java - 单击按钮打开时，新 JFrame 以禁用状态打开

Question

我遇到了一个非常不寻常的情况。我有一个类“ScreenSizeSelector”，它有一个方法“getSelectedScreenSize”。该方法的工作是创建一个 UI，用户拖动 UI 和方法返回窗口大小。

现在我通过以下方式调用类的方法:

1. 一个简单的类(非 GUI)
2. 在按钮上从 JFrame 单击

在第一种情况下，它工作得很好(即大小选择器窗口打开，用户拖动它，调整它的大小并返回窗口坐标)但在第二种情况下，窗口打开但处于禁用模式，用户无法无法在窗口上执行任何操作，甚至无法关闭窗口。

这是我使用的代码

屏幕尺寸选择器类:

package screenrecorder;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Rectangle;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;

import javax.swing.BorderFactory;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.Border;


class ScreenSizeSelector {

    private JFrame sizeSelectorWindow;
    private JButton btnOk;
    private Border emptyBorder;
    private Rectangle screenArea = null;
    private static Object lock = new Object();



    public Rectangle getSelectedScreenSize(){

        screenSizeSelectorUI();

        Thread t = new Thread() {
            public void run() {
                synchronized(lock) {
                    while (sizeSelectorWindow.isVisible())
                        try {
                            lock.wait();
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                }
            }
        };

        t.start();
        try {
            t.join();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        return screenArea;
    }


    public void screenSizeSelectorUI() {
        emptyBorder = BorderFactory.createEmptyBorder();

        sizeSelectorWindow = new JFrame("Select screen area");

        btnOk = new JButton("Start");
        sizeSelectorWindow.setUndecorated(true);
        sizeSelectorWindow.getRootPane().setWindowDecorationStyle(3);
        sizeSelectorWindow.setBackground( new Color(0, 0, 0, 0) );
        sizeSelectorWindow.setSize(400,400);

        sizeSelectorWindow.addWindowListener(new WindowEventHandler());
        sizeSelectorWindow.setAlwaysOnTop(true);
        sizeSelectorWindow.setLocationRelativeTo(null);


        btnOk.setToolTipText("Click this button after deciding the screen area");
        btnOk.addActionListener(new ButtonEventHandler());


        JPanel buttonPanel = new JPanel(new FlowLayout(FlowLayout.RIGHT));
        buttonPanel.setBackground(new Color(0,0,0,0));
        buttonPanel.add(btnOk);
        sizeSelectorWindow.add(buttonPanel,BorderLayout.SOUTH);

        sizeSelectorWindow.setVisible(true);
        sizeSelectorWindow.setEnabled(true);

    }

class ButtonEventHandler implements ActionListener {

@Override
public void actionPerformed(ActionEvent e) {

    int x = (int)(sizeSelectorWindow.getBounds().getX());
    int y = (int) (sizeSelectorWindow.getBounds().getY());
    int width = sizeSelectorWindow.getWidth();
    int height = sizeSelectorWindow.getHeight();

    screenArea = new Rectangle(x,y,width,height);
    sizeSelectorWindow.dispatchEvent(new WindowEvent(sizeSelectorWindow, WindowEvent.WINDOW_CLOSING));
}


}

class WindowEventHandler implements WindowListener{

    @Override
    public void windowOpened(WindowEvent e) {
    }

    @Override
    public void windowClosing(WindowEvent e) {

        synchronized (lock) {
            sizeSelectorWindow.setVisible(false);
            lock.notify();
        }
    }

    @Override
    public void windowClosed(WindowEvent e) {
    }

    @Override
    public void windowIconified(WindowEvent e) {
        sizeSelectorWindow.setState(JFrame.NORMAL);
        Toolkit.getDefaultToolkit().beep();
    }

    @Override
    public void windowDeiconified(WindowEvent e) {}

    @Override
    public void windowActivated(WindowEvent e) {}

    @Override
    public void windowDeactivated(WindowEvent e) {}


    }

}

测试 1 类:

package screenrecorder;

import java.awt.Rectangle;

public class Test1{

    public static void main(String[] args){
        System.out.println(new ScreenSizeSelector().getSelectedScreenSize());
    }
}

测试2类:

package screenrecorder;

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;

public class Test2 extends JFrame{

    public Test2(){

        JButton btn = new JButton("Click ME");
        btn.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                System.out.println(new ScreenSizeSelector().getSelectedScreenSize());

            }
        });

        getContentPane().add(btn);
        setSize(100,100);
        setVisible(true);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    }

    public static void main(String[] args){
        new Test2();
    }

}

感谢任何帮助。

Answer 1

当您单击按钮时， Action 监听器等待 getSelectedScreenSize() 函数返回。 getSelectedScreenSize() 函数正在等待由 screenSelectorUI() 创建的第二个窗口不可见。 screenSelectorUI() 确实创建了第二个窗口，但您可以像这样设置颜色:

sizeSelectorWindow.setBackground( new Color(0, 0, 0, 0) );

如果您查看颜色构造函数 javadocs:

public Color(int r,
                int g,
                int b,
                int a)

Creates an sRGB color with the specified red, green, blue, and alpha values in the range (0 - 255).
Parameters:

• r - the red component
• g - the green component
• b - the blue component
• a - the alpha component

您将 alpha 值设置为 0，使其完全不可见。 (alpha 值是透明的)另外，第二个窗口是未修饰的并且不会在关闭时退出，所以您甚至根本不知道它在那里。

我完全不明白 test1 是如何工作的。旁注:当我在 Mac 上尝试测试 1 时，它只显示按钮，我所能做的就是单击它。该按钮将消失，但应用程序仍将运行。

这基本上完全是猜测，但是很多 swing 组件向操作系统发出请求，而不是命令。有点像说，“嘿，我可以调整到 400、400 吗？”操作系统在技术上不必按照您说的去做。我在读How does Java handle multithreading?这表示多线程确实取决于操作系统。我有一种感觉，当 screenSelectorUI() 被自己调用时，它只是在某个地方搞砸了，但当它在某个按钮的线程内时，它以某种方式得到了正确。