WideCountActivity

package com.hitungluas.rohim.hitungluas.fragment;

import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import com.hitungluas.rohim.hitungluas.R;

public class HitungLuasActivity extends Fragment {

    private EditText panjang, lebar;
    private Button hitung;
    private TextView luas;

    public HitungLuasActivity() {

    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState){
    View view = inflater.inflate(R.layout.activity_hitung_luas, container, false);

        panjang     = (EditText) view.findViewById(R.id.edt_panjang);
        lebar       = (EditText) view.findViewById(R.id.edt_lebar);
        hitung      = (Button) view.findViewById(R.id.btn_hitung);
        luas        = (TextView) view.findViewById(R.id.tv_luas);

        hitung.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String strPanjang = panjang.getText().toString().trim();
                String strLebar = lebar.getText().toString().trim();

                double p = Double.parseDouble(strPanjang);
                double l = Double.parseDouble(strLebar);

                double dblLuas = p * l;

                luas.setText("Luas : " + dblLuas);
            }
        });
    }
}