App Inventor 2
Programming mobile phones with Android 
by App Inventor 2 - Juan Antonio Villalpando

- Initiation Tutorial App Inventor 2 -

Return to tutorial index

____________________________

47.- Countdown. If then. Clock. Sound.

ip47_count_down

- Presentation.

- Write a number, press the Start button and Label an account is displayed down to zero, plus a sound is heard.
- When it reaches zero, another sound finishing hear, the screen turns red.
- When you press the Stop button, for the account, but if pressed again, the account continues.

_________________
Design

- The TextgBox has Properties "NumberOnly". Hight = 40.
- At Buttons and Labels put them to the desired size. Label the X has a size of 80.

- The Clock we put a TimeInterval 1000 (this is a second). And uncheck TimerEnabled.

- Upload two Sound files. In the Property Source of them we put their names.

beep11.mp3

beep15.mp3

_________________
Blocks

When you press the Button, initial conditions are set:
- Enable the Clock.
- Set the number of TextBox1 in variable n.
- Put the BackGroundColor screen in white.

When the clock starts counting:

Subtracts one to the variable n.
Put the Label value of n.
Rings Sound1.
Compare if n is zero, in this case Pause Sound1 and rings Sound2, for the clock, puts the BackGroundColor screen in Red .

When you press the Button2, you see how is the Clock, if enabled of disabled and if disabled is enabled.

In addition, the text is changed Button2.

____________________

Proposal

- Modify the code so that the number entered must be between 10 and 30 , ie, when you press Button1 will check if the number is between these values.

- If it is not, will a notification to this effect.

Try something like this ...

If x <10 O x> 30 Then

Error Notifier.

__________________________________