我在使用Java Awt 的 Graphics类时,使用getGraphics()得到相关Component的Graphics context,然后在上面进行绘图,而不是采用重写paint()方法。但是遇到一个问题,必须在组件被实现后,调用Thread.sleep()方法才能使得之后的绘图线条显示出来。并且sleep()时间还不能太短。。比如我的程序Thread.sleep(100)可以,Thread.sleep(20)就不行了。完整代码如下:package com.han;import java.awt.Color;
import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.Graphics;import javax.swing.JButton;
import javax.swing.JFrame;public class Graphics_1 extends JFrame { /**
*
*/
private static final long serialVersionUID = -5861565474703590207L; JButton button = new JButton("JButton");
Container container;
public Graphics_1() {
// TODO Auto-generated constructor stub
container = getContentPane();
container.setLayout(new FlowLayout());
container.add(button);
}
void paintJButton() {
/*
* Creates a graphics context for Container (you can also try it for
* JFrame)
*/
Graphics g = container.getGraphics();
g.setColor(Color.BLACK); /*
* Draws a line, using the current color, between the points (x1, y1)
* and (x2, y2) in this graphics context's coordinate system.
*/
g.drawLine(5, 5, 15, 5);
System.out.println("here"); } /**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
final Graphics_1 frame = new Graphics_1();
frame.setTitle("Painting figures on the JButton");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setBounds(100, 100, 300, 200);
frame.setVisible(true);
try {
Thread.sleep(100); // Thread.sleep(20); does not work !
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
frame.paintJButton();
}}希望哪位大侠予以解释。
import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.Graphics;import javax.swing.JButton;
import javax.swing.JFrame;public class Graphics_1 extends JFrame { /**
*
*/
private static final long serialVersionUID = -5861565474703590207L; JButton button = new JButton("JButton");
Container container;
public Graphics_1() {
// TODO Auto-generated constructor stub
container = getContentPane();
container.setLayout(new FlowLayout());
container.add(button);
}
void paintJButton() {
/*
* Creates a graphics context for Container (you can also try it for
* JFrame)
*/
Graphics g = container.getGraphics();
g.setColor(Color.BLACK); /*
* Draws a line, using the current color, between the points (x1, y1)
* and (x2, y2) in this graphics context's coordinate system.
*/
g.drawLine(5, 5, 15, 5);
System.out.println("here"); } /**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
final Graphics_1 frame = new Graphics_1();
frame.setTitle("Painting figures on the JButton");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setBounds(100, 100, 300, 200);
frame.setVisible(true);
try {
Thread.sleep(100); // Thread.sleep(20); does not work !
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
frame.paintJButton();
}}希望哪位大侠予以解释。
import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.Graphics;import javax.swing.JButton;
import javax.swing.JFrame;public class Graphics_1 extends JFrame { /**
*
*/
private static final long serialVersionUID = -5861565474703590207L; JButton button = new JButton("JButton");
@SuppressWarnings("serial")
Container container = new Container() {
public void paint(Graphics g) {
g.setColor(Color.BLACK);
g.drawLine(5, 5, 15, 5);
}
};
public Graphics_1() {
// TODO Auto-generated constructor stub
this.add(container);
container.setLayout(new FlowLayout());
container.add(button);
}
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
final Graphics_1 frame = new Graphics_1();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setBounds(100, 100, 300, 200);
frame.setVisible(true);
}}
public void paint(Graphics g) {
super.paint(g); // 增加这句话很重要,否则resize时就父类就没机会执行重绘了
g.setColor(Color.BLACK);
g.drawLine(5, 5, 15, 5);
}
当然还有一个负责特定控件重绘的函数是:paintComponents(Graphics g)
因为你没有把这个函数也给重写了,所以当“我鼠标移动到JButton所在位置时”,这个函数发挥效用了。
感觉不爽
我刚刚查了API文档,那个Container类的paint()被重写的话,是必须使用super.paint();才能正确渲染其Children componnets。但是对于Canvas类的paint(), API上写道:need not to use super.paint();,这是否意味着Canvas并不允许在上面存放component组件?我查了下API,Canvas类好像也没有像Container类的那种添加组件的add()方法希望能给于答复,谢谢