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دوستان کسی تا حالا با ViewPager بدون TabHost در Nested Fragment کار کرده

کد پی‌اچ‌پی:
Logcat : 

03-03 05:17:37.300 1415-1415/com.olomrayan.obituary D/AndroidRuntime: Shutting down VM
03-03 05:17:37.305 1415-1415/com.olomrayan.obituary E/AndroidRuntime: FATAL EXCEPTION: main
                                                                      Process: com.olomrayan.obituary, PID: 1415
                                                                      java.lang.NullPointerException: Attempt to invoke virtual method 'int java.util.ArrayList.size()' on a null object reference
                                                                          at android.support.v4.app.FragmentManagerImpl.getFragment(FragmentManager.java:667)
                                                                          at android.support.v4.app.FragmentStatePagerAdapter.restoreState(FragmentStatePagerAdapter.java:211)
                                                                          at android.support.v4.view.ViewPager.onRestoreInstanceState(ViewPager.java:1319)
                                                                          at android.view.View.dispatchRestoreInstanceState(View.java:14746)
                                                                          at android.view.ViewGroup.dispatchRestoreInstanceState(ViewGroup.java:3121)
                                                                          at android.view.ViewGroup.dispatchRestoreInstanceState(ViewGroup.java:3127)
                                                                          at android.view.View.restoreHierarchyState(View.java:14724)
                                                                          at android.support.v4.app.Fragment.restoreViewState(Fragment.java:468)
                                                                          at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1094)
                                                                          at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1248)
                                                                          at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:738)
                                                                          at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1613)
                                                                          at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:517)
                                                                          at android.os.Handler.handleCallback(Handler.java:739)
                                                                          at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                          at android.os.Looper.loop(Looper.java:148)
                                                                          at android.app.ActivityThread.main(ActivityThread.java:5417)
                                                                          at java.lang.reflect.Method.invoke(Native Method)
                                                                          at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                                                                          at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 

MainActivity:

کد پی‌اچ‌پی:
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.widget.Toast;

import java.io.IOException;
import java.io.InputStream;

public class MainActivity extends AppCompatActivity implements OnFragmentInteractionListener {

    NewFragment newFragment = null;
    MainFragment mainFragment = null;
    String CurrentFragment = "MainActivity";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        final Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        initFirstLoad();

        Bitmap bitmap = null;
        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        try {
            InputStream is = getAssets().open("images/new.png");
            bitmap = BitmapFactory.decodeStream(is);
        } catch (IOException e) {
            e.printStackTrace();
        }

        fab.setImageBitmap(bitmap);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                if (newFragment == null) {
                    newFragment = NewFragment.newInstance();
                }

                if (newFragment.isVisible()) {
                    return;
                }

                CurrentFragment = "NewFragment";
                FragmentManager fragmentManager = getSupportFragmentManager();
                FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
                fragmentTransaction.add(R.id.mainfragment, newFragment, "NewFragment").addToBackStack("NewFragment");
                fragmentTransaction.commit();
            }
        });
    }

    @Override
    public void onBackPressed() {

            if (CurrentFragment.equals("NewFragment") && newFragment.isVisible()) {
                getSupportFragmentManager().popBackStack();
                CurrentFragment = getSupportFragmentManager().getFragments().get(0).getTag();
                if (CurrentFragment == null)
                    CurrentFragment = "MainActivity";

                //noinspection ConstantConditions
                getSupportActionBar().setTitle(R.string.app_name);
            }
        //super.onBackPressed();
    }

//    @Override
//    public void onBackPressed() {
//        Log.d("MYLOG",String.valueOf(getFragmentManager().getBackStackEntryCount()));
//        if (getFragmentManager().getBackStackEntryCount() > 0) {
//            getFragmentManager().popBackStack();
//        } else {
//            super.onBackPressed();
//        }
//    }

    private void initFirstLoad() {
        if (mainFragment == null) {
            mainFragment = MainFragment.newInstance();
        }
        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        fragmentTransaction.add(R.id.mainfragment, mainFragment, "MainFragment").addToBackStack("MainFragment");
        fragmentTransaction.commit();

    }


    @Override
    public void onFragmentInteraction(String fragmentName, String[] Values) {

        switch (fragmentName) {
            case "AboutFragment":
                Toast.makeText(MainActivity.this, "MainActivity onFragmentInteraction From About Fragment : Uri " + Values[0], Toast.LENGTH_SHORT).show();
                break;
        }
    }
} 

MainFragment:

کد پی‌اچ‌پی:
import android.app.ProgressDialog;
import android.content.Context;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.TypedValue;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.WindowManager;
import android.widget.Toast;

import com.olomrayan.obituary.Adapters.CustomAdapterRecyclerView;
import com.olomrayan.obituary.Database.DBAccess;
import com.olomrayan.obituary.Database.DBHelper;
import com.olomrayan.obituary.Models.ObituaryItem;

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

import jp.wasabeef.recyclerview.adapters.AlphaInAnimationAdapter;
import jp.wasabeef.recyclerview.adapters.ScaleInAnimationAdapter;
import jp.wasabeef.recyclerview.animators.SlideInLeftAnimator;


public class MainFragment extends Fragment implements OnFragmentInteractionListener {

    private OnFragmentInteractionListener mListener;
    ProgressDialog mProgressDialog;
    View mRootView;
    List<ObituaryItem> mObituaryItemList;
    DBAccess mDBAccess;

    public MainFragment() {

    }


    public static MainFragment newInstance() {

        return new MainFragment();
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        mRootView = inflater.inflate(R.layout.fragment_main, container, false);
        return mRootView;
    }

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



        mObituaryItemList = new ArrayList<>();

        LoadingData loadingData = new LoadingData();
        loadingData.execute();

        RecyclerView recyclerView = (RecyclerView) mRootView.findViewById(R.id.recyclerview);
        recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
        CustomAdapterRecyclerView customAdapterRecyclerView = new CustomAdapterRecyclerView(mObituaryItemList);

        AlphaInAnimationAdapter alphaInAnimationAdapter = new AlphaInAnimationAdapter(customAdapterRecyclerView);
        recyclerView.setItemAnimator(new SlideInLeftAnimator());
        recyclerView.getItemAnimator().setChangeDuration(1000);
        alphaInAnimationAdapter.setDuration(1000);
        alphaInAnimationAdapter.setFirstOnly(false);
        alphaInAnimationAdapter.setHasStableIds(true);
        recyclerView.setAdapter(new ScaleInAnimationAdapter(alphaInAnimationAdapter));
    }

    public void onButtonPressed(String fragmentName, String[] Values ) {
        if (mListener != null) {
            mListener.onFragmentInteraction(fragmentName, Values);
        }
    }


    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        if (context instanceof OnFragmentInteractionListener) {
            mListener = (OnFragmentInteractionListener) context;
        } else {
            throw new RuntimeException(context.toString()
                    + " must implement OnFragmentInteractionListener");
        }
    }

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

    @Override
    public void onFragmentInteraction(String fragmentName, String[] Values) {
        switch (fragmentName) {
            case "AboutFragment":
                Toast.makeText(getActivity(), "MainFragment onFragmentInteraction From About Fragment : Uri " + Values[0], Toast.LENGTH_SHORT).show();
                break;
            default:
        }
    }

    class LoadingData extends AsyncTask<String,String,List<ObituaryItem>> {


        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            mDBAccess = DBAccess.getInstance(getActivity());

            mProgressDialog = new ProgressDialog(getActivity());
            mProgressDialog.setIndeterminate(true);
            mProgressDialog.setCancelable(false);
            mProgressDialog.setProgressStyle(android.R.attr.progressBarStyleSmall);
            mProgressDialog.show();
            WindowManager.LayoutParams params = mProgressDialog.getWindow().getAttributes();
            params.x = -20;
            params.height = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 150f, getResources().getDisplayMetrics());
            params.width = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 180f, getResources().getDisplayMetrics());
            params.y = -10;
            mProgressDialog.getWindow().setAttributes(params);
            mProgressDialog.setContentView(R.layout.loadgin_data_progressbar);
        }
        @Override
        protected List<ObituaryItem> doInBackground(String... params) {

            return mDBAccess.getSelectData(DBHelper.DB_TABLE_NAME, DBHelper.TABLE_COLUMNS_NAMES,null,null,null,null,DBHelper.TABLE_COLUMNS_CREATEDATE + " DESC");
        };



        @Override
        protected void onProgressUpdate(String... values) {
            super.onProgressUpdate(values);
        }

        @Override
        protected void onPostExecute(List<ObituaryItem> obituaryItemList) {

            mProgressDialog.dismiss();
        }
    }
} 

NewFragment:

کد پی‌اچ‌پی:
import android.content.Context;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;

import android.support.v4.view.ViewPager;
import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.KeyEvent;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;

import com.olomrayan.obituary.Adapters.CustomPagerAdapter;


public class NewFragment extends Fragment implements View.OnKeyListener {


    int CurrnetPagerItem = 1;

    private OnFragmentInteractionListener mListener;

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


    public static NewFragment newInstance() {
        new NewFragment();

        return new NewFragment();
    }

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

    }


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

        View rootView = inflater.inflate(R.layout.fragment_new, container, false);

        //noinspection ConstantConditions
        final ViewPager viewPager = (ViewPager) rootView.findViewById(R.id.viewPager);

        FragmentManager fragmentManager = getChildFragmentManager();
        CustomPagerAdapter customPagerAdapter = new CustomPagerAdapter(fragmentManager);
        //customPagerAdapter.setPrimaryItem(viewPager,0,StepOneFragment.newInstance());
        Log.d("MYLOG", String.valueOf(customPagerAdapter.getCount()));
        viewPager.setAdapter(customPagerAdapter);

        viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            @Override
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

            }

            @Override
            public void onPageSelected(int position) {
                Log.d("MYLOG", String.valueOf(position));
                CurrnetPagerItem = position;
            }

            @Override
            public void onPageScrollStateChanged(int state) {

            }
        });


        Button btnNext = (Button) rootView.findViewById(R.id.btnNext);

        btnNext.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {


                if (CurrnetPagerItem > 1)
                    CurrnetPagerItem = 0;

                viewPager.setCurrentItem(CurrnetPagerItem);

                CurrnetPagerItem++;

            }
        });

        ActionBar toolbar = ((AppCompatActivity) getActivity()).getSupportActionBar();

        if (toolbar != null) {
            toolbar.setHomeButtonEnabled(true);
            toolbar.setDisplayShowTitleEnabled(true);
            toolbar.setDisplayShowHomeEnabled(true);
            toolbar.setTitle("New Obituary");
        }

        return rootView;
    }

    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);


    }

    public void onButtonPressed(String[] Values) {
        if (mListener != null) {
            mListener.onFragmentInteraction("NewFragment", Values);
        }
    }


    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        if (context instanceof OnFragmentInteractionListener) {
            mListener = (OnFragmentInteractionListener) context;
        } else {
            throw new RuntimeException(context.toString()
                    + " must implement OnFragmentInteractionListener");
        }
    }

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

    }


    @Override
    public boolean onKey(View v, int keyCode, KeyEvent event) {
//        if (event.getAction() == KeyEvent.ACTION_DOWN) {
//            if (keyCode == KeyEvent.KEYCODE_BACK) {
//                return true;
//            }
//        }
        return false;
    }

} 

CustomPagerAdapter:

کد پی‌اچ‌پی:
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.util.Log;

import com.olomrayan.obituary.StepOneFragment;
import com.olomrayan.obituary.StepTwoFragment;

public class CustomPagerAdapter extends FragmentPagerAdapter {



    int count = 2;
    public CustomPagerAdapter(FragmentManager fm) {
        super(fm);
        Log.d("MYLOG", "Custom Created");

    }

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

    @Override
    public Fragment getItem(int position) {
        Fragment fragment;
        Log.d("MYLOG", String.valueOf(position));

        switch (position) {

            case 0:
                fragment = StepOneFragment.newInstance();
            break;
            case 1:
                fragment =  StepTwoFragment.newInstance();
                break;

            default:
                fragment =  null;
        }

        return fragment;
    }

} 

OnFragmentInteraction Interface :

کد پی‌اچ‌پی:
public interface OnFragmentInteractionListener {
    void onFragmentInteraction(String fragmentName,String[] Values);
} 

mainavtivity.xml

کد پی‌اچ‌پی:
<?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:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:context="com.olomrayan.obituary.MainActivity">

    <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>

    <fragment
        android:layout_marginTop="64dp"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/mainfragment"
        class ="com.olomrayan.obituary.MainFragment"
        tools:layout="@layout/fragment_main" />

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        app:rippleColor="@color/colorAccent"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|end"
        app:backgroundTint="@color/textColorPrimary"
        android:scrollbars="vertical"
        android:layout_margin="@dimen/fab_margin"
        android:src="@drawable/newo"
        app:theme="@style/MyFloatingButton"/>
</android.support.design.widget.CoordinatorLayout> 

mainfragment.xml

کد پی‌اچ‌پی:
<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.olomrayan.obituary.MainFragment">

<android.support.v7.widget.RecyclerView
    android:layout_width="match_parent"
    android:fitsSystemWindows="true"
    android:layout_below="@android:id/empty"
    android:layout_alignWithParentIfMissing="true"
    android:layout_height="match_parent"
    android:id="@+id/recyclerview">

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

</RelativeLayout> 

newfragment.xml

کد پی‌اچ‌پی:
<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:weightSum="100"
    android:background="@color/navigationBarColor"
    tools:context="com.olomrayan.obituary.NewFragment"
    android:orientation="vertical">


    <android.support.v4.view.ViewPager
        android:id="@+id/viewPager"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="100">
    </android.support.v4.view.ViewPager>

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/btnNext"
        android:text="Next Page" />

</LinearLayout> 

مشکل برطرف شد.

اشکال در مدیریت چرخه حیات NewFragment بود
بار اول که NewFragment ساخته میشه ViewPager میاد و customPagerAdapter رو راه اندازی میکنه.
CustomPagerAdapter هم میاد StepOneFragment و stepTwoFragment رو راه اندازی میکنه
چون در پیاده سازی CustomPagerAdapter از FragmentStatePagerAdapter استفاده شده قسمتی از Content و تعدا اونها در چرخه حیات ViewPager و NewFragment ذخیره میشه.

چون ما در طراحی انجام شده هنوز قسمت OnDetach مربوط به NewFragment و بقیه Fragmentها رو پیاده سازی نکردیم برای هیمن از چرخه حیات خارج نمیشن و هنگامی که دوباره NewFragment راه اندازی میشه اطلاعات قبلی مربوط به NewFragment بازگردانی میشه ولی این بار چون هنوز StepOneFragment و StepTwoFragment راه اندازی نشدن . ViewPager با اطلاعات غلط یا اشتباه پر میشه و هنوز فکر میکنه که دو Fragment گفته شده راه اندازی شدن . در حالی که راه اندازی نشدن و هیچ اطلاعاتی ازشون موجوذد نیست.
برای همین منظور پیغام خطای زیر رو میده

کد پی‌اچ‌پی:
NullPointerException: Attempt to invoke virtual method 'int java.util.ArrayList.size()' on a null object reference
                                                                          at android.support.v4.app.FragmentManagerImpl.getFragment(FragmentManager.java:667)
                                                                          at android.support.v4.app.FragmentStatePagerAdapter.restoreState(FragmentStatePagerAdapter.java:211)
                                                                          at android.support.v4.view.ViewPager.onRestoreInstanceState(ViewPager.java:1319)
                                                                          at android.view.View.dispatchRestoreInstanceState(View.java:14746) 

نکته : در استفاده از Fragment ها و NestedFragmentها همیشه با Onattach و OnDetach دقت کنید

فراموش کردم بگم
این هم کد مربوط به برطرف کردن مشکل

در MainActivity در رویداد onclicklistener مربوط به floatingactionbutton یا fab کد زیر رو جایگزین کنید

کد پی‌اچ‌پی:
کد قدیمی 

if (newFragment == null) {
                    newFragment = NewFragment.newInstance();
                }

                if (newFragment.isVisible()) {
                    return;
                }

                CurrentFragment = "NewFragment";
                FragmentManager fragmentManager = getSupportFragmentManager();
                FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
                fragmentTransaction.add(R.id.mainfragment, newFragment, "NewFragment").addToBackStack("NewFragment");
                fragmentTransaction.commit();
            } 

کد پی‌اچ‌پی:
کد جدید

FragmentManager fragmentManager = getSupportFragmentManager();
                FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
                newFragment = (NewFragment) fragmentManager.findFragmentByTag("NewFragment");

                if (newFragment == null) {
                    Log.d("MYLOG","NewFragment Is Nulled");
                    newFragment = NewFragment.newInstance();
                }

                if (newFragment.isVisible()) {
                    return;
                }

                Log.d("MYLOG","CurrentFragment Is "+CurrentFragment);
                CurrentFragment = "NewFragment";
                Log.d("MYLOG","CurrentFragment Is Changed To NewFragment");

                fragmentTransaction.add(R.id.mainfragment, newFragment, "NewFragment").addToBackStack("NewFragment");
                fragmentTransaction.commit(); 

نکته : بنا بر طراحی خاص برنامه . الگوی singleton بر روی کلاس NewFragment پیاده سازی ( شبیه سازی ) شده. هرچند Fragment ها به این خاطر طراحی شدن تا بشه از اونها چندین بار استفاده کرد.

mahdi10539

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