AppletTalk.com Java discussions newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  to insert an image in a Label (awt, not swing)          AppletTalk.com Forum Index -> Java GUI Toolkits View previous topic :: View next topic   Author Message Marco Guest Posted: Sun Nov 23, 2003 6:01 pm    Post subject: to insert an image in a Label (awt, not swing) I want insert a JPG (or jpg?) image in a Label (the Label is a Component of a Frame; I don't want to use swing for compatibility with browsers that don't support it). This is a part of my "class finestra extends Frame": Image img = vuota.getToolkit().getImage(new URL("http://www.pippo.it/pluto.jpg")); ImageProducer im = img.getSource(); vuota.createImage(im); // but the image is still not visible Graphics g = vuota.getGraphics(); g.drawImage(img,0,0,this); // appletviewer reports "java.lang.NullPointerException": g is null. And now? How I must proceed? Back to top Marco Guest Posted: Sun Nov 23, 2003 6:03 pm    Post subject: Re: to insert an image in a Label (awt, not swing) Quote: Image img = vuota.getToolkit().getImage(new URL("http://www.pippo.it/pluto.jpg")); P.S. "vuota" is a Label. Back to top VisionSet Guest Posted: Sun Nov 23, 2003 7:56 pm    Post subject: Re: to insert an image in a Label (awt, not swing) "Marco" <mNmOeScPgAfMl (AT) excite (DOT) it> wrote Quote: Image img = vuota.getToolkit().getImage(new URL("http://www.pippo.it/pluto.jpg")); ImageProducer im = img.getSource(); vuota.createImage(im); // but the image is still not visible Graphics g = vuota.getGraphics(); g.drawImage(img,0,0,this); // appletviewer reports "java.lang.NullPointerException": g is null. And now? How I must proceed? If I remember correctly createImage returns immediately so it won't have loaded the image when it returns and will therefore have a null graphics context. You can use MediaTracker (example of useage in API) to wait for the image to load. -- Mike W Back to top Andrew Thompson Guest Posted: Sun Nov 23, 2003 8:39 pm    Post subject: Re: to insert an image in a Label (awt, not swing) A complete, self contained, compilable example would be great, whereas 'code snippets' are ..not "Marco" <mNmOeScPgAfMl (AT) excite (DOT) it> wrote Quote: Image img = vuota.getToolkit().getImage(new URL("http://www.pippo.it/pluto.jpg")); P.S. "vuota" is a Label. My understanding is that JLabels can accept images, but Labels cannot. I realise what you are doing is not quite standard, but if your are not using a Label as a Label, you may as well _not_ use it, but instead draw your graphics directly to a Panel or some other more appropriate component. [ At this point I am hoping the GUI gurus can jump in to clarify, this is not one of my main areas.. ] -- Andrew Thompson * http://www.PhySci.org/ PhySci software suite * http://www.1point1C.org/ 1.1C - Superluminal! * http://www.AThompson.info/andrew/ personal site Back to top ak Guest Posted: Sun Nov 23, 2003 9:03 pm    Post subject: Re: to insert an image in a Label (awt, not swing) "Marco" <mNmOeScPgAfMl (AT) excite (DOT) it> schrieb im Newsbeitrag news:bpqsmp$o27$1 (AT) lacerta (DOT) tiscalinet.it... Quote: I want insert a JPG (or jpg?) image in a Label (the Label is a Component of a Frame; I don't want to use swing for compatibility with browsers that don't support it). This is a part of my "class finestra extends Frame": Image img = vuota.getToolkit().getImage(new URL("http://www.pippo.it/pluto.jpg")); ImageProducer im = img.getSource(); vuota.createImage(im); // but the image is still not visible Graphics g = vuota.getGraphics(); g.drawImage(img,0,0,this); // appletviewer reports "java.lang.NullPointerException": g is null. g is null means that your Panel is not displayable! use instead paint(Graphics g) method to draw your image: public void paint(Graphics g) { super.paint(g); g.drawImage(img,0,0,this); } Back to top Marco Guest Posted: Mon Nov 24, 2003 2:55 pm    Post subject: Re: to insert an image in a Label (awt, not swing) Quote: My understanding is that JLabels can accept images, but Labels cannot. It is possible, I don't know well, but I read in http://programmazione.html.it/java/java_30.htm that "volendo disegnare una immagine in un componente Gui, si può usare il metodo createImage() della classe Component" (for drawing an image in a Gui component, it is possible to use the method createImage() of the class Component). A Label is a Component. But how to use createImage? Quote: draw your graphics directly to a Panel I tested this, but the result is the same: the graphic context g is null, and the image is not visible (or it is visible only a moment, after the second display of the Frame). Quote: If I remember correctly createImage returns immediately so it won't have loaded the image when it returns and will therefore have a null graphics context. You can use MediaTracker (example of useage in API) to wait for the image to load. I have used MediaTracker too, but the image is visible only for a moment, from the second display of the frame. With Canvas, the graphic context is always null. FOR DISPLAYING THE IMAGE IN A COMPONENT OF A FRAME (NON A JFRAME), WHAT IS THE PROCEDURE? HOW CAN I KNOW THE GRAPHIC CONTEXT g OF THE COMPONENT FOR USING g.drawImage? OR THERE IS AN ANOTHER PROCEDURE? Thank you for your help. Marco (remove NOSPAM or reply in this newsgroup) Back to top Adam Guest Posted: Wed Nov 26, 2003 8:07 am    Post subject: Re: to insert an image in a Label (awt, not swing) Quote: FOR DISPLAYING THE IMAGE IN A COMPONENT OF A FRAME (NON A JFRAME), WHAT IS THE PROCEDURE? HOW CAN I KNOW THE GRAPHIC CONTEXT g OF THE COMPONENT FOR USING g.drawImage? OR THERE IS AN ANOTHER PROCEDURE? Thank you for your help. Marco Poor Marco... I don't think anyone will help you after that... And you were given specific instructions to render your image in paint method. You just try to render it once, even when it can't be rendered. But to keep your image on screen you need to render it during every repaint. So: 1. Subclass the component on which you want to render the image 2. override its paint method as you were told 3. Load the image in the constructor of your component Oh, one more thing. createImage is used to create offscreen images for double buffering (in general). For loading external image use Toolkit.getImage and MediaTracker regs, Adam Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         AppletTalk.com Forum Index -> Java GUI Toolkits All times are GMT Page 1 of 1   Jump to: Select a forum Java Newsgroups----------------Java DiscussionsWeb-based java games comp.lang.java 3D Graphics API's for Java Java: Support and criticism Java System Announcements comp.lang.java.api JavaBeans Java and CORBA Java and Databases comp.lang.java.developer Java GUI Toolkits Java Help comp.lang.java.javascript JVM, native methods and hardware comp.lang.java.misc Java Language Programming Security and Java comp.lang.java.setup Java Software Tools comp.lang.java.tech ibm.software.java.linux  Non-English Java Newsgroups----------------Java Language (German)Language Java (Français)Java (Italian)  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.