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Thread: Understanding Graphics2d, canvas and shapes

  1. #1
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    Default Understanding Graphics2d, canvas and shapes


    I am learning the basics of java games programming and I am confused about a few things.
    I know you use the "canvas" class to create a blank canvas and then use the paint method to create stuff.

    But what does graphics2d? I have seen people using the grahpics2d class to create a canvas for example

    Graphics2D g2d = (Graphics2D) g;

    now why did they use the grahpics2d and not the canvas?

    also I have seen people creating shapes like a rectangle by using:
    Rectangle r = new Rectangle();

    but some people have created them like:

    Shape shape = new Rectangle2D.Double(value1,valu2,valu3,valu4);

    Whats the difference between these two?

    Thanks in advance.


  2. #2
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    Default Re: Understanding Graphics2d, canvas and shapes

    Welcome to the Forum! Please read this topic to learn how to post code correctly and other useful tips for newcomers.

    There are typically many ways to accomplish the same, or nearly the same, thing in Java. The way chosen is often personal preference, what was learned first, or a specific approach that supports the rest of the design, so therefore dependent on the requirements of a larger context than you've provided.

    You can learn about the differences in the approaches you've mentioned by studying the API for the classes being used. It's better that you do that research than to rely on someone else to do it for you.

  3. #3
    Crazy Cat Lady KevinWorkman's Avatar
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    Default Re: Understanding Graphics2d, canvas and shapes

    Like Greg said, the API is your best friend: Java Platform SE 8

    You also need some familiarity with OOP. The Graphics class is an abstract class, and Graphics2D is the concrete implementation of it. The paintComponent() method takes a Graphics argument, but in actuality the argument is an instance of Graphics2D.

    Your question of "why did they use the grahpics2d and not the canvas" doesn't make any sense. You paint *with* an instance of Graphics2D (which is just a subclass of Graphics) *to* a Component such as Canvas or JPanel. You question is like asking "why did the artist paint with the brush instead of the canvas".

    Recommended reading: Lesson: Performing Custom Painting (The Java™ Tutorials > Creating a GUI With JFC/Swing)
    Useful links: How to Ask Questions the Smart Way | Use Code Tags | Java Tutorials
    Static Void Games - Play indie games, learn from game tutorials and source code, upload your own games!

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