Androidx Null Pointer Exception Error, Invoke method

Question

I am getting this error. This is my logcat. I don't know what exactly is wrong. I get revoke error or we can say NullExceptionError. I tried everything but nothing workout.

 java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.RelativeLayout.setVisibility(int)' on a null object reference
    at com.nazeefawann.truemate.Profile.AccountSettingActivity.setViewPager(AccountSettingActivity.java:52)
    at com.nazeefawann.truemate.Profile.AccountSettingActivity$2.onItemClick(AccountSettingActivity.java:71)
    at android.widget.AdapterView.performItemClick(AdapterView.java:303)
    at android.widget.AbsListView.performItemClick(AbsListView.java:1151)
    at android.widget.AbsListView$PerformClick.run(AbsListView.java:3065)
    at android.widget.AbsListView$3.run(AbsListView.java:3878)
    at android.os.Handler.handleCallback(Handler.java:739)
    at android.os.Handler.dispatchMessage(Handler.java:95)
    at android.os.Looper.loop(Looper.java:135)
    at android.app.ActivityThread.main(ActivityThread.java:5538)
    at java.lang.reflect.Method.invoke(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:372)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller
    .run(ZygoteInit.java:960)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)

I am making an app and I want to make fragment in the settings activity instead of separate so that I can add more feature easily. I have created the 2 fragment but when I click on it return back to the previous activity. I don't know why

public void setViewPager(int fragmentNumbers){
    mRelativeLayout.setVisibility(View.GONE);
    Log.d(TAG,"setViewPager: navigating to fragment #:" + fragmentNumbers);
    viewPager.setAdapter(pagerAdapter);
    viewPager.setCurrentItem(fragmentNumbers); 

this is my AccountSettingActivity

 import androidx.annotation.Nullable;
 import androidx.appcompat.app.AppCompatActivity;
 import androidx.viewpager.widget.ViewPager;

public class AccountSettingActivity extends AppCompatActivity {
private Context mContext;
private SectionStatePagerAdapter pagerAdapter;
private ViewPager viewPager;
private RelativeLayout mRelativeLayout;
private String TAG;

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    viewPager = (ViewPager) findViewById(R.id.container);
    mRelativeLayout = (RelativeLayout) findViewById(R.id.relaytiveLayout11);
    mContext = AccountSettingActivity.this;
    setContentView(R.layout.activity_accountsettings);
    setupSettingList();
    setupFragment();
    ImageView backArrow = (ImageView) findViewById(R.id.backArrow);
    backArrow.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            finish();
        }
    });
}
private void setupFragment(){
    pagerAdapter = new SectionStatePagerAdapter(getSupportFragmentManager());
    pagerAdapter.addFragment(new EditProfileFragment(), getString(R.string.edit_profile_fragment)); //fragment 0
    pagerAdapter.addFragment(new SignOutFragment(), getString(R.string.sign_out_fragment)); //fragment 1
}
public void setViewPager(int fragmentNumbers){
    mRelativeLayout.setVisibility(View.GONE);
    Log.d(TAG,"setViewPager: navigating to fragment #:" + fragmentNumbers);
    viewPager.setAdapter(pagerAdapter);
    viewPager.setCurrentItem(fragmentNumbers);

}
private void setupSettingList(){
    ListView listView = (ListView) findViewById(R.id.lvAccountSettings);

    ArrayList<String> options = new ArrayList<>();
    options.add(getString(R.string.edit_profile_fragment)); //fragment 0
    options.add(getString(R.string.sign_out_fragment)); //fragement 1

    ArrayAdapter adapter = new ArrayAdapter(mContext, android.R.layout.simple_list_item_1, options);
    listView.setAdapter(adapter);

    listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            setViewPager(position);
        }
    });

}

}

this is my xml file

<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">

<include layout="@layout/layout_center_viewpager"></include>
<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/relaytiveLayout11">
    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/relLayout2">
        <include layout="@layout/snippet_top_settingtoolbar"/>

    </RelativeLayout>
    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/relLayout3"
        android:layout_below="@id/relLayout2"
        android:layout_marginBottom="50dp">

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

    </RelativeLayout>


</RelativeLayout>

i am using android x library may i am getting error because of this library

I am unable to find the error in this code I did a lot of experiment on it but nothing works out I am sure some of you would help me out THANKS IN ADVANCE

Answer 1

Do not call any findViewById i.e. mRelativeLayout = (RelativeLayout) findViewById(R.id.relaytiveLayout11); before calling setContentView. Make sure you call it before accessing any view.

Reorient your code like this

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mContext = AccountSettingActivity.this;
        setContentView(R.layout.activity_accountsettings);
        viewPager = (ViewPager) findViewById(R.id.container);
        mRelativeLayout = (RelativeLayout) findViewById(R.id.relaytiveLayout11);
        setupSettingList();
        setupFragment();
        ImageView backArrow = (ImageView) findViewById(R.id.backArrow);
        backArrow.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                finish();
            }
        });
    }