Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setVisibility(int)' on a null object reference

Question

My app is crashing even though I instantiated my buttons to my activity. What am I doing wrong? Here is my xml and java code. Please help me I really need help right now. I don't know what to do. Here is my error stack:

Process: com.example.dith.finalproject3, PID: 9301
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.dith.finalproject3/com.example.dith.finalproject3.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setVisibility(int)' on a null object reference
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2913)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:193)
        at android.app.ActivityThread.main(ActivityThread.java:6669)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setVisibility(int)' on a null object reference
        at com.example.dith.finalproject3.MainActivity.expansions(MainActivity.java:193)
        at com.example.dith.finalproject3.MainActivity.onCreate(MainActivity.java:63)
        at android.app.Activity.performCreate(Activity.java:7136)
        at android.app.Activity.performCreate(Activity.java:7127)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271)

Here is my java code:

public void expansions()
{
        btnCalendar = (ImageButton) findViewById(R.id.btnCalendar);
        btnCalendarHide = (Button) findViewById(R.id.btnCalendarHide);
        expCalendar = (View) findViewById(R.id.expCalendar);
        expCalendar.setVisibility(View.INVISIBLE);
}

Written below is my XML file:

<LinearLayout
                        android:id="@+id/expCalendar"
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        android:orientation="vertical">

                        <TextView
                            android:id="@+id/txtCalendar"
                            android:layout_width="wrap_content"
                            android:layout_height="wrap_content"
                            android:padding="@dimen/spacing_large"
                            android:text="Calendar Placeholder" />

                        <View
                            android:layout_width="match_parent"
                            android:layout_height="1dp"
                            android:background="@color/grey_10" />

                        <LinearLayout
                            android:layout_width="match_parent"
                            android:layout_height="wrap_content"
                            android:gravity="end"
                            android:orientation="horizontal">

                            <Button
                                android:id="@+id/btnCalendarHide"
                                style="@style/Widget.AppCompat.Button.Borderless"
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:gravity="center"
                                android:text="HIDE" />

                        </LinearLayout>

Thank you very much enjoy your day!

Can you edit your question and include the full formatted error stack? — Mark Stewart, Mar 26 '19 at 03:58
Remove that line where you are setting the visibility of the View to GONE and try again — Beast77, Mar 26 '19 at 04:09
how do you call the `expansions()` method. Is it after `setContentView()`? — ישו אוהב אותך, Mar 26 '19 at 05:01
Possible duplicate of [What is a NullPointerException, and how do I fix it?](https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — Zoe, Mar 26 '19 at 08:33

score 0 · Answer 1 · answered Mar 26 '19 at 06:44

Your problem is here:

    expCalendar = (View) findViewById(R.id.expCalendar);
    expCalendar.setVisibility(View.INVISIBLE);

The findViewById method is returning null. This means expCalendar is null, which means you're trying to call the setVisibility method on an object that doesn't exist. The straightforward answer is to check expCalendar for nullity before you use it:

    expCalendar = (View) findViewById(R.id.expCalendar);
    if (expCalendar != null){
        expCalendar.setVisibility(View.INVISIBLE);
    }

However, that doesn't address the implied question as to whether you care about expCalendar not being found at all. Unfortunately I don't know enough about Android to help you with that one.

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setVisibility(int)' on a null object reference

1 Answers1