Java：Swing：按下按钮后隐藏框架

Java : Swing : Hide frame after button pressed

提问by Zac

I have a button in a java frame that when pressed it reads a value from a text field and uses that string as a port name attempting to connect to a serial device.

我在 java 框架中有一个按钮，按下它时它会从文本字段中读取一个值，并将该字符串用作尝试连接到串行设备的端口名称。

If this connection is successful the method returns true if not it returns false. If it returns true I want the frame to disappear. A series of other frames specifed in other classes will then appear with options to control the serial device.

如果此连接成功，则该方法返回 true，否则返回 false。如果它返回 true，我希望框架消失。其他类中指定的一系列其他帧将出现，并带有控制串行设备的选项。

My problem is: the button is connected to an action listener, when pressed this method is invoked. If I try to use the frame.setVisible(true); method java throws a abstract button error because I'm effectively telling it to disappear the frame containing the button before the button press method has exited. Removing the frame.setVisible(true); allow the program to run correctly however I am left with a lingering connection frame that is no longer any use.

我的问题是：按钮连接到动作侦听器，按下时调用此方法。如果我尝试使用 frame.setVisible(true); 方法 java 抛出一个抽象按钮错误，因为我有效地告诉它在按钮按下方法退出之前消失包含按钮的框架。移除 frame.setVisible(true); 允许程序正确运行，但是我留下了一个不再使用的挥之不去的连接框架。

How to I get the frame to disappear upon pressing a the button?

按下按钮后如何让框架消失？

package newimplementation1;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;


/**
 *
 * @author Zac
 */

public class ConnectionFrame extends JPanel implements ActionListener {


private JTextField textField;
private JFrame frame;
private JButton connectButton;
private final static String newline = "\n";

public ConnectionFrame(){

    super(new GridBagLayout());

    textField = new JTextField(14);
    textField.addActionListener(this);
    textField.setText("/dev/ttyUSB0");

    connectButton = new JButton("Connect");

    //Add Components to this panel.
    GridBagConstraints c = new GridBagConstraints();
    c.gridwidth = GridBagConstraints.REMAINDER;

    c.fill = GridBagConstraints.HORIZONTAL;
    add(textField, c);

    c.fill = GridBagConstraints.BOTH;
    c.weightx = 1.0;
    c.weighty = 1.0;
    add(connectButton, c);



    connectButton.addActionListener(new ActionListener() {

        public void actionPerformed(ActionEvent e)
        {

            boolean success = Main.mySerialTest.initialize(textField.getText());

            if (success == false) {System.out.println("Could not connect"); return;}

            frame.setVisible(false);  // THIS DOES NOT WORK!!

            JTextInputArea myInputArea = new JTextInputArea();
            myInputArea.createAndShowGUI();

            System.out.println("Connected");


        }
    });

}

    public void actionPerformed(ActionEvent evt) {

            // Unimplemented required for JPanel

    }

    public void createAndShowGUI() {

    //Create and set up the window.
    frame = new JFrame("Serial Port Query");
    frame.setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE);


    //Add contents to the window.
    frame.add(new ConnectionFrame());
    frame.setLocation(300, 0);


    //Display the window.
    frame.pack();
    frame.setVisible(true);

            frame.addComponentListener(new ComponentAdapter() {
        @Override
        public void componentHidden(ComponentEvent e) {
            System.out.println("Exiting Gracefully");
            Main.mySerialTest.close();
            ((JFrame)(e.getComponent())).dispose();
            System.exit(0);
        }
    });


}

}

回答by kleopatra

Running your snippet (after removing/tweaking around the custom classes), throws an NPE. Reason is that the frame you'r accessing is null. And that's because it's never set. Better not rely on any field, let the button find its toplevel ancestor and hide that, like in

运行您的代码段（在删除/调整自定义类之后），会引发 NPE。原因是您访问的框架为空。那是因为它从未设置过。最好不要依赖任何字段，让按钮找到它的顶级祖先并隐藏它，就像

        public void actionPerformed(final ActionEvent e) {

            boolean success = true;
            if (success == false) {
                System.out.println("Could not connect");
                return;
            }

            Window frame = SwingUtilities.windowForComponent((Component) e
                    .getSource());
            frame.setVisible(false); //no problem :-)

        }

回答by Hovercraft Full Of Eels

Your problem is with this line:

您的问题出在这一行：

  frame.add(new ConnectionFrame());

You're creating a new ConnectionFrame object, and so the frame that your button tries to close on is not the same as the one being displayed, and this is the source of your problem.

您正在创建一个新的 ConnectionFrame 对象，因此您的按钮尝试关闭的框架与正在显示的框架不同，这就是问题的根源。

If you change it to,

如果你改成

  //!! frame.add(new ConnectionFrame());
  frame.add(this);

so that the two JFrames are one and the same, things may work more smoothly.

这样两个 JFrame 是一回事，事情可能会更顺利。

But having said that, your whole design smells bad and I'd rethink it in a more OOP and less static fashion. Also, use dialogs where dialogs are needed, not frames, and rather than dialogs consider swapping views (JPanels) via CardLayout as a better option still.

但话虽如此，你的整个设计闻起来很糟糕，我会以更面向对象和更少静态的方式重新考虑它。此外，在需要对话框的地方使用对话框，而不是框架，而不是对话框，考虑通过 CardLayout 交换视图 (JPanels) 作为更好的选择。

Myself, I'd create a "dumb" GUI for this, one that creates a JPanel (here in my example it extends a JPanel for simplicity, but I'd avoid extending if not necessary), and I'd let whoever is calling this code decide what to do with the information via some control. For e.g.,

我自己，我会为此创建一个“愚蠢”的 GUI，一个创建 JPanel 的 GUI（在我的示例中，为了简单起见，它扩展了一个 JPanel，但如果没有必要，我会避免扩展），并且我会让任何调用此代码通过某种控制决定如何处理信息。例如，

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

@SuppressWarnings("serial")
public class ConnectionPanel extends JPanel {

   private JTextField textField;
   private JButton connectButton;
   private ConnectionPanelControl control;

   public ConnectionPanel(final ConnectionPanelControl control) {
      super(new GridBagLayout());
      this.control = control;

      ActionListener listener = new ActionListener() {
         public void actionPerformed(ActionEvent e) {
            if (control != null) {
               control.connectButtonAction();
            }
         }
      };

      textField = new JTextField(14);
      textField.addActionListener(listener);
      textField.setText("/dev/ttyUSB0");

      connectButton = new JButton("Connect");

      GridBagConstraints c = new GridBagConstraints();
      c.gridwidth = GridBagConstraints.REMAINDER;

      c.fill = GridBagConstraints.HORIZONTAL;
      add(textField, c);

      c.fill = GridBagConstraints.BOTH;
      c.weightx = 1.0;
      c.weighty = 1.0;
      add(connectButton, c);

      connectButton.addActionListener(listener);
   }

   public String getFieldText() {
      return textField.getText();
   }

}

Again, something outside of the simple GUI would make decisions on what to do with the text that the textfield contains and what to do with the GUI that is displaying this JPanel:

同样，简单 GUI 之外的东西将决定如何处理文本字段包含的文本以及如何处理显示此 JPanel 的 GUI：

public interface ConnectionPanelControl {

   void connectButtonAction();

}

Also, you will likely do any connecting in a background thread so as to not freeze your GUI, probably a SwingWorker. Perhaps something like this:

此外，您可能会在后台线程中进行任何连接，以免冻结您的 GUI，可能是 SwingWorker。也许是这样的：

import java.awt.event.ActionEvent;
import java.util.concurrent.ExecutionException;

import javax.swing.*;

@SuppressWarnings("serial")
public class MyMain extends JPanel {
   public MyMain() {
      add(new JButton(new ConnectionAction("Connect", this)));
   }

   private static void createAndShowGui() {
      JFrame frame = new JFrame("My Main");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(new MyMain());
      frame.pack();
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }
}

@SuppressWarnings("serial")
class ConnectionAction extends AbstractAction {
   private MyMain myMain;
   private ConnectionPanel cPanel = null;
   private JDialog dialog = null;

   public ConnectionAction(String title, MyMain myMain) {
      super(title);
      this.myMain = myMain;
   }

   @Override
   public void actionPerformed(ActionEvent e) {
      if (dialog == null) {
         dialog = new JDialog(SwingUtilities.getWindowAncestor(myMain));
         dialog.setTitle("Connect");
         dialog.setModal(true);
         cPanel = new ConnectionPanel(new ConnectionPanelControl() {

            @Override
            public void connectButtonAction() {
               final String connectStr = cPanel.getFieldText();
               new MySwingWorker(connectStr).execute();
            }
         });
         dialog.getContentPane().add(cPanel);
         dialog.pack();
         dialog.setLocationRelativeTo(null);
      }
      dialog.setVisible(true);
   }

   private class MySwingWorker extends SwingWorker<Boolean, Void> {
      private String connectStr = "";

      public MySwingWorker(String connectStr) {
         this.connectStr = connectStr;
      }

      @Override
      protected Boolean doInBackground() throws Exception {
         // TODO: make connection and then return a result
         // right now making true if any text in the field
         if (!connectStr.isEmpty()) {
            return true;
         }
         return false;
      }

      @Override
      protected void done() {
         try {
            boolean result = get();
            if (result) {
               System.out.println("connection successful");
               dialog.dispose();
            } else {
               System.out.println("connection not successful");
            }
         } catch (InterruptedException e) {
            e.printStackTrace();
         } catch (ExecutionException e) {
            e.printStackTrace();
         }
      }
   }
}

回答by JB Nizet

Your code would be much more readable if you named JFrame instances xxxFrame, and JPanel instances xxxPanel. Naming JPanel instances xxxFrame makes things very confusing.

如果您将 JFrame 实例命名为 xxxFrame，并将 JPanel 实例命名为 xxxPanel，您的代码将更具可读性。命名 JPanel 实例 xxxFrame 使事情变得非常混乱。

It would also help if you pasted the stack trace of the exception.

如果您粘贴异常的堆栈跟踪，它也会有所帮助。

I suspect the problem comes from the fact that frame is null. This is due to the fact that the frame field is only initialized in the createAndShowGUI method, but this method doesn't display the current connection panel, but a new one, which thus have a null frame field:

我怀疑问题来自框架为空的事实。这是因为只有在 createAndShowGUI 方法中对 frame 字段进行了初始化，但该方法不显示当前的连接面板，而是一个新的，因此具有空的 frame 字段：

ConnectionFrame firstPanel = new ConnectionFrame();
// The firstPanel's frame field is null
firstPanel.createAndShowGUI();
// the firstPanel's frame field is now not null, but
// the above call opens a JFrame containing another, new ConnectionFrame, 
// which has a null frame field

The code of createAndShowGUI should contain

createAndShowGUI 的代码应该包含

frame.add(this);

rather than

而不是

frame.add(new ConnectionFrame());

回答by mKorbel

for Swing GUI is better create only once JFrameand another Top-Level Containerswould be JDialogor JWindow(un-decorated by default),

对于 Swing GUI 最好只创建一次JFrame，另一个顶级容器将是JDialog或JWindow（默认情况下未装饰），

simple example here

简单的例子在这里

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class SuperConstructor extends JFrame {

    private static final long serialVersionUID = 1L;

    public SuperConstructor() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setPreferredSize(new Dimension(300, 300));
        setTitle("Super constructor");
        Container cp = getContentPane();
        JButton b = new JButton("Show dialog");
        b.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent evt) {
                FirstDialog firstDialog = new FirstDialog(SuperConstructor.this);
            }
        });
        cp.add(b, BorderLayout.SOUTH);
        JButton bClose = new JButton("Close");
        bClose.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent evt) {
                System.exit(0);
            }
        });
        add(bClose, BorderLayout.NORTH);
        pack();
        setVisible(true);
    }

    public static void main(String args[]) {
        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                SuperConstructor superConstructor = new SuperConstructor();
            }
        });
    }

    private class FirstDialog extends JDialog {

        private static final long serialVersionUID = 1L;

        FirstDialog(final Frame parent) {
            super(parent, "FirstDialog");
            setPreferredSize(new Dimension(200, 200));
            setLocationRelativeTo(parent);
            setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);
            setModalityType(Dialog.ModalityType.DOCUMENT_MODAL);
            JButton bNext = new JButton("Show next dialog");
            bNext.addActionListener(new ActionListener() {

                @Override
                public void actionPerformed(ActionEvent evt) {
                    SecondDialog secondDialog = new SecondDialog(parent, false);
                }
            });
            add(bNext, BorderLayout.NORTH);
            JButton bClose = new JButton("Close");
            bClose.addActionListener(new ActionListener() {

                @Override
                public void actionPerformed(ActionEvent evt) {
                    setVisible(false);
                }
            });
            add(bClose, BorderLayout.SOUTH);
            pack();
            setVisible(true);
        }
    }
    private int i;

    private class SecondDialog extends JDialog {

        private static final long serialVersionUID = 1L;

        SecondDialog(final Frame parent, boolean modal) {
            //super(parent); // Makes this dialog unfocusable as long as FirstDialog is visible
            setPreferredSize(new Dimension(200, 200));
            setLocation(300, 50);
            setModal(modal);
            setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);
            setTitle("SecondDialog " + (i++));
            JButton bClose = new JButton("Close");
            bClose.addActionListener(new ActionListener() {

                @Override
                public void actionPerformed(ActionEvent evt) {
                    setVisible(false);
                }
            });
            add(bClose, BorderLayout.SOUTH);
            pack();
            setVisible(true);
        }
    }
}

better would be re-use Top-Level Containers, as create lots of Top-Level Containers on Runtime (possible memory lack)

最好重用顶级容器，因为在运行时创建大量顶级容器（可能内存不足）