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
        tabLayout.setupWithViewPager(mViewPager);

        for (NavSection section : NavSectionProvider.sections()) {

            tabLayout.getTabAt(section.getPosition()).
               setIcon(section.getImageResId());
        }

    }

    @Override
    public void didSelectTabPosition(int tabPosition) {
        mViewPager.setCurrentItem(tabPosition);
    }

    public static final String IMAGE_ID = "image_id";

    @Override
    public void loadImage(int imagesrc) {
        if(getResources().getConfiguration().orientation == 
          Configuration.ORIENTATION_LANDSCAPE){

        /*The below line is giving errror. detailFragment is getting null 
          reference. ProfileDetailFragment not able to read 
          R.id.profile_detail_fragment. */

          ProfileDetailFragment detailFragment = (ProfileDetailFragment) 
            getSupportFragmentManager().
            findFragmentById(R.id.profile_detail_fragment);
          detailFragment.setImageView(imagesrc);
        } else{
            Intent intent = new Intent(this.getBaseContext(), 
              ProfileDetailActivity.class);
          intent.putExtra(IMAGE_ID, imagesrc);
          startActivity(intent);
        }
    }

    private void manageHomeButton(int position) {
        getSupportActionBar().setDisplayHomeAsUpEnabled(false);
        getSupportActionBar().setHomeButtonEnabled(false)
    }

    private void manageTitle(int position) {
        NavSection section = NavSectionProvider.sections().get(position);
        getSupportActionBar().setTitle(section.getTitle(this));
    }

    public class SectionsPagerAdapter extends FragmentPagerAdapter {

        private final List<Fragment> mFragmentList = new ArrayList<>();
        private final List<Integer> mFragmentTitleList = new ArrayList<>();

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

        public void addFragment(Fragment fragment, Integer title) {
            mFragmentList.add(fragment);
            mFragmentTitleList.add(title);
        }

        @Override
        public Fragment getItem(int position) {
        NavSection section = NavSectionProvider.sections().get(position);

           if (section.getPosition() == NavSectionProvider.POS_PROFILE) {
                return mFragmentList.get(NavSectionProvider.POS_PROFILE);
            } else if (section.getPosition() == NavSectionProvider.POS_ABOUT) {
                return mFragmentList.get(NavSectionProvider.POS_ABOUT);
            } else if (section.getPosition() == 
                     NavSectionProvider.POS_Applications) {
                return mFragmentList.get(NavSectionProvider.POS_Applications);
            } else {
                return null;
            }
        }




    @Override
    public int getCount() {
        return NavSectionProvider.sections().size();
    }

        @Override
        public CharSequence getPageTitle(int position) {
            return "";
        }
    }

}

我在引发异常的地方添加了注释。 *下面的线是错误的。 detailFragment正在获取空引用。 ProfileDetailFragment无法读取R.id.profile_detail_fragment。 * /

下面是activity_tab_bar.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout 
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/main_content"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/white"
android:fitsSystemWindows="true"

tools:context="c.TabBarActivity">

<android.support.design.widget.AppBarLayout
 android:id="@+id/appbar"
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 android:paddingTop="@dimen/appbar_padding_top"
 android:theme="@style/AppTheme.AppBarOverlay">

 <android.support.v7.widget.Toolbar
  android:id="@+id/toolbar"
  android:layout_width="match_parent"
  android:layout_height="?attr/actionBarSize"
  android:background="?attr/colorPrimary"
  app:popupTheme="@style/AppTheme.PopupOverlay">

  </android.support.v7.widget.Toolbar>

  <android.support.design.widget.TabLayout
   android:id="@+id/tabs"
   android:layout_width="match_parent"
   android:layout_height="wrap_content"
   app:tabGravity="fill"
   app:tabIndicatorColor="@color/logo_grey"
   app:tabMaxWidth="0dp"
   app:tabMode="fixed"
   app:tabSelectedTextColor="@color/logo_grey"
   app:tabTextColor="@color/white" />

   </android.support.design.widget.AppBarLayout>

  <android.support.v4.view.ViewPager 
   xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/pager"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior">

   </android.support.design.widget.CoordinatorLayout>

下面是我的MasterProfileFragment.java类。

    import android.content.Intent;
    import android.content.res.Configuration;
    import android.os.Bundle;
    import android.support.v4.app.Fragment;
    import android.view.LayoutInflater;
    import android.view.View;
    import android.view.ViewGroup;

    public class MasterProfileFragment extends Fragment {

        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
        }

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

            View view = inflater.inflate(R.layout.fragment_master_profile, container, false);
            return view;
        }

    }

下面是我的Profile ListView片段。 ProfileFragment.java

    import android.app.Activity;
    import android.content.Context;
    import android.content.Intent;
    import android.content.res.Configuration;
    import android.support.annotation.NonNull;
    import android.support.annotation.Nullable;
    import android.support.v4.app.Fragment;
    import android.os.Bundle;
    import android.view.LayoutInflater;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.AdapterView;
    import android.widget.ArrayAdapter;
    import android.widget.

    public class ProfileFragment extends Fragment implements AdapterView.OnItemClickListener {


        private String[] imageName = new String[]{
                "Image1", "Image2", "Image3", "Image4"
        };

        private int[] imagesFromRes = new int[]{
                R.drawable.pic1,
                R.drawable.pic2,
                R.drawable.pic3,
                R.drawable.pic4,
                R.drawable.pic5,
                R.drawable.pic6,
                R.drawable.pic7
        };

        private HandleCallBack handleCallBack;

        private static final String SELECTED_POSITION = "selected";
        private int position = -1;
        private ListView imageListView;

        @Override
        public void onAttach(Context context) {
            super.onAttach(context);
            if (context instanceof HandleCallBack) {
                handleCallBack = (HandleCallBack) context;
            }
        }

        @Override
        public void onCreate(@Nullable Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
            ViewGroup viewGroup = (ViewGroup) inflater.inflate(R.layout.fragment_profile_list, container, false);

            imageListView = (ListView) viewGroup.findViewById(R.id.imagelist);
            imageListView.setOnItemClickListener(this);
            imageListView.setChoiceMode(ListView.CHOICE_MODE_SINGLE);
            ArrayAdapter<String> adapter = new ArrayAdapter<>(getActivity(), android.R.layout.simple_list_item_activated_1, imageName);
            imageListView.setAdapter(adapter);

            return viewGroup;
        }

        @Override
        public void onActivityCreated(@Nullable Bundle savedInstanceState) {
            super.onActivityCreated(savedInstanceState);

            if(savedInstanceState != null){
                position = savedInstanceState.getInt(SELECTED_POSITION);
                imageListView.setItemChecked(position, true);
                handleCallBack.loadImage(imagesFromRes[position]);
            }
        }

        @Override
        public void onSaveInstanceState(@NonNull Bundle outState) {
            outState.putInt(SELECTED_POSITION, position);
            super.onSaveInstanceState(outState);
        }

        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            this.position = position;
            handleCallBack.loadImage(imagesFromRes[position]);
        }

    }

下面是ProfileDetailedFragment.java

    import android.os.Bundle;
    import android.support.v4.app.Fragment;
    import android.view.LayoutInflater;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.ImageView;

    public class ProfileDetailFragment extends Fragment {

        private ImageView imageView;

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
            ViewGroup viewGroup = (ViewGroup) inflater.inflate(R.layout.fragment_profile_detail, container, false);

            imageView = (ImageView) viewGroup.findViewById(R.id.mainimage);
            return viewGroup;
        }

        public void setImageView(int imgresid) {
            imageView.setImageResource(imgresid);
        }
    }

我已经为“个人资料详细信息”创建了一个活动。请参见下面的代码。

    import android.content.res.Configuration;
    import android.os.Bundle;
    import android.support.annotation.Nullable;
    import android.support.v7.app.ActionBar;
    import android.support.v7.app.AppCompatActivity;
    import android.view.MenuItem;
    import TabBarActivity;

    public class ProfileDetailActivity extends AppCompatActivity {

        @Override
        protected void onCreate(@Nullable Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_profile_detail);

            if(getResources().getConfiguration().orientation == Configuration.ORIENTATION_LANDSCAPE){
                finish();
                return;
            }

            ProfileDetailFragment detailFragment = (ProfileDetailFragment) getSupportFragmentManager().findFragmentById(R.id.profile_detail_fragment);

            ActionBar actionBar = getSupportActionBar();
            actionBar.setDisplayHomeAsUpEnabled(true);
            actionBar.setTitle("Back");

            Bundle bundle = getIntent().getExtras();

            if(bundle != null){
                detailFragment.setImageView(bundle.getInt(TabBarActivity.IMAGE_ID));
            }
        }

        @Override
        public boolean onOptionsItemSelected(MenuItem item) {
            if(item.getItemId() == android.R.id.home){
                finish();
            }

            return super.onOptionsItemSelected(item);
        }
    }

一个用于处理回调的接口。 HandleCallBack.java

    public interface HandleCallBack {

        public void loadImage(int imageres);
    }

activity_profile_detail.xml

    <?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <fragment
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:id="@+id/profile_detail_fragment"
            android:name=".ProfileDetailFragment"/>

    </LinearLayout>

“个人资料肖像”视图的布局。 fragment_master_profile.xml

  <?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <fragment
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:id="@+id/profile_list_fragment"
            android:name=".ProfileFragment"/>

    </LinearLayout>

“轮廓横向”视图的布局。 fragment_master_profile.xml

  <?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="horizontal"
        android:baselineAligned="false">

        <fragment
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:id="@+id/profile_list_fragment"
            android:name=".ProfileFragment"/>

        <fragment
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="2"
            android:id="@+id/profile_detail_fragment"
            android:name=".ProfileDetailFragment"/>

    </LinearLayout>

fragment_profile_list.xml

<?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <ListView
            android:id="@+id/imagelist"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:listSelector="@color/colorAccent"/>

    </LinearLayout>

fragment_profile_detail.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">

<TextView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="Detail View"
    android:padding="10dp"
    android:background="@android:color/black"
    android:textColor="@android:color/white"
    android:gravity="center"
    android:layout_alignParentTop="true"
    android:id="@+id/title"/>

<ImageView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/mainimage"
    android:contentDescription="@string/app_name"
    android:layout_below="@id/title"/>

我为纵向和横向视图创建了单独的布局。该应用在“人像”视图中正常运行。当我将手机转到横向视图并单击该项目时，其回调会引发错误。当我调试代码时，我发现TabBarActivity.java中的loadImage函数引起了问题。

@Override
public void loadImage(int imagesrc) {
    if(getResources().getConfiguration().orientation == Configuration.ORIENTATION_LANDSCAPE){
        ProfileDetailFragment detailFragment = (ProfileDetailFragment) getSupportFragmentManager().findFragmentById(R.id.profile_detail_fragment);
        detailFragment.setImageView(imagesrc);
    } else{
        Intent intent = new Intent(this.getBaseContext(), ProfileDetailActivity.class);
        intent.putExtra(IMAGE_ID, imagesrc);
        startActivity(intent);
    }
}

ProfileDetailFragment detailFragment =（ProfileDetailFragment）getSupportFragmentManager（）。findFragmentById（R.id.profile_detail_fragment）;正在重用null。无法初始化片段。

如何将这个主从视图放入viewpager中。首先将其加载到viewpager容器中。但是，在纵向视图中，当我单击某个项目时，它将在viewpager容器外部打开详细视图。我想将其粘贴在页面容器中。请帮助我是android编程的新手。如果您在viewpager内还有其他任何主/详细视图的工作示例，请分享。任何帮助都感激不尽。