JavaFX 2 - Can´t import .css File

问题

I´m currentl trying to get into JavaFX 2.0 but I can´t get .css Stylesheets to work within my application. I´ve followed the guide at http://docs.oracle.com/javafx/2/get_started/css.htm#BABBGJBI but whenever I try to import a .css file via

        scene.getStylesheets().add(Login.class.getResource("loginform.css").toExternalForm());

I get the following Error:

    Exception in Application start method
Exception in thread "main" java.lang.RuntimeException: Exception in Application start method
    at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:399)
    at com.sun.javafx.application.LauncherImpl.access$000(LauncherImpl.java:47)
    at com.sun.javafx.application.LauncherImpl$1.run(LauncherImpl.java:115)
    at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.NullPointerException
    at Login.start(Login.java:68)
    at com.sun.javafx.application.LauncherImpl$5.run(LauncherImpl.java:315)
    at com.sun.javafx.application.PlatformImpl$4.run(PlatformImpl.java:174)
    at com.sun.javafx.application.PlatformImpl$3.run(PlatformImpl.java:141)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.access$100(WinApplication.java:29)
    at com.sun.glass.ui.win.WinApplication$2$1.run(WinApplication.java:62)
    ... 1 more

The css path is located in my eclipse project path: C:\Users\UserName\Dropbox\Documents\Eclipse\FirstExamples\loginform.css

I´d appreciate any help, I can´t get it working, not with absolute paths nor with relative ones like shown in the example.

回答1:

Check the compiled output path of your eclipse project and ensure that loginform.css is in the same directory as Login.class

I´ve solved the problem by putting stylesheets into my src folder not a very nice solution but going up by ../formm.css doesn´t seem to work dunno why

You are requesting the css file via the class.getResource method, which will look for the resource in the same location the class is located. When you put the stylesheet in your src folder, then whatever build system you are using is copying the stylesheet to the same directory as Login.class during the build. When you don't place it in that src folder, then the copy is not occuring.

If you don't want to place the css file in the same directory as your Java source, then either set your build system up to copy it across from another directory OR don't use the classloader mechanism when you add a stylesheet, e.g. use an absolute file or http url or a file url based on the user.dir system property (current working directory) instead.

Really though, just placing leaving the stylesheet in the src folder and accessing it in the manner you are doing is fine and it also makes resource location easy when you deploy the app to different environments.

回答2:

If you use anything as a resource, you have to prefix the name of it with "/" and that resource has to be on the classpath.

I have the setup with a directory e.g. resources, which contains the .css. Then I use this:

scene.getStylesheets().add(Login.class.getResource("/loginform.css").toExternalForm());

The directory 'resources' which contains the .css file is added to the classpath (in Eclipse, for example, just make it be a source folder).

It is however pity that the exception is totally useless; I've noticed that the .css was the problem when I added it for the first time.

来源：https://stackoverflow.com/questions/10859920/javafx-2-can%c2%b4t-import-css-file

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