Tip calculator

package com.example.viraj.tipcalculator;

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

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    private EditText enteramount;
    private SeekBar seekbar_tip_sleekbar;
    private TextView seekbar_text_amount;
    private Button caluclate_button;
    private TextView text_your_tip_is;
    private TextView total_amount_final;

    private int seekbarpercentage;
    private float enterbillfloat;

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

        enteramount = (EditText) findViewById(R.id.id_enteramount);
        seekbar_tip_sleekbar = (SeekBar) findViewById(R.id.id_seekbar);
        seekbar_text_amount = (TextView) findViewById(R.id.id_text_seekpercentage);
        caluclate_button = (Button) findViewById(R.id.id_submitbutton);
        text_your_tip_is = (TextView) findViewById(R.id.id_text_yourtip_is);
        total_amount_final = (TextView) findViewById(R.id.id_text_totalamount);
        //----------------------------
        seekbar_text_amount.setText("YOU SELECT " + seekbar_tip_sleekbar.getProgress() + "%");
        //-----------------------------
        caluclate_button.setOnClickListener(this);
        //-----------------------------
        seekbar_tip_sleekbar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {

            @Override
            public void onProgressChanged(SeekBar seekBar, int i, boolean b) {
                seekbar_text_amount.setText("YOU SELECT " + String.valueOf(seekbar_tip_sleekbar.getProgress()) + "%");
            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {
                Toast.makeText(getApplicationContext(), "START", Toast.LENGTH_LONG).show();
            }

            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {
                seekbarpercentage = seekbar_tip_sleekbar.getProgress();
                //Toast.makeText(getApplicationContext(), "STOP", Toast.LENGTH_LONG).show();
            }
        });
    }

    //-----------------------------
    @Override
    public void onClick(View view) {
        calculate();
    }

    public void calculate() {
        float result = 0.0f;
        if (!enteramount.getText().toString().equals("")) {

            enterbillfloat = Float.parseFloat(enteramount.getText().toString());
            result=(enterbillfloat*seekbarpercentage/100);
            text_your_tip_is.setText("TIP ->" + String.valueOf(result));

            total_amount_final.setText("TOTAL AMOUNT IS ->"+ String.valueOf(enterbillfloat + result)+"- RS");

        } else {
Toast.makeText(getApplicationContext(), "PLZ ENTER AMOUNT", Toast.LENGTH_LONG).show();
        }

    }
}

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.viraj.tipcalculator.MainActivity">

    <EditText
        android:id="@+id/id_enteramount"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="16dp"
        android:ems="10"
        android:hint="Enter amount"
        android:inputType="number"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.503"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="32dp"
        android:text="SELECT TIP PERCENTAGE"
        android:textSize="24sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/id_enteramount" />

    <SeekBar
        android:id="@+id/id_seekbar"
        android:layout_width="297dp"
        android:layout_height="26dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="32dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.507"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView" />

    <TextView
        android:id="@+id/id_text_seekpercentage"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="36dp"
        android:text="0%"
        android:textSize="24sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/id_seekbar" />

    <Button
        android:id="@+id/id_submitbutton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="40dp"
        android:text="Button"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/id_text_seekpercentage" />

    <TextView
        android:id="@+id/id_text_yourtip_is"
        android:layout_width="130dp"
        android:layout_height="32dp"
        android:layout_marginEnd="208dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="28dp"
        android:text="YOUR TIP IS"
        android:textSize="24sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/id_submitbutton" />

    <TextView
        android:id="@+id/id_text_totalamount"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="28dp"
        android:text="YOUR TOTAL AMOUNT IS "
        android:textSize="18sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.116"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/id_text_yourtip_is" />
</android.support.constraint.ConstraintLayout>