An event handler is an event and a sequence of responses. It is a "when" block in app inventor and all the blocks within. When something happens, e.g., a button click, the app responds.
In HelloPurr, when the user clicks the button, the meow sound is played.
But what if your app needs to make a decision, e.g.,
Every time you click a button a different picture appears on the button.
This requires a conditional (IF) block and a way to generate a random number.
if, and if-else both in the math drawer
the test can be any boolean condition, e.g., is a number 1?
Demo: build a game where clicking on an image button changes the image back and forth.
randomInteger in the math drawer. You can get a random number for any range of possibilities.
Demo: build a game where the image changes randomly between two things.
Create a silly animal game that randomly shows 1 of 2 animal pictures and plays a corresponding animal sound.
Modify your silly animal game so that it randomly shows 1 of 3 pictures and plays a corresponding animal sound. Note that you'll need to use a variable and a nested if-else block.For help, see the chapters on variables and decision-making