Have set int as final but final int cannot be assigned

Question

I am a beginner with both java and android. In an app I was trying to make, I was using the following for loop:

for(int current = 0; current < cityDetailsArray.size(); current++) {
            row = new TableRow(this);

            OnClickListener rowClickListener = new OnClickListener() {

                @Override
                public void onClick(View v) {
                    // TODO Auto-generated method stub
                    showDetailsView(cityDetailsArray.get(current)); //error - Cannot refer to a non-final variable current inside an inner class defined in a different method
                }
            };

            row.setOnClickListener(rowClickListener);
                    //rest of the loop
}

So as shown in the comment an error popped up, the fix was to add final to the int current. I did just that and then this error popped up in the final int current line:

The final local variable current cannot be assigned. It must be blank and not using a compound assignment

For which the fix is not shown, but obviously it is to remove the final. What can I do to resolve this?

Answer 1

A better option would be using enhanced for loop, so you won't need the final int variable nor the int variable:

for (final CityDetail cityDetail : cityDetailsArray) {
    OnClickListener rowClickListener = new OnClickListener() {
        @Override
        public void onClick(View v) {
            showDetailsView(cityDetail);
        }
    };
    row.setOnClickListener(rowClickListener);
    //rest of the loop
}

Note that when passing data from the current method to an anonymous class you need to use a final variable since the anonymous inner class should not be able to modify the reference (on in case of a primitive, it's value).

Answer 2

The only option you have is to declare another variable inside the for loop:

for(int current = 0; current < cityDetailsArray.size(); current++) {
            row = new TableRow(this);
            final int currentCopy = current;

            OnClickListener rowClickListener = new OnClickListener() {

                @Override
                public void onClick(View v) {
                    showDetailsView(cityDetailsArray.get(currentCopy)); 
                }
            };

            row.setOnClickListener(rowClickListener);
                    //rest of the loop
}

You of course cannot make the loop variable current final, as you are incrementing it in the increment/decrement section of the loop itself. Also, you can't use a non-final local variable inside an anonymous inner class. You could have made current an instance variable, but that is hardly an acceptable way.

So, to use current inside the anonymous class, you can create the copy of that variable, and make currentCopy final. So for each iteration of the loop, you'll create a new variable having the same value as current, and that will serve your purpose.

Answer 3

You could create a final field in your listener and assign it the value of current.

Answer 4

declare current variable as global..

int current = 0; // declare global..

and do like this..

for(; current < cityDetailsArray.size(); current++) { row = new TableRow(this);

        OnClickListener rowClickListener = new OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                showDetailsView(cityDetailsArray.get(current)); //error - Cannot refer to a non-final variable current inside an inner class defined in a different method
            }
        };

        row.setOnClickListener(rowClickListener);
                //rest of the loop

}