That would be true, except for a subtle programming point: Doing that would be relying on the assumption that small will already have a value at the point in time when dotsize is assigned its value. You might wonder whether it would be better programming style to make the initial value of dotsize be the value of small rather than 2. Similar to small, define a global variable big, whose value is 8.įinally, define a global variable dotsize and give it an initial value of 2. You've now defined a global variable named small whose value is the number 2. (The second value listed in the menu is the math block atan2 which you won't use here.) The yellow warning mark will disappear, because the empty socket has been filled. Click on the first one, which is the number 2 itself, and a number block with the value 2 should appear. A menu will appear, showing you all the possible blocks that include '2' in their name. To create the number block, type the number 2.

You need to fill in the socket with a number block that specifies the value for 'small' - use 2 as the value.

If you mouse over this you'll see a warning message explaining that the block has an empty socket. A yellow warning exclamation mark will appear on the block.

Change the text that reads 'variable' to read 'small'.

In the Blocks Editor, in the Built-In column, open the Definitions drawer.

Your phone should show the buttons and the canvas you built previously.

Open the Blocks Editor if it isn't already open and connect the phone.

Start by creating names for these values: Use r = 2 for small dots and r = 8 for large dots. To change the thickness, all we need to do is use different values for r.

The size of the dots drawn on the canvas is determined in the when DrawingCanvas.Touched event handler where call Drawing.DrawCircle is called with r, the radius of the circle, equal to 5. After saving a copy, you should see PaintPotV2 in the Designer. Name the copy 'PaintPotV2' (with no spaces). Use the Save As button to make a copy of PaintPot so you can work on the new version without affecting the original version. Start where you left off at the end of Part 1, with the project open in App Inventor. Make sure you've completed the Set Up process and you have your completed project from PaintPot Part 1 loaded. Part 2 extends Part 1 of the tutorial to create both large and small dots, as a demonstration of how to use global variables.

This tutorial has two parts: Part 1 | Part 2

What are the mac paint pots used for