visual c++ programming: concepts and projects chapter 6b methods (tutorial)

VISUAL C++ PROGRAMMING: CONCEPTS AND PROJECTS

Chapter 6BMethods (Tutorial)

Tutorial: Planetary Motion

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Problem Analysis Create a program with a planet that orbits

around a central sun Planets orbit in an elliptical path The program will draw the planet at a new

location at regular intervals To calculate the next position of the planet you

need to know the x coordinate of the center of the ellipse The length of the semimajor axis of the ellipse The angle of the planet from the semimajor axis

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Design

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Interface sketch Controls

PictureBox to draw on Timer control to execute commands at regular

intervals Constants

Center of the ellipse Length of the semimajor and semiminor axes

Instance variables Graphics and Drawing objects

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Design (continued)

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Algorithm Algorithm for Timer1_Tick()

Refresh the PictureBox Draw the sun Draw the planet Increase the angle

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Development

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Create the interface Assign an image file to the PictureBox to

appear in the background Important: to make the image appear

Download the image Place it in your Project folder (within your

Solution folder of the same name) Project6 (Solution folder)

Project6 (Project folder) Use the Properties window to assign the image

to the PictureBox

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Development (continued)

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Coding Declare and assign static constants Declare handles for Graphics object and

Drawing objects Form1_Load()

Construct graphics and drawing objects btnStart_Click()

Start the Timer control btnStop_Click()

Stop the Timer control

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Development (continued)

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Coding Timer1_Tick() Declare local variables Refresh the pictureBox Draw the sun Draw the planet

Convert angle from degrees to radians Calculate planet x and y coordinates Draw the planet

Increase angle by 5 degrees

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On Your Own

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Instance methods with return values (Planets version 2) ConvertToRadians()

Instance methods with value parameters (Planets version 3) DrawPlanets()

Instance methods with reference parameters (Planets version 4) SetXY()