My App keeps stopping. How can i solve this?

Question

I am new to coding in Android Studio and have been trying to make an application for school and i'm trying to make a youtube streaming application using navigation drawer. But, everytime i run it, I get the message:

My Application keeps stopping

What can i do to solve this?

Here is the main activity:

package com.example.myapplication;

import android.content.Intent;
import android.os.Bundle;

import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.StringRequest;
import com.android.volley.toolbox.Volley;
import com.example.myapplication.Adapter.MyCustomAdapter;
import com.example.myapplication.Model.VideoDetails;

import androidx.core.view.GravityCompat;
import androidx.navigation.NavController;
import androidx.navigation.Navigation;
import androidx.navigation.ui.AppBarConfiguration;
import androidx.navigation.ui.NavigationUI;

import com.example.myapplication.ui.gallery.GalleryFragment;
import com.google.android.material.navigation.NavigationView;
import com.google.android.youtube.player.YouTubePlayerView;

import androidx.drawerlayout.widget.DrawerLayout;

import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;
import androidx.recyclerview.widget.RecyclerView;

import android.provider.MediaStore;
import android.view.Menu;

import android.view.MenuItem;
import android.widget.ListView;
import android.widget.Toast;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener {

    YouTubePlayerView playerView;
    private RecyclerView rvVideo;
    String API_KEY = "xxxxxx";
    String url = "https://www.googleapis.com/youtube/v3/search?part=snippet&maxResults=25&type=video&q=larva&key=xxxxxxxxx";
    ListView listView;
    MyCustomAdapter myCustomAdapter;
    ArrayList<VideoDetails> videoDetailsArrayList;
    private AppBarConfiguration mAppBarConfiguration;

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

        videoDetailsArrayList = new ArrayList<>();

        myCustomAdapter = new MyCustomAdapter(MainActivity.this, videoDetailsArrayList);


        rvVideo= findViewById(R.id.rv_video);
        rvVideo.setHasFixedSize(true);

        displayVideos();

        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        DrawerLayout drawer = findViewById(R.id.drawer_layout);
        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);
        mAppBarConfiguration = new AppBarConfiguration.Builder(
                R.id.nav_home, R.id.nav_about)
                .setDrawerLayout(drawer)
                .build();
        NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment);
        NavigationUI.setupActionBarWithNavController(this, navController, mAppBarConfiguration);
        NavigationUI.setupWithNavController(navigationView, navController);
    }

    private boolean displayVideos() {
        RequestQueue requestQueue = Volley.newRequestQueue(getApplicationContext());
        StringRequest stringRequest = new StringRequest(Request.Method.GET, url, new Response.Listener<String>() {

            @Override
            public void onResponse(String response) {
                try {
                    JSONObject jsonObject = new JSONObject(response);
                    JSONArray jsonArray = jsonObject.getJSONArray("items");

                    for (int i = 0; i < jsonArray.length(); i++) {
                        JSONObject jsonObject1 = jsonArray.getJSONObject(i);
                        JSONObject jsonVideoID = jsonObject1.getJSONObject("id");
                        JSONObject jsonObjectSnippet = jsonObject1.getJSONObject("snippet");

                        JSONObject jsonObjectDefault = jsonObjectSnippet.getJSONObject("thumbnails").getJSONObject("medium");

                        String video_id = jsonVideoID.getString("videoId");

                        VideoDetails vd = new VideoDetails();
                        vd.setVideoId(video_id);
                        vd.setTitle(jsonObjectSnippet.getString("title"));
                        vd.setDescription(jsonObjectSnippet.getString("description"));
                        vd.setUrl(jsonObjectDefault.getString("url"));

                        videoDetailsArrayList.add(vd);

                    }

                    listView.setAdapter(myCustomAdapter);

                } catch (JSONException e) {
                    e.printStackTrace();
                }
            }
            },new Response.ErrorListener(){

                @Override
                public void onErrorResponse (VolleyError error){
                    Toast.makeText(getApplicationContext(), error.getMessage(), Toast.LENGTH_LONG).show();
                }
                }
                );

        requestQueue.add(stringRequest);


        return false;
    }



        @Override
        public boolean onSupportNavigateUp () {
            NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment);
            return NavigationUI.navigateUp(navController, mAppBarConfiguration)
                    || super.onSupportNavigateUp();
        }

    @Override
    public void onBackPressed() {
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        if(drawer.isDrawerOpen(GravityCompat.START)){
            drawer.closeDrawer(GravityCompat.START);
        } else {
            super.onBackPressed();
        }
    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @SuppressWarnings("StatementWithEmptyBody")
    @Override
    public boolean onNavigationItemSelected(MenuItem item) {
        // Handle navigation view item clicks here.
        int id = item.getItemId();

        if (id == R.id.nav_gallery) {
            Intent intentku= new Intent(MainActivity.this, GalleryFragment.class);
            startActivity(intentku);

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

here is the manifest:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.myapplication">

    <uses-permission android:name="android.permission.INTERNET" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".VideoPlayActivity"></activity>
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name"
            android:theme="@style/AppTheme.NoActionBar">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

here is the logcat error:

   Process: com.example.myapplication, PID: 25434
        java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.myapplication/com.example.myapplication.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.recyclerview.widget.RecyclerView.setHasFixedSize(boolean)' on a null object reference
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2817)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892)
            at android.app.ActivityThread.-wrap11(Unknown Source:0)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593)
            at android.os.Handler.dispatchMessage(Handler.java:105)
            at android.os.Looper.loop(Looper.java:164)
            at android.app.ActivityThread.main(ActivityThread.java:6541)
            at java.lang.reflect.Method.invoke(Native Method)
            at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
         Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.recyclerview.widget.RecyclerView.setHasFixedSize(boolean)' on a null object reference
            at com.example.myapplication.MainActivity.onCreate(MainActivity.java:66)
            at android.app.Activity.performCreate(Activity.java:6975)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1213)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2770)

here my activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.drawerlayout.widget.DrawerLayout 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:id="@+id/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:openDrawer="start">

    <include
        layout="@layout/app_bar_main"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <com.google.android.material.navigation.NavigationView
        android:id="@+id/nav_view"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:fitsSystemWindows="true"
        app:headerLayout="@layout/nav_header_main"
        app:menu="@menu/activity_main_drawer" />


</androidx.drawerlayout.widget.DrawerLayout>

here is the HomeFragment:

package com.example.myapplication.ui.home;

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import androidx.annotation.Nullable;
import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.lifecycle.Observer;
import androidx.lifecycle.ViewModelProviders;

import com.example.myapplication.R;

public class HomeFragment extends Fragment {

    private HomeViewModel homeViewModel;

    public View onCreateView(@NonNull LayoutInflater inflater,
                             ViewGroup container, Bundle savedInstanceState) {
        homeViewModel =
                ViewModelProviders.of(this).get(HomeViewModel.class);
        View root = inflater.inflate(R.layout.fragment_home, container, false);
        final TextView textView = root.findViewById(R.id.text_home);
        homeViewModel.getText().observe(this, new Observer<String>() {
            @Override
            public void onChanged(@Nullable String s) {
                textView.setText(s);
            }
        });
        return root;
    }
}

here is the fragment home.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"
    >
  <TextView
      android:id="@+id/text_home"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:layout_marginStart="8dp"
      android:layout_marginTop="8dp"
      android:layout_marginEnd="8dp"
      android:textAlignment="center"
      android:textSize="20sp"
      app:layout_constraintEnd_toEndOf="parent"
      app:layout_constraintStart_toStartOf="parent"
      app:layout_constraintTop_toTopOf="parent"/>

  <androidx.recyclerview.widget.RecyclerView
      android:id="@+id/rv_video"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      tools:listitem="@layout/item_video" />

</RelativeLayout>

Does this answer your question? [What is a NullPointerException, and how do I fix it?](https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — Vladyslav Matviienko, Nov 26 '19 at 12:33
Not the answer to the question but it also looks like you are trying to launch a `Fragment` with an `Intent` at `Intent intentku= new Intent(MainActivity.this, GalleryFragment.class);` which is not the way to do it. You should be using a `FragmentTransaction` for that ([doc](https://developer.android.com/guide/components/fragments#Adding)) — patrick.elmquist, Nov 26 '19 at 12:40
your recylcerview is in fragment but trying to access it from activity. — AkashToSky, Nov 26 '19 at 13:54

score 0 · Answer 1 · answered Nov 26 '19 at 12:36

0

You are trying to access recyclerview from activity where you have recyclerview in fragment not in activity.

so in fragment's oncreateview method add your code related to fragment not in activity.

answered Nov 26 '19 at 12:36

Soham Pandya

386
1
14

My App keeps stopping. How can i solve this?

1 Answers1