如何在Java中的JButton上添加ActionListener [英] How do you add an ActionListener onto a JButton in Java

问题描述

private JButton jBtnDrawCircle = new JButton("Circle");
private JButton jBtnDrawSquare = new JButton("Square");
private JButton jBtnDrawTriangle = new JButton("Triangle");
private JButton jBtnSelection = new JButton("Selection");

如何向这些按钮添加动作侦听器，以便从主方法中调用 actionperformed 关于它们，所以点击它们我可以在我的程序中调用它们吗？

How do I add action listeners to these buttons, so that from a main method I can call actionperformed on them, so when they are clicked I can call them in my program?

推荐答案

两种方式：

1。在您的类中实现ActionListener，然后使用 jBtnSelection.addActionListener（this） ; 稍后，你必须定义一个menthod， public void actionPerformed（ActionEvent e）。但是，对多个按钮执行此操作可能会造成混淆，因为 actionPerformed 方法必须检查每个事件的来源（ e.getSource（））查看它来自哪个按钮。

1. Implement ActionListener in your class, then use jBtnSelection.addActionListener(this); Later, you'll have to define a menthod, public void actionPerformed(ActionEvent e). However, doing this for multiple buttons can be confusing, because the actionPerformed method will have to check the source of each event (e.getSource()) to see which button it came from.

2。使用匿名内部类：

jBtnSelection.addActionListener(new ActionListener() { 
  public void actionPerformed(ActionEvent e) { 
    selectionButtonPressed();
  } 
} );

稍后，你必须定义 selectionButtonPressed（ ）。
当你有多个按钮时，这会更好用，因为你对单个方法的调用就是按钮的定义。

Later, you'll have to define selectionButtonPressed(). This works better when you have multiple buttons, because your calls to individual methods for handling the actions are right next to the definition of the button.

第二个方法还允许您直接调用选择方法。在这种情况下，你可以调用 selectionButtonPressed（），如果发生其他一些动作 - 比如，当一个计时器关闭或某事（但在这种情况下，你的方法将是命名不同的东西，可能 selectionChanged（））。

The second method also allows you to call the selection method directly. In this case, you could call selectionButtonPressed() if some other action happens, too - like, when a timer goes off or something (but in this case, your method would be named something different, maybe selectionChanged()).

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