IMPORTANT: Remember to add your package name before you copy and paste this java code into the JustJava app's MainActivity.java file.

MainActivity.java

/**
 * IMPORTANT: Make sure you are using the correct package name. 
 * This example uses the package name:
 * package com.example.android.justjava
 * If you get an error when copying this code into Android studio, update it to match teh package name found
 * in the project's AndroidManifest.xml file.
 **/
 
 package com.example.android.justjava; 
 


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

/**
 * This app displays an order form to order coffee.
 */
public class MainActivity extends AppCompatActivity {

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

    /**
     * This method is called when the order button is clicked.
     */
    public void submitOrder(View view) {
        display(1);
    }

    /**
     * This method displays the given quantity value on the screen.
     */
    private void display(int number) {
        TextView quantityTextView = (TextView) findViewById(R.id.quantity_text_view);
        quantityTextView.setText("" + number);
    }
}

Hi there,

if you have the latest version od Android studio, you won't have the .java document, but it will be in Kotlin. You need to translate Java into the Kotlin (it is done automatically) and than you'll have only 2 issues with mainActivity and quantity_text_view. This is how it is solved:

`package com.example.justjava;

import android.R import android.os.Bundle import android.view.View import android.widget.TextView import androidx.appcompat.app.AppCompatActivity

/**

This app displays an order form to order coffee. */ class MainActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(com.example.justjava.R.layout.activity_main) }

/**
 * This method is called when the order button is clicked.
 */
fun submitOrder(view: View?) {
    display(1)
}

/**
 * This method displays the given quantity value on the screen.
 */
private fun display(number: Int) {
    val quantityTextView = findViewById<View>(com.example.justjava.R.id.quantity_text_view) as TextView
    quantityTextView.text = "" + number
}

}`

Thank you so much totally worked for me and was looking for it since so long

This is what worked for me:

/**

• IMPORTANT: Make sure you are using the correct package name.
• This example uses the package name:
• package com.example.android.justjava
• If you get an error when copying this code into Android studio, update it to match teh package name found
• in the project's AndroidManifest.xml file.
  */
  package android.example.justjava

import android.os.Bundle
import android.view.View
import android.widget.TextView
import androidx.appcompat.app.AppCompatActivity

/**

• This app displays an order form to order coffee.
  */
  class MainActivity : AppCompatActivity() {
  override fun onCreate(savedInstanceState: Bundle?) {
  super.onCreate(savedInstanceState)
  setContentView(R.layout.activity_main)
  }

  /**

  • This method is called when the order button is clicked.
    */
    fun submitOrder(view: View?) {
    display(1)
    }

  /**

  • This method displays the given quantity value on the screen.
    */
    private fun display(number: Int) {
    val quantityTextView = findViewById(R.id.quantity_text_view) as TextView
    quantityTextView.text = "" +number
    }
    }