"AWT-EventQueue-0" java.lang.NullPointerException 问题

Question

请教：我的程序在编译之后的报错怎么改啊？Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
        at videocapture.Frame_Init.playerClose(Frame_Init.java:588)
        at videocapture.Frame_Init.jComboBox_filmsize_itemStateChanged(Frame_Init.java:800)
        at videocapture.Frame_Init$Frame_Init_jComboBox_filmsize_itemAdapter.itemStateChanged(Frame_Init.java:828)
        at javax.swing.JComboBox.fireItemStateChanged(JComboBox.java:1207)
        at javax.swing.JComboBox.selectedItemChanged(JComboBox.java:1255)
        at javax.swing.JComboBox.contentsChanged(JComboBox.java:1311)
。。程序
   public void  playerClose( )
      {
         
                if ( player != null )
                {
                    player.close();  
                    player.deallocate();  //出错
                    player = null;
                    jPanel_visual.remove(visualComponent);  
                    jPanel_visual.remove(controlComponent);  
                }
            }
和
  public void jComboBox_filmsize_itemStateChanged(ItemEvent e) {
    Panelthread pt=new Panelthread();
    pt.start();
    playerClose(); //也出错
    startmonitor();
    pt.stop();
    }谢谢求教！急！！！

Answer 1

是不是前面已经关闭了，后面再进行操作就出问题了。把这一句和那个 close 换一下看看

Answer 2

javax.media.ClockStartedError: deallocate cannot be used on a started controller.
        at com.sun.media.BasicController.deallocate(BasicController.java:1143)
        at videocapture.Frame_Init.playerClose(Frame_Init.java:587)换了之后，还是不行啊，deallocate不能成为开头语句

Answer 3

有的时候还会报
Exception in thread "Thread-7" java.lang.NullPointerException
        at videocapture.Frame_Init.playerClose(Frame_Init.java:588)
        at videocapture.Frame_Init$Panelthread$Deal.jpanel_init_show(Frame_Init.java:643)
        at videocapture.Frame_Init$Panelthread$jpanel_init_Thread.run(Frame_Init.java:679)
所以一直没有弄明白

Answer 4

Sometimes it happens when you don't handle the "null" exception...Please check it out...