mainactivty.java

package com.akanksha.calculator;

import androidx.appcompat.app.AppCompatActivity;

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

public class MainActivity extends AppCompatActivity {
    Button btn1, btn2, btn3, btn4, btn5, btn6, btn7, btn8, btn9, mul, div, sub, add, clear, space, zero, equal;
    EditText text1;
    float value1, value2;
    boolean eadd, esub, emul, ediv;


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

        btn1 = (Button) findViewById(R.id.btn1);
        btn2 = (Button) findViewById(R.id.btn2);
        btn3 = (Button) findViewById(R.id.btn3);
        btn4 = (Button) findViewById(R.id.btn4);
        btn5 = (Button) findViewById(R.id.btn5);
        btn6 = (Button) findViewById(R.id.btn6);
        btn7 = (Button) findViewById(R.id.btn7);
        btn8 = (Button) findViewById(R.id.btn8);
        btn9 = (Button) findViewById(R.id.btn9);

        add = (Button) findViewById(R.id.add);
        sub = (Button) findViewById(R.id.sub);
        mul = (Button) findViewById(R.id.mul);
        div = (Button) findViewById(R.id.div);

        space = (Button) findViewById(R.id.space);
        zero = (Button) findViewById(R.id.zero);
        clear = (Button) findViewById(R.id.clear);
        equal = (Button) findViewById(R.id.equal);
        text1 = (EditText) findViewById(R.id.text1);

        btn1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                text1.setText(text1.getText() + "1");
            }
        });
        btn2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                text1.setText(text1.getText() + "2");
            }
        });
        btn3.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                text1.setText(text1.getText() + "3");
            }
        });
        btn4.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                text1.setText(text1.getText() + "4");
            }
        });
        btn5.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                text1.setText(text1.getText() + "5");
            }
        });
        btn6.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                text1.setText(text1.getText() + "6");
            }
        });
        btn7.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                text1.setText(text1.getText() + "7");
            }
        });
        btn8.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                text1.setText(text1.getText() + "8");
            }
        });
        btn9.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                text1.setText(text1.getText() + "9");
            }
        });
        zero.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                text1.setText(text1.getText() + "0");
            }
        });
        space.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                text1.setText(text1.getText() + ".");
            }
        });
        add.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                value1 = Float.parseFloat(text1.getText() + "");
                eadd = true;
                text1.setText(null);
            }
        });
        sub.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                value1 = Float.parseFloat(text1.getText() + "");
                esub = true;
                text1.setText(null);
            }
        });
        div.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                value1 = Float.parseFloat(text1.getText() + "");
                ediv = true;
                text1.setText(null);
            }
        });
        mul.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                value1 = Float.parseFloat(text1.getText() + "");
                emul = true;
                text1.setText(null);
            }
        });
        equal.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                value2 = Float.parseFloat(text1.getText() + "");
                if (eadd) {
                    text1.setText((value1 + value2) + "");
                    eadd = false;
                }
                if (esub) {
                    text1.setText((value1 - value2) + "");
                    esub = false;
                }
                if (emul) {
                    text1.setText((value1 * value2) + "");
                    emul = false;
                }
                if (ediv) {
                    text1.setText((value1 / value2) + "");
                    ediv = false;
                }
            }
        });
        clear.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                text1.setText("");
            }
        });
    }
}