Why is this code throwing an error "local variable addition defined in enclosing scope should be final or effectievely final".

Question

plus.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v)
{screen.setText(screen.getText()+"+");
addition=true;
}
});

I even added "final" before addition like the below code , but now it shows float expected and not final.

plus.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v)
{screen.setText(screen.getText()+"+");
final addition=true;
}
});

Answer 1

//plus.setOnClickListener(v -> screen.setText(screen.getText() + "+"));

plus.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v)
{screen.setText(screen.getText()+"+");
addition=true;
}
});

//addition
if(screen != null){
equals.setOnClickListener(new View.OnClickListener(){

@Override
public void onClick(View v)
{

String[]x=screen.getText().toString().split("\\+");
screen.setText(String.valueOf(Integer.parseInt(x[0])+Integer.parseInt(x[1])));
}
});
}

}

}

Part-3

Answer 2

divide=(Button)findViewById(R.id.divide);
cancel=(Button)findViewById(R.id.cancel);*/
plus=(Button)findViewById(R.id.plus);
equals=(Button)findViewById(R.id.equals);
screen=(EditText)findViewById(R.id.screen);

//the hard way of showing clicks on screen
class MyListener implements View.OnClickListener {
@Override
public void onClick(View v) {
screen.setText(screen.getText() + "1");
}
}
MyListener listener = new MyListener();
one.setOnClickListener(listener);

//simplified way of showing clicks on screen

two.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v)
{screen.setText(screen.getText() + "2");}
});

//using lambda to simplify even more..
//You can now use some of the Java 8 features in Android development including lambda expression and method references.And you can use lamdas in your projects.
//With lambda expression,

Part-2

Answer 3

I think you missed the boolean type to declare, or you are doing it wrong (way).

I think something like this would be genuine, but the problem is final variables can't be changed or modified.

final boolean addition;
plus.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v)
{screen.setText(screen.getText()+"+");
addition=true;
}
});

Or if you want an alternative to this , without using final than you need to declare your addition variable as class field (something similar to the global variable).

i.g

public class MainActivity extends Activity {

//Static field
public static boolean addition;

@Override
protected void onCreate(Bundle savedInstanceState) {
//Other stuff here

plus.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v){
screen.setText(screen.getText()+"+");
addition=true;
}};
}

Answer 4

import android.app.Activity;
import android.os.Bundle;

import android.view.View;
import android.widget.Button;
import android.widget.EditText;

public class MainActivity extends Activity {

Button one,plus,two,three,four,five,six,seven,eight,nine,zero,cancel,multiply,divide,minus,equals;
EditText screen;
boolean addition;

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

// one,two etc...
one=(Button)findViewById(R.id.one);
two=(Button)findViewById(R.id.two);
/*three=(Button)findViewById(R.id.three);
four=(Button)findViewById(R.id.four);
five=(Button)findViewById(R.id.five);
six=(Button)findViewById(R.id.six);
seven=(Button)findViewById(R.id.seven);
eight=(Button)findViewById(R.id.eight);
nine=(Button)findViewById(R.id.nine);
zero=(Button)findViewById(R.id.zero);
minus=(Button)findViewById(R.id.minus);
multiply=(Button)findViewById(R.id.multiply)

Part-1