While storing and accessing an array from another class getting "java.lang.NullPointerException: Attempt to read from null array" error

Question

I am trying to access an array przezwiska located in data.java from my AlarmReciever. The array is used to access a random position from the array in order to generate a notification. I imported the data file, but after i compile it and run, i get java.lang.NullPointerException: Attempt to read from null array.

My AlarmReciever.java:

public void onReceive(Context context, Intent intent) {

    int x = (int) getRandomNumber();

    long when = System.currentTimeMillis();
    NotificationManager notificationManager = (NotificationManager) context
            .getSystemService(Context.NOTIFICATION_SERVICE);

    Intent notificationIntent = new Intent(context, MainActivity.class);
    notificationIntent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);

    PendingIntent pendingIntent = PendingIntent.getActivity(context, 0,
            notificationIntent, PendingIntent.FLAG_UPDATE_CURRENT);

    Uri alarmSound = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);

    NotificationCompat.Builder mNotifyBuilder = new NotificationCompat.Builder(
            context).setSmallIcon(R.mipmap.ic_launcher)
            .setContentTitle("My title text "+ data.przezwiska[x] + data.sercoweOczyStr)
            .setContentText("My content text " + data.smileyStr).setSound(alarmSound)
            .setAutoCancel(true).setWhen(when)
            .setContentIntent(pendingIntent)
            .setVibrate(new long[]{500, 250, 250, 250});
    notificationManager.notify(0, mNotifyBuilder.build());
}

data.java:

package com.example.palidon.myapplication.Data;

public class data {


public static int kotekSerce = 0x1F63B;
public static int slonce = 0x1F31E;
public static int sercoweOczy = 0x1F60D;
public static int serce = 0x1F49E;
public static int zloteSerce = 0x1F49B;
public static int smiley = 0x1F60A;


public static String kotekSerceStr = getEmojiByUnicode(kotekSerce);
public static String slonceStr = getEmojiByUnicode(slonce);
public static String sercoweOczyStr = getEmojiByUnicode(sercoweOczy);
public static String serceStr = getEmojiByUnicode(serce);
public static String smileyStr = getEmojiByUnicode(smiley);

public static String[] przezwiska;

public static void main(String[] args) {

    przezwiska = new String[20];
    przezwiska[0] = "kotku! " + kotekSerceStr;
    przezwiska[1] = "słońce! " + slonceStr;
    przezwiska[2] = "kochanie! " + serceStr;
    }
}

Ben P. · Accepted Answer · 2018-08-07 18:03:47Z

2

Change your main() method into a static initializer. This:

public static void main(String[] args) {

    przezwiska = new String[20];
    przezwiska[0] = "kotku! " + kotekSerceStr;
    przezwiska[1] = "słońce! " + slonceStr;
    przezwiska[2] = "kochanie! " + serceStr;
}

should become this:

static {
    przezwiska = new String[20];
    przezwiska[0] = "kotku! " + kotekSerceStr;
    przezwiska[1] = "słońce! " + slonceStr;
    przezwiska[2] = "kochanie! " + serceStr;
}

You need to do this because nothing about the Android system will call the main() method for you, so your array will never be initialized. A static initializer block, on the other hand, will be automatically called, so your array will be correctly initialized when you try to use it.

answered Aug 7, 2018 at 18:03

Ben P.

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1 Comment

Palidon Over a year ago

Thank you for the explanation. That solved my problem.

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