非常基本的OOP问题 [英] Very basic OOP question

问题描述

我的任务是在OOP的帮助下模拟一个收音机。



我有3个类：一个GUI类对于带有名为lblFreq的标签的广播，我想创建Sender.java的不同频道的类和执行不同任务的控制类。



我的频道有2个属性：频率为频率（双倍），频道名称为频道（字符串）。

Hi,
my task is to simulate a radio with the help of OOP.

I have 3 classes: a GUI class for the radio with a label called "lblFreq", a class for the different channels I want to create "Sender.java" and a control class to do the different tasks.

My channels have 2 atributes: "Freq" for the frequency (double) and "Channel" for the name of the channel (String).

public class Sender {
  
  private double Freq;
  private String Channel;
  
  public Sender(double Freq, String Channel) {
    this.Freq = Freq;
    this.Channel = Channel;
  }

  public double getFreq() {
    return Freq;
  }

  public String getChannel() {
    return Channel;
  }

}

我的控制类应该用名称和频率填写它：

my control class should fill it with a name and a frequency:

public class Steuerung {
  
  private RadioGUI dieGUI;
  private Sender dieSender;
  Sender bigFM = new Sender(89.5, "BigFM");


}

我想在GUI中显示标签中的频率我按下按钮btnForward：

and I want to show the frequency in the label in my GUI when I press the button "btnForward":

 private Steuerung dieST;
(....)
 public void btnForward_ActionPerformed(ActionEvent evt) {
    lblFreq.setText(String.valueOf(dieST.bigFM.getFreq()));
    
  }

我按此按钮后出现错误，错误日志为下面。



我想这是因为我搞砸了什么？

I'm getting an error as soon as I press this button, the error log is below.

I think it's because I messed something up at

lblFreq.setText(String.valueOf(dieST.bigFM.getFreq()));

我想。



感谢您的帮助。





错误日志：

I guess.

Thanks for any help.


Error log:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
	at RadioGUI.btnForward_ActionPerformed(RadioGUI.java:249)
	at RadioGUI$2.actionPerformed(RadioGUI.java:77)
	at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
	at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
	at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
	at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
	at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
	at java.awt.Component.processMouseEvent(Component.java:6505)
	at javax.swing.JComponent.processMouseEvent(JComponent.java:3320)
	at java.awt.Component.processEvent(Component.java:6270)
	at java.awt.Container.processEvent(Container.java:2229)
	at java.awt.Component.dispatchEventImpl(Component.java:4861)
	at java.awt.Container.dispatchEventImpl(Container.java:2287)
	at java.awt.Component.dispatchEvent(Component.java:4687)
	at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
	at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
	at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
	at java.awt.Container.dispatchEventImpl(Container.java:2273)
	at java.awt.Window.dispatchEventImpl(Window.java:2719)
	at java.awt.Component.dispatchEvent(Component.java:4687)
	at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:735)
	at java.awt.EventQueue.access$200(EventQueue.java:103)
	at java.awt.EventQueue$3.run(EventQueue.java:694)
	at java.awt.EventQueue$3.run(EventQueue.java:692)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
	at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
	at java.awt.EventQueue$4.run(EventQueue.java:708)
	at java.awt.EventQueue$4.run(EventQueue.java:706)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:705)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)

我尝试过：



在lblFreq.setText尝试了其他代码......但它大多以相同的错误结束，或者它甚至都不会开始。

What I have tried:

Tried other codes at the lblFreq.setText... but it mostly ended with the same error or it wont even start.

推荐答案

2.actionPerformed（RadioGUI.java:77）
在javax.swing。 AbstractButton.fireActionPerformed（AbstractButton.java:2018）
at javax.swing.AbstractButton

2.actionPerformed(RadioGUI.java:77) at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018) at javax.swing.AbstractButton

Handler.actionPerformed（AbstractButton.java:2341)
at javax.swing。 DefaultButtonModel.fireActionPerformed（DefaultButtonModel.java:402）
at javax.swing.DefaultButtonModel.setPressed（DefaultButtonModel.java:259）
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased（BasicButtonListener.java： 252）
at java.awt.Component.processMouseEvent（Component.java:6505）
at javax.swing.JComponent.processMouseEvent（JComponent.java:3320）
at java.awt.Component .processEvent（Component.java:6270）
at java.awt.Container.processEvent（Container.java:2229)
at java.aw t.Component.dispatchEventImpl（Component.java:4861）
at java.awt.Container.dispatchEventImpl（Container.java:2287)
at java.awt.Component.dispatchEvent（Component.java:4687）
at java.awt.LightweightDispatcher.retargetMouseEvent（Container.java:4832）
at java.awt.LightweightDispatcher.processMouseEvent（Container.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent （Container.java:4422）
at java.awt.Container.dispatchEventImpl（Container.java:2273)
at java.awt.Window.dispatchEventImpl（Window.java:2719)
at java.awt.Component.dispatchEvent（Component.java:4687）
at java.awt.EventQueue.dispatchEventImpl（EventQueue.java:735)
at java.awt.EventQueue.access

Handler.actionPerformed(AbstractButton.java:2341) at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402) at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259) at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252) at java.awt.Component.processMouseEvent(Component.java:6505) at javax.swing.JComponent.processMouseEvent(JComponent.java:3320) at java.awt.Component.processEvent(Component.java:6270) at java.awt.Container.processEvent(Container.java:2229) at java.awt.Component.dispatchEventImpl(Component.java:4861) at java.awt.Container.dispatchEventImpl(Container.java:2287) at java.awt.Component.dispatchEvent(Component.java:4687) at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832) at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492) at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422) at java.awt.Container.dispatchEventImpl(Container.java:2273) at java.awt.Window.dispatchEventImpl(Window.java:2719) at java.awt.Component.dispatchEvent(Component.java:4687) at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:735) at java.awt.EventQueue.access

200（EventQueue.java:103）
at java.awt.EventQueue

200(EventQueue.java:103) at java.awt.EventQueue

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