Question

I released a game on the android market recently and got my first error report through ACRA today. The exception is:

java.lang.NullPointerException
at com.sweee.db.AndroidDBHelper.java.util.ArrayList getScores()(SourceFile:65)
at sweee.com.screens.HighScoreScreen.void show()(SourceFile:180)
at com.badlogic.gdx.Game.void setScreen(com.badlogic.gdx.Screen)(SourceFile:59)
at sweee.com.screens.LevelDoneScreen.void render$133aeb()(SourceFile:46)
at com.badlogic.gdx.Game.void render()(SourceFile:46)
at com.sweee.main.SweeeMain.void render()(SourceFile:125)
at com.badlogic.gdx.backends.android.AndroidGraphics.void
onDrawFrame(javax.microedition.khronos.opengles.GL10)(SourceFile:452)
at android.opengl.GLSurfaceView$GLThread.guardedRun(GLSurfaceView.java:1462)
at android.opengl.GLSurfaceView$GLThread.run(GLSurfaceView.java:1216)

Through ACRA I know the device was an Acer Iconia A100 with ICS 4.03 running. I unfortuntly cannot reproduce the error on the emulator (tried connected to the internet and airplane mode). The line on which it claims to throw the NPE, is a call to my Function “isConnected()” which does this:

public boolean isConnected() {
        final ConnectivityManager connectManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);

        // Return true if connected, either in 3G or wi-fi
        final boolean connected = (connectManager.getNetworkInfo(ConnectivityManager.TYPE_MOBILE).getState() == NetworkInfo.State.CONNECTED || connectManager.getNetworkInfo(
            ConnectivityManager.TYPE_WIFI).getState() == NetworkInfo.State.CONNECTED);
        return connected;
}

I am pretty much clueless and would like to fix this bug. Is there any general problem with this method to check for an existing internet connection that is specific to ICS 4.03 or the Iconia A100?

Maybe someone who owns an Iconia A100 could do me a favor and try to reproduce the failure? The game is free on android market here. Thank you very much for your time and any possible answer or hint.

edit:

@Override
    public ArrayList<Score> getScores() {

    Cursor c = getWritableDatabase().query("scores", null, null, null, null, null, "points DESC");
    if (c.moveToFirst()) {
        do {
            Score s = new Score(c.getString(1), c.getInt(2), getBoolFromInt(c.getInt(3)), getBoolFromInt(c.getInt(4)));
            if (!scores.contains(s)) {
                scores.add(s);
            }
        } while (c.moveToNext());
    }

    if (isConnected()) {

        syncDB();
    }

    return scores;
}

this is the function that causes the NPE. Line 65 would be

if(isConnected()) {

the ArrayList scores is instantiated when the class gets (one of the first calls of the app, this does not get called before, should therefore not be null).
neither a call to scores.contains(s) nor add should cause a NPE, right?
I just don’t get it. Especially as this code is running fine on meanwhile 9 other devices…

I really appreciate any more help. Thanks!

Answer 1

I think the error is on this line

final boolean connected =
        (connectManager.getNetworkInfo(ConnectivityManager.TYPE_MOBILE).getState() == NetworkInfo.State.CONNECTED 
        || connectManager.getNetworkInfo(ConnectivityManager.TYPE_WIFI).getState() == NetworkInfo.State.CONNECTED);

That happens because (ConnectivityManager)context.getSystemService(Context.CONNECTIVITY_SERVICE); returns null.

Look at the documentation. It says
Returns: The service or null if the name does not exist. According to this, the name Context.CONNECTIVITY_SERVICE does not exist. Could it be an OS implementation issue? Probably.

I had a somewhat “similar” situation: I wanted to start an activity to handle the android.provider.Settings.ACTION_DATA_ROAMING_SETTINGS, and on my device it worked (OS 2.3.7), but on some other devices (OS version above and below 2.3.7) it didn’t work. Could it be an OS implementation issue? Most likely.

Since you can not reproduce the crash,

1. buy an Acer Iconia A100 with ICS 4.03 and test on it
2. use some trickery. By this I mean the following:

Release an update with the following code and hope that your user with the Acer Iconia updates the app:

public boolean isConnected() {
    final ConnectivityManager connectManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);

    // trickery
    if (connectManager == null) {
        throw new RuntimeException("connectManager is null!");
    }
    // end trickery

    // Return true if connected, either in 3G or wi-fi
    final boolean connected =
        (connectManager.getNetworkInfo(ConnectivityManager.TYPE_MOBILE).getState() == NetworkInfo.State.CONNECTED 
        || connectManager.getNetworkInfo(ConnectivityManager.TYPE_WIFI).getState() == NetworkInfo.State.CONNECTED);
    return connected;
}

This way you could get a crash report with this specific message. This way you could deduce some conclusions.

Anyway, if you just want to make your app work, check connectManager against null.

Hope this helps.

EDIT:

Or, just do the following:

public boolean isConnected() {
    // final ConnectivityManager connectManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);

    final ConnectivityManager connectManager = null;

    // Return true if connected, either in 3G or wi-fi
    final boolean connected =
        (connectManager.getNetworkInfo(ConnectivityManager.TYPE_MOBILE).getState() == NetworkInfo.State.CONNECTED 
        || connectManager.getNetworkInfo(ConnectivityManager.TYPE_WIFI).getState() == NetworkInfo.State.CONNECTED);
    return connected;
}

and see if the stacktrace is the same.