java - 如何从 mouseClicked 传递参数？

Question

我正在使用 java3D 并希望将单击的项目的 ID 传递给我的类。但它没有成功。它可以打印 ID，也可以将其传递给字符串文本。但它在 game.btClicked(text); 行中显示 nullPointerException;我如何将 ID 传递给我的类(class)？

public class GUI extends JFrame implements ActionListener, MouseListener {

  private Game game;
  private String text;

  public GUI(Game game /*...*/) {

    this.game = game;
    //.......
  }

  //.......
  public void mouseClicked(MouseEvent e) {
    pickCanvas.setShapeLocation(e);
    Primitive pickedShape = null;
    PickResult result = pickCanvas.pickClosest();

    if (result != null) {
      pickedShape = (Primitive) result.getNode(PickResult.PRIMITIVE);
    }

    //actions to be carried out when object is clicked
    if (pickedShape != null) {
      System.out.println("clicked: " + pickedShape.getName());
      String text = pickedShape.getName();
      System.out.println(text);
      game.btClicked(text);
    } else {
    }
  }
}

公开课游戏{

public Game(){

//......

}

public void btClicked(String text) {
    spielfeld.disableAll();
    int buttonNr = Integer.parseInt(text);
    System.out.println("step: "+step+ " nr: "+buttonNr);
   // .......

}}

以下是堆栈跟踪:

点击次数:38

38

线程“AWT-EventQueue-0”java.lang.NullPointerException 中出现异常

at spiel.Game.btClicked(Game.java:403)

at spiel.SpielGUI.mouseClicked(GUI.java:552)

at java.awt.AWTEventMulticaster.mouseClicked(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$500(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

这是相当多的，但大多数是由于其他问题，我正在为游戏编写一个新的 GUI，所以仍然有一些代码需要更改。所以只看第一行。
“GUI.java:552”指的是“game.btClicked(text);”
“Game.java:403”指的是“spielfeld.disableAll();”但我确信这条线没问题。

Answer 1

您提供的代码中没有构造函数。您有一个看起来非常像构造函数的方法。我假设游戏没有初始化。

构造函数不定义返回类型。就你而言，你有

public void GUI(Game game ....)

当你真正需要的时候

public GUI(Game game ....)

这是一个例子:

public class GUI {
    boolean b = false;
    public static void main(String[] args) {
        GUI g = new GUI();
        System.out.println(g.b);
    }
    public void GUI() {
        b = true;
    }
}

提供输出:

run:
false
BUILD SUCCESSFUL (total time: 2 seconds)

正确的构造函数是:

public class GUI {
    boolean b = false;
    public static void main(String[] args) {
        GUI g = new GUI();
        System.out.println(g.b);
    }
    public GUI() {
        b = true;
    }
}

这给出:

run:
true
BUILD SUCCESSFUL (total time: 1 second)