Why value I'm trying to invoke method setVisibility() is null?

Question

I have this stack trace from Firebase Craslytics:

Fatal Exception: java.lang.NullPointerException Attempt to invoke virtual method 'void android.widget.ImageView.setVisibility(int)' on a null object reference com.accenture.vrmobile.BaseActivity.setDrawerVisibility(BaseActivity.java:497)

It's reporting crash in this method:

    public void setDrawerVisibility(Boolean visible) {
    if (mButtonActionBarLeft == null)
        mButtonActionBarLeft = (ImageView) findViewById(R.id.button_actionbar_left);
    if (mButtonActionBarRight == null)
        mButtonActionBarRight = (ImageView) findViewById(R.id.button_actionbar_right);
    if (visible) {
        mButtonActionBarLeft.setVisibility(View.VISIBLE); //crashes at this line
        mButtonActionBarRight.setVisibility(View.VISIBLE);
    } else {
        mButtonActionBarLeft.setVisibility(View.INVISIBLE);
        mButtonActionBarRight.setVisibility(View.INVISIBLE);
    }
}

I had this crash before, so I added these lines to the method:

if (mButtonActionBarLeft == null)
        mButtonActionBarLeft = (ImageView) findViewById(R.id.button_actionbar_left);
    if (mButtonActionBarRight == null)
        mButtonActionBarRight = (ImageView) findViewById(R.id.button_actionbar_right);

But it's still crashing and reporting nullPointerException. mButtonActionBarLeft and mButtonActionBarRight are buttons that opens/closes navigation drawer. I have no idea why is this happening. Maybe someone has experience with this? Thank you!

P.S. I was never able to reproduce this crash, it happens really rarely. I only have stack trace from Firebase.

Normally it is. It's a navigation drawer button. But as I wrote before I can't reproduce this crash. — Sandra Boguša, Jul 04 '18 at 12:08

score 0 · Answer 1 · answered Jul 04 '18 at 12:11

Create the instance of your ImageView into your Activity onCreate() callback

also make sure that you are creating instance which is present in your layout file with given id.

public void onCreate(Bundle savedInstanceState)
{
        if (mButtonActionBarLeft == null)
            mButtonActionBarLeft = (ImageView) findViewById(R.id.button_actionbar_left);
        if (mButtonActionBarRight == null)
            mButtonActionBarRight = (ImageView) findViewById(R.id.button_actionbar_right);
}

Learn more about NullPointerException:-What is a NullPointerException, and how do I fix it?

Thank you! But I'll already have that. And crash is still happening — Sandra Boguša, Jul 05 '18 at 07:04

score 0 · Answer 2 · answered Jul 04 '18 at 12:23

0

you must add View as input of function. for example,

public void setVisible(View view){
    view.setVisibility(View.VISIBLE);
}
setVisible(toolbarText);

answered Jul 04 '18 at 12:23

Mehrdad

1,477
15
17

Thank you for answer! I don't really see how this changes anything. Why do I need to add view to input? – Sandra Boguša Jul 05 '18 at 07:02
because you can change all Views visibility. this is better – Mehrdad Jul 05 '18 at 08:31

score 0 · Answer 3 · answered Jul 04 '18 at 13:24

Try this

    if (visible) {
        if(mButtonActionBarLeft.getVisibility()==View.INVISIBLE)
            mButtonActionBarLeft.setVisibility(View.VISIBLE);
        if(mButtonActionBarRight.getVisibility()==View.INVISIBLE)
            mButtonActionBarRight.setVisibility(View.VISIBLE);
    } else {
        if(mButtonActionBarLeft.getVisibility()==View.VISIBLE)
            mButtonActionBarLeft.setVisibility(View.INVISIBLE); 
        if(mButtonActionBarRight.getVisibility()==View.VISIBLE)
            mButtonActionBarRight.setVisibility(View.INVISIBLE);
    }

Thank you! But the problem is, that you can't call get/set visibility on Null. What you are going here is just adding more of those calls. — Sandra Boguša, Jul 05 '18 at 07:03

Why value I'm trying to invoke method setVisibility() is null?

3 Answers3