Android Donation Homework

package com.example.matan.donationhomework2;

import android.content.res.ColorStateList;
import android.graphics.Color;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.animation.Animation;
import android.view.animation.Transformation;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.NumberPicker;
import android.widget.ProgressBar;
import android.widget.RadioGroup;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    double payPalToDollar = 1 / 3.5;
    double sum = 0;
    double currentPercent = 0;
    double bitCoinToDollar = 3000 / 3.5;
    double target = 10000;

    private Button btnDonate;
    private RadioGroup rgMethod;
    private NumberPicker npAmount;
    private ProgressBar progressBar;
    private TextView txtPercent;
    private TextView txtAmount;
    private ImageView imageView;


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

    private void init() {
        btnDonate = findViewById(R.id.btnDonate);
        rgMethod = findViewById(R.id.rgMethod);
        npAmount = findViewById(R.id.npAmount);
        progressBar = findViewById(R.id.progressBar);
        txtPercent = findViewById(R.id.txtPercent);
        txtAmount = findViewById(R.id.txtAmount);
        imageView = findViewById(R.id.imageView);


        npAmount.setMinValue(1);
        npAmount.setMaxValue(1000);

        btnDonate.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View view) {
                int radioId = rgMethod.getCheckedRadioButtonId();
                sum += radioId == R.id.rbPaypal? payPalToDollar * (double)npAmount.getValue() : bitCoinToDollar * (double)npAmount.getValue();
                double future = (sum / target) * 100;
                ProgressBarAnimation anim = new ProgressBarAnimation(progressBar, currentPercent, future);
                anim.setDuration(500);
                progressBar.startAnimation(anim);
                currentPercent = (sum / target) * 100;
                txtPercent.setText((int)currentPercent + "%");
                txtAmount.setText((int) sum  + "$/10000$");
                System.out.println(sum + " HI   " + future );

                if(currentPercent >= 25){
                    progressBar.setProgressTintList(ColorStateList.valueOf(Color.GREEN));
                }if(currentPercent >= 50){
                    progressBar.setProgressTintList(ColorStateList.valueOf(Color.BLACK));
                }if(currentPercent >= 75) {
                    progressBar.setProgressTintList(ColorStateList.valueOf(Color.BLUE));
                }if(currentPercent >= 100) {
                    imageView.setVisibility(View.VISIBLE);
                }

                int amount = npAmount.getValue();
                String method = radioId == R.id.rbPaypal ? "Paypal" : "Bitcoin";
                Toast.makeText(getApplicationContext(), "You donated " + amount + " via " + method, Toast.LENGTH_SHORT).show();
            }
        });
    }

    public class ProgressBarAnimation extends Animation {
        //ProgressBar progressBar;
        private double from;
        private double to;

        public ProgressBarAnimation(ProgressBar progressBar, double from, double to) {
            super();
            //this.progressBar = progressBar;
            this.from = from;
            this.to = to;
        }

        @Override
        protected void applyTransformation(float interpolatedTime, Transformation t) {
            super.applyTransformation(interpolatedTime, t);
            double value = from + (to - from) * interpolatedTime;
            progressBar.setProgress((int) value);
        }
    }
}



XML:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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.matan.donationhomework2.MainActivity">

    <TextView
        android:id="@+id/txtTitle"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:text="Welcome..."
        android:textSize="30sp"
        android:textStyle="bold" />

    <TextView
        android:id="@+id/txtSubtitle"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/txtTitle"
        android:text="Please give me money..."
        android:textSize="16sp" />

    <RadioGroup
        android:id="@+id/rgMethod"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentStart="true"
        android:layout_below="@id/txtSubtitle">

        <RadioButton
            android:id="@+id/rbPaypal"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:checked="true"
            android:text="Paypal" />

        <RadioButton
            android:id="@+id/rbBitcoin"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Bitcoin" />

    </RadioGroup>

    <NumberPicker
        android:id="@+id/npAmount"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignEnd="@id/txtTitle"
        android:layout_alignParentEnd="true"
        android:layout_alignTop="@id/rgMethod">

    </NumberPicker>

    <ProgressBar
        android:id="@+id/progressBar"
        style="@style/Base.Widget.AppCompat.ProgressBar.Horizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_above="@+id/btnDonate"
        android:layout_alignParentStart="true"
        android:layout_marginBottom="64dp" />

    <Button
        android:id="@+id/btnDonate"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:text="Donate" />

    <TextView
        android:id="@+id/txtPercent"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/progressBar"
        android:layout_centerHorizontal="true"
        android:text="0%"
        android:textStyle="bold" />

    <TextView
        android:id="@+id/txtAmount"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/progressBar"
        android:layout_alignParentStart="true"
        android:text="0$/10000$"
        android:textStyle="bold" />

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:src="@drawable/congratulations"
        android:visibility="invisible" />

    <TextView
        android:id="@+id/txtPaypal"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentStart="true"
        android:layout_below="@+id/rgMethod"
        android:text="Paypal = 1₪" />

    <TextView
        android:id="@+id/txtBitcoin"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentStart="true"
        android:layout_below="@+id/txtPaypal"
        android:text="Bitcoin = 3000₪" />

</RelativeLayout>