Solved

Initializing a Graphics object?

Posted on 1997-04-16
1
579 Views
Last Modified: 2006-11-17
I need to draw some graphics into a frame(drawRect, drawLine, drawPolygon).  I am doing this in an APPLICATION.  This requires a Graphics object.  I have tried Graphics g= someComponent.getGraphics(); but this does not work.  I get a nullPointerException when I run the program.  The window frame appears, but I get no graphics.  I need to know how to initialize the Graphics object.  I have had several people tell me to use a paint method, but this does not instantiate the Graphics object.
0
Comment
Question by:FRAYSER
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
1 Comment
 

Accepted Solution

by:
Ted Hopp earned 100 total points
ID: 1219589
If you getGraphics() before the component's addNotify() method has been called, it will return null. This function generally does not get called until the component's show() method is called. Things will probably work fine if you delay calling getGraphics() on your component until after the component is visible.

You can be fancy, and override someComponent's addNotify() method as follows:

public synchronized void addNotify() {
      super.addNotify();            // Creates peer
      // ... inform the app that getGraphics() will work.
}

0

Featured Post

Technology Partners: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

For beginner Java programmers or at least those new to the Eclipse IDE, the following tutorial will show some (four) ways in which you can import your Java projects to your Eclipse workbench. Introduction While learning Java can be done with…
Introduction This article is the first of three articles that explain why and how the Experts Exchange QA Team does test automation for our web site. This article explains our test automation goals. Then rationale is given for the tools we use to a…
Viewers learn about the third conditional statement “else if” and use it in an example program. Then additional information about conditional statements is provided, covering the topic thoroughly. Viewers learn about the third conditional statement …
Viewers will learn one way to get user input in Java. Introduce the Scanner object: Declare the variable that stores the user input: An example prompting the user for input: Methods you need to invoke in order to properly get  user input:
Suggested Courses

624 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question