java.lang.RuntimeException: Impossible de démarrer l'activité ComponentInfo java.lang.NullPointerException

Question

Je crée une application Android pour interroger des personnes sur des sujets, le backend est écrit en Java et il lit et analyse le fichier CSV (URL codée en dur) , et l'extrémité avant est mon application Android.

Voici mon erreur:

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 

Ce qui provoque mon programme de tomber en panne.

Voilà ma classe:

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); 
    } 

Voici ma classe datawhare maison:

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); 
} 

Je pense que la question a causé peut-être parce que l'analyseur se prépare à null.

Answer 1

Placez le fichier questions.csv dans votre classpath et faire ceci:

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

Pour charger le fichier correctement.

Answer 2

Pas assez d'informations de ligne mais je pense que ClassLoader.getSystemResource("questions.csv") n'est pas ce que vous vouliez vraiment, il est très inhabituel de le voir dans Android au moins dans mon expérience.

Je mettrais le fichier dans le répertoire assets et utiliserais AssetManager pour lire le fichier.