[英]paint method is not being called
我不知道为什么,但我不能从代码中调用方法paint(Graphics g)
。 我有MouseListeners
:
@Override
public void mouseReleased(MouseEvent e) {
pointstart = null;
}
@Override
public void mousePressed(MouseEvent e) {
pointstart = e.getPoint();
}
和MouseMotionListeners
:
@Override
public void mouseMoved(MouseEvent e) {
pointend = e.getPoint();
}
@Override
public void mouseDragged(MouseEvent arg0) {
pointend = arg0.getPoint();
// ==========================================================================
// call repaint:
repaint();
// ==========================================================================
}
和我的paint
方法:
public void paint(Graphics g){
super.paint(g); //here I have my breakpoint in debugger
g.translate(currentx, currenty);
if(pointstart!=null){
g.setClip(chartPanel.getBounds());
g.setColor(Color.BLACK);
g.drawLine(pointstart.x, pointstart.y, pointend.x, pointend.y);
}
}
在初始化方法中:
currentx = chartPanel.getLocationOnScreen().x;
currenty = Math.abs(chartPanel.getLocationOnScreen().y - frame.getLocationOnScreen().y);
所有在课堂上,这是我的工作框架,它扩展了JFrame
。
问题是,该程序不会call
paint方法。 我在调试器中检查过。 我试过paintComponent
,没有super.paint(g)
。 最好的是,我从我的其他项目复制的代码,它工作得很好。
更新:这是我想在面板上绘制线条的代码(无论是面板/图表面板/等)。 而且它不会画画。 我尝试通过paint(Graphics g){super.paint(g).....}来做到这一点,但它也没有。 单击“线”按钮后,绘画应该是有效的。
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Point;
import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.BorderLayout;
import javax.swing.JButton;
import javax.swing.JToolBar;
import javax.swing.SwingConstants;
import javax.swing.JScrollPane;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
public class Window extends JFrame {
private JFrame frame;
public JPanel panelbuttons;
public JPanel panelscrollpane;
public JButton btnLine;
public JToolBar toolBar;
public JScrollPane scrollPane;
public JPanel panel;
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
Window window = new Window();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
public Window() {
initialize();
}
private void initialize() {
frame = new JFrame();
frame.setBounds(100, 100, 644, 430);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
panel = new JPanel();
panelbuttons = new JPanel();
frame.getContentPane().add(panelbuttons, BorderLayout.WEST);
panelbuttons.setLayout(new BorderLayout(0, 0));
toolBar = new JToolBar();
toolBar.setOrientation(SwingConstants.VERTICAL);
panelbuttons.add(toolBar, BorderLayout.WEST);
btnLine = new JButton("line");
btnLine.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
panel.addMouseListener(mouselistenerLine);
panel.addMouseMotionListener(mousemotionlistenerLine);
}
});
toolBar.add(btnLine);
panelscrollpane = new JPanel();
frame.getContentPane().add(panelscrollpane, BorderLayout.CENTER);
panelscrollpane.setLayout(new BorderLayout(0, 0));
scrollPane = new JScrollPane(panel);
panel.setLayout(new BorderLayout(0, 0));
scrollPane.setViewportBorder(null);
panelscrollpane.add(scrollPane);
panelscrollpane.revalidate();
}
Point pointstart = null;
Point pointend = null;
private MouseListener mouselistenerLine = new MouseListener() {
@Override
public void mouseReleased(MouseEvent e) {
System.out.println("I'm in first listener. - mouse Released");
pointstart = null;
}
@Override
public void mousePressed(MouseEvent e) {
System.out.println("I'm in first listener. - mousePressed");
pointstart = e.getPoint();
}
@Override
public void mouseExited(MouseEvent e) {
}
@Override
public void mouseEntered(MouseEvent e) {
}
@Override
public void mouseClicked(MouseEvent e) {
}
};
private MouseMotionListener mousemotionlistenerLine = new MouseMotionListener() {
@Override
public void mouseMoved(MouseEvent e) {
System.out.println("I'm in second listener. - mouseMoved");
pointend = e.getPoint();
}
@Override
public void mouseDragged(MouseEvent arg0) {
System.out.println("I'm in second listener. - mouseDragged");
pointend = arg0.getPoint();
repaint();
}
};
public void paintComponent(Graphics g){
System.out.println("I'm in paintComponent method.");
if(pointstart!=null){
System.out.println("I'm drawing.");
g.setClip(scrollPane.getBounds());
g.setColor(Color.BLACK);
g.drawLine(pointstart.x, pointstart.y, pointend.x, pointend.y);
}
}
}
您正在创建两个单独的JFrame实例,并且只显示一个。
创建一个实例是因为Window
类扩展了JFrame
,第二个是在initialize
方法中创建的。
要在没有很多代码更改的情况下修复此问题,请执
private void initialize() {
frame = this;
frame.setBounds(100, 100, 644, 430);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
BTW。 将paintComponent(Graphic g)
更改为paint(Graphic g)
因为JFrame
不是JComponent
。
调用repaint()
将触发调用paint(Graphics g)
方法。 因此,您不必显式调用paint()
。
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