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Thread: Drawing in response to mouse input

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    Default Drawing in response to mouse input

    I want to draw in response to mouse events. The only way I know how to draw is using a Graphics2D object, as passed to paintComponent(). I tried saving that object in an instance variable, and then using it in mouse event handlers, but no drawing occurs. What am I doing wrong?

    Is there a way to get a Graphics2D object from a panel or a frame? Where does paintComponent() get invoked and where does the Graphics2D object come from?


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    Default Re: Drawing in response to mouse input

    Useful links: How to Ask Questions the Smart Way | Use Code Tags | Java Tutorials
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    Default Re: Drawing in response to mouse input

    I read this, and it doesn't answer my question.

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    Default Re: Drawing in response to mouse input

    Think of it from a Model/View/Controller perspective (which Swing is based upon). The view is the JComponent you are drawing to through the paintComponent method. The controller is some type of user input, for instance a MouseListener. The workflow would then be to have the Controller update the model, then tell the view to do the drawing. For instance, if you want to draw a dot where the user's mouse clicked, 1) get the point from the mouse listener 2) save it to your 'model' 3) call repaint on the component 4) within the paintComponent, draw your model (in this case the point). The link Kevin provided above has a great example of doing just this.

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    Default Re: Drawing in response to mouse input

    Quote Originally Posted by daved View Post
    I read this, and it doesn't answer my question.
    I read this reply, and it doesn't ask a question.

    You need to be more specific- the tutorial I posted tells you exactly how to obtain a Graphics instance to draw with, and how to setup an application that performs custom drawing. What part of that confused you? What did you try?
    Useful links: How to Ask Questions the Smart Way | Use Code Tags | Java Tutorials
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