Intent nullPointer Exception

Question

I know here exists a lot of topics with this header but I am new on android developing and tried many things but don't reach a solution.

I have a MainClass with a TextView. The MainClass calls a Method in a second Class ("Check"). The second Class should only create an intent with a string which i print out in textview of the mainClass. (Later it should be more complex but first I have to get that).

Here my Code of MainClass:

    package com.projektarbeit;

    import android.app.Activity;
    import android.content.Intent;
    import android.os.Bundle;
    import android.widget.TextView;

    public class MainActivity extends Activity {

        public static TextView output = null;

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

            //Variable initialisieren
            output = (TextView) findViewById(R.id.output);
            //App gestartet ausgeben
            output.setText("App started");

            Check check1 = new Check();
            check1.doCheck();

            Intent intent = getIntent();
            String myString = intent.getStringExtra("Test");
            output.setText(myString);
        }
    }

Here my Code of CheckClass:

    package com.projektarbeit;

    import android.app.Activity;
    import android.content.Intent;
    import android.os.Bundle;
    import android.view.Menu;
    import android.view.MenuItem;

    public class Check extends Activity {

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

        public void doCheck (){

            Intent intent = new Intent(getApplicationContext(), MainActivity.class);
            intent.putExtra("Test", "This is a test");
            startActivity(intent);

        }

    }

Am I totally wrong or what is my mistake?

you can use startActivityforResult see this example http://developer.android.com/intl/es/training/basics/intents/result.html — Rajesh, Nov 10 '15 at 04:50
i think because of its context its throwing null pointer exception .Can you share crashlog — Parag Chauhan, Nov 10 '15 at 04:54

score 4 · Answer 1 · answered Nov 10 '15 at 04:37

4

Why you are using Intent, What exactly you want to do?

If you really want to check only string then following Piece of code will work:

 public String doCheck (){ 

   return "This is a test";

 }

And to set this text in your textView you just have to call this method like this:

    output.setText(check1.doCheck());

answered Nov 10 '15 at 04:37

Anjali

1
1
13
20

because the method doCheck is in an other acivity than the TextView. And I want to handle the result in the view of the MainActivity! – HobbyCoder Nov 11 '15 at 13:30

score 0 · Answer 2 · edited May 23 '17 at 12:31

0

Check check1 = new Check();  
check1.doCheck();

You should not instantiate an Activity.
To start Check from your MainActivity you should do something like this:

Intent intent = new Intent(MainActivity.this, Check.class);
startActivity(intent);

Also, as Md. Dinar has suggested, don't forget to declare the Activity on your AndroidManifest file.

edited May 23 '17 at 12:31

Community

1
1

answered Nov 10 '15 at 04:58

rlukas

16
2

I tried it like you promt here but than the Textview is emtpy :( – HobbyCoder Nov 11 '15 at 13:31

score -1 · Answer 3 · answered Nov 10 '15 at 04:34

-1

Have you added your activities in android manifest? If yes Try

Intent intent = new Intent(Check.this, MainActivity.class);

instead of

Intent intent = new Intent(getApplicationContext(), MainActivity.class);

answered Nov 10 '15 at 04:34

Mohammad Mahmudul Hasan

189
2
12

If activity is not added to AndroidManifest.xml then error will be "ClassNotFound" not "NullPointer". – Chirag Savsani Nov 10 '15 at 04:37

Intent nullPointer Exception

3 Answers3