55 lines
1.6 KiB
Markdown
55 lines
1.6 KiB
Markdown
# On Button Pressed
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Start an [event handler](/reference/event-handler) (part of the program that will run when something happens, like when a button is pressed).
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This handler works when button `A` or `B` is pressed, or `A` and `B` together.
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When you are using this function in a web browser, click the buttons on the screen instead of the ones
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on the @boardname@.
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* For button `A` or `B`: This handler works when the button is pushed down and released within 1 second.
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* For `A` and `B` together: This handler works when `A` and `B` are both pushed down, then one of them is released within 1.5 seconds of pushing down the second button.
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```sig
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input.onButtonPressed(Button.A, () => {})
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```
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Find out how buttons provide input to the @boardname@ in this video:
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https://www.youtube.com/watch?v=t_Qujjd_38o
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## Example: count button clicks
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This example counts how many times you press the `A` button.
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Each time you press the button, the [LED screen](/device/screen) shows the `count` variable getting bigger.
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```blocks
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let count = 0
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basic.showNumber(count)
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input.onButtonPressed(Button.A, () => {
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count++;
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basic.showNumber(count);
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})
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```
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## Example: roll dice
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This example shows a number from 1 to 6 when you press the `B` button.
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```blocks
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input.onButtonPressed(Button.B, () => {
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let dice = randint(0, 5) + 1
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basic.showNumber(dice)
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})
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```
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## ~hint
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This program adds a `1` to `random(5)` so the numbers on the dice will come out right.
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Otherwise, sometimes they would show a `0`.
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## ~
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## See also
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[button is pressed](/reference/input/button-is-pressed), [forever](/reference/basic/forever), [random](/blocks/math)
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