BmiApplication_java

package com.example.myapplication;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {
    // 1
    EditText etHeight;
    EditText etWeight;
    Button btnCalculate;
    TextView tvBmi;
    ImageView imageView;

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

        // 2
        etHeight = findViewById(R.id.etHeight);
        etWeight = findViewById(R.id.etWeight);
        btnCalculate = findViewById(R.id.btnCalculate);
        tvBmi = findViewById(R.id.tvBmi);
        imageView = findViewById(R.id.imageView);
    }

    public void calaculate(View view) {
        String stw = etWeight.getText().toString();
        String sth = etHeight.getText().toString();

        if (stw.length() > 0 && sth.length() > 0) {
            double weight = Double.parseDouble(stw);

            double height = Double.parseDouble(sth);

            double bmi = weight / Math.pow(height, 2);

            if (bmi >= 20 && bmi <= 24) {
                Toast.makeText(this, "Very good", Toast.LENGTH_LONG).show();
            }


            String msg = "";
            int imgId;
            if (bmi < 18) {
                msg = "too fat";
                imgId = R.drawable.bmi1;
            } else if (bmi <= 24) {
                msg = "normal";
                imgId = R.drawable.bmi2;
            } else if (bmi < 30) {
                msg = "fat";
                imgId = R.drawable.bmi3;
            } else if (bmi <= 40) {
                msg = "too fat";
                imgId = R.drawable.bmi4;
            } else {
                msg = "very very fat";
                imgId = R.drawable.bmi5;
            }

            tvBmi.setText((int) bmi + " (" + msg + ")");


            imageView.setImageResource(imgId);
            imageView.setVisibility(View.VISIBLE);
        } else {
            Toast.makeText(this, "Error: Weight or Height is empty!", Toast.LENGTH_LONG).show();
        }
    }

    public void exit(View view) {
        finish();
    }

}