/MainActivity.java

DDXG · 2016-07-11T12:52:46Z

vinyllover · 2016-07-12T19:35:02Z

For me, two changes resolved all errors and allowed my app to run.

make sure the package referenced in the first line has the same name as the package named under java
change the reference to ActionBarActivity into a reference to AppCompatActivity.

I hope this helps.

Nahidaa · 2016-07-12T20:38:04Z

@SumanUtd
@Rohit5479
@aryansaurabhbhardwaj

You guys can try adding an id to the"0" TextView to say android:id="@+id/zero_text_view" then going in the MainActivity.java and changing it where you see:

private void display(int number) {
TextView quantityTextView = (TextView) findViewById(
R.id.quantity_text_view);
quantityTextView.setText("" + number);

so it looks like this:

private void display(int number) {
TextView zeroTextView = (TextView) findViewById(
R.id.zero_text_view);
zeroTextView.setText("" + number);

it worked for me :)

suuuukheeee · 2016-07-13T04:46:45Z

@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

jmandl · 2016-07-19T01:33:33Z

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);
}

}

ghost · 2016-07-22T16:08:49Z

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);
  }
  }

hassanAzeet · 2016-07-24T12:46:38Z

jamal3e · 2016-08-29T16:25:19Z

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));
}

vikrmgodara · 2016-08-31T07:46:46Z

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);
  }
  }

Howie2017 · 2016-10-07T19:17:43Z

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

marioseifert · 2016-12-21T13:15:36Z

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.

BappaDas · 2017-01-15T10:05:17Z

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

BappaDas · 2017-01-15T10:11:39Z

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

kenny-io · 2017-03-31T13:38:53Z

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

evolarray · 2017-10-22T15:52:57Z

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);
  }
  }

forchx · 2017-12-11T18:04:37Z

@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?

rifatkhanweb · 2018-02-05T09:20:11Z

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!

vipul1999 · 2019-03-02T13:26:19Z

**change two things

ActionBarActivity into AppCompatActivity
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****

sourav2002 · 2020-10-16T10:33:41Z

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.

Vaibhav-Tiwari · 2021-05-28T13:14:36Z

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

shamimekps · 2021-06-24T21:01:31Z

just change

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

all error solved

FelippeGomes · 2021-08-13T13:04:12Z

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);
  }
  }

PangPang1999 · 2022-05-14T09:30:45Z

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);
  }
  }

/MainActivity.java

DDXG commented Jul 11, 2016

vinyllover commented Jul 12, 2016

Nahidaa commented Jul 12, 2016 •

edited

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suuuukheeee commented Jul 13, 2016

jmandl commented Jul 19, 2016

ghost commented Jul 22, 2016

hassanAzeet commented Jul 24, 2016

jamal3e commented Aug 29, 2016 •

edited

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vikrmgodara commented Aug 31, 2016

Howie2017 commented Oct 7, 2016

marioseifert commented Dec 21, 2016

BappaDas commented Jan 15, 2017 •

edited

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BappaDas commented Jan 15, 2017

kenny-io commented Mar 31, 2017

evolarray commented Oct 22, 2017

forchx commented Dec 11, 2017

rifatkhanweb commented Feb 5, 2018 •

edited

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vipul1999 commented Mar 2, 2019 •

edited

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sourav2002 commented Oct 16, 2020

Vaibhav-Tiwari commented May 28, 2021

shamimekps commented Jun 24, 2021

FelippeGomes commented Aug 13, 2021

PangPang1999 commented May 14, 2022

	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);
	}
	}

/MainActivity.java

DDXG commented Jul 11, 2016

vinyllover commented Jul 12, 2016

Nahidaa commented Jul 12, 2016 • edited Loading

suuuukheeee commented Jul 13, 2016

jmandl commented Jul 19, 2016

My Code

ghost commented Jul 22, 2016

hassanAzeet commented Jul 24, 2016

jamal3e commented Aug 29, 2016 • edited Loading

vikrmgodara commented Aug 31, 2016

Howie2017 commented Oct 7, 2016

marioseifert commented Dec 21, 2016

BappaDas commented Jan 15, 2017 • edited Loading

BappaDas commented Jan 15, 2017

kenny-io commented Mar 31, 2017

evolarray commented Oct 22, 2017

forchx commented Dec 11, 2017

rifatkhanweb commented Feb 5, 2018 • edited Loading

vipul1999 commented Mar 2, 2019 • edited Loading

sourav2002 commented Oct 16, 2020

Vaibhav-Tiwari commented May 28, 2021

shamimekps commented Jun 24, 2021

FelippeGomes commented Aug 13, 2021

PangPang1999 commented May 14, 2022

Nahidaa commented Jul 12, 2016 •

edited

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jamal3e commented Aug 29, 2016 •

edited

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BappaDas commented Jan 15, 2017 •

edited

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rifatkhanweb commented Feb 5, 2018 •

edited

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vipul1999 commented Mar 2, 2019 •

edited

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