NullPointerException on initialized variable?

Question

I have a problem with TextView [?], I initialized textview because I want to make it scrollable but I've got an error.

public void onCreate(Bundle savedInstanceState)
{
     super.onCreate(savedInstanceState);
     dc = new DigitalClock(this);
     textViewMesssage = new TextView(this);
     dc = (DigitalClock) findViewById(R.id.digitalClock1);
     textViewMesssage = (TextView) findViewById(R.id.textV);
     textViewMesssage.setMovementMethod(new ScrollingMovementMethod());
     setContentView(R.layout.main);
     addListenerOnButton();

}
public void addListenerOnButton() {
    buttonTest = (Button) findViewById(R.id.button_id);
    buttonTest.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View arg0) {
                                  Calendar c = Calendar.getInstance();
                                  SimpleDateFormat sdf = new SimpleDateFormat("dd:MMMM:yyyy HH:mm:ss a");
                                  String strDate = sdf.format(c.getTime());
        }

    });
}

main.xml

<TextView  
    android:id="@+id/textV"
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 
    android:text="MainActivity"
    android:layout_gravity="left"
    android:scrollbars = "vertical"
    />
<Button
    android:id="@+id/button_id"  
    android:layout_width="100dp" 
    android:layout_height="wrap_content" 
    android:text="Hello"
    android:layout_gravity="right"

    />

and error

20:36:04.407 18740 XXX.X ERROR AndroidRuntime Caused by: java.lang.NullPointerException 20:36:04.407 18740 XXX.X ERROR AndroidRuntime at XXX.X.MainActivity.onCreate(MainActivity.java:40) 40 line is textViewMesssage.setMovementMethod(new ScrollingMovementMethod());

I'm using API lvl 8

Where is line 40 of MainActivity.java? – Code-Apprentice Oct 04 '14 at 20:06 — Code-Apprentice, Oct 04 '14 at 20:06
@Code-Apprentice He told that, look closer. – Dici Oct 04 '14 at 20:07 — Dici, Oct 04 '14 at 20:07

score 6 · Accepted Answer · answered Oct 04 '14 at 20:07

6

setContentView(R.layout.main); must be called before you try getting any views from the layout XML.

answered Oct 04 '14 at 20:07

gosr

4,593
9
46
82

score 2 · Answer 2 · answered Oct 04 '14 at 20:07

Put :

setContentView(R.layout.main);

at the top of onCreate, also this code makes no sense:

 dc = new DigitalClock(this);
 textViewMesssage = new TextView(this);
 dc = (DigitalClock) findViewById(R.id.digitalClock1); //<< overwrites dc, and is not present in layout

score 1 · Answer 3 · answered Oct 04 '14 at 20:09

You create a new text view with

textViewMesssage = new TextView(this);

and then promptly throw it away with

textViewMesssage = (TextView) findViewById(R.id.textV);

which can potentially return null. In this case it does because at this point in your code, you have not yet call setContentView();. Remember that you must call setContentView(); before calling findViewById(). Because of this, I suggest writing setContentView() as the second line of every onCreate() method (after super.onCreate()`).

score 0 · Answer 4 · answered Oct 04 '14 at 20:08

0

why do you need these two lines, delete them check if it works

 dc = new DigitalClock(this);
 textViewMesssage = new TextView(this);

and add

setContentView(R.layout.main);

answered Oct 04 '14 at 20:08

Shaz

302
3
13

1

This is a good observation, but doesn't solve the OP's NPE problems. – Code-Apprentice Oct 04 '14 at 20:10
@Code-Apprentice edited my answer. hope this one works – Shaz Oct 04 '14 at 20:12

NullPointerException on initialized variable?

4 Answers4

Linked