App crashes when I try to go to Next Activity Page in App

Question

I'm making a pretty basic 6-7 activity app, trying to keep it really simple. I've succesfully added 4 other instances where at the bottom of the app you press "NEXT" and it takes you to the next activity in the app. However, I'm stuck and can't figure out how to continue. I've tried debugging and can't figure out what the error message means. THanks for your help.

The error message from Logcat:

java.lang.IllegalStateException: Could not execute method for android:onClick
                                                                                 at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:293)
                                                                                 at android.view.View.performClick(View.java:4785)
                                                                                 at android.view.View$PerformClick.run(View.java:19884)
                                                                                 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:5343)
                                                                                 at java.lang.reflect.Method.invoke(Native Method)
                                                                                 at java.lang.reflect.Method.invoke(Method.java:372)
                                                                                 at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:905)
                                                                                 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:700)
                                                                              Caused by: java.lang.reflect.InvocationTargetException
                                                                                 at java.lang.reflect.Method.invoke(Native Method)
                                                                                 at java.lang.reflect.Method.invoke(Method.java:372)
                                                                                 at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
                                                                                 at android.view.View.performClick(View.java:4785) 
                                                                                 at android.view.View$PerformClick.run(View.java:19884) 
                                                                                 at android.os.Handler.handleCallback(Handler.java:739) 
                                                                                 at android.os.Handler.dispatchMessage(Handler.java:95) 
                                                                                 at android.os.Looper.loop(Looper.java:135) 
                                                                                 at android.app.ActivityThread.main(ActivityThread.java:5343) 
                                                                                 at java.lang.reflect.Method.invoke(Native Method) 
                                                                                 at java.lang.reflect.Method.invoke(Method.java:372) 
                                                                                 at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:905) 
                                                                                 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:700) 
                                                                              Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.CharSequence android.widget.TextView.getText()' on a null object reference
                                                                                 at com.example.android.budgeit10.expenses.fourthNext(expenses.java:86)
                                                                                 at java.lang.reflect.Method.invoke(Native Method) 
                                                                                 at java.lang.reflect.Method.invoke(Method.java:372) 
                                                                                 at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288) 
                                                                                 at android.view.View.performClick(View.java:4785) 
                                                                                 at android.view.View$PerformClick.run(View.java:19884) 
                                                                                 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:5343) 
                                                                                 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:905) 
                                                                                 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:700)

 

JAVA:

        package com.example.android.budgeit10;

    import android.content.Intent;
    import android.support.v7.app.AppCompatActivity;
    import android.os.Bundle;
    import android.text.TextUtils;
    import android.view.View;
    import android.widget.Button;
    import android.widget.EditText;
    import android.widget.TextView;

    public class expenses extends AppCompatActivity {

        AppCompatActivity appCompatActivity;
        EditText housingExpense;
        EditText foodExpense;
        EditText transportExpense;
        EditText otherExpense;
        Button expensesButton;
        TextView addExpenses;
        EditText income;

        double housing, food, transport, other, sum;


        @Override
        public void onCreate(Bundle savedInstanceState) {

            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_expenses);
            housingExpense = (EditText) findViewById(R.id.housingExpense);
            foodExpense = (EditText) findViewById(R.id.foodExpense);
            transportExpense = (EditText) findViewById(R.id.transportExpense);
            otherExpense = (EditText) findViewById(R.id.otherExpense);
            expensesButton = (Button) findViewById(R.id.expensesButton);
            addExpenses = (TextView) findViewById(R.id.totalMonthlyExpenses);
            income = (EditText) findViewById(R.id.monthlyIncome);


            expensesButton.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    housing = Double.parseDouble(housingExpense.getText().toString());
                    try {
                        Double.parseDouble(housingExpense.getText().toString());
                    } catch (NumberFormatException nfe) {
                    }
                    food = Double.parseDouble(foodExpense.getText().toString());
                    transport = Double.parseDouble(transportExpense.getText().toString());
                    other = Double.parseDouble(otherExpense.getText().toString());
                    sum = housing + food + transport + other;
                    addExpenses.setText(Double.toString(sum));

                }
            });

            expensesButton.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {


                    if (TextUtils.isEmpty(housingExpense.getText().toString()) ||
                            TextUtils.isEmpty(foodExpense.getText().toString()) ||
                            TextUtils.isEmpty(otherExpense.getText().toString()) ||
                            TextUtils.isEmpty(transportExpense.getText().toString())) {

                        addExpenses.setText("Please fill all fields."); // if any of the fields is empty, add nothing to textview

                    } else {
                        Double housing = Double.parseDouble(housingExpense.getText().toString());
                        Double food = Double.parseDouble(foodExpense.getText().toString());
                        Double transport = Double.parseDouble(transportExpense.getText().toString());
                        Double other = Double.parseDouble(otherExpense.getText().toString());
                        Double sum = housing + food + transport + other;
                        addExpenses.setText(Double.toString(sum));
                    }
                }
            });
        }
        public void fourthNext(View view) {
            Intent intent = new Intent(this, Goals.class);
            TextView textView = (TextView) findViewById(R.id.totalMonthlyIncome);

            String income = textView.getText().toString();
            startActivity(intent);

        }

XML from Button:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.android.budgeit10.incomePage">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:text="MONTHLY EXPENSES"
        android:textSize="24dp" />

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal">

        <TextView
            android:id="@+id/totalMonthlyIncome"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:paddingBottom="16dp"
            android:paddingTop="16dp"
            android:text="Enter Monthly Income"
            android:textSize="22dp"
            android:textStyle="bold" />


        <EditText
            android:id="@+id/monthlyIncome"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="@string/income_on_expenses"
            android:inputType="phone"
            android:paddingLeft="16dp"
            android:paddingRight="16dp"
            android:textSize="16dp" />

    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="2dp"
        android:background="#2E7D32" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">


        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:padding="8dp"
            android:text="HOUSING"
            android:textSize="22dp"
            android:textStyle="bold" />

        <EditText
            android:id="@+id/housingExpense"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:hint="@string/housing"
            android:inputType="phone"
            android:paddingLeft="16dp"
            android:paddingRight="16dp" />

    </LinearLayout>


    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:padding="8dp"
            android:paddingTop="16dp"
            android:text="FOOD"
            android:textSize="22dp"
            android:textStyle="bold" />

        <EditText
            android:id="@+id/foodExpense"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:hint="@string/food"
            android:inputType="phone"
            android:paddingLeft="16dp"
            android:paddingRight="16dp" />

    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:padding="8dp"
            android:paddingTop="16dp"
            android:text="TRANSPORTATION"
            android:textSize="22dp"
            android:textStyle="bold" />

        <EditText
            android:id="@+id/transportExpense"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:hint="@string/transport"
            android:inputType="phone"
            android:paddingLeft="16dp"
            android:paddingRight="16dp" />
    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:padding="8dp"
            android:paddingTop="16dp"
            android:text="EVERYTHING ELSE"
            android:textSize="22dp"
            android:textStyle="bold" />

        <EditText
            android:id="@+id/otherExpense"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:hint="@string/other"
            android:inputType="phone"
            android:paddingLeft="16dp"
            android:paddingRight="16dp" />

    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="2dp"
        android:background="#2E7D32" />

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:paddingTop="16dp">

        <Button
            android:id="@+id/expensesButton"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:background="#C8E6C9"
            android:onClick="submitOrder"
            android:padding="16dp"
            android:text="TOTAL EXPENSES"
            android:textSize="16dp"
            android:textStyle="bold" />

        <TextView
            android:id="@+id/totalMonthlyExpenses"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="@string/monthly_expenses"
            android:inputType="phone"
            android:paddingLeft="16dp"
            android:paddingRight="16dp"
            android:textSize="16dp" />
    </LinearLayout>

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:paddingTop="8dp"
            android:text="Extra $ : "
            android:textSize="24dp"
            android:textStyle="bold" />

        <TextView
            android:id="@+id/extra_cash"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="@string/extra_cash"
            android:inputType="phone"
            android:paddingLeft="16dp"
            android:paddingRight="16dp"
            android:textSize="16dp" />
    </LinearLayout>

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="horizontal">

        <Button
            android:id="@+id/fourthNext"
            android:layout_width="match_parent"
            android:layout_height="100dp"
            android:layout_alignParentBottom="true"
            android:background="#C8E6C9"
            android:onClick="fourthNext"
            android:text="NEXT"
            android:textSize="34dp">

        </Button>
    </RelativeLayout>


</LinearLayout>

Manifest:

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.android.budgeit10">

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

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

Answer 1

You should have a TextView with id 'totalMonthlyIncome' in your XML layout. (According to the Java code) Just make sure that's there and it will solve the issue.

"Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.CharSequence android.widget.TextView.getText()' on a null object reference

at com.example.android.budgeit10.expenses.fourthNext( expenses.java:86 )"

According to the logcat error is in expenses.java - line 86