Android for Beginners : Negative Number of Cups of Coffee Extra Challenge Solution

Code snippet from MainActivity.java

    /**
     * This method is called when the plus button is clicked.
     */
    public void increment(View view) {
        if (quantity == 100) {
            // Show an error message as a toast 
            Toast.makeText(this, "You cannot have more than 100 coffees", Toast.LENGTH_SHORT).show();
            // Exit this method early because there's nothing left to do
            return;
        }
        quantity = quantity + 1;
        displayQuantity(quantity);
    }

    /**
     * This method is called when the minus button is clicked.
     */
    public void decrement(View view) {
        if (quantity == 1) {
            // Show an error message as a toast 
            Toast.makeText(this, "You cannot have less than 1 coffee", Toast.LENGTH_SHORT).show();
            // Exit this method early because there's nothing left to do
            return;
        }
        quantity = quantity - 1;
        displayQuantity(quantity);
    }

it is better to write
public void decrement (View view){
if (quantity<=1){
// show an error message as a Toast.
Toast.makeText(this,"You cannot have less than 1 coffe",Toast.LENGTH_SHORT).show();
return;
// Exit this method early because there is nothing left to do.
}
quantity=quantity-1;
displayQuantity(quantity);
}
because once first implement , the decrement method get minus and the number of coffees will get less than 0 .

Why the "return;" make the method increment and decrement not go further
` public void increment(View view) {

    if (quantity == 100) {
        // Show an error message as a toast
        Toast.makeText(this, "You cannot have more than 100 coffees", Toast.LENGTH_SHORT).show();
        // Exit this method early because there's nothing left to do
        return;
    }
    quantity = quantity + 1;
    displayQuantity(quantity);

}

public void decrement(View view) {

    if (quantity == 1) {
        // Show an error message as a toast
        Toast.makeText(this, "You cannot have less than 1 coffee", Toast.LENGTH_SHORT).show();
        // Exit this method early because there's nothing left to do
       return;
    }
    quantity = quantity - 1;
    displayQuantity(quantity);
}`

In question no.4 there is mistake as when you click answer quantity==100 it tells you to try again.
Only accepts the answer when you pick quantity<=100...

Works fine with me.

/**
* This method is called when the plus button is clicked.
* this is the increment method
*/
public void increment(View view) {
if (quantity >= 100){
//show an error message as a toast
Toast.makeText(this, "Mehr als 100 Tassen gibt es nicht", Toast.LENGTH_SHORT).show();
return;
}
quantity = quantity + 1;
display(quantity);
// TextView quantityTextView = (TextView) findViewById(R.id.quantity_text_view);
// quantityTextView.setText("" + quantity);
}

/**
 * This method is called when the minus button is clicked.
 * This is the decrement method
 */
public void decrement(View view) {
    if (quantity < 1){
        //show an error message as a toast
        Toast.makeText(this, "Weniger als 1 Tasse gibt es nicht", Toast.LENGTH_SHORT).show();
       return;
    }
    quantity = quantity - 1;
    display(quantity);
    //TextView quantityTextView = (TextView) findViewById(R.id.quantity_text_view);
    //quantityTextView.setText("" + quantity);
}

public void increment(View view) {

    if (quantity == 100) {
        Toast.makeText(this, "You cannot have more than 100 coffees", Toast.LENGTH_SHORT).show();
        return;
    }
    quantity++;
    display(quantity);

}

/**
 * This method is called when the  minus button is clicked.
 */
public void decrement(View view) {
    if (quantity == 1) {
        Toast.makeText(this, "You cannot have less than 1 coffee", Toast.LENGTH_SHORT).show();
        return;
    }
    quantity--;
    display(quantity);

/**
* This method is called when the plus button is clicked.
*/
public void increment(View view) {
if(quantity>=0){
quantity = quantity + 1;
displayQuantity(quantity);}
if(quantity>=100){
quantity = 100;
displayQuantity(quantity);
}
}

/**
 * This method is called when the minus button is clicked.
 */
public void decrement(View view) {
    if(quantity<=100){
    quantity = quantity - 1;
    displayQuantity(quantity);}
    if(quantity<=0){
        quantity=0;
        displayQuantity(quantity);
    }
}

This my code and work well

/**
* This method is called when the plus button is clicked.
*/
public void increment(View view) {

    //to prevent the user adding more than 100 cups
    if (quantity > 99){
        //to display a toast message
        Context context = getApplicationContext();
        CharSequence text = "you cannot have more than 100 cups";
        int duration = Toast.LENGTH_SHORT;
        Toast toast = Toast.makeText(context, text, duration);
        toast.show();
        return;
    }
    else {quantity = quantity + 1;}
    displayQuantity(quantity);
}

/**
 * This method is called when the minus button is clicked.
 */
public void decrement(View view) {


    //to prevent the user adding less than 1 cup
    if (quantity < 2){
        //to display a toast message
        Context context = getApplicationContext();
        CharSequence text = "you cannot have less than 1 cups";
        int duration = Toast.LENGTH_SHORT;
        Toast toast = Toast.makeText(context, text, duration);
        toast.show();
        return;
    }
    else {quantity = quantity - 1;}
    displayQuantity(quantity);
}

use it for every solution

/**
* This method is called when the plus button is clicked.
*/
public void increment(View view) {
if (quantity >= 100) {
// Show an error message as a toast
Toast.makeText(this, "You cannot have more than 100 coffees", Toast.LENGTH_SHORT).show();
// Exit this method early because there's nothing left to do
return;
}
quantity = quantity + 1;
displayQuantity(quantity);
}

/**
 * This method is called when the minus button is clicked.
 */
public void decrement(View view) {
    if (quantity <= 1) {
        // Show an error message as a toast 
        Toast.makeText(this, "You cannot have less than 1 coffee", Toast.LENGTH_SHORT).show();
        // Exit this method early because there's nothing left to do
        return;
    }
    quantity = quantity - 1;
    displayQuantity(quantity);
}

this is right code for any problem

DONE

Hi ...
@RandomYogi has been noticed that quantity become "0" when rotate the phone ... seems that the class MainActivity re-create... can anyone explain the reason.. to try to avoid that

thanx

Done

Done

Update: Solved!!! I forgot to import the toast widget!

I did the code correct, but toast is not resolved... how should I correct it? Thanks

Going back to the quiz

I used this method and it's OK:
`` public void increment(View view) {
if (quantity<=99) {
quantity = quantity + 1;
}else {
Toast.makeText(this, "You cannot have more than 100 cups", Toast.LENGTH_SHORT).show();
}
displayQuantity(quantity);

}

/**
 * this method is called when the - button is clicked
 */
public void decrement(View view) {


    if (quantity>=2) {
        quantity = quantity - 1;
    }else {
        Toast.makeText(this, "You cannot have less than 1 coffee", Toast.LENGTH_SHORT).show();
    }

    displayQuantity(quantity);

}

thanks

I used this code and it works perfectly.

``
`

/**
 * This method is called when the plus button is clicked.
 */
public void increment(View view) {
    if (quantity < 100) quantity = quantity +1;
    else {
        // Show an error message as a toast
        Toast.makeText(this, "You cannot have more than 100 coffees", Toast.LENGTH_SHORT).show();
    }
    displayQuantity(quantity);

}
/**
 * This method is called when the minus button is clicked.
 */
public void decrement (View view) {
    if (quantity > 1) quantity = quantity -1;
    else {
        // Show an error message as a toast
        Toast.makeText(this, "You cannot have less than 1 coffee", Toast.LENGTH_SHORT).show();
    }
    displayQuantity(quantity);

}

`

anyone can share the full java code ?

i can use this solution?

public void decrement(View view) { if (quantity > 1) { quantity--; } else { Toast.makeText(this,"You cannot have less than 1 coffee",Toast.LENGTH_SHORT).show(); } displayQuantity(quantity); }

If someone is dumb enough to need a TOAST message telling them that they can't order less than 1 cup... they shouldn't be ordering hot drinks. 8P Just use: if (quantity > 0) --- see below

int quantity = 0;
/**
* This method is called when the minus button is clicked.
/
public void decrement(View view) {
if (quantity > 0)
quantity = quantity - 1;
displayQuantity(quantity);
}
/*
* This method is called when the plus button is clicked.
*/
public void increment(View view) {
if (quantity == 100) {
// Show error message as toast
Toast.makeText(this, "You cannot order more than 100 cups", Toast.LENGTH_SHORT).show();
return;
}
quantity = quantity + 1;
displayQuantity(quantity);
}

Well, I guess they could order toppings only, but if this were a real app I wouldn't use this layout anyway.

The solution code has flaw if the quantity variable is initialised with 0 value, as some here have found out. Clicking on minus sign would make the number go down to smaller than 1 (even to minus). The solution is to set the initial quantity value to 1:
int quantity = 1;

public void increment(View view) {
    if (quantity > 99){
        Context context = getApplicationContext();
        CharSequence text = "The maximum of Coffee cups is 100!";
        int duration = Toast.LENGTH_SHORT;
        Toast toast = Toast.makeText(context, text, duration);
        toast.show();
    }else{
        quantity = quantity + 1;
    }


    displayQuantity(quantity);
}

/**
 * This method is called when the minus button is clicked.
 */
public void decrement(View view) {
    if (quantity < 2){
        Context context = getApplicationContext();
        CharSequence text = "The minimum of Coffee cups is 1!";
        int duration = Toast.LENGTH_SHORT;
        Toast toast = Toast.makeText(context, text, duration);
        toast.show();
                }else{
        quantity = quantity - 1;
    }

    displayQuantity(quantity);
}

This is mine

     public void increment(View view) {
            if (quantity == 10) {
                Context context = getApplicationContext();
                CharSequence text = "You can't order more than 10";
                int duration = Toast.LENGTH_SHORT;
                Toast toastMessage = Toast.makeText(context, text, duration);
                toastMessage.show();
                return;
            }
            quantity = quantity + 1;
            displayQuantity(quantity);
        }

        public void decrement(View view) {
            if (quantity == 1) {
                Context context = getApplicationContext();
                CharSequence text = "You can't order less than 1";
                int duration = Toast.LENGTH_SHORT;
                Toast toastMessage = Toast.makeText(context, text, duration);
                toastMessage.show();
                return;
            }
            quantity = quantity - 1;
            displayQuantity(quantity);
        }

to solve this I preferred to use this code...

 if (quantity > 0) {
           quantity = quantity - 1;
        } else {
            Toast.makeText(this, "You cannot have less than 1 coffee", Toast.LENGTH_SHORT).show();
        }
        displayQuantity(quantity);

this way solves the problem @tompad2, but as Katherine said, there are many ways of solving these issues

is better to give quantity variable =1
and make if statement start with 1
if (quantity >1 )
so you can't get less than 1 cup

here is another method ( I start with quantity=2)
public void increment (View view) {
if (quantity<100){
quantity++;
display(quantity);
} else {
Toast.makeText(this, "You cannot have more than 100 coffees", Toast.LENGTH_SHORT).show();
return;
}
}
public void decrement (View view) {

    if (quantity>=2){
        quantity--;
        display(quantity);
    } else {
        Toast.makeText(this, "You cannot have less than 1 coffee", Toast.LENGTH_SHORT).show();
        return;
    }
}

to solve this I preferred to use this code...

 if (quantity > 0) {
           quantity = quantity - 1;
        } else {
            Toast.makeText(this, "You cannot have less than 1 coffee", Toast.LENGTH_SHORT).show();
        }
        displayQuantity(quantity);

this way solves the problem @tompad2, but as Katherine said, there are many ways of solving these issues

to solve this I preferred to use this code...

 if (quantity > 0) {
           quantity = quantity - 1;
        } else {
            Toast.makeText(this, "You cannot have less than 1 coffee", Toast.LENGTH_SHORT).show();
        }
        displayQuantity(quantity);

this way solves the problem @tompad2, but as Katherine said, there are many ways of solving these issues

i also solved this way:

if(quantity == 0){
Toast.makeText(MainActivity.this, "You can not have less than 1 cup of coffee", Toast.LENGTH_SHORT).show();
return;
}

instead of 1 i used 0 ===> Happy Coding

i also solved this way:

if(quantity == 0){
Toast.makeText(MainActivity.this, "You can not have less than 1 cup of coffee", Toast.LENGTH_SHORT).show();
return;
}

instead of 1 i used 0 ===> Happy Coding

Hi ...
@RandomYogi has been noticed that quantity become "0" when rotate the phone ... seems that the class MainActivity re-create... can anyone explain the reason.. to try to avoid that

thanx

Isnt quantity set to 0?? If so... if you start to click decrement when app is just started it would be doing -1....or?

Hi, I think that will work well
//AS quantity =2
// increase quantity by 1
public void increment(View view) {

    if (quantity == 100) {
        quantity = 100;
        Toast toast = Toast.makeText(context, "It isn't available, Try again", Toast.LENGTH_SHORT);
        toast.show();
             } else {
        quantity = quantity + 1;
    }
    display(quantity);
}

// decrease quantity by 1
public void decrement(View view) {


    if (quantity == 1) {
        quantity = 1;
        Toast.makeText(this, "You cannot have less than 1 coffee", Toast.LENGTH_SHORT).show();
    } else {
        quantity -= 1;
    }
    display(quantity);
}

nice code

nice this is nice lecture