Calculator

Day 3 :Messages

Create It With

in cooperation with

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Understanding the

MESSAGES

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Calculator App

What is a Message?

A message is indeed like a chat. When some kind of event happens - like the user clicks a button, LiveCode will send a message to your the program.

The question is what do you want to do when you get the message. Your reply is the code you write in LiveCode. This is how you “chat” with LiveCode.

Click Me

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Calculator App

More on Messages

There are lots of more resources available on the message path. They do a good job explaining the concept.

As you can see in the video. The Dictionary located in the LiveCode IDE will give you full access on all events.

Some are much more advanced, like Richard Gaskin’s Extending the LiveCode Message path.

The LiveCode Message Path

Messages in LiveCode

Advanced [only for reference]:

Extending the LiveCode Message Path

LESSONS

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Calculator App

This message hierarchy allows us to place the code needed by several interface controls into a higher level, available to all of those controls.

One such case will be with the calculator's number buttons; each one needs to do exactly the same thing, and by putting that code into the card level, each of them can make use of that single handler.

Running the sample App and watching the video will help you understand.

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Calculator App

Message Path

The pass command tells LiveCode that after the control has processed the message, it will be “passed” up to the next level of the hierarchy along the message path for a mouseUp handler, which could be that in a group or card script, for example.

If an appropriate handler is found, it will then execute that handler in the group or card script and stop moving up the levels unless there is also a pass command in that handler.

Note: When the pass command is executed, any remaining statements in the handler are skipped, so this command is almost always placed at the end of a handler or within an if-control structure.

Passon mouseDown

beep

-- keep passing the message on pass mouseDown

end mouseDown

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Calculator App

mouseDown: Handle the mouseDown message to perform an action when the user presses the mouse button, before the mouse button is released.

mouseEnter: Handle the mouseEnter message to perform an action (for example, display additional information or highlight a button) when the mouse pointer enters an object.

mouseLeave: Handle the mouseLeave message to update a control when the mouse pointer moves outside it.

mouseMove: Handle the mouseMove message if you want to perform some action (such as updating a field) when the user moves the mouse, or if you want to keep continuous track of the mouse pointer's position.

mouseUp: Handle the mouseUp message to perform an action when the user releases the mouse button after clicking.

Mouse Messages

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deleteField: Handle the deleteField message if you want to perform cleanup before a field is removed from the stack.

enterInField: Handle the enterInField message when you want to perform an action when the user presses Enter in a field.

exitField: Handle the exitField message if you want to do something when the user leaves a field that hasn't been changed.

openField: Handle the openField message if you want to do something when the user enters a field.

returnInField: Handle the returnInField message when you want to perform an action (such as adding a column of figures) when the user presses Return in a field.

Field Messages

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Calculator App

deleteField: Handle the deleteField message if you want to perform cleanup before a field is removed from the stack.

enterInField: Handle the enterInField message when you want to perform an action when the user presses Enter in a field.

exitField: Handle the exitField message if you want to do something when the user leaves a field that hasn't been changed.

openField: Handle the openField message if you want to do something when the user enters a field.

returnInField: Handle the returnInField message when you want to perform an action (such as adding a column of figures) when the user presses Return in a field.

Field Messages

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Calculator App

openBackground: Handle the openBackground message to change a group's objects, or perform other updates, when a card with the group on it is opened.

preOpenCard: Handle the preOpenCard message to update a card's appearance before the card appears on screen.

openCard: Handle the openCard message to change a card's objects, or perform other updates, when the card is visited.

preOpenStack: Handle the preOpenStack message to update a card's appearance before the card appears on screen.

openStack: Handle the openStack message to change a stack's objects, or perform other updates, when the stack is opened.

Open/Close Messages

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Calculator App

keyDown: Handle the keyDown message if you want to do something special when the user presses any key or a particular key you check for in the handler.

keyUp: Handle the keyUp message if you want to do something special when the user releases any key (or a particular key you check for in the handler).

deleteKey: Handle the deleteKey message if you want to do something special when the user presses the forward delete key.

escapeKey: Handle the escapeKey message if you want to perform some action when the user presses Escape.

tabKey: Handle the tabKey message when you want to perform an action (such as going to the next card) when the user presses the Tab key.

Keyboard Messages

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Calculator App

pushNotificationReceived: Sent when the application receives a push notification from a Push Notification Server.

purchaseStateUpdate: Sent by the store to notify the app of any changes in state to the purchase request.

movieTouched: Handle the movieTouched message to perform an action when a full screen movie is playing and the user touches the screen.

adLoaded: Sent when an ad had loaded (or reloaded).

adClicked: Handle the adClicked message if you want to perform an action when a user clicks on an ad.

touchStart: Sent when a user touches a control in a mobile application

Mobile Messages

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Calculator App

If you wish to learn more… Visit LiveCode

Congrats on learning:Messages

Calculator App

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