鼠標懸停之前不顯示JButton

Question

我正在創建一個具有2個面板的GUI。 首次加載gui時，只有一個面板可見，並且當按下按鈕時，將顯示新面板。 問題在於，在第二個面板上加載按鈕時，它們是不可見的，僅當鼠標懸停在它們上方時才顯示。 最重要的是，當您移動屏幕時，它們再次變得不可見，需要將鼠標懸停以再次顯示。 我真的不知道嘗試什么，因為我研究了具有多個面板的方法，這似乎是最好的方法，而且按鈕的實現方式與我為第一個面板實現它們的方式相同，並且它們呈現正確。

完整代碼

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

public class Gui {
    private JFrame frame;
    private JPanel panel1;
    private JPanel panel2;
    private JButton btnShip1, btnShip2, btnShip3, btnTutorial, btnLeftControl, btnHull, btnTargeting, btnRadar, btnWarning, btnRightControl;
    private JTextField txtCharacterName, txtShipName;
    private JLabel welcome, background;

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

    public Gui(){
        createWindow();
        addButtons();
        addFields();
        addWelcome();

        frame.add(panel1);
        frame.setVisible(true);

        addBackground();
        addShipControls();
    }

    public void createWindow(){
        frame = new JFrame();
        frame.setTitle("Space Battle");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(642, 518);

        panel1 = new JPanel();
        panel1.setLayout(null);
        panel1.setBackground(Color.decode("#242627"));

        panel2 = new JPanel();
        panel2.setLayout(null);
        panel2.setBackground(Color.decode("#242627"));
    }

    public void addButtons(){
        btnShip1 = new JButton ();
        try 
        {
            ImageIcon img = new ImageIcon ("resources/cruiserSelectBtn.jpg");
            btnShip1.setIcon(img);
        } 
        catch (Exception e) {}
        try 
        {
            ImageIcon img = new ImageIcon ("resources/button_1_hover.gif");
            btnShip1.setRolloverIcon(img);
        } 
        catch (Exception e) {}
        btnShip1.setBounds(246,0,380,160);
        btnShip1.setMargin(new Insets(0, 0, 0, 0));
        btnShip1.addActionListener(new cruiserSelectHandler());
        btnShip1.setBorder(null);
        panel1.add (btnShip1);

        btnShip2 = new JButton ();
        try 
        {
            ImageIcon img = new ImageIcon ("resources/fighterSelectBtn.jpg");
            btnShip2.setIcon(img);
        } 
        catch (Exception e) {}
        try 
        {
            ImageIcon img = new ImageIcon ("resources/button_2_hover.gif");
            btnShip2.setRolloverIcon(img);
        } 
        catch (Exception e) {}
        btnShip2.setBounds(246,160,380,160);
        btnShip2.setMargin(new Insets(0, 0, 0, 0));
        btnShip2.addActionListener(new fighterSelectHandler());
        btnShip2.setBorder(null);
        panel1.add (btnShip2);

        btnShip3 = new JButton ();
        try 
        {
            ImageIcon img = new ImageIcon ("resources/battleSelectBtn.jpg");
            btnShip3.setIcon(img);
        } 
        catch (Exception e) {}
        try 
        {
            ImageIcon img = new ImageIcon ("resources/button_3_hover.gif");
            btnShip3.setRolloverIcon(img);
        } 
        catch (Exception e) {}
        btnShip3.setBounds(246,320,380,160);
        btnShip3.setMargin(new Insets(0, 0, 0, 0));
        btnShip3.addActionListener(new battleSelectHandler());
        btnShip3.setBorder(null);
        panel1.add (btnShip3);

        btnTutorial = new JButton ();
        try 
        {
            ImageIcon img = new ImageIcon ("resources/tutorialBtn.jpg");
            btnTutorial.setIcon(img);
        } 
        catch (Exception e) {}
        btnTutorial.setBounds(5,426,234,49);
        btnTutorial.setMargin(new Insets(0, 0, 0, 0));
        panel1.add (btnTutorial);
    }

    public void addFields(){
        txtCharacterName = new JTextField("Insert Character Name");
        txtCharacterName.setBounds(12,260,220,35);
        panel1.add(txtCharacterName);

        txtShipName = new JTextField("Insert Ship Name");
        txtShipName.setBounds(12,315,220,35);
        panel1.add(txtShipName);
    }

    public void addWelcome(){
        welcome =  new JLabel ();
        try 
        {
            ImageIcon img = new ImageIcon ("resources/welcome.jpg");
            welcome.setIcon(img);
        } 
        catch (Exception e) {}
        welcome.setBounds(0,0,247,229);
        panel1.add(welcome);
    }
    //Class used to change panels
    class cruiserSelectHandler implements ActionListener {
        public void actionPerformed(ActionEvent even) {
            frame.add(panel2);
            panel1.setVisible(false);
        }
    }

    class fighterSelectHandler implements ActionListener {
        public void actionPerformed(ActionEvent even) {
            frame.add(panel2);
            panel1.setVisible(false);
        }
    }

    class battleSelectHandler implements ActionListener {
        public void actionPerformed(ActionEvent even) {
            frame.add(panel2);
            panel1.setVisible(false);
        }
    }

    public void addBackground(){
            //Is the background interfering?
        background =  new JLabel ();
        try 
        {
            ImageIcon img = new ImageIcon ("resources/background.jpg");
            background.setIcon(img);
        } 
        catch (Exception e) {}
        background.setBounds(0,0,640,480);
        panel2.add(background);
    }

    //Class used to add controls/buttons
    public void addShipControls(){
        btnLeftControl = new JButton ();
        try 
        {
            ImageIcon img = new ImageIcon ("resources/left_controls.png");
            btnLeftControl.setIcon(img);
        } 
        catch (Exception e) {}
        btnLeftControl.setBounds(-8,319,131,160);
        btnLeftControl.setMargin(new Insets(0, 0, 0, 0));
        btnLeftControl.setBorder(null);
        panel2.add (btnLeftControl);

        btnHull = new JButton ();
        try 
        {
            ImageIcon img = new ImageIcon ("resources/hull_controls.png");
            btnHull.setIcon(img);
        } 
        catch (Exception e) {}
        btnHull.setBounds(123,319,91,160);
        btnHull.setMargin(new Insets(0, 0, 0, 0));
        btnHull.setBorder(null);
        panel2.add (btnHull); 

        btnTargeting = new JButton ();
        try 
        {
            ImageIcon img = new ImageIcon ("resources/targeting_controls.png");
            btnTargeting.setIcon(img);
        } 
        catch (Exception e) {}
        btnTargeting.setBounds(214,319,202,160);
        btnTargeting.setMargin(new Insets(0, 0, 0, 0));
        btnTargeting.setBorder(null);
        panel2.add (btnTargeting);

        btnWarning = new JButton ();
        try 
        {
            ImageIcon img = new ImageIcon ("resources/warning_controls.png");
            btnWarning.setIcon(img);
        } 
        catch (Exception e) {}
        btnWarning.setBounds(416,411,86,68);
        btnWarning.setMargin(new Insets(0, 0, 0, 0));
        btnWarning.setBorder(null);
        panel2.add (btnWarning);

        btnRadar = new JButton ();
        try 
        {
            ImageIcon img = new ImageIcon ("resources/radar_idea.gif");
            btnRadar.setIcon(img);
        } 
        catch (Exception e) {}
        btnRadar.setBounds(416,319,86,92);
        btnRadar.setMargin(new Insets(0, 0, 0, 0));
        btnRadar.setBorder(null);
        panel2.add (btnRadar);

        btnRightControl = new JButton ();
        try 
        {
            ImageIcon img = new ImageIcon ("resources/right_controls.png");
            btnRightControl.setIcon(img);
        } 
        catch (Exception e) {}
        btnRightControl.setBounds(502,319,131,160);
        btnRightControl.setMargin(new Insets(0, 0, 0, 0));
        btnRightControl.setBorder(null);
        panel2.add (btnRightControl);

    }
}

Answer 1

當按下按鈕時，將顯示新面板。

問題是：

1. 您正在使用空布局
2. 您將在框架中添加兩個不同的面板。

默認情況下，Swing以相反的順序繪制組件。

因此，當添加panel1時，它是框架中唯一的面板，因此將其繪制。

然后單擊一個按鈕並添加panel2。 因此，Swing繪制panel2，然后在頂部重新繪制panel1，因此panel2被隱藏。 當您將鼠標懸停在按鈕上時，它會出現，因為按鈕會監聽mouseEntered事件，並且按鈕會重新繪制。

調整屏幕大小時，首先繪制了panel2的顏色，然后又繪制了panel1的顏色，所以您再次遇到問題。

解決方案是使用適當的布局管理器。 在您的情況下，您應該使用卡片布局。 卡布局將交換面板，以確保一次只能看到一個面板。 閱讀有關使用卡布局的Swing教程。 然后擺脫所有的null布局和setBounds（）方法。