我有一个简单的 GUI 程序,我正在尝试开始工作。当用户按下底部按钮时,我试图绘制一些形状。当我摆脱paint()中的if(buttonClicked)时,一切都显示正常,但paint()似乎是自动执行的,并且形状出现时没有任何按钮单击。当我用 if(buttonClicked) 添加包围 Paint() 主体时,无论 ButtonHandler 类如何处理它,我的其余组件甚至不会显示在框架中。我不知道为什么会发生这种情况。在 Paint() 中使用或不使用 if 逻辑测试代码,您将看到发生了什么。
public class GUI extends JFrame {
//declare components
Container container;
JPanel centerPanel, northPanel, southPanel, eastPanel, westPanel, mouseClickPanel;
JLabel topLabel;
JTextArea textArea;
JButton buttonA, buttonB, drawButton;
boolean buttonClicked;
public GUI(String title) {
super(title); // invoke JFrame Constructor
container = getContentPane();
container.setLayout(new BorderLayout());
centerPanel = new JPanel();
centerPanel.setBackground(Color.CYAN);
northPanel = new JPanel();
northPanel.setBackground(Color.GREEN);
southPanel = new JPanel();
southPanel.setBackground(Color.MAGENTA);
eastPanel = new JPanel();
eastPanel.setBackground(Color.ORANGE);
westPanel = new JPanel();
westPanel.setBackground(Color.YELLOW);
mouseClickPanel = new JPanel();
mouseClickPanel.setBackground(Color.GRAY);
mouseClickPanel.setPreferredSize(new Dimension(400, 400));
topLabel = new JLabel("Press either button to make something happen");
topLabel.setFont(new Font("Calibri", Font.PLAIN, 16));
topLabel.setHorizontalAlignment(JLabel.CENTER);
textArea = new JTextArea(3, 20);
textArea.setEditable(false);
buttonA = new JButton("Press Here");
buttonB = new JButton("Press Here");
drawButton = new JButton("Press here");
container.add(centerPanel, BorderLayout.CENTER);
container.add(northPanel, BorderLayout.NORTH);
container.add(southPanel, BorderLayout.SOUTH);
container.add(eastPanel, BorderLayout.EAST);
container.add(westPanel, BorderLayout.WEST);
northPanel.add(topLabel, BorderLayout.NORTH);
centerPanel.add(buttonA);
centerPanel.add(textArea);
centerPanel.add(buttonB);
centerPanel.add(mouseClickPanel);
centerPanel.add(drawButton);
buttonClicked = false;
ButtonHandler buttonHandler = new ButtonHandler(buttonA, drawButton, textArea, buttonClicked);
buttonA.addActionListener(buttonHandler); // add actionListeners to buttonA and B
buttonB.addActionListener(buttonHandler);
drawButton.addActionListener(buttonHandler);
setSize(525, 600);
setVisible(true);
}
public void paint(Graphics g) {
if (buttonClicked) {
super.paint(g);
g.setColor(Color.RED);
g.fillOval(150, 150, 50, 50);
g.draw3DRect(200, 200, 50, 50, true);
}
}
}
处理程序类:
public class ButtonHandler extends JFrame implements ActionListener {
private JButton buttonA, drawButton;
private JTextArea textArea;
boolean buttonClicked;
public ButtonHandler(JButton buttonA, JButton drawButton, JTextArea textArea, boolean buttonClicked) {
this.buttonA = buttonA;
this.textArea = textArea;
this.drawButton = drawButton;
this.buttonClicked = buttonClicked;
}
@Override
public void actionPerformed(ActionEvent e) {
if (e.getSource() == buttonA) {
textArea.setText(" <- You pressed left button");
}
else if (e.getSource() == drawButton) {
textArea.setText("You pressed button to draw rectangle");
buttonClicked = true;
repaint();
}
else {
textArea.setText("You pressed right button ->");
}
}
}
最佳答案
将 super.paint(g);
从 if 语句中取出。将其作为第一行。否则,除非单击该按钮,否则根本不会进行任何绘制(包括 JPanel 内部结构,例如背景)。
关于java - 导致其他组件不显示的绘制方法,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/29547479/