为什么putextra没有传递价值？

Question

I'm trying to send a result from my MainActivity to SecondActivity, but it always returns a default value, not the result. I'm a begginer, if there is someone that could help me it would be nice.

I've tried everything that came to my mind, but nothing worked.

 btnPlus.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String prvi=etPrviBroj.getText().toString().trim();
                String drugi=etDrugiBroj.getText().toString().trim();
                prviBroj=Integer.parseInt(prvi);
                drugiBroj=Integer.parseInt(drugi);
                rez=prviBroj+drugiBroj; //declared as an int and set to 0
                Intent intent=new 
Intent(MainActivity.this,SecondActivity.class);
                intent.putExtra("rez",rez);
            }
        });

//and in the second activity
rezultat=getIntent().getIntExtra("rez",0);

Answer 1

in first activity :

btnSum.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        if (!edt1.getText().toString().isEmpty() && !edt2.getText().toString().isEmpty()) {
            sum = Integer.parseInt(edt1.getText().toString()) + Integer.parseInt(edt2.getText().toString());
            Intent intent = new Intent(Main2Activity.this, MainActivity.class);
            intent.putExtra("RESULT", sum);
            startActivity(intent);
            txtAns.setText("" + sum);
        } else if (edt1.getText().toString().isEmpty()) {
            edt1.setError("Please enter no1 ");
        } else if (edt2.getText().toString().isEmpty()) {
            edt2.setError("Please enter no2 ");

        }
    }
});

second activity

int sum= getIntent().getIntExtra("RESULT",0);

You can store your sum of two variables in one int variable. When you click of your second button make instant of Intent and call startactivity at that time.

Answer 2

You're creating an Intent just to set the variable you want to pass to the second activity but in your code this Intent is not linked to the new Activity. If you want to pass a value between two activities with this method, you have to start the second activity with the Intent you gave the extra value to.

Intent intent=new Intent(MainActivity.this,SecondActivity.class);
intent.putExtra("rez",rez);
startActivity(intent);

If you want to start the second activity with another Intent you have to pass the value in another way.

Answer 3

Intent intent=new Intent(MainActivity.this,SecondActivity.class);

intent.putExtra("rez",rez);

startActivity(intent);

In SecondActivity Intent intent = getIntent(); String abc = intent.getStringExtra("rez");