Java - Cannot refer to a non-final variable

Question

New to android. What should I edit to get rid of a strange "cannot refer to a non-final variable button inside an inner class defined in a different method?

@Override
    public void onCreate(Bundle SavedInstanceState) {
        super.onCreate(SavedInstanceState);
        setContentView(R.layout.activity_main);
        Button button1 = (Button)findViewById(R.id.button1);
        Button button2 = (Button)findViewById(R.id.button2);
        //Listeneři
        button1.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                button1.setText("ok");

Did you try googling what the error means? Its not an android specific problem, its a Java related problem. — JoxTraex, Oct 26 '13 at 13:44

score 2 · Answer 1 · edited Jun 20 '20 at 09:12

What you are doing is not possible.

JLS # chapter 8

Any local variable, formal parameter, or exception parameter used but not declared in an inner class must be declared final.

Any local variable used but not declared in an inner class must be definitely assigned (§16) before the body of the inner class.

Make that variable as final before using it in innerclass,So that you can get permission to use it.

final Button button1 = (Button)findViewById(R.id.button2);

Like wise, make remaining also final, If you are using them inside listener..

score 1 · Accepted Answer · answered Oct 26 '13 at 11:58

Change to this..

 final Button button1 = (Button)findViewById(R.id.button2);
    //Listeneři
    button1.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            button1.setText("ok");

or

you can declare the button variable reference as global..

score 0 · Answer 3 · answered Oct 26 '13 at 12:00

0

You need to set the button variables as 'final' as below

final Button button1 = (Button)findViewById(R.id.button1);
final Button button2 = (Button)findViewById(R.id.button2);

so,that button1 and button2 cannot be re-initialized.

answered Oct 26 '13 at 12:00

Keerthivasan

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Why `button2` should be final ? – Alexis C. Oct 26 '13 at 12:01
we need to make any references as final before we attach listeners to them. so, that it will ensure that there is no change after listeners are set – Keerthivasan Oct 26 '13 at 12:02
Assuming button2 is also gonna be attached to listener. – Keerthivasan Oct 26 '13 at 12:04
Awesome. I got another error, tho: onclicklistener cannot be resolved to a type? – Oct 26 '13 at 12:05
@user2890391 You just `import` that. – Suresh Atta Oct 26 '13 at 12:06
that's it :) it will do – Keerthivasan Oct 26 '13 at 12:09
onClickListener is already imported. I also have a problem: onclicklistener is not applicable for teh argumentz: new onClickListener – Oct 26 '13 at 12:10
@user2890391 Post complete code, You may have some syntax error. – Suresh Atta Oct 26 '13 at 12:11

score 0 · Answer 4 · answered Oct 26 '13 at 12:05

try this...

 @Override
 public void onCreate(Bundle SavedInstanceState) {
    super.onCreate(SavedInstanceState);
    setContentView(R.layout.activity_main);
    Button button1 = (Button)findViewById(R.id.button1);
    Button button2 = (Button)findViewById(R.id.button2);
    //Listeneři
    button1.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            Button button = (Button)v;
            button.setText("ok");
        }
    }

no need make the variable as final also...

score 0 · Answer 5 · answered Oct 26 '13 at 12:10

Are you using Eclipse? If so, using the quick fix menu will help you solve issues such as non-final variables, and missing import statements.

http://help.eclipse.org/juno/index.jsp?topic=%2Forg.eclipse.jdt.doc.user%2Fconcepts%2Fconcept-quickfix-assist.htm

On Windows, place the cursor on the error and press Ctrl+1 to open the quick fix menu. Pressing enter will (usually) solve the error satisfactorily.

score 0 · Answer 6 · answered Oct 26 '13 at 12:26

U have two ways to slove the problem, 1. change Button button1 = (Button)findViewById(R.id.button1);

to final Button button1 = (Button)findViewById(R.id.button1);

2.define the button1 out of the function.like this:

public class MainActivity extends Activity
{
    Button button1 = (Button)findViewById(R.id.button1);
    Button button2 = (Button)findViewById(R.id.button2);
@Override
public void onCreate(Bundle SavedInstanceState) {
    super.onCreate(SavedInstanceState);
    setContentView(R.layout.activity_main);

    //Listeneři
    button1.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            button1.setText("ok");

Surely that will try to find the buttons when the activity is created (ie before onCreate is called), but the buttons don't exist until setContentView is called...? — Jules, Oct 26 '13 at 13:03

Java - Cannot refer to a non-final variable

6 Answers6