My first Android app after following the udacity course "One Million Arab Coders". the app calcutes the BMI after giving height and weight

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:layout_margin="10dp"
    tools:context=".MainActivity">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Calculate you MBI"
        android:textSize="20sp"
        android:padding="5dp"
        android:background="#336699"
        android:textColor="@android:color/white" />
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="14sp"
        android:padding="2dp"
        android:text="@string/BMIinfo"/>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="WEIGHT:"/>
        <EditText
            android:id="@+id/weight_edit_text"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"/>
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="KG"/>
    </LinearLayout>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:padding="5dp"
        android:orientation="horizontal">
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="HEIGHT:"/>
        <EditText
            android:id="@+id/height_edit_text"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"/>
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="CM"/>
    </LinearLayout>
    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:padding="5dp"
        android:text="Check BMI"
        android:onClick="checkBMI"/>
    <TextView
        android:id="@+id/BMI_text_view"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:padding="10dp"
        android:textSize="25sp"
        android:text="your BMI is: "/>
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="20sp"
        android:padding="5dp"
        android:background="#336699"
        android:textColor="@android:color/white"
        android:text="BMI Categories"/>
    <TextView
        android:id="@+id/underweight_text_view"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="14sp"
        android:padding="2dp"
        android:text="@string/underweight"/>
    <TextView
        android:id="@+id/normalweight_text_view"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="14sp"
        android:padding="2dp"
        android:text="@string/normalweight"/>
    <TextView
        android:id="@+id/overweight_text_view"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="14sp"
        android:padding="2dp"
        android:text="@string/overweight"/>
    <TextView
        android:id="@+id/obesity_text_view"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="14sp"
        android:padding="2dp"
        android:text="@string/obesity"/>


</LinearLayout>

mainActivity.java

package com.example.myfirstapp;

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

import java.text.NumberFormat;

import static android.graphics.Color.parseColor;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
    public void checkBMI(View view){
        EditText weight = findViewById(R.id.weight_edit_text);
        EditText height = findViewById(R.id.height_edit_text);
        double w = Double.valueOf(weight.getText().toString());
        double h = Double.valueOf(height.getText().toString());
        double BMI = w/(Math.pow(h/100,2));
        display(BMI);
        if(BMI < 18.5) {
            findViewById(R.id.underweight_text_view).setBackgroundColor(parseColor("#AAAAAA"));
        }else {
            findViewById(R.id.underweight_text_view).setBackgroundColor(parseColor("#FFFFFF"));
        }
        if(BMI >= 18.5 && BMI < 25){
            findViewById(R.id.normalweight_text_view).setBackgroundColor(parseColor("#AAAAAA"));
        } else {
            findViewById(R.id.normalweight_text_view).setBackgroundColor(parseColor("#FFFFFF"));
        }
        if(BMI >= 25 && BMI < 30){
            findViewById(R.id.overweight_text_view).setBackgroundColor(parseColor("#AAAAAA"));
        }else{
            findViewById(R.id.overweight_text_view).setBackgroundColor(parseColor("#FFFFFF"));
        }
        if(BMI >= 30){
                findViewById(R.id.obesity_text_view).setBackgroundColor(parseColor("#AAAAAA"));
        }else{
            findViewById(R.id.obesity_text_view).setBackgroundColor(parseColor("#FFFFFF"));
        }
    }
    private void display(double number){
        TextView BMITextView = findViewById(R.id.BMI_text_view);
        BMITextView.setText("your BMI is: "+ String.format("%.1f",number));
    }
}

strings.xml

<resources>
    <string name="app_name">BMI Calculator</string>
    <string name="underweight"><![CDATA[Underweight = <18.5]]></string>
    <string name="normalweight">Normal weight = 18.5–24.9</string>
    <string name="overweight">Overweight = 25–29.9</string>
    <string name="obesity">Obesity = BMI of 30 or greater</string>
    <string name="BMIinfo">BMI stands for Body Mass Index,do you have the perfect body?</string>
</resources>