Android ViewPager不显示片段

我不能让它工作。基本应用程序的功能与预期相同，但其中一个布局文件上的ViewPager根本没有显示任何片段。我多次检查代码，但没有发现错误。当我试着调试它时，我注意到它甚至没有初始化当您选择一个选项卡时应该初始化的片段类。 我的主要活动：

public class MainActivity extends AppCompatActivity
    implements NavigationView.OnNavigationItemSelectedListener {

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

    new GetData(this).execute();

    TabLayout tab_layout = (TabLayout) findViewById(R.id.tab_layout);
    tab_layout.addTab(tab_layout.newTab().setText("CASUAL"));
    tab_layout.addTab(tab_layout.newTab().setText("RANKED"));
    tab_layout.setTabGravity(TabLayout.GRAVITY_FILL);

    final ViewPager viewPager = (ViewPager) findViewById(R.id.view_pager);
    PagerAdapter adapter = new PagerAdapter(getSupportFragmentManager(), tab_layout.getTabCount());
    viewPager.setAdapter(adapter);
    tab_layout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
        @Override
        public void onTabSelected(TabLayout.Tab tab) {
            viewPager.setCurrentItem(tab.getPosition());
        }

        @Override
        public void onTabUnselected(TabLayout.Tab tab) {

        }

        @Override
        public void onTabReselected(TabLayout.Tab tab) {

        }
    });

}

@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 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);
}

@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
    // Handle navigation view item clicks here.
    int id = item.getItemId();

    if (id == R.id.nav_stats) {
        // Handle the camera action
    } else if (id == R.id.nav_about) {

    }

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

我的PagerAdapter：

public class PagerAdapter extends FragmentStatePagerAdapter {
int mNumOfTabs;

public PagerAdapter(FragmentManager fm, int NumOfTabs) {
    super(fm);
    this.mNumOfTabs = NumOfTabs;
    }

@Override
public Fragment getItem(int position) {

    switch (position) {
        case 0:
            CasualStats tab1 = new CasualStats();
            return tab1;
        case 1:
            RankedStats tab2 = new RankedStats();
            return tab2;
        default:
            return null;
        }
     }

@Override
public int getCount() {
    return mNumOfTabs;
    }
}

使用ViewPager的布局：

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

        android:id="@+id/pager"
        android:layout_width="match_parent"
        android:layout_height="fill_parent"
        android:layout_below="@id/tab_layout"/>
]]>

<android.support.design.widget.TabLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true"
    android:layout_alignParentStart="true"
    android:id="@+id/tab_layout">

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

<view
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    class="android.support.v4.view.ViewPager"
    android:layout_alignParentStart="true"
    android:id="@+id/view_pager"
    android:layout_below="@+id/tab_layout" />

</RelativeLayout>

应该显示在ViewPager中的选项卡片段的类只是正常的自动生成的AndroidStudio片段类

其中一个片段：

public class CasualStats extends Fragment{
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";

// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;

private OnFragmentInteractionListener mListener;

public CasualStats() {
    // Required empty public constructor
}

/**
 * Use this factory method to create a new instance of
 * this fragment using the provided parameters.
 *
 * @param param1 Parameter 1.
 * @param param2 Parameter 2.
 * @return A new instance of fragment CasualStats.
 */
// TODO: Rename and change types and number of parameters
public static CasualStats newInstance(String param1, String param2) {
    CasualStats fragment = new CasualStats();
    Bundle args = new Bundle();
    args.putString(ARG_PARAM1, param1);
    args.putString(ARG_PARAM2, param2);
    fragment.setArguments(args);
    return fragment;
}

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    if (getArguments() != null) {
        mParam1 = getArguments().getString(ARG_PARAM1);
        mParam2 = getArguments().getString(ARG_PARAM2);
    }
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    return inflater.inflate(R.layout.fragment_casual_stats, container, false);
}

// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
    if (mListener != null) {
        mListener.onFragmentInteraction(uri);
    }
}

@Override
public void onDetach() {
    super.onDetach();
    mListener = null;
}

/**
 * This interface must be implemented by activities that contain this
 * fragment to allow an interaction in this fragment to be communicated
 * to the activity and potentially other fragments contained in that
 * activity.
 * <p>
 * See the Android Training lesson <a href=
 * "http://developer.android.com/training/basics/fragments/communicating.html"
 * >Communicating with Other Fragments</a> for more information.
 */
public interface OnFragmentInteractionListener {
    // TODO: Update argument type and name
    void onFragmentInteraction(Uri uri);
}
}

xml：

<RelativeLayout 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"
tools:context="com.app.anzel.r6s.CasualStats">

<!-- TODO: Update blank fragment layout -->

<TextView
    android:text="1st fragment"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true"
    android:layout_alignParentStart="true"
    android:layout_marginStart="28dp"
    android:layout_marginTop="22dp"
    android:id="@+id/textView"
    android:visibility="visible" />
</RelativeLayout>

您缺少ViewPager的设置，并且不需要SetOnAbsSelectedListener：

让我们看看这里：

您还必须覆盖适配器中的getPageTitle，并返回选项卡标题

最后，不要在xml中使用，创建普通xml视图：

 <android.support.v4.view.ViewPager 
     android:layout_width="wrap_content"
     android:layout_height="wrap_content"
     android:layout_alignParentStart="true"
     android:id="@+id/view_pager"
     android:layout_below="@+id/tab_layout"/>

试试这个：

在布局中：

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

<android.support.design.widget.TabLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true"
    android:layout_alignParentStart="true"
    android:id="@+id/tab_layout">

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

<android.support.v4.view.ViewPager
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_alignParentStart="true"
    android:id="@+id/view_pager"
    android:layout_below="@+id/tab_layout" />

</RelativeLayout>

PagerAdapter：

    public class PagerAdapter extends FragmentStatePagerAdapter {
int mNumOfTabs;

// an array of tab titles
    private String tabTitles[] = new String[]{"CASUAL", "RANKED"};

public PagerAdapter(FragmentManager fm, int NumOfTabs) {
    super(fm);
    this.mNumOfTabs = NumOfTabs;
    }

@Override
public Fragment getItem(int position) {

    switch (position) {
        case 0:
            CasualStats tab1 = new CasualStats();
            return tab1;
        case 1:
            RankedStats tab2 = new RankedStats();
            return tab2;
        default:
            return null;
        }
     }

    @Override
    public int getCount() {
        return mNumOfTabs;
        }

     @Override
    public CharSequence getPageTitle(int position) {
        return tabTitles[position];
    }
}

---

我觉得有点傻。正如我所怀疑的，问题出在ViewPager上。经过3小时的代码调试，我刚刚将ViewPager从带有选项卡的布局移动到另一个布局，该布局基本上连接了所有布局。

下面的示例代码与ViewPager和选项卡一起工作正常。试试看

主要活动布局

---

问题是您有嵌套的片段并使用getFragmentManager；您应该改用getChildFragmentManager

爪哇：

科特林：

如果在NestedScrollView中使用任何带有viewpager的TableLayout，请确保将android:fillViewport=true 在嵌套的滚动视图中。请注意，如果您使用的是导航抽屉，您的片段可能没有嵌套的滚动视图，但您的活动片段容器可能在嵌套的滚动视图中。因为即使是带有调试问题背景色的空布局也不会显示，所以在我的例子中，这不是视图寻呼机的问题，而是嵌套滚动视图的问题

调试提示：放置一些布局并设置 背景色，以查看布局是否可见。如果布局本身 不可见，则您对父布局有问题，大多数 可能是嵌套的滚动视图

---

这只会使我的选项卡标题消失，而viewpager仍然无法显示片段。我仍然无法让viewpager显示片段：没有错误它只是不想显示适当的片段选择选项卡时的任何片段代码是否进入getItem？您可以发布片段代码吗？为其中一个片段添加了类和布局xml文件，该片段在选择选项卡时应显示在viewpager中。请尝试如下操作：1。为您的viewpager创建适配器。2.在视图寻呼机上设置适配器。3.使用tabLayout.setupWithViewPageryour_viewpager；4.确保使用getSupportFragmentManager或getchildFragmentManager，如果viewpager处于活动状态或在另一个片段中。5.适配器必须重写public CharSequence getPageTitleint位置，以便为选项卡布局的每个片段提供标题。是否尝试确保片段确实不可见？我的意思是，您似乎没有在textview中放置任何内容，尝试更改背景或在textview中设置一些文本只是为了测试。更改了片段的背景颜色，但没有显示它。运气不好，结果与以前相同，viewpager没有查看任何内容。添加viewpager.setOffScreenPagilemit2；调用setupWithViewPager后，如果代码被调用到getItemint位置，也要调试代码。它调用这个方法，我用Log也检查了viewPager.setOffscreenPageLimit2；没有帮助：虽然我发现当选择一个选项卡时它不会调用任何片段创建一个新的runnable没有任何作用。请检查我的答案，希望有帮助。是的。那正是我的问题。使用父FragmentManager，它获取以前使用的片段，而不是重新创建它们。无论如何，它都不起作用。使用getChildFragmentManager创建一个逐片段FragmentManager，它解决了这个问题。谢谢，当我在片段中使用viewpager时，它对我很有用。

 TabLayout tab_layout = (TabLayout) findViewById(R.id.tab_layout);
    tab_layout.addTab(tab_layout.newTab().setText("CASUAL"));
    tab_layout.addTab(tab_layout.newTab().setText("RANKED"));
    tab_layout.setTabGravity(TabLayout.GRAVITY_FILL);

    final ViewPager viewPager = (ViewPager) findViewById(R.id.view_pager);
    PagerAdapter adapter = new PagerAdapter(getSupportFragmentManager(), tab_layout.getTabCount());
    viewPager.setAdapter(adapter);
    viewPager.setOffscreenPageLimit(2);
    tab_layout.post(new Runnable() {
    @Override
    public void run() {
        tab_layout.setupWithViewPager(viewPager);
      }
   });
    tab_layout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
        @Override
        public void onTabSelected(TabLayout.Tab tab) {
            viewPager.setCurrentItem(tab.getPosition());
        }

        @Override
        public void onTabUnselected(TabLayout.Tab tab) {

        }

        @Override
        public void onTabReselected(TabLayout.Tab tab) {

        }
    });

    public class PagerAdapter extends FragmentStatePagerAdapter {
int mNumOfTabs;

// an array of tab titles
    private String tabTitles[] = new String[]{"CASUAL", "RANKED"};

public PagerAdapter(FragmentManager fm, int NumOfTabs) {
    super(fm);
    this.mNumOfTabs = NumOfTabs;
    }

@Override
public Fragment getItem(int position) {

    switch (position) {
        case 0:
            CasualStats tab1 = new CasualStats();
            return tab1;
        case 1:
            RankedStats tab2 = new RankedStats();
            return tab2;
        default:
            return null;
        }
     }

    @Override
    public int getCount() {
        return mNumOfTabs;
        }

     @Override
    public CharSequence getPageTitle(int position) {
        return tabTitles[position];
    }
}

<android.support.design.widget.AppBarLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    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.design.widget.AppBarLayout>

<android.support.design.widget.TabLayout
    android:id="@+id/tab_container"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginTop="?attr/actionBarSize" />

<include layout="@layout/content_main" />

<android.support.design.widget.FloatingActionButton
    android:id="@+id/fab"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="bottom|end"
    android:layout_margin="@dimen/fab_margin"
    app:srcCompat="@android:drawable/ic_dialog_email" />

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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/content_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_marginTop="?attr/actionBarSize"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="com.test.myapplication.MainActivity"
    tools:showIn="@layout/app_bar_main">

    <android.support.v4.view.ViewPager
        android:id="@+id/page_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="#FF0000" />
</RelativeLayout>

package com.test.myapplication;

import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.design.widget.TabLayout;
import android.support.v4.app.*;
import android.support.v4.app.Fragment;
import android.support.v4.view.ViewPager;
import android.view.View;
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);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });

        ViewPager pager = (ViewPager)findViewById(R.id.page_container);
        pager.setAdapter(new Adapter(getSupportFragmentManager()));
        TabLayout tabs = (TabLayout)findViewById(R.id.tab_container);
        tabs.setupWithViewPager(pager, true);
        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 void onBackPressed() {
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        if (drawer.isDrawerOpen(GravityCompat.START)) {
            drawer.closeDrawer(GravityCompat.START);
        } else {
            super.onBackPressed();
        }
    }

    @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);
    }

    @SuppressWarnings("StatementWithEmptyBody")
    @Override
    public boolean onNavigationItemSelected(MenuItem item) {
        // Handle navigation view item clicks here.
        int id = item.getItemId();

        if (id == R.id.nav_camera) {
            // Handle the camera action
        } else if (id == R.id.nav_gallery) {

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

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

        } 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;
    }


    public static class Adapter extends FragmentStatePagerAdapter {
        private String[] titles = new String[] {"ONE", "TWO"};

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

        @Override
        public Fragment getItem(int position) {
            switch (position){
                case 0:
                    return new com.test.myapplication.Fragment();
                case 1:
                    return new Fragment1();
            }
            return null;
        }

        @Override
        public int getCount() {
            return 2;
        }

        @Override
        public CharSequence getPageTitle(int position) {
            return titles[position];
        }
    }
}

viewPagerAdapter = new PagerAdapter(getChildFragmentManager())

viewPagerAdapter = PagerAdapter(childFragmentManager)