3

我一直在为我的所有 JSlider 使用上述 MetalSliderUI 解决方案。Windows 用户对此感到满意。我很高兴在 stackoverflow.com 上找到此解决方案 该解决方案已在此处讨论： JSlider question: Position after leftclick

现在最近一个 MAC OSX/64 位用户正在尝试使用我的软件，他从 MetalSliderUI 引用中获得了空指针异常。

我添加到 JFrame 的构造函数的代码示例：

// Radio Window Elecraft K3 RFPWR Slider - when click on slider
            // go to the value instead of going up/down one tick.
            jSliderElecraftK3RFPWR.setUI(
                new MetalSliderUI() {
                    protected void scrollDueToClickInTrack(int direction) {
                        int value = jSliderElecraftK3RFPWR.getValue();
                        if (jSliderElecraftK3RFPWR.getOrientation() == JSlider.HORIZONTAL) {
                            value = this.valueForXPosition(jSliderElecraftK3RFPWR.getMousePosition().x);
                        } else if (jSliderElecraftK3RFPWR.getOrientation() == JSlider.VERTICAL) {
                            value = this.valueForYPosition(jSliderElecraftK3RFPWR.getMousePosition().y);
                        }
                        jSliderElecraftK3RFPWR.setValue(value);
                    }
                }
            );

没有在我的代码中引用确切行的异常：

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException at 
javax.swing.plaf.metal.MetalSliderUI.installUI(MetalSliderUI.java:92) at 
javax.swing.JComponent.setUI(JComponent.java:662) at 
javax.swing.JSlider.setUI(JSlider.java:300) at 
HamRadioIntegrator_N3ZH.JFrameRadio.(JFrameRadio.java) at 
HamRadioIntegrator_N3ZH.JFrameRadio$550.run(JFrameRadio.java) at
java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209) at 
java.awt.EventQueue.dispatchEventImpl(EventQueue.java:678) at 
java.awt.EventQueue.access$000(EventQueue.java:86) at 
java.awt.EventQueue$1.run(EventQueue.java:639) at 
java.awt.EventQueue$1.run(EventQueue.java:637) at 
java.security.AccessController.doPrivileged(Native Method) at 
java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87) 
at java.awt.EventQueue.dispatchEvent(EventQueue.java:648) at 
java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:296) at 
java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:211) at 
java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:201) at
java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:196) at 
java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:188) at  
java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

您对解决仅在 Mac 上发生的此问题有什么建议吗？

霍华德

4

2 回答 2

1

The problem is in line 92 of MetalSliderUI, which wants a UI default value named Slider.trackWidth, among others. The value does not appear in com.apple.laf.AquaSliderUI. 

trackWidth = ((Integer)UIManager.get("Slider.trackWidth")).intValue();

A simple alternative is to use BasicSliderUI. A more complex approach is to initialize the MetalLookAndFeel and save a reference to your subclass for later use.

LookAndFeel save = UIManager.getLookAndFeel();
LookAndFeel laf = new MetalLookAndFeel();
UIManager.setLookAndFeel(laf);
SliderUI mySliderUI = new MetalSliderUI() { ... };
UIManager.setLookAndFeel(save);
于 2011-06-04T17:21:38.170 回答
1

没有SSCCE很难说（没有 Mac 就更难测试了），但这些问题通常是由于未能在 EDT 上更新 GUI 造成的。有关更多详细信息，请参阅Java 教程的Swing 中的并发课程。

于 2011-06-04T14:11:28.117 回答