Null pointer Exception on .setOnClickListener

Question

I am having an issue with a click listener for a login modal submit button.

This is the error.

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference

I have a reasonable understanding of what a null pointer exception is and I have search thoroughly for an issue similar to mine. I have tried to reformat the click listener in several ways, made sure I have the correct view ID etc.

package...
import...
public class MainActivity extends ActionBarActivity implements     NavigationDrawerFragment.NavigationDrawerCallbacks {

    //Variables
    String currentPage = "";
    Stack<String> crumbs = new Stack<String>();
    //Fragment managing the behaviors, interactions and presentation of the navigation drawer.
    private NavigationDrawerFragment mNavigationDrawerFragment;
    // Used to store the last screen title. For use in {@link #restoreActionBar()}.
    public CharSequence mTitle;
    //temp
    AuthenticateUserTokenResult authenticateUserTokenResult;
    String loginErrorMessage = "";
    String loginErrorTitle = "";
    Boolean logonSuccessful = false;
    Dialog loginDialog;

    // Login EditTexts
    EditText Username;
    EditText CompanyID;
    EditText Password;
    Button Submit;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mNavigationDrawerFragment = (NavigationDrawerFragment) getSupportFragmentManager().findFragmentById(R.id.navigation_drawer);
        mTitle = getTitle();  // Set up the drawer.
        mNavigationDrawerFragment.setUp(R.id.navigation_drawer, (DrawerLayout) findViewById(R.id.drawer_layout));

        if(authenticateUserTokenResult == null) {
            attemptLogin();
        }
    }

    public void attemptLogin() {
        loginDialog = new Dialog(this,android.R.style.Theme_Translucent_NoTitleBar);
        loginDialog.requestWindowFeature(Window.FEATURE_NO_TITLE);
        loginDialog.setContentView(R.layout.login_modal);
        loginDialog.setCancelable(false);
        //loginDialog.setOnCancelListener(cancelListener);
        loginDialog.show();
        Submit = (Button)findViewById(R.id.Submit);
        Submit.setOnClickListener(new View.OnClickListener() // the error is on this line (specifically the .setOnClickListener)
        {
            @Override
            public void onClick(View v)
            {
                ClyxUserLogin user = new ClyxUserLogin();
                Username = (EditText)findViewById(R.id.Username);
                user.logon = Username.getText().toString();
                CompanyID = (EditText)findViewById(R.id.CompanyID);
                user.idCompany = Integer.parseInt(CompanyID.getText().toString());
                Password = (EditText)findViewById(R.id.Password);
                user.password = Password.getText().toString();
                user.idApplication = 142;
                authenticate(user);
            }
        });
    }

There is more, obviously, but not relevant to the topic I think. Here is the XML file for the dialog that has the button on it.

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:background="#3366FF">

    <RelativeLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:background="#FFFFFF" >

        <TextView
            android:id="@+id/LoginTitle"
            android:layout_width="200dp"
            android:layout_height="wrap_content"
            android:gravity="center_horizontal"
            android:layout_marginTop="10dp"
            android:layout_marginStart="10dp"
            android:textColor="#000000"
            android:textSize="20sp"
            android:text="Login" />

        <EditText
            android:id="@+id/Username"
            android:layout_width="200dp"
            android:layout_height="wrap_content"
            android:layout_below="@+id/LoginTitle"
            android:layout_margin="10dp"
            android:hint="Username" />

        <EditText
            android:id="@+id/CompanyID"
            android:layout_width="200dp"
            android:layout_height="wrap_content"
            android:layout_below="@+id/Username"
            android:layout_alignStart="@+id/Username"
            android:inputType="number"
            android:hint="Company ID" />

        <EditText
            android:id="@+id/Password"
            android:layout_width="200dp"
            android:layout_height="wrap_content"
            android:layout_below="@+id/CompanyID"
            android:layout_alignStart="@+id/Username"
            android:layout_marginTop="10dp"
            android:layout_marginBottom="10dp"
            android:inputType="textPassword"
            android:hint="Password" />

        <Button
            android:id="@+id/Submit"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_below="@+id/Password"
            android:layout_marginBottom="10dp"
            android:layout_centerHorizontal="true"
            android:text="Login" />

    </RelativeLayout>

</RelativeLayout>

Any help would be greatly appreciated.

Coming back here almost a year later and it feels good how much I've improved and leant from silly mistakes like this one. Everyone starts somewhere and I love that Stack will support you every step of the way. — Jack.Ramsden, Feb 02 '16 at 10:46
I still have this issue, just that my Button is not in the `Login Dialog`. How can I fix it, @Jack.Ramsden? — EnigmaTech, Sep 04 '18 at 12:54

score 59 · Accepted Answer · edited May 23 '17 at 11:54

59

Submit is null because it is not part of activity_main.xml

When you call findViewById inside an Activity, it is going to look for a View inside your Activity's layout.

try this instead :

Submit = (Button)loginDialog.findViewById(R.id.Submit);

Another thing : you use

android:layout_below="@+id/LoginTitle"

but what you want is probably

android:layout_below="@id/LoginTitle"

See this question about the difference between @id and @+id.

edited May 23 '17 at 11:54

Community

1
1

answered Jan 28 '15 at 13:37

2Dee

8,609
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Thank you, a good habit to get into instead of copy pasting other id's. I didn't understand the significance of the + before. Never thought to look into it. (Added as accepted for a slightly more developed answer and a little extra help) – Jack.Ramsden Jan 28 '15 at 13:45
I have a similar issue, however my button is not in a Dialog window. How do I rectify it, @2Dee? – EnigmaTech Sep 04 '18 at 12:51
1

@DerryckDX it's hard to know without seeing your code, which we shouldn't do in the comments section. Please post a new questions after having checked for duplicates. Don't forget to include all relevant code and error stacktraces. – 2Dee Sep 05 '18 at 07:51

score 8 · Answer 2 · answered Jan 28 '15 at 13:35

8

android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference

Because Submit button is inside login_modal so you need to use loginDialog view to access button:

Submit = (Button)loginDialog.findViewById(R.id.Submit);

answered Jan 28 '15 at 13:35

ρяσѕρєя K

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Wow how did I not see that. I think its because the exception points to the line below. Thanks for the help – Jack.Ramsden Jan 28 '15 at 13:38
What if my button is not inside `login_modal`, but I still get the same error, @ρяσѕρєя K? ? – EnigmaTech Sep 04 '18 at 12:50

score 0 · Answer 3 · answered Aug 11 '15 at 02:14

Try giving your Button in your main.xml a more descriptive name such as:

<Button
                android:id="@+id/buttonXYZ"

(use lowercase in your xml files, at least, the first letter)

And then in your MainActivity class, declare it as:

Button buttonXYZ;

In your onCreate(Bundle savedInstanceState) method, define it as:

buttonXYZ = (Button) findViewById(R.id.buttonXYZ);

Also, move the Buttons/TextViews outside and place them before the .setOnClickListener - it makes the code cleaner.

Username = (EditText)findViewById(R.id.Username);
CompanyID = (EditText)findViewById(R.id.CompanyID);

score 0 · Answer 4 · answered Jul 13 '18 at 12:10

I too got similar error when i misplaced the code

text=(TextView)findViewById(R.id.text);// this line has to be below setcontentview
setContentView(R.layout.activity_my_otype);
//this is the correct place
text.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            }
    });

I got it working on placing the code in right order as shown below

setContentView(R.layout.activity_my_otype);
text=(TextView)findViewById(R.id.text);
 text.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            }
    });

Null pointer Exception on .setOnClickListener

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