Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.widget.FrameLayout.getId()' on a null object reference

Question

**Logcat at com.example.appkhushveehoreca.MainActivity.setFragment(MainActivity.java:174) at com.example.appkhushveehoreca.MainActivity.onCreate(MainActivity.java:55) The app crashes on start can anyone please suggest me what to do.

I looked around on both Google and StackOverflow and I have found some information. However, I have not got it to work. Now I hope that I can get help with my code.

I'm relatively inexperienced in Android development.

package com.example.appkhushveehoreca;

import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.Bundle;
import android.view.MenuItem;
import android.view.Menu;
import android.view.View;
import android.widget.FrameLayout;
import android.widget.ImageView;

import com.bumptech.glide.Glide;
import com.google.android.material.navigation.NavigationView;

import androidx.annotation.NonNull;
import androidx.appcompat.app.ActionBarDrawerToggle;
import androidx.core.view.GravityCompat;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentTransaction;
import androidx.navigation.ui.AppBarConfiguration;
import androidx.drawerlayout.widget.DrawerLayout;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;

public class MainActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener {


private static final int HOME_FRAGMENT = 0;
private static final int REWARDS_FRAGMENT = 1;
private static final int ACCOUNT_FRAGMENT = 2;
private static final int WISHLIST_FRAGMENT = 3;


private FrameLayout frameLayout;
private ImageView actionBarLogo;
private int currentFragment = -1;
private NavigationView navigationView;
private Toolbar toolbar;

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


    ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
            this,drawer,toolbar,R.string.navigation_drawer_open, 
    R.string.navigation_drawer_close);
    drawer.addDrawerListener(toggle);
    toggle.syncState();
    setFragment(new HomeFragment(),HOME_FRAGMENT);


    navigationView = findViewById(R.id.nav_view);
    navigationView.setNavigationItemSelectedListener(this);
    navigationView.getMenu().getItem(0).setChecked(true);
    
    frameLayout = findViewById(R.id.main_frame_layout);

    
}

@Override
public void onBackPressed(){
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    if(drawer.isDrawerOpen(GravityCompat.START)){
        drawer.closeDrawer(GravityCompat.START);
    }else{
        if(currentFragment == HOME_FRAGMENT){
            currentFragment = -1;
            super.onBackPressed();
        }else{
            actionBarLogo.setVisibility(View.VISIBLE);
            invalidateOptionsMenu();
            setFragment(new HomeFragment(),HOME_FRAGMENT);
            navigationView.getMenu().getItem(0).setChecked(true);
        }
    }

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.

    if(currentFragment == HOME_FRAGMENT) {
        getMenuInflater().inflate(R.menu.main, menu);
        getSupportActionBar().setDisplayShowTitleEnabled(false);
    }
//        else{
//            getSupportActionBar().setDisplayShowTitleEnabled(true);
//        }
    return true;
}

@Override
public boolean onOptionsItemSelected(@NonNull MenuItem item) {
    int id = item.getItemId();
    if(id ==  R.id.main_search_icon){

        /// todo: search

        return true;
    }else if(id == R.id.main_notification_icon){

        /// todo: notification

        return true;
        }else if (id == R.id.main_cart_icon){

        /// todo: cart

        return true;
    }

    return super.onOptionsItemSelected(item);
}

public void goToFragment(String title,Fragment fragment, int fragmentNo){
    actionBarLogo.setVisibility(View.GONE);
    getSupportActionBar().setDisplayShowTitleEnabled(true);
    getSupportActionBar().setTitle(title);
    invalidateOptionsMenu();
    setFragment(fragment,fragmentNo);
  //        if(fragmentNo == REWARDS_FRAGMENT){
 //            navigationView.getMenu().getItem(1).setChecked(true);
//        }
}

@Override
public boolean onNavigationItemSelected(MenuItem item) {

    ////// Handle navigation view clicks here ///////

    int id = item.getItemId();
    if(id == R.id.nav_my_khushveeHoreca){
        actionBarLogo.setVisibility(View.VISIBLE);
        invalidateOptionsMenu();
        setFragment(new HomeFragment(),HOME_FRAGMENT);
    }else if(id == R.id.nav_my_account){
        goToFragment("My Account",new MyAccountFragment(),ACCOUNT_FRAGMENT);
    }else if(id == R.id.nav_my_offers){
        goToFragment("My Rewards",new MyRewardsFragment(),REWARDS_FRAGMENT);
    }else if(id == R.id.nav_my_wishlist){
        goToFragment("My WishList",new MyWishlistFragment(),WISHLIST_FRAGMENT);
    }else if(id == R.id.nav_sign_out) {

    }
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    drawer.closeDrawer(GravityCompat.START);
    return true;
}

private void setFragment(Fragment fragment,int fragmentNo){
    if(fragmentNo != currentFragment) {
        currentFragment = fragmentNo;
        FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
        fragmentTransaction.replace(frameLayout.getId(),fragment);
        fragmentTransaction.commit();
    }
}
 }

Answer 1

First call frameLayout = findViewById(R.id.main_frame_layout); then call setFragment(new HomeFragment(),HOME_FRAGMENT);