CODEWITHSUNDEEP
javaandroidandroid-studioandroid-viewpagerruntime-error
Alina
Alina

Reputation: 444

ViewPager FATAL EXCEPTION: main

I created ViewPager with fragments. But when I switch to another fragment in this Activity, the app crashes. Debugger shows a very long list of errors. When I tap on page title the app crashes immediately but when I slide it the app crashes after more than one slide. Here is Debug Console log, Java and XML codes from my app. Please write in comments if you need to see more code.

Debug Console

E/InputEventReceiver: Exception dispatching input event.
E/MessageQueue-JNI: Exception in MessageQueue callback: handleReceiveCallback
                    java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Class java.lang.Object.getClass()' on a null object reference
                        at android.support.v4.app.BackStackRecord.doAddOp(BackStackRecord.java:392)
                        at android.support.v4.app.BackStackRecord.add(BackStackRecord.java:387)
                        at android.support.v4.app.FragmentPagerAdapter.instantiateItem(FragmentPagerAdapter.java:104)
                        at android.support.v4.view.ViewPager.addNewItem(ViewPager.java:1004)
                        at android.support.v4.view.ViewPager.populate(ViewPager.java:1218)
                        at android.support.v4.view.ViewPager.populate(ViewPager.java:1086)
                        at android.support.v4.view.ViewPager$3.run(ViewPager.java:267)
                        at android.support.v4.view.ViewPager.completeScroll(ViewPager.java:1999)
                        at android.support.v4.view.ViewPager.onInterceptTouchEvent(ViewPager.java:2129)
                        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1965)
                        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2438)
                        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2060)
                        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2438)
                        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2060)
                        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2438)
                        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2060)
                        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2438)
                        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2060)
                        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2438)
                        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2060)
                        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2438)
                        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2060)
                        at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:2386)
                        at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1730)
                        at android.app.Activity.dispatchTouchEvent(Activity.java:2757)
                        at android.support.v7.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:68)
                        at android.support.v7.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:68)
                        at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:2347)
                        at android.view.View.dispatchPointerEvent(View.java:8681)
                        at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:4123)
                        at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:3989)
                        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3544)
                        at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3597)
                        at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3563)
                        at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3680)
                        at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3571)
                        at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:3737)
                        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3544)
                        at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3597)
                        at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3563)
                        at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3571)
                        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3544)
                        at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:5817)
                        at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:5791)
                        at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:5762)
                        at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:5907)
                        at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:185)
                        at android.os.MessageQueue.nativePollOnce(Native Method)
                        at android.os.MessageQueue.next(MessageQueue.java:143)
                        at android.os.Looper.loop(Looper.java:122)
                        at android.app.ActivityThread.main(ActivityThread.java:5345)
                        at java.lang.reflect.Method.invoke(Native Method)
                        at java.lang.r
D/AndroidRuntime: Shutting down VM
E/AndroidRuntime: FATAL EXCEPTION: main
                  Process: com.example.chatting, PID: 13816
                  java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Class java.lang.Object.getClass()' on a null object reference
                      at android.support.v4.app.BackStackRecord.doAddOp(BackStackRecord.java:392)
                      at android.support.v4.app.BackStackRecord.add(BackStackRecord.java:387)
                      at android.support.v4.app.FragmentPagerAdapter.instantiateItem(FragmentPagerAdapter.java:104)
                      at android.support.v4.view.ViewPager.addNewItem(ViewPager.java:1004)
                      at android.support.v4.view.ViewPager.populate(ViewPager.java:1218)
                      at android.support.v4.view.ViewPager.populate(ViewPager.java:1086)
                      at android.support.v4.view.ViewPager$3.run(ViewPager.java:267)
                      at android.support.v4.view.ViewPager.completeScroll(ViewPager.java:1999)
                      at android.support.v4.view.ViewPager.onInterceptTouchEvent(ViewPager.java:2129)
                      at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1965)
                      at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2438)
                      at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2060)
                      at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2438)
                      at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2060)
                      at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2438)
                      at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2060)
                      at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2438)
                      at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2060)
                      at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2438)
                      at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2060)
                      at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2438)
                      at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2060)
                      at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:2386)
                      at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1730)
                      at android.app.Activity.dispatchTouchEvent(Activity.java:2757)
                      at android.support.v7.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:68)
                      at android.support.v7.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:68)
                      at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:2347)
                      at android.view.View.dispatchPointerEvent(View.java:8681)
                      at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:4123)
                      at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:3989)
                      at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3544)
                      at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3597)
                      at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3563)
                      at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3680)
                      at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3571)
                      at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:3737)
                      at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3544)
                      at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3597)
                      at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3563)
                      at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3571)
                      at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3544)
                      at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:5817)
                      at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:5791)
                      at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:5762)
                      at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:5907)
                      at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:185)
                      at android.os.MessageQueue.nativePollOnce(Native Method)
                      at android.os.MessageQueue.next(MessageQueue.java:143)
                      at android.os.Looper.loop(Looper.java:122)
                      at android.app.ActivityThread.main(ActivityThread.java:5345)
                    at

MainActivity.java

public class MainActivity extends AppCompatActivity {

    private android.support.v7.widget.Toolbar mToolbar;
    private FirebaseAuth mAuth;

    private ViewPager myViewPager;
    private TabLayout myTabLayout;
    private TabsPagerAdapter myTabsPagerAdapter;

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

        mAuth = FirebaseAuth.getInstance();

        //Tabs for MainActivity
        myViewPager = (ViewPager) findViewById(R.id.main_tabs_pager);
        myTabsPagerAdapter = new TabsPagerAdapter(getSupportFragmentManager());
        myViewPager.setAdapter(myTabsPagerAdapter);
        myTabLayout = (TabLayout) findViewById(R.id.main_tabs);
        myTabLayout.setupWithViewPager(myViewPager);


        mToolbar = (android.support.v7.widget.Toolbar) findViewById(R.id.main_page_toolbar);
        setSupportActionBar(mToolbar);
        getSupportActionBar().setTitle("Chatting");
    }

    @Override
    protected void onStart() {
        super.onStart();

        FirebaseUser currentUser = mAuth.getCurrentUser();

        if (currentUser == null){

            LogOutUser();
        }
    }

    private void LogOutUser() {

        Intent startPageIntent = new Intent(MainActivity.this, StartPageActivity.class);
        startPageIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
        startActivity(startPageIntent);
        finish();

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        super.onCreateOptionsMenu(menu);

        getMenuInflater().inflate(R.menu.main_menu, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        super.onOptionsItemSelected(item);

        if (item.getItemId() == R.id.main_logout_button){

            mAuth.signOut();

            LogOutUser();
        }

        return true;
    }
}

MainActivity.xml

<?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:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

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

        <include
            layout="@layout/app_bar_layout"
            android:id="@+id/main_page_toolbar">
        </include>

        <android.support.design.widget.TabLayout
            android:id="@+id/main_tabs"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">
        </android.support.design.widget.TabLayout>

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

    <android.support.v4.view.ViewPager
        android:id="@+id/main_tabs_pager"
        android:layout_width="match_parent"
        android:layout_height="464dp"
        android:layout_alignParentBottom="true"
        android:layout_alignParentStart="true"

        android:layout_alignParentLeft="true"></android.support.v4.view.ViewPager>


</RelativeLayout>

TabsPagerAdapter.java

import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;

class TabsPagerAdapter extends FragmentPagerAdapter {



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

    @Override
    public Fragment getItem(int position) {

        switch (position){
            case 0:
                RequestsFragment requestsFragment = new RequestsFragment();
                return requestsFragment;

            case 1:
                ChatsFragment chatsFragment = new ChatsFragment();
                return chatsFragment;

            case 3:
                FriendsFragment friendsFragment = new FriendsFragment();
                return friendsFragment;

            default:
                return null;

        }

    }

    @Override
    public int getCount() {
        return 3;
    }

    public CharSequence getPageTitle(int position){

        switch (position){

            case 0:
                return "Requests";

            case 1:
                return "Chats";

            case 2:
                return "Friends";

            default:
                return null;

        }
    }

}

Upvotes: 0

Views: 173

Answers (1)

mudit_sen
mudit_sen

Reputation: 1510

@Override
    public Fragment getItem(int position) {

        switch (position){
            case 0:
                RequestsFragment requestsFragment = new RequestsFragment();
                return requestsFragment;

            case 1:
                ChatsFragment chatsFragment = new ChatsFragment();
                return chatsFragment;

            case 3:
                FriendsFragment friendsFragment = new FriendsFragment();
                return friendsFragment;

            default:
                return null;

        }

where is case 2, my friend? And do not return null in the default case. Just return any one of declared fragments. 

@Override
    public int getCount() {
        return 3;
    }

will make it run three times. for 0,1 and 2 positions but for case 2, default fragment is returned which is null. Resulting in null pointer exception.

case 3:
                    FriendsFragment friendsFragment = new FriendsFragment();
                    return friendsFragment;

change this to 

case 2:
                    FriendsFragment friendsFragment = new FriendsFragment();
                    return friendsFragment;

Upvotes: 1

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