为什么我的图标处理代码会抛出 NullPointerException? [英] Why does my icon handling code throw a NullPointerException?

问题描述

我已经为我的按钮添加了一个图像，但是当我运行该框架时会抛出这个异常.为什么?请帮助我.

I have added an image for my button,but when I run that frame this exception will be thrown .why?please help me.

init:

deps-jar:
compile-single:
run-single:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
        at javax.swing.ImageIcon.<init>(ImageIcon.java:138)
        at ClientGUI.IdAndPasswordFrame.initComponents(IdAndPasswordFrame.java:91)
        at ClientGUI.IdAndPasswordFrame.<init>(IdAndPasswordFrame.java:22)
        at ClientGUI.IdAndPasswordFrame$4.run(IdAndPasswordFrame.java:200)
        at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)
BUILD SUCCESSFUL (total time: 1 second)

第 138 行:

public ImageIcon (URL location) {
    this(location, location.toExternalForm());
}

第 91 行:

 jButton1.setIcon(new javax.swing.ImageIcon(getClass().getResource("/Images/yahoo_1.gif"))); // NOI18N

我使用这种糟糕的检查(Peter Lang 推荐)它是:System.out.println(getClass().getResource("/Images/yahoo_1.gif"));它返回null，为什么?请帮帮我.

推荐答案

这意味着，getClass().getResource("/Images/yahoo_1.gif") 返回 null.

JavaDoc 指出如果

找不到资源或调用者没有足够的权限来获取资源.

the resource could not be found or the invoker doesn't have adequate privileges to get the resource.

1. 检查getResource是否真的返回null:
   System.out.println(getClass().getResource("/Images/yahoo_1.gif"));

确保您的路径正确并且在您的类路径中.

Make sure that your path is correct and that it is in your classpath.

编辑:

我刚刚用 NetBeans 试过了.我创建了以下结构

I just tried it with NetBeans. I created the following structure

Source Packages
  Images
    yahoo_1.gif

并且您的代码运行良好.这是你的结构吗?

and your code worked fine. Is this your structure?

尝试右键单击您的应用程序并选择 Clean and Build.

Try to right-click on your application and select Clean and Build.

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