: Attempt to invoke interface method 'int java.util.List.size()'

Question

I don't know what to do, please help

'E/AndroidRuntime: FATAL EXCEPTION: main Process: com.is2all.so2al_ijaba, PID: 13051 java.lang.RuntimeException: Unable to resume activity {com.is2all.so2al_ijaba/com.is2all.so2al_ijaba.windows_asila}: java.lang.NullPointerException: Attempt to invoke interface method 'int java.util.List.size()' on a null object reference at android.app.ActivityThread.performResumeActivity(ActivityThread.java:3103) at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:3134) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2481) at android.app.ActivityThread.-wrap11(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:5417) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) Caused by: java.lang.NullPointerException: Attempt to invoke interface method 'int java.util.List.size()' on a null object reference at com.is2all.so2al_ijaba.windows_asila.table(windows_asila.java:204) at com.is2all.so2al_ijaba.windows_asila.onResume(windows_asila.java:439) at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1258) at android.app.Activity.performResume(Activity.java:6312) at android.app.ActivityThread.performResumeActivity(ActivityThread.java:3092)'

the code :

public void table() {

        handler.removeCallbacks(run);
        count=30 ;
        rnd = rand.nextInt(mDataList.size());
        id = mDataList.get(rnd).ID ;
        btn.setText(mDataList.get(rnd).Question);
        btn2.setText(mDataList.get(rnd).Answer_1);
        btn3.setText(mDataList.get(rnd).Answer_2);
        btn4.setText(mDataList.get(rnd).Answer_3);
        btn5.setText(mDataList.get(rnd).Answer_4);
        count_b = mDataList.get(rnd).ID_answer;
        timer();
        if (mInterstitialAd.isLoaded() & rnd == 2 || rnd == 4 || rnd == 8 || rnd ==16 || rnd == 32 || rnd == 64 || rnd == 128 ) {
            handler.removeCallbacks(run);
            mInterstitialAd.show();
        }
}

    @Override
    protected void onResume() {
        super.onResume();
        table();

        SharedPreferences savechange =  this.getSharedPreferences
            ("savechange", Context.MODE_PRIVATE);
        int Point = savechange.getInt("Point",point);
        this.point = Point;
        btn7.setText("+نقط : "+point);
    }

The error results from mDataList being null. Where was it initialized? — Ian Mc, Jan 31 '18 at 17:29

score 0 · Answer 1 · answered Jan 31 '18 at 17:29

0

It looks like your "mDataList" is null, so when you call rnd = rand.nextInt(mDataList.size());

it is giving you the error.

answered Jan 31 '18 at 17:29

scottymack

78
1
9

how can i fix it – abdo Jan 31 '18 at 19:24
Where are you setting the list data? It sounds like most likely when you are trying to set the list data, it isn't actually getting set – scottymack Jan 31 '18 at 21:09

Rainmaker · Answer 2 · 2018-01-31T17:44:27.630

0

Well, the problem is stated in your log . Your mDataList is null when your activity returns from background and resumes (as it seems) and you attempt to call mDataList.size() on a null object reference

You can always add check to prevent your app from crashing

if(mDataList != null) {
   rnd = rand.nextInt(mDataList.size());
}

Maybe you initialize mDataList in onCreate and when your app returns from background it just goes directly to onResume or maybe you don't initialize it at all

edited Jan 31 '18 at 17:44

answered Jan 31 '18 at 17:31

Rainmaker

10,294
9
54
89

it steel doesn't work – abdo Jan 31 '18 at 19:24

: Attempt to invoke interface method 'int java.util.List.size()'

2 Answers2