create calculator by android

Create a simple calculator consists of four operations addition, subtraction, multiplication and division using the Android system

code:

package show.a1s2.com.calproject;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    private TextView result;
    private EditText a;
    private EditText b;
    private Button add;
    private Button sub;
    private Button mul;
    private Button div;

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

        result = (TextView) findViewById(R.id.result);
        a = (EditText) findViewById(R.id.a);
        b = (EditText) findViewById(R.id.b);
        add = (Button) findViewById(R.id.add);
        sub = (Button) findViewById(R.id.sub);
        mul = (Button) findViewById(R.id.mul);
        div = (Button) findViewById(R.id.div);
        add.setOnClickListener(this);
        sub.setOnClickListener(this);
        mul.setOnClickListener(this);
        div.setOnClickListener(this);
    }

    public void onClick(View v) {
        float n1 = 0;
        float n2 = 0;
        float z = 0;

        n1 = Float.parseFloat(a.getText().toString());
        n2 = Float.parseFloat(b.getText().toString());

        if (n1 < 0 || n2 < 0) {
            result.setText("positive plz");
        } else {
            switch (v.getId()) {
                case R.id.add:
                    z = n1 + n2;
                    break;
                case R.id.sub:
                    z = n1 - n2;
                    break;
                case R.id.mul:
                    z = n1 * n2;
                    break;
                case R.id.div:
                    z = n1 / n2;
                    break;
            }
            result.setText("" + z);
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}

Results:-

create calculator by android

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