Prime factors of given number from editview to textview

Question

I am doing an activity in which you you write number in editview (usernumber) and then you get prime factors in textview next to it (primefactor). i used some strips of code for prime fators but I don't understand it much, so I will be thankful for any help. EDIT: Did some changes to code as suggested, but code still doesn't do anything:

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.widget.EditText;
import android.widget.TextView;

public class activityone extends AppCompatActivity {
    EditText usernumber;
    TextView primefactor;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_one);
        usernumber = (EditText) findViewById(R.id.number);
        primefactor = (TextView) findViewById(R.id.primefactor);
        usernumber.addTextChangedListener(prvoWatcher);
    }
    private final TextWatcher prvoWatcher = new TextWatcher() {

        double f,
                c;
        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {

        }

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {

        }

        @Override
        public void afterTextChanged(Editable s) {
            if (s.toString().equals("")){
                f = Double.parseDouble(s.toString());
                while (f%2==0)
                {
                    primefactor.setText(2 + " ");
                    f /= 2;
                }

                int i;
                for (i = 3; i <= Math.sqrt(f); i+= 2)
                {
                    // While i divides f, print i and divide n
                    while (f%i == 0)
                    {
                        primefactor.setText(i + " ");
                        f /= i;
                    }
                }

                // This condition is to handle the case whien
                // f is a prime number greater than 2
                if (f > 2)
                    primefactor.setText(String.valueOf(f));
            }



        }
    };
}

Thanks in advance.

Answer 1

Error is String.valueOf(int);

It expects a integer or float variable not the datatype.

Answer 2

primefactor.setText(String.valueOf(int));

That's not how it works, you can't just put a primitive type in there as an argument. Either replace int by i or by f , depending on what you want to show.

So it looks like

primefactor.setText(String.valueOf(i));

or

primefactor.setText(String.valueOf(f));

EDIT: Of course, if you want to use the i variable, you have to declare if before the for-loop, and not in it.

int i;
for (i = 3; i <= Math.sqrt(f); i+= 2)
{
    // While i divides n, print i and divide n
    while (f%i == 0)
    {
        primefactor.setText(i + " ");
        f /= i;
    }
}

Answer 3

primefactor.setText(String.valueOf(int));

什么是 int ？