HelloConstraint Homework

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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=".MainActivity">

    <TextView
        android:id="@+id/show_count"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        android:background="#FFFF00"
        android:gravity="center"
        android:text="@string/label_count_initial"
        android:textAlignment="center"
        android:textColor="@color/purple_500"
        android:textSize="160sp"
        android:textStyle="bold"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toEndOf="@+id/button_toast"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/button_count"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:backgroundTint="@color/purple_700"
        android:onClick="countUp"
        android:text="@string/button_label_count"
        android:textColor="@color/white"
        app:layout_constraintBottom_toBottomOf="@+id/show_count"
        app:layout_constraintStart_toStartOf="parent" />

    <Button
        android:id="@+id/button_toast"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:backgroundTint="@color/purple_200"
        android:onClick="showToast"
        android:text="@string/button_label_toast"
        android:textColor="@color/white"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="@+id/show_count" />

    <Button
        android:id="@+id/button_zero"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:backgroundTint="@android:color/darker_gray"
        android:onClick="countReset"
        android:text="@string/button_label_zero"
        android:textColor="@color/white"
        app:layout_constraintBottom_toTopOf="@+id/button_count"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button_toast" />

</androidx.constraintlayout.widget.ConstraintLayout>

MainActivity.java

package com.example.helloconstraint;

import android.content.res.ColorStateList;
import android.os.Bundle;
import android.view.View;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;

import com.example.helloconstraint.databinding.ActivityMainBinding;

public class MainActivity extends AppCompatActivity {
    private int mCount = 0;
    private int mCountBackgroundTint = 0xFF3700B3;
    private ActivityMainBinding binding;
    private boolean zeroFlag = true;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // findViewById Replacement
        // https://developer.android.com/topic/libraries/view-binding
        binding = ActivityMainBinding.inflate(getLayoutInflater());
        setContentView(binding.getRoot()); // Set Activity (UI) yang akan digunakan.
    }

    private void setShowCountText() {
        binding.showCount.setText(Integer.toString(mCount));
    }

    private void changeCountButton() {
        mCountBackgroundTint = (mCount%2 == 0) ? 0xFF3700B3 : 0xFF018786;
        binding.buttonCount.setBackgroundTintList(ColorStateList.valueOf(mCountBackgroundTint));
    }

    public void showToast(View view) {
        Toast toast = Toast.makeText(this, R.string.toast_message, Toast.LENGTH_SHORT);
        toast.show();
    }

    public void countUp(View view) {
        mCount++;

        if (mCount > 0 && zeroFlag) {
            binding.buttonZero.setBackgroundTintList(ColorStateList.valueOf(0xFFCC0000));
            zeroFlag = false;
        }
        changeCountButton();
        setShowCountText();
    }

    public void countReset(View view) {
        mCount = 0;

        if (!zeroFlag) {
            view.setBackgroundTintList(ColorStateList.valueOf(0xFFAAAAAA));
            zeroFlag = true;
        }
        changeCountButton();
        setShowCountText();
    }
}