package com.example.aplikacja3;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.TextView;

import org.w3c.dom.Text;

public class MainActivity extends AppCompatActivity {

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

        int orderCount=0;
        public void sendOrder(View view) {
            ++orderCount;
            TextView textView = (TextView) findViewById(R.id.order_count);
            textView.setText(""+orderCount);
        }
      //Log.d("HelloWorldApplication", "orderCount: "+ orderCount)
    }

--------------------
<?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">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <TextView
            android:id="@+id/textView"
            android:layout_width="64dp"
            android:layout_height="38dp"
            android:text="Ilość"
            android:textSize="24sp" />

        <TextView
            android:id="@+id/order_count"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="0"
            android:textSize="24sp" />

        <Button
            android:id="@+id/button"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:onClick="sendOrder"
            android:text="Zamów" />

    </LinearLayout>

</androidx.constraintlayout.widget.ConstraintLayout>