这里要讲的是如何利用回调获取自拟定DiaLog的返回值，首先看下问题的背景。我们经常会用到Dialog，系统提供了一些常用的Dialog，可以参考这篇博客
点击打开链接
。那其中一个常用Dialog做讲解，
<span style="font-size:14px;">String returnString = JOptionPane.showInputDialog("title");</span>
当执行到这条语句时，将弹出一个对话框，程序被阻塞，直到Dialog被关闭，返回retrunString。但很多情况下并不够用，所以我们通常会自拟定自己的Dialog。可是如何从Dialog返回值到主窗口这是问题了，有些人可能会把MyDialog设置为内部类，这样容易导致代码重复和臃肿。所以这里将MyDialog设置为单独类，利用回调返回MyDialog中填入的值。关于回调的讲解，这里有篇博客讲的很通俗，值得大家看下，xiaanming的博客点击打开链接。
以下是自己码的实例代码：
回调的接口：
public interface DialogListener {
public void getInputString(String inputString);
}
MyDialog类：
public class MyDialog extends JDialog {
/**
*
*/
private static final long serialVersionUID = 1L;
private JButton comfirmBtn;
private JButton cancelBtn;
private JTextField inputField;
private DialogListener dialogListener;
public MyDialog(String title){
Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
this.setSize(screenSize.width/4, screenSize.height/4);
this.setLocation(3*screenSize.width/8, 3*screenSize.height/8);
JPanel mainPanel = new JPanel(new GridLayout(4,1, 10,10));
JLabel label = new JLabel(title);
label.setFont(new Font("宋体", Font.BOLD ,30));
inputField = new JTextField();
inputField.setFont(new Font("宋体", Font.BOLD ,30));
JPanel btnPanel = new JPanel(new GridLayout(1,2,20,20));
comfirmBtn = new JButton("确认");
cancelBtn = new JButton("取消");
comfirmBtn.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
//调用回调函数返回Dialog输入的内容
dialogListener.getInputString(inputField.getText());
}
});
cancelBtn.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
dialogListener.getInputString("");
}
});
btnPanel.add(comfirmBtn);
btnPanel.add(cancelBtn);
mainPanel.add(label);
mainPanel.add(inputField);
mainPanel.add(btnPanel);
this.getContentPane().add(mainPanel);
this.setVisible(true);
this.setAlwaysOnTop(true);
}
public void setOnDialogListener(DialogListener listener){
this.dialogListener = listener;//将Main的实例传递过来
}
}
Main类：
public class Main extends JFrame implements DialogListener{
private JLabel label;
private JButton btn;
private MyDialog dialog;
public Main(){
JPanel panel = new JPanel();
btn = new JButton("对话窗口");
btn.setFont(new Font("宋体", Font.BOLD ,30));
label = new JLabel();
label.setFont(new Font("宋体", Font.BOLD ,30));
panel.add(btn);
panel.add(label);
btn.addActionListener(new ActionListener(){
@Override
public void actionPerformed(ActionEvent e){
//String str = JOptionPane.showInputDialog("title");
//label.setText(str);
dialog = new MyDialog("title");
dialog.setOnDialogListener(Main.this);
//此时不会阻塞，将继续执行下面语句
System.out.println("continue");
}
});
this.getContentPane().add(panel);
this.setSize(600,600);
this.setVisible(true);
}
@Override
public void getInputString(String returnString){
//重载回调函数
label.setText(returnString);
dialog.dispose();
}
public static void main(String[] args) {
// TODO Auto-generated method stub
Main main = new Main();
}
}
Main这里实现接口，重载回调函数可以参考设置JButton的监听。如上是一种方式，还有通过如下方式实现Main：
public class Main extends JFrame {
private JLabel label;
private JButton btn;
private MyDialog dialog;
public Main(){
JPanel panel = new JPanel();
btn = new JButton("对话窗口");
btn.setFont(new Font("宋体", Font.BOLD ,30));
label = new JLabel();
label.setFont(new Font("宋体", Font.BOLD ,30));
panel.add(btn);
panel.add(label);
btn.addActionListener(new ActionListener(){
@Override
public void actionPerformed(ActionEvent e){
//String str = JOptionPane.showInputDialog("title");
//label.setText(str);
dialog = new MyDialog("title");
dialog.setOnDialogListener(new DialogListener(){
@Override
public void getInputString(String returnString){
//重载回调函数
label.setText(returnString);
dialog.dispose();
}
});
//此时不会阻塞，将继续执行下面语句
System.out.println("continue");
}
});
this.getContentPane().add(panel);
this.setSize(600,600);
this.setVisible(true);
}
public static void main(String[] args) {
// TODO Auto-generated method stub
Main main = new Main();
}
}
