这让我想起了我在 StackOverflow 上使用 Window.setLocationByPlatform(true) 发表的一篇非常喜欢的帖子。
How to best position Swing GUIs
编辑 1：
您可以将FocusListener 添加到您的JDialog 和focusGained(...) 方法上，您可以将setLocationRelativeTo(null) 用于JFrame 和JDialog，以便它们都位于中心屏幕，无论他们以前在哪里。
import java.awt.*;
import java.awt.event.FocusEvent;
import java.awt.event.FocusListener;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
/**
* Created with IntelliJ IDEA.
* User: Gagandeep Bali
* Date: 1/14/13
* Time: 7:34 PM
* To change this template use File | Settings | File Templates.
*/
public class FrameFocus
{
private JFrame mainwindow;
private CustomDialog customDialog;
private void displayGUI()
{
mainwindow = new JFrame("Frame Focus Window Example");
customDialog = new CustomDialog(mainwindow, "Modal Dialog", true);
mainwindow.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
JPanel contentPane = new JPanel();
JButton mainButton = new JButton(
"Click me to open a MODAL Dialog");
mainButton.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
if (!customDialog.isShowing())
customDialog.setVisible(true);
}
});
contentPane.add(mainButton);
mainwindow.setContentPane(contentPane);
mainwindow.pack();
mainwindow.setLocationByPlatform(true);
mainwindow.setVisible(true);
}
public static void main(String... args)
{
EventQueue.invokeLater(new Runnable()
{
@Override
public void run()
{
new FrameFocus().displayGUI();
}
});
}
}
class CustomDialog extends JDialog
{
private JFrame mainWindow;
public CustomDialog(JFrame owner, String title, boolean modal)
{
super(owner, title, modal);
mainWindow = owner;
JPanel contentPane = new JPanel();
JLabel dialogLabel = new JLabel(
"I am a Label on JDialog.", JLabel.CENTER);
contentPane.add(dialogLabel);
setContentPane(contentPane);
pack();
addFocusListener(new FocusListener() {
@Override
public void focusGained(FocusEvent e) {
mainWindow.setLocationRelativeTo(null);
setLocationRelativeTo(null);
}
@Override
public void focusLost(FocusEvent e) {
/*
* Nothing written for this part yet
*/
}
});
}
}
编辑 2：
我在这里和那里搜索了一下，在我看来，实际上你的应用程序首先出现在哪个Monitor Screen 上，将确定它是GraphicsConfiguration。虽然当我在 API 中漫游时，对于上述 GraphicsConfiguration 事物只有一个 getter 方法，而没有相同的 setter 方法（您仍然可以通过任何顶级窗口的构造函数指定一个，即 JFrame(...)/JDialog(...) )。
现在你可以用这段代码来占据你的头了，它可以用来确定你想要设置的适当位置，同样，在我看来，你可能必须使用focusGain() 方法，以满足你的条件 2题。看一下附带的代码，虽然不需要创建new JFrame/JDialog，只是看如何获取屏幕坐标（您可以在focusGain()方法中添加以确定整个应用程序的位置。）
GraphicsEnvironment ge = GraphicsEnvironment.
getLocalGraphicsEnvironment();
GraphicsDevice[] gs = ge.getScreenDevices();
for (int j = 0; j < gs.length; j++) {
GraphicsDevice gd = gs[j];
GraphicsConfiguration[] gc =
gd.getConfigurations();
for (int i=0; i < gc.length; i++) {
JFrame f = new
JFrame(gs[j].getDefaultConfiguration());
Canvas c = new Canvas(gc[i]);
Rectangle gcBounds = gc[i].getBounds();
int xoffs = gcBounds.x;
int yoffs = gcBounds.y;
f.getContentPane().add(c);
f.setLocation((i*50)+xoffs, (i*60)+yoffs);
f.show();
}
}
编辑 3：
尝试改变这一点：
int x = loc.getX() + (mainWindow.getWidth() - getWidth()) / 2;
int y = loc.getY() + (mainWindow.getHeight() - getHeight()) / 2;
setLocation(x, y);
只是：
setLocationRelativeTo(mainWindow);
为了测试上述内容，我按原样使用了我的 FrameFocus 类，尽管我已将您的更改添加到我的 CustomDialog 方法中，如修改后的 CustomDialog 类所示。
class CustomDialog extends JDialog
{
private JFrame mainWindow;
public CustomDialog(JFrame owner, String title, boolean modal)
{
super(owner, title, modal);
mainWindow = owner;
JPanel contentPane = new JPanel();
JLabel dialogLabel = new JLabel(
"I am a Label on JDialog.", JLabel.CENTER);
contentPane.add(dialogLabel);
setContentPane(contentPane);
pack();
addFocusListener(new FocusListener() {
@Override
public void focusGained(FocusEvent e) {
//mainWindow.setLocationRelativeTo(null);
//setLocationRelativeTo(null);
GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
GraphicsDevice[] gs = ge.getScreenDevices();
for (int j = 0; j < gs.length; j++) {
GraphicsDevice gd = gs[j];
GraphicsConfiguration[] gc = gd.getConfigurations();
for (int i=0; i < gc.length; i++) {
Rectangle gcBounds = gc[i].getBounds();
Point loc = mainWindow.getLocationOnScreen();
if (gcBounds.contains(loc)) {
System.out.println("at " + j + " screen");
int x = gcBounds.x + (gcBounds.width - mainWindow.getWidth()) / 2;
int y = gcBounds.y + (gcBounds.height - mainWindow.getHeight()) / 2;
mainWindow.setLocation(x, y);
//x = (int) (loc.getX() + (mainWindow.getWidth() - CustomDialog.this.getWidth()) / 2);
//y = (int) (loc.getY() + (mainWindow.getHeight() - CustomDialog.this.getHeight()) / 2);
//CustomDialog.this.setLocation(x, y);
CustomDialog.this.setLocationRelativeTo(mainWindow);
break;
}
}
}
}
@Override
public void focusLost(FocusEvent e) {
/*
* Nothing written for this part yet
*/
}
});
}
}