我无法访问扩展JPanel
的类MyPanel
的公共(public)方法。在 MyPanel
中,我之前有名为 moveSquare
的 private
方法,但为了使其适用于外部请求,我将其更改为 public
,但它仍然不起作用?如何让它发挥作用?
import javax.swing.SwingUtilities;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.BorderFactory;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseMotionListener;
import java.awt.event.MouseMotionAdapter;
public class mull {
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
JPanel p = createAndShowGUI();
iterate(p);
// "The method iterate(MyPanel) in the type mull is not applicable for the arguments (JPanel)"
}
});
}
private static JPanel createAndShowGUI() {
System.out.println("Created GUI on EDT? "+
SwingUtilities.isEventDispatchThread());
JFrame f = new JFrame("Swing Paint Demo");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// how to grab link to this panel - in order to use it in iteration loop ?
MyPanel p = new MyPanel();
f.add(p);
// f.add(new MyPanel());
f.pack();
f.setVisible(true);
return p;
}
private static void iterate(JPanel p){
// the loop should change square position on each iteration
// how to implement ?
for (int i = 0; i < 999; i++){
((MyPanel) p).moveSquare(100 + i*10, 200 + i*10); // here is problem:
//"Cannot make a static reference to the non-static method moveSquare(int, int) from the type MyPanel"
}
}
}
class MyPanel extends JPanel {
private int squareX = 50;
private int squareY = 50;
private int squareW = 200;
private int squareH = 200;
public MyPanel() {
setBorder(BorderFactory.createLineBorder(Color.black));
addMouseListener(new MouseAdapter() {
public void mousePressed(MouseEvent e) {
moveSquare(e.getX(),e.getY());
}
});
addMouseMotionListener(new MouseAdapter() {
public void mouseDragged(MouseEvent e) {
moveSquare(e.getX(),e.getY());
}
});
}
// originally this method was private - in orger to access it within mull, it vas changed to public
public void moveSquare(int x, int y) {
int OFFSET = 1;
if ((squareX!=x) || (squareY!=y)) {
repaint(squareX,squareY,squareW+OFFSET,squareH+OFFSET);
squareX=x;
squareY=y;
repaint(squareX,squareY,squareW+OFFSET,squareH+OFFSET);
}
}
public Dimension getPreferredSize() {
return new Dimension(900,700);
}
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawString("This is my custom Panel!",10,20);
g.setColor(Color.RED);
g.fillRect(squareX,squareY,squareW,squareH);
g.setColor(Color.BLACK);
g.drawRect(squareX,squareY,squareW,squareH);
}
}
此语法的作用是什么 ((MyPanel) p).moveSquare(100 + i*10, 200 + i*10);
?
如何在 iterate(p)
中绘制自定义形状(椭圆形)?
最佳答案
看起来您甚至没有调用iterate()
。
但无论如何,您的 moveSquare
方法都不是静态的,因此需要特定的 MyPanel
实例来工作。因此,您可能需要保留对面板的引用。比如说,您可以使用:而不是 f.add(new MyPanel())
:
MyPanel p = new MyPanel();
f.add(p);
然后将 p
传递给 iterate
并在其中调用 p.moveSquare(100,200)
。
关于java - 如何访问外部类的公共(public)方法以便在 JPanel 上重绘?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/8247419/