TextView.setText throws NullPointerException despite given String not being null

Question

When I try to set the Author and the Date for my Program the TextView.setText method throws a NullPointerException: Content of the Custom Object

Error 1:

E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.jokestarapplication, PID: 10886 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.jokestarapplication/com.example.jokestarapplication.ActivityJokeDetail}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2913) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048) at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) at android.app .ActivityThread$H.handleMessage(ActivityThread.java:1808) at android.os.Handler.dispatchMessage(Handler.java:106) at android.os.Looper.loop(Looper.java:193) at android.app.ActivityThread.main(ActivityThread.java:6669) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference at com.example.jokestarapplication.ActivityJokeDetail.onCreate(ActivityJokeDetail.java:44) at android.app.Activity.performCreate(Activity.java:7136) at android.app.Activity.performCreate(Activity.882132469 45888:7127) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2893) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048) at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808) at android.os.Handler.dispatchMessage(Handler.java:106) at android.os.Looper.loop(Looper.java:193) at android.app.ActivityThread.main(ActivityThread.java:6669) at java.lang.reflect.Method.invoke(Native Method) at 88 168970007088.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)

Error 2:

E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.jokestarapplication, PID: 11116 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.jokestarapplication/com.example.jokestarapplication.ActivityJokeDetail}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2913) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048) at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) at android.app .ActivityThread$H.handleMessage(ActivityThread.java:1808) at android.os.Handler.dispatchMessage(Handler.java:106) at android.os.Looper.loop(Looper.java:193) at android.app.ActivityThread.main(ActivityThread.java:6669) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference at com.example.jokestarapplication.ActivityJokeDetail.onCreate(ActivityJokeDetail.java:45) at android.app.Activity.performCreate(Activity.java:7136) at android.app.Activity.performCreate(Activity.882132469 45888:7127) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2893) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048) at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808) at android.os.Handler.dispatchMessage(Handler.java:106) at android.os.Looper.loop(Looper.java:193) at android.app.ActivityThread.main(ActivityThread.java:6669) at java.lang.reflect.Method.invoke(Native Method) at 88 168970007088.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)

Activity

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

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.LinearLayout;
import android.widget.TextView;

import java.util.List;

public class ActivityJokeDetail extends AppCompatActivity {

    public static final String KEY_JOKEDETAILS = "JOKEDETAILS";
    private Joke joke;
    private TextView tvJokeText, tvJokeVote, tvAuthor, tvPostedDate;
    private EditText etNewComment;
    private Button btJokeUp, btJokeDown, btSendComment ;
    private RecyclerView recyclerView;
    private View include;
    private AdapterJokeDetail mAdapter;

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

        joke = getIntent().getParcelableExtra(KEY_JOKEDETAILS);

        include = findViewById(R.id.include);
        tvJokeText = include.findViewById(R.id.tvCommentText);
        tvJokeVote = include.findViewById(R.id.tvCommentVotes);
        tvAuthor = include.findViewById(R.id.tvAuthor);
        tvPostedDate = include.findViewById(R.id.tvPostDate);
        btJokeUp = include.findViewById(R.id.btCommentUp);
        btJokeDown = include.findViewById(R.id.btCommentDown);

        tvJokeText.setText(joke.getText());
        tvJokeVote.setText(Integer.toString(joke.getVotes()));
        // TODO: tvAuthor.setText(joke.getAuthor());
        // TODO: tvPostedDate.setText(joke.getPostedDate().toString());
        etNewComment = findViewById(R.id.etNewComment);
        btSendComment = findViewById(R.id.btSendComment);


        recyclerView = findViewById(R.id.rvComments);

        LinearLayoutManager layoutManager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(layoutManager);
        recyclerView.setHasFixedSize(true);

        mAdapter = new AdapterJokeDetail(joke.getComments());
        recyclerView.setAdapter(mAdapter);

        btSendComment.setOnClickListener(v -> {
            SendComment();
            mAdapter.notifyDataSetChanged();
        });
    }


    private void SendComment() {
        Comment comment = new Comment(etNewComment.getText().toString(),0,"author"); //TODO: add author
        joke.getComments().add(comment);
    }
}

Joke

package com.example.jokestarapplication;

import android.os.Parcel;
import android.os.Parcelable;

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

public class Joke  implements Parcelable {
    private String text;
    private int votes;
    private Date postedDate;
    private String author;
    private String authorId;
    private String category;
    private List<Comment> comments;

    public Joke(String text, Date postedDate, String category, String author, String authorId, List<Comment> arrayList) {
        this.text = text;
        this.votes = 0;
        this.postedDate = postedDate;
        this.author = author;
        this.authorId = authorId;
        this.category = category;
        this.comments = arrayList;
    }


    protected Joke(Parcel in) {
        text = in.readString();
        votes = in.readInt();
        postedDate = new Date(in.readLong());
        author = in.readString();
        authorId = in.readString();
        category = in.readString();
        comments = in.createTypedArrayList(Comment.CREATOR);
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeString(text);
        dest.writeInt(votes);
        dest.writeLong(postedDate.getTime());
        dest.writeString(author);
        dest.writeString(authorId);
        dest.writeString(category);
        dest.writeTypedList(comments);
    }

    public static final Creator<Joke> CREATOR = new Creator<Joke>() {
        @Override
        public Joke createFromParcel(Parcel in) {
            return new Joke(in);
        }

        @Override
        public Joke[] newArray(int size) {
            return new Joke[size];
        }
    };

    public String getText() {
        return text;
    }

    public int getVotes() {
        return votes;
    }

    public Date getPostedDate() {
        return postedDate;
    }

    public String getAuthor() {
        return author;
    }

    public String getAuthorId() {
        return authorId;
    }

    public String getCategory() {
        return category;
    }

    public List<Comment> getComments() {
        return comments;
    }

    @Override
    public int describeContents() {
        return 0;
    }


    public void JokeVoteUp(){
        votes+=1;
    }
    public void JokeVoteDown(){
        votes-=1;
    }
}

The problematic lines are in // TODO:

Update

Layout

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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=".ActivityJokeDetail">

    <include
        android:id="@+id/include"
        layout="@layout/list_item_comment"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="24dp"
        android:layout_marginLeft="24dp"
        android:layout_marginTop="32dp"
        android:layout_marginEnd="24dp"
        android:layout_marginRight="24dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/tvPostedFrom"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="32dp"
        android:layout_marginLeft="32dp"
        android:layout_marginTop="32dp"
        android:text="@string/DEPostedFrom"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/include" />

    <TextView
        android:id="@+id/tvPostedOn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="32dp"
        android:layout_marginLeft="32dp"
        android:layout_marginTop="16dp"
        android:text="@string/DEPostedOn"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/tvPostedFrom" />

    <TextView
        android:id="@+id/tvAuthor"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="32dp"
        app:layout_constraintStart_toEndOf="@+id/tvPostedFrom"
        app:layout_constraintTop_toBottomOf="@+id/include" />

    <TextView
        android:id="@+id/tvPostDate"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="16dp"
        app:layout_constraintStart_toEndOf="@+id/tvPostedFrom"
        app:layout_constraintTop_toBottomOf="@+id/tvAuthor" />

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/rvComments"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="32dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="1.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/etNewComment" />

    <EditText
        android:id="@+id/etNewComment"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="32dp"
        android:ems="10"
        android:hint="@string/DEAddComment"
        android:inputType="textPersonName"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/tvPostDate" />

    <Button
        android:id="@+id/btSendComment"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="32dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:text="@string/DESend"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/tvPostDate" />

</androidx.constraintlayout.widget.ConstraintLayout>

Answer 1

Assuming that you have whole layout in one file for activity and assuming they are really present in the layout.

You do not really need to use include variable.

instead of:

tvAuthor = include.findViewById(R.id.tvAuthor);

use:

tvAuthor = findViewById(R.id.tvAuthor);

Answer 2

You can't set a int value to the TextView field, it crashed the app. Either you need to concat with a string or use String.valueof

int value = 23;
 tvAuthor.setText(String.valueof(value));