java - FocusGained 和 FocusLost 不起作用？

Question

这是我在事件方法中的代码:

Code

private void txtCampusSearchFocusGained(java.awt.event.FocusEvent evt) {                                            
    this.txtCampusSearch.setText(null);
}                                           

private void txtCampusSearchFocusLost(java.awt.event.FocusEvent evt) {                                          
    this.txtCampusSearch.setText("Search...");
}                                         

private void txtBuildingSearchFocusGained(java.awt.event.FocusEvent evt) {                                              
    this.txtCampusSearch.setText(null);
}                                             

private void txtBuildingSearchFocusLost(java.awt.event.FocusEvent evt) {                                            
    this.txtCampusSearch.setText("Search...");
}  

但是，当我实际运行应用程序时，当获得/失去焦点时，这些方法似乎不会被激活。 Application Running

Answer 1

您必须向文本字段添加焦点监听器。

JTextField textField = new JTextField("A TextField");
 textField.addFocusListener(new MyFocusListener());

https://docs.oracle.com/javase/tutorial/uiswing/events/focuslistener.html