Create a Paint App in App Inventor

Tutorial plan

1- Objective of Paint mobile application

2- Description of Designer Interface

3- Description of Blocks part

Objective of Paint mobile application

The objective of creating a Paint app in MIT App Inventor is to develop a mobile application that allows users to draw lines in various colors on a digital canvas using touch gestures. This project aims to:

1- Introduce users to mobile app development through a creative, hands-on project.

2- Teach how to use the Canvas component to detect touch and drag events for drawing.

3- Enable drawing of lines in different colors by letting users choose colors dynamically.

4- Demonstrate how to use buttons, color pickers, or other UI elements to change drawing colors.

5- Promote understanding of event-driven programming and how user actions control app behavior.

6- Encourage creativity and experimentation through an interactive drawing experience.

Description of Designer Interface

The Designer Interface in MIT App Inventor is where the visual layout of the Paint app is created. It allows you to place and arrange components that users will interact with on their screens.

Main Components Used

1. Canvas

Component: Canvas1

Purpose: The drawing area where users can draw lines with their fingers.

Properties:

Width and Height set to Fill Parent or a specific size.

BackgroundColor can be set to white or any color.

PaintColor determines the color of lines drawn.

2. Buttons for Color Selection

ButtonRed → Text: “Red”

ButtonBlue → Text: “Blue”

ButtonGreen → Text: “Green”

Purpose: Allow the user to change the color of the lines before drawing on the canvas.

3. Clear Button

ButtonClear → Text: “Clear”

Purpose: Clears all drawings from the canvas so the user can start fresh.

4. Layouts for Organization

HorizontalArrangement or VerticalArrangement:

Used to arrange color buttons in a neat row or column.

Helps keep the user interface tidy and easy to navigate.

Description of Blocks part

The Blocks part in MIT App Inventor defines how the Paint app behaves when the user interacts with it—for example, when drawing on the canvas or selecting different colors.

Explanation of Each Block 

Block	Description
	The block is an event handler in MIT App Inventor that defines what happens when the user taps the red color button in the Paint app.
	The block set Canvas.PaintColor is a property setter block in MIT App Inventor used to change the color of lines or shapes drawn on the Canvas. It defines the red color used for drawing on the canvas.
	The block when Clear.Click do is an event handler in MIT App Inventor. It defines what happens when the user taps the Clear button in the Paint app.
	The block is a method block in MIT App Inventor used to erase everything that has been drawn on the canvas.
	The block is an event handler in MIT App Inventor that defines what happens when the user taps the yellow color button in the Paint app.
	The block set Canvas.PaintColor is a property setter block in MIT App Inventor used to change the color of lines or shapes drawn on the Canvas. It defines the yellow color used for drawing on the canvas.
	The block is an event handler in MIT App Inventor that defines what happens when the user taps the blue color button in the Paint app.
	The block set Canvas.PaintColor is a property setter block in MIT App Inventor used to change the color of lines or shapes drawn on the Canvas. It defines the blue color used for drawing on the canvas.
	The block is an event handler in MIT App Inventor. It defines what happens when the user touches the canvas and moves their finger across it the key action for drawing lines in the Paint app.
	The block is a method block in MIT App Inventor. It’s used to draw a straight line on the canvas between two points.