java.lang.RuntimeException: Unable to start activity ComponentInfo java.lang.NullPointerException

Question

I'm building an Android app to quiz people on subjects, the backend is written in Java and it reads and parses CSV file (hard coded URL) , and the front end is my Android app.

Here is my error:

05-08 01:19:00.792: E/AndroidRuntime(790): java.lang.RuntimeException: Unable to start activity ComponentInfo{cs314.adamnick.p4/cs314.adamnick.p4.QuizTakerGUI}: java.lang.NullPointerException
05-08 01:19:00.792: E/AndroidRuntime(790):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
05-08 01:19:00.792: E/AndroidRuntime(790):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
05-08 01:19:00.792: E/AndroidRuntime(790):  at android.app.ActivityThread.access$2300(ActivityThread.java:125)
05-08 01:19:00.792: E/AndroidRuntime(790):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
05-08 01:19:00.792: E/AndroidRuntime(790):  at android.os.Handler.dispatchMessage(Handler.java:99)
05-08 01:19:00.792: E/AndroidRuntime(790):  at android.os.Looper.loop(Looper.java:123)
05-08 01:19:00.792: E/AndroidRuntime(790):  at android.app.ActivityThread.main(ActivityThread.java:4627)
05-08 01:19:00.792: E/AndroidRuntime(790):  at java.lang.reflect.Method.invokeNative(Native Method)
05-08 01:19:00.792: E/AndroidRuntime(790):  at java.lang.reflect.Method.invoke(Method.java:521)
05-08 01:19:00.792: E/AndroidRuntime(790):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
05-08 01:19:00.792: E/AndroidRuntime(790):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
05-08 01:19:00.792: E/AndroidRuntime(790):  at dalvik.system.NativeStart.main(Native Method)
05-08 01:19:00.792: E/AndroidRuntime(790): Caused by: java.lang.NullPointerException
05-08 01:19:00.792: E/AndroidRuntime(790):  at wharehouse.QuizAndroidGUI.<init>(QuizAndroidGUI.java:36)
05-08 01:19:00.792: E/AndroidRuntime(790):  at cs314.adamnick.p4.QuizTakerGUI.onCreate(QuizTakerGUI.java:38)
05-08 01:19:00.792: E/AndroidRuntime(790):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
05-08 01:19:00.792: E/AndroidRuntime(790):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
05-08 01:19:00.792: E/AndroidRuntime(790):  ... 11 more

Which causes my program to crash.

Here's my class:

public class QuizTakerGUI extends Activity {

    private RadioButton answer1;
    private RadioButton answer2;
    private RadioButton answer3;
    private RadioButton answer4;

    private Button submit; 
    private Button previous; 
    private Button next; 
    private Button finish; 

    private TextView questionArea; 

    private QuizAndroidGUI dataWharehouse;
    private QuizQuestion currentQuestion;

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

        dataWharehouse = new QuizAndroidGUI(this);

        answer1 = (RadioButton) findViewById(R.id.answer1);
        answer2 = (RadioButton) findViewById(R.id.answer2);
        answer3 = (RadioButton) findViewById(R.id.answer3);
        answer4 = (RadioButton) findViewById(R.id.answer4);

        questionArea = (TextView) findViewById(R.id.quizQuestion); 


        submit = (Button) findViewById(R.id.submitAnswer);
        previous = (Button) findViewById(R.id.prev);
        next = (Button) findViewById(R.id.next);
        finish = (Button) findViewById(R.id.finish);

        submit.setOnClickListener(submitHandler);
        previous.setOnClickListener(previousHandler);
        next.setOnClickListener(nextHandler);
        finish.setOnClickListener(finishHandler);
    }

Here's my datawhare house class:

public QuizAndroidGUI(QuizTakerGUI app){
    URL path = ClassLoader.getSystemResource("questions.csv");
    this.androidApplication = app; 
    NUMBERofQUIZES = 10; 
    // since we implement quiz ui we pass in the current program 
    quizTaker = new QuizTaker(this);
    try {
        // passing in the csv file hard coded 
        parser = new QuestionParser(new File(path.toURI()));
    } catch (FileNotFoundException e) {
        parser = null; 
        e.printStackTrace();
    } catch (URISyntaxException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    quizTaker.startAndDisplayQuiz("Android Quiz", this.NUMBERofQUIZES, this.parser);
}

I think the issue maybe caused because the parser is getting set to null.

Answer 1

Not enough line info but I suspect that ClassLoader.getSystemResource("questions.csv") isn't what you really wanted, it's highly unusual to see it in android at least in my experience.

I would put the file in assets directory and use AssetManager to read the file.

Answer 2

Put the questions.csv file into your classpath and do this:

ClassLoader loader = Thread.currentThread().getContextClassLoader();
URL resource = loader.getResource("myfile");

To load the file properly.