您需要绘制范围内的所有内容paint
方法。这actionPerformed
应该只改变某物的状态already in the paint
方法,然后调用repaint
。例如
boolean drawHello = true;
boolean drawWorld = false;
protected void paintComponent(Graphics g) {
super.paintCompoent(g);
if (drawHello)
g.drawString("Hello", 50, 50);
if (drawWorld)
g.drawString("World", 10, 10);
}
然后在你的actionPerformed
,你可以改变状态drawWorld
to true
并打电话repaint()
.
public void actionPerformed(ActionEvent e) {
drawWorld = true;
repaint();
}
正如您所看到的,所有内容都应该绘制在paintComponent
方法。您可以隐藏并绘制渲染图,然后制作它们“可见的”来自动作命令。您应该已经预定义了可能绘制的内容。然后只需改变它的渲染状态
正如 @MadPrgrammer 指出的,你不应该在顶级容器上绘画,比如JFrame
。而是在自定义上绘制JPanel
or JComponent
并覆盖paintComponent
方法,而不是JFrame
and paint
这是一个示例,每次按下按钮时我都会绘制一个新的正方形。如果查看代码,您会发现在paintComponent
方法,我循环遍历一个列表Square
并绘制它们,然后在actionPerformed
我所做的就是添加一个新的Square
to the List
并打电话repaint()
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class AddSquares {
private int R = 0;
private int G = 0;
private int B = 0;
private int xLoc = 0;
private int yLoc = 0;
List<Square> squares = new ArrayList<>();
private JButton addSquare = new JButton("Add Square");
private RectsPanel panel = new RectsPanel();
public AddSquares() {
addSquare.addActionListener(new ActionListener(){
@Override
public void actionPerformed(ActionEvent e) {
Color color = new Color(R, G, B);
squares.add(new Square(xLoc, yLoc, color));
panel.repaint();
R += 10;
G += 20;
B += 30;
xLoc += 20;
yLoc += 20;
}
});
JFrame frame = new JFrame("Draw Squares");
frame.add(panel, BorderLayout.CENTER);
frame.add(addSquare, BorderLayout.SOUTH);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setVisible(true);
}
private class RectsPanel extends JPanel {
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
for (Square square : squares) {
square.drawSquare(g);
}
}
@Override
public Dimension getPreferredSize() {
return new Dimension(250, 250);
}
}
private class Square {
int x = 0;
int y = 0;
Color color;
public Square(int x, int y, Color color) {
this.x = x;
this.y = y;
this.color = color;
}
public void drawSquare(Graphics g) {
g.setColor(color);
g.fillRect(x, y, 75 ,75);
}
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
AddSquares addSquares = new AddSquares();
}
});
}
}