Setting value to static variable returns error

Question

I basically try to save the current state of mRecyclerView into a static Parcelable variable to keep it safe onPause and restore it to the mRcyclerView onResume.

Here is my static variable's class:

public class MySavedState {
private static MySavedState ourInstance = new MySavedState();

private Parcelable state;

static MySavedState getInstance() {
    if(ourInstance == null){
        ourInstance = new MySavedState();
    }
    return ourInstance;
}

private MySavedState() {
}

public Parcelable getState() {
    return state;
}

public void setState(Parcelable state) {
    this.state = state;
}

}

And here is the line where I try to set a value:

@Override
public void onPause() {
    super.onPause();

    Parcelable newState = mRecyclerView.onSaveInstanceState();
    state.setState(newState);


}

And the error message:

java.lang.RuntimeException: Unable to pause activity {com.gunaya.tasmaew/com.gunaya.tasmaew.Controller.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.gunaya.tasmaew.Model.MySavedState.setState(android.os.Parcelable)' on a null object reference
                  at android.app.ActivityThread.performPauseActivity(ActivityThread.java:3745)
                  at android.app.ActivityThread.performPauseActivity(ActivityThread.java:3704)
                  at android.app.ActivityThread.handlePauseActivity(ActivityThread.java:3679)
                  at android.app.ActivityThread.access$1100(ActivityThread.java:177)
                  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1460)
                  at android.os.Handler.dispatchMessage(Handler.java:102)
                  at android.os.Looper.loop(Looper.java:145)
                  at android.app.ActivityThread.main(ActivityThread.java:5951)
                  at java.lang.reflect.Method.invoke(Native Method)
                  at java.lang.reflect.Method.invoke(Method.java:372)
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1388)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1183)
               Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.gunaya.tasmaew.Model.MySavedState.setState(android.os.Parcelable)' on a null object reference
                  at com.gunaya.tasmaew.Controller.mListFragment.onPause(mListFragment.java:117)

And as an extra question, i keep having this error message in my debugger:

((Bundle)parce).mClassLoader = Cannot find local variable 'parce'

Thank you very much for your time guys.

MySavedState state; state is null Isn't this the proper way to declare it in my class? — Adem, Jul 17 '18 at 05:11
here is what I've got in newState before using the setter: Bundle[{layout-manager-state=android.support.v7.widget.LinearLayoutManager$SavedState@198ebe35, super-state=android.support.v7.widget.RecyclerView$SavedState@31b952ca}] — Adem, Jul 17 '18 at 05:14

score 1 · Accepted Answer · answered Jul 17 '18 at 05:17

1

Your Singleton looks OK but it looks like you are not retrieving it

MySavedState state = MySavedState.getInstance ();

answered Jul 17 '18 at 05:17

Scary Wombat

44,617
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Thank you sir, you're right. I was trying to get the variable but this pattern works with the instance. Much appreciated :) – Adem Jul 17 '18 at 05:25

Setting value to static variable returns error

1 Answers1