无法在片段之间交换，文本也未在 tablayout 中显示

Question

我使用了视图寻呼机和 Tablayout for tabbed activity.clicking 选项卡正在改变，但问题是我无法在片段之间交换，片段中的文本未显示。使用 tabLayout.setupWithViewPager(viewPager); 使我的选项卡不可见这是我的 activity_main 代码：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">
    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@android:color/transparent"
        android:minHeight="?attr/actionBarSize"
        android:theme="@style/Theme.AppCompat.DayNight.DarkActionBar"
        app:popupTheme="@style/ThemeOverlay.AppCompat.Light">
        <TextView
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:paddingTop="10dp"
            android:gravity="center_horizontal"
            android:text="Sample ViewPager"
            android:textColor="@color/colorPrimary"
            android:textSize="20sp"
            android:textStyle="bold"
            android:theme="@style/Theme.AppCompat.DayNight.DarkActionBar"
            />
    </android.support.v7.widget.Toolbar>
    <android.support.design.widget.TabLayout
        android:id="@+id/tablayout"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:background="@android:color/transparent"
        android:minHeight="?attr/actionBarSize"
        android:theme="@style/Theme.AppCompat.DayNight.DarkActionBar"
        app:tabMode="scrollable"
        app:tabTextColor="@color/colorPrimary">
    </android.support.design.widget.TabLayout>
    <android.support.v4.view.ViewPager
        android:id="@+id/viepager"
        android:layout_width="match_parent"
        android:layout_height="match_parent">
    </android.support.v4.view.ViewPager>
</LinearLayout>

这是主要内容 Activity:

package com.example.sidrajawaid.demoviewpager;

import android.net.Uri;
import android.support.design.widget.TabLayout;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.Toolbar;

public class MainActivity extends AppCompatActivity implements tab1.OnFragmentInteractionListener,tab2.OnFragmentInteractionListener,tab3.OnFragmentInteractionListener {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        final ViewPager viewPager=findViewById(R.id.viepager);
        TabLayout tabLayout=findViewById(R.id.tablayout);
        PagerAdapter pagerAdapter=new PagerAdapter(getSupportFragmentManager(),tabLayout.getTabCount());
        tabLayout.addTab(tabLayout.newTab().setText("Log In"));
        tabLayout.addTab(tabLayout.newTab().setText("RecyclerView"));
        tabLayout.addTab(tabLayout.newTab().setText("Coordinator"));
        tabLayout.addTab(tabLayout.newTab().setText("ListView"));
        tabLayout.addTab(tabLayout.newTab().setText("Log In"));
        tabLayout.addTab(tabLayout.newTab().setText("RecyclerView"));
        tabLayout.addTab(tabLayout.newTab().setText("Coordinator"));
        tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);
        viewPager.setAdapter(pagerAdapter);
        //tabLayout.setupWithViewPager(viewPager);
        viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
        tabLayout.addOnTabSelectedListener(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 onFragmentInteraction(Uri uri) {

    }
}

这是我的适配器 class 代码：

package com.example.sidrajawaid.demoviewpager;

import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.app.FragmentStatePagerAdapter;

public class PagerAdapter extends FragmentStatePagerAdapter {
    int numberOfTabs;
    public PagerAdapter(FragmentManager fm,int tabs) {
        super(fm);
        this.numberOfTabs=tabs;
    }
    @Override
    public Fragment getItem(int position) {
        {
            switch (position){
                case 0:
                    tab1 tab_1=new tab1();
                    return tab_1;
                case 1:
                    tab2 tab_2=new tab2();
                    return tab_2;
                case 2:
                    tab3 tab_3=new tab3();
                    return tab_3;
            }
            return null;
        }
    }

    @Nullable
    @Override
    public CharSequence getPageTitle(int position) {
        return super.getPageTitle(position);
    }
    @Override
    public int getCount() {
        return 0;
    }
}

这里是tab1.xml

<?xml version="1.0" encoding="utf-8"?>
<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"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    tools:context=".tab1">
    <!-- TODO: Update blank fragment layout -->
    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center"
        android:text="@string/hello_blank_fragment" />
</RelativeLayout>

解决我的2个问题： 1- 在选项卡之间切换。 2- 片段中未显示的内容。

Answer 1

问题在这里

 PagerAdapter pagerAdapter=new PagerAdapter(getSupportFragmentManager(),tabLayout.getTabCount());

第二个参数是 0，因为还没有添加标签。所以剪下线并将其粘贴到

上方

 viewPager.setAdapter(pagerAdapter);

in onCreate() 片段中的方法，请同时检查适配器中的 getCount()。确保它返回正确的值。

无法在片段之间交换，文本也未在 tablayout 中显示

Unable to swap between fragments and text is not shown either in tablayout

android

android-fragments

android-viewpager

android-tablayout