Java 从活动连接片段

我有一个活动，已经制作了片段。在我的活动中，当我单击登录按钮时，加载程序将显示。在加载程序变得不可见之后，我只需要附加该片段。该片段已在其他一些类中创建。当

循环加载程序

不可见并且我的片段已经在其他类中创建时，我只需要附加该片段，但我只需要附加该片段

MainActivity.java

handler = new Handler();
runnable = new Runnable() {
    @Override
    public void run() {
        if (loader_fragment != null) {
            AVLoadingIndicatorView loader = loader_fragment.getView().findViewById(R.id.loder_login);
            loader.setVisibility(View.INVISIBLE);
            timer.cancel();
        }

        Home_Screen home_screen = (Home_Screen) getFragmentManager().findFragmentById(R.id.Home_screen_fragment);
        fragmentManager1 = getFragmentManager();
        fragmentTransaction1 = fragmentManager1.beginTransaction();
        fragmentTransaction1.setCustomAnimations(
                R.animator.slide_in_left,
                R.animator.slide_out_left,
                R.animator.slide_in_right,
                R.animator.slide_out_right);
        Home_screen_student home_screen_student = new Home_screen_student();
        fragmentTransaction1.attach(R.id.Home_screen_fragment, home_screen_student);
        fragmentTransaction1.commit();
    }
};

package com.example.user.attendance;

import android.app.AlertDialog;
import android.app.Fragment;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.content.Intent;
import android.graphics.Color;
import android.graphics.drawable.ColorDrawable;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.design.widget.NavigationView;
import android.support.design.widget.NavigationView.OnNavigationItemSelectedListener;
import android.support.design.widget.Snackbar;
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.view.LayoutInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.Toast;


public class Home_Screen extends Fragment implements OnNavigationItemSelectedListener {
    DrawerLayout navigation_drawer;
    NavigationView navigationView;
    Button logout_Yes_button,logout_no_button, home_screen_take_attendance_button;

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

        // Inflate the layout for this fragment
        View Home_screen = inflater.inflate(R.layout.navigation_drawer,container,false);
        android.support.v7.widget.Toolbar toolbar =
                (android.support.v7.widget.Toolbar) Home_screen.findViewById(R.id.custom_action_bar);
        ((AppCompatActivity) getActivity()).setSupportActionBar(toolbar);
        navigation_drawer = (DrawerLayout) Home_screen.findViewById(R.id.drawer_layout);
        navigationView = (NavigationView) Home_screen.findViewById(R.id.Navigation_view_for_teacher);

HomeScreenFragment.java

handler = new Handler();
runnable = new Runnable() {
    @Override
    public void run() {
        if (loader_fragment != null) {
            AVLoadingIndicatorView loader = loader_fragment.getView().findViewById(R.id.loder_login);
            loader.setVisibility(View.INVISIBLE);
            timer.cancel();
        }

        Home_Screen home_screen = (Home_Screen) getFragmentManager().findFragmentById(R.id.Home_screen_fragment);
        fragmentManager1 = getFragmentManager();
        fragmentTransaction1 = fragmentManager1.beginTransaction();
        fragmentTransaction1.setCustomAnimations(
                R.animator.slide_in_left,
                R.animator.slide_out_left,
                R.animator.slide_in_right,
                R.animator.slide_out_right);
        Home_screen_student home_screen_student = new Home_screen_student();
        fragmentTransaction1.attach(R.id.Home_screen_fragment, home_screen_student);
        fragmentTransaction1.commit();
    }
};

package com.example.user.attendance;

import android.app.AlertDialog;
import android.app.Fragment;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.content.Intent;
import android.graphics.Color;
import android.graphics.drawable.ColorDrawable;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.design.widget.NavigationView;
import android.support.design.widget.NavigationView.OnNavigationItemSelectedListener;
import android.support.design.widget.Snackbar;
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.view.LayoutInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.Toast;


public class Home_Screen extends Fragment implements OnNavigationItemSelectedListener {
    DrawerLayout navigation_drawer;
    NavigationView navigationView;
    Button logout_Yes_button,logout_no_button, home_screen_take_attendance_button;

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

        // Inflate the layout for this fragment
        View Home_screen = inflater.inflate(R.layout.navigation_drawer,container,false);
        android.support.v7.widget.Toolbar toolbar =
                (android.support.v7.widget.Toolbar) Home_screen.findViewById(R.id.custom_action_bar);
        ((AppCompatActivity) getActivity()).setSupportActionBar(toolbar);
        navigation_drawer = (DrawerLayout) Home_screen.findViewById(R.id.drawer_layout);
        navigationView = (NavigationView) Home_screen.findViewById(R.id.Navigation_view_for_teacher);

Logcat错误：

04-22 18:45:31.966 26404-26404/？E/合子：无v2 04-22 18:45:54.221 26404-26404/com.example.user.attention E/AndroidRuntime:FATAL EXCEPTION:main 流程：com.example.user.attention，PID:26404 java.lang.NullPointerException:尝试写入空对象引用上的字段“android.app.FragmentManagerImpl android.app.Fragment.MFFragmentManager” 位于android.app.backbackrecord.doAddOp（backbackrecord.java:461） 在android.app.BackStackRecord.replace（BackStackRecord.java:496） 在android.app.BackStackRecord.replace（BackStackRecord.java:488） 位于com.example.user.attention.MainActivity$3$2.run（MainActivity.java:181） 位于android.os.Handler.handleCallback（Handler.java:739） 位于android.os.Handler.dispatchMessage（Handler.java:95） 位于android.os.Looper.loop（Looper.java:148） 位于android.app.ActivityThread.main（ActivityThread.java:7402） 位于java.lang.reflect.Method.invoke（本机方法） 在com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run上（ZygoteInit.java:1230） 位于com.android.internal.os.ZygoteInit.main（ZygoteInit.java:1120）

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帮帮我。

在活动中是否使用viewPager？ 您可能需要从一个活动处理到另一个活动 试试这个预告片：

  ViewPager viewPager = (ViewPager) findViewById(R.id.rew1);
  viewPager.setAdapter(new CustomPagerAdapter(this));
  TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);

  viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
  tabLayout.addOnTabSelectedListener(new TabLayout.ViewPagerOnTabSelectedListener(viewPager));

//

//

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太长了…解决方案你有一个较短的解决方案吗？是的，我有，我已经实现了，而且正在运行。顺便说一下，谢谢你的回答。。。