MainActivity.java

package com.example.android.justjava;

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

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

    @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);
    }
}

@sharad99kr

thanks
i solved my problem following your advice

but i am still wondering what is different between Replaceing package com.example.android.justjava; with package app.com.example.android.justjava; at the top of file

i think it is just making one more folder named "app" that encompass the "com" folder

please help me

Please update the code to the newest version available at Google (2.1.2 [May, 26 2016])

My Code

package com.example.justjava;

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

public class JustJava extends AppCompatActivity {

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

/**
 * 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);
}

}

2 errors: "Cannot resolve symbol 'R'" (the R. on **R.**layout.activity_main and **R.**id.quantity_text_view)

package com.example.roberto.justjava;

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

/**

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

  @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);
    }
    }

Please tell me why I am getting error here? I got errors here , priceTextView.setText(NumberFormat.getCurrencyInstance().format(number));

/**
* This method displays the given quantity value on the screen.
*/
private void displayPrice(int number) {
TextView priceTextView = (TextView) findViewById(R.id.price_text_view);
priceTextView.setText(NumberFormat.getCurrencyInstance().format(number));
}

Hi,

can anybody help me out for this line of code while i am new in android development and not have any experience in Java language too .

my code is

i am getting error at the end of this line of code "quantityTextView.setText("" + number);"

Error is : java.lang.runtimeexception java.lang.nullpointerexception

Using plateform : android studio TextView.setText("" + number)

package com.example.android.justjava;

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

/**

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

  @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);
    }
    }

Im having trouble with the practice XML code:

<TextView
    android:id="@+id/quantity_text_view"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="0"
    android:textSize="16sp"
    android:textColor= "@android:color/black"

<Button
    android:layout_height="wrap_content"
    android:layout_width="wrap_content"
    android:layout_marginTop="16dp"
    android:text="Order"
    android:onClick="submitOrder"
    android:id="@+id/button" />

It gave me an error.

Can you help

I actually had no error at all, but nothing happened when I clicked the Button. When I tried to debug the "submitOrder" Method, I noticed, that the breakpoint was completely ignored. I finally found the solution in a StackOverflow post where someone said to run "Build"-"Clean Project" ("Build" is a Menu in the top bar of Android Studio). After that everything worked as expected. Just wanted to leave this information here if someone struggles with the same problem.

i've a problem with R does not exist so pleas help for i attached with problem screen shots. i'm waiting..

I SOLVED MY PROBLEM ................. THANK YOU.

How did you solve it, just ran into the same problem now

Will, after a lot of hours spending by watching the tutorial from 1 to 31, finally I have made it, so here the answer.

note: please watch the tutorial its really an educational one, but at the same time, its confusing I guess. That is why i ended up 9 hrs of making the program to work.

code for
==== activity_main.xml=====

   <TextView
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:layout_marginBottom="16dp"
       android:text="Quantity"
       android:textAllCaps="true" />

   <LinearLayout
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:orientation="horizontal">

       <Button
           android:layout_width="48dp"
           android:layout_height="48dp"
           android:onClick="decrement"
           android:text="-" />

       <TextView
           android:id="@+id/quantity_text_view"
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:layout_marginLeft="8dp"
           android:layout_marginRight="8dp"
           android:text=""
           android:textColor="@android:color/black"
           android:textSize="16sp" />

       <Button
           android:layout_width="48dp"
           android:layout_height="48dp"
           android:onClick="increment"
           android:text="+" />

   </LinearLayout>

   <TextView
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:layout_marginTop="16dp"
       android:text="Price"
       android:textAllCaps="true" />

   <TextView
       android:id="@+id/price_text_view"
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:layout_marginTop="16dp"
       android:text=""
       android:textColor="@android:color/black"
       android:textSize="16sp" />

   <Button
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:layout_marginTop="16dp"
       android:onClick="submitOrder"
       android:text="Order" />

and the code for
=========MainActivity.java===========

package com.example.android.justjava;

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

import java.text.NumberFormat;

/**

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

  int quantity =0;

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

  /**

  • This method is called when the plus button is clicked.
    */
    public void increment(View view ){
    quantity=quantity+1;
    display(quantity);
    }

  /**
  *This method is called when the minus button is clicked.
  */
  public void decrement(View view){
  quantity=quantity-1;
  display(quantity);
  }

  /**

  • This method is called when the order button is clicked.
    /
    public void submitOrder(View view) {
    int price=quantity5;
    String priceMessage= "Total: $" + price + "\n Thank you! \n";
    displayMessage(priceMessage);
    }

  /**

  • 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);
    }

  /**

  • This method displays the given price value on the screen.
    */
    private void displayPrice(int number) {
    TextView priceTextView = (TextView) findViewById(R.id.price_text_view);
    priceTextView.setText(NumberFormat.getCurrencyInstance().format(number));
    }

  /**

  • This method displays the given text on the screen.
    */
    private void displayMessage(String message) {
    TextView priceTextView = (TextView) findViewById(R.id.price_text_view);
    priceTextView.setText(message);
    }
    }

@evolarray kindly explain what you did, i copied yours n i got another headache.... or should i go thru the 31 episodes to understand too?

You'll need to update the code a bit >>

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);
    }
}

The >>ActionBarActivity<< is depricated!

**change two things

1. ActionBarActivity into AppCompatActivity
2. see name of folder in java folder in project tree in which MainActivity File exists.....only that file should be while importing pakage in first line...
   This will definately help if you will reach upto here in comment #section****

I still gets an error with R . package.com.example.android.justjava is underlined... Could someone please help me ?

You need to Import your package.

very confused regarding the errors , the course is not up to date and the code in the notes does not open .
can anyone help me by telling the code i should right in my java file to make my code run without the errors. It would be great help

just change

ActionBarActivity-----------into---------- AppCompatActivity

all error solved

TO USE THIS:

package com.example.android.justjava;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;

/**

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

  @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);
    }
    }

Use this, Keep your package name unchanged.

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;

/**

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

  @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);
    }
    }