getApplicationContext causes a NullPointerException

Question

I just started trying to learn development in Android Studio, and while I was trying to make my first application work ( I'm also new to stackoverflow, so sry if the way I present this thread isn't satisfactory ), I ran into a brickwall of nullpointerexceptions. I just wanted to make a button that displays a text message (toast) when I click on it. It probably is a typical newbie mistake, but I just can't seem to find out what the problem is exactly. Can somebody enlighten me please?

The relevant part of the error message as far as I can tell is:

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.Context android.content.Context.getApplicationContext()' on a null object reference

Heres the code:

public class FirstActivity extends AppCompatActivity {

    private static FirstActivity instance;



    Context context = getApplicationContext();
    CharSequence text = "A text that appears for a short time";
    int duration = Toast.LENGTH_SHORT;

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


    }

    public void buttonclick(View view){
        Toast toast1 = Toast.makeText(context,text,duration);

    }

}

and the xml:

    <?xml version="1.0" encoding="utf-8"?>
    <android.support.constraint.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="com.rayaqin.myfirstandroidapp.FirstActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="259dp"
        android:text="Press Me"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Me"
        tools:layout_editor_absoluteX="-498dp"
        tools:layout_editor_absoluteY="527dp"
        android:onClick="buttonclick"/>

</android.support.constraint.ConstraintLayout>

Possible duplicate of [What is a NullPointerException, and how do I fix it?](http://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — EJoshuaS - Stand with Ukraine, May 16 '17 at 20:32

score 3 · Accepted Answer · answered May 14 '17 at 09:02

3

getApplicationContext() is an instance method and you're trying to call it from a static context.

Simply move it to onCreate().

But Activity doesn't need application Context as itself it extends it. Use this in

Toast toast1 = Toast.makeText(this,text,duration);

and to show it

Toast.makeText(this,text,duration).show();

answered May 14 '17 at 09:02

LukeJanyga

1,115
9
16

thanks for the answer, now I understand this whole thing a bit more cheers – rayaqin May 14 '17 at 09:15

score 0 · Answer 2 · answered May 14 '17 at 09:03

0

You should do that assignment in onCreate().

And use context = this;.

answered May 14 '17 at 09:03

greenapps

11,154
2
16
19

Haris ali · Answer 3 · 2017-05-14T09:15:51.977

-2

Just replace your toast with

Toast toast1 = Toast.makeText(this,text,duration).show();

edited May 14 '17 at 09:15

answered May 14 '17 at 09:03

Haris ali

773
1
13
19

getApplicationContext causes a NullPointerException

3 Answers3