App Inventor programming uses graphical components to layout program functionality. But the official App Inventor documentation uses a traditional programming textual description. When you reference the documentation you see a (mostly) textual description of \u201cProperties\u201d, \u201cMethods\u201d and \u201cEvents\u201d.<\/p>\n
In the App Inventor Designer, you should see a question mark inside a circle\u00a0 next to each component (just to the right) in the Palette. Clicking on the question mark brings up a pop up dialog box with a brief description of the component. At the bottom is usually a \u201cMore information\u201d hyper link. When you click on that link, documentation pages open in a new browser tab. And this is where you will see information described in \u201cProperties\u201d, \u201cMethods\u201d and \u201cEvents\u201d sections.<\/p>\n
Inside App Inventor (and within Android) lie the concept of an \u201cevent driven\u201d programming model and object oriented programming. The former is easy to understand: a \u201cWhen xxx.Click Do\u201d block describes what to do when an \u201cevent\u201d occurs such as a user presses a button on the screen. That button push is an event.\u00a0 Our program blocks respond to events – and specify what our program does when the event occurs.<\/p>\n
You have seen properties on the Designer page \u2013 at the right hand side, you can change the color of buttons or change the text of a label. Each of these values is a \u201cproperty\u201d of the component.<\/p>\n
The concept of a property is easy to understand by seeing how properties apply to every day objects.\u00a0 A car might have the property “blue in color”.\u00a0 A house might have a property “yellow in color”.\u00a0 A dog might have a property like “breed is german shepherd” or “small dog” or “large dog”.<\/p>\n
Real world objects can have multiple properties. For example, a car could be “blue in color”, “4 wheel drive”, “4 door” and “140 horsepower engine”. Each of these attributes is a property that helps to describe the car.<\/p>\n
In App Inventor, each component may have a set of properties. For example, a button might be square or oval, or blue or gray in color. Each of these attributes is a property – for example, the color property might be set to “blue”.<\/p>\n
\u201cMethods\u201d describe the actions or services the component can provide for a program. A method labeled \u201cStart()\u201d is an action that the component can perform.<\/p>\n
Another way to describe \u201cproperties\u201d and \u201cmethods\u201d is to describe them in terms of human language \u2013 a property is like a noun \u201csmall\u201d, \u201clarge\u201d, \u201cblue\u201d (as in color) and a method is like a verb describing an action.<\/p>\n
In this way, each component is an \u201cobject\u201d that has properties and can provide services and perform an action (the methods).<\/p>\n
In terms of real world objects, a car might have methods such as “start engine”, “stop engine”, “increase throttle”, “decrease throttle” and “set throttle” (to a specify speed).<\/p>\n
When you look at the App Inventor documentation online, you will see a list of properties, events and methods.<\/p>\n
For example, the media player plays audio or sound. It has a property \u201cVolume\u201d set between 0 and 100 to adjust the player volume. And it has methods such as \u201cStart()\u201d to begin playing the sound and \u201cStop()\u201d to end playing the sound.<\/p>\n
Now that you know what “properties”, “events” and “methods” actually mean, you should find reading the documentation to be a bit easier!<\/p>\n","protected":false},"excerpt":{"rendered":"
Using App Inventor\u2019s Official Documentation App Inventor programming uses graphical components to layout program functionality. But the official App Inventor documentation uses a traditional programming textual description. When you reference the documentation you see a (mostly) textual description of \u201cProperties\u201d, \u201cMethods\u201d and \u201cEvents\u201d. In the App Inventor Designer, you should see a question mark inside … Continue reading Using App Inventor’s Official Documentation pages<\/span>