我在我的class MainFrame extends JFrame
类中有这两个方法:
// METHOD 1
private void connectBtnActionPerformed(ActionEvent evt) {
controller.connectDatabase();
}
// METHOD 2
public void exitBtnActionPerformed(WindowEvent evt) {
int confirmed = JOptionPane.showConfirmDialog(null,
"Are you sure you want to exit the program?", "Exit Program Message Box",
JOptionPane.YES_NO_OPTION);
if (confirmed == JOptionPane.YES_OPTION) {
controller.exitApplication();
}
}
为什么这个可以调用方法1:
JMenuItem mntmOpenDatabase = new JMenuItem("Open a Database");
mntmOpenDatabase.addActionListener(this::connectBtnActionPerformed);
...替换为此内容:
mntmConnectToDB.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent evt) {
connectBtnActionPerformed(evt);
}
});
但在这个(class MainFrame extends JFrame
的初始化器中):
addWindowListener(this::exitBtnActionPerformed);
... 调用方法2时,无法替换以下内容:
addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent evt) {
exitBtnActionPerformed(evt);
}
});
相反,它给了我这个错误:
- The method addWindowListener(WindowListener) in the type Window is not applicable for the arguments
(this::exitBtnActionPerformed)
- The target type of this expression must be a functional interface