按照你的要求,编写的Java程序如下
import?java.awt.Color;
import?java.awt.Graphics;
import?javax.swing.JFrame;
public?class?F?extends?JFrame?implements?Runnable{
Color[]?colors?=?{Color.red,Color.orange,Color.yellow,Color.green,Color.cyan,Color.blue,Color.magenta,Color.black};?
int?i=0;
F(){
setTitle("变色正方形");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLocationRelativeTo(null);
setVisible(true);
}
public?void?paint(Graphics?g){
g.setColor(colors[i]);
public?void?run()?{
while(true){
try?{
Thread.sleep(1000);
}?catch?(InterruptedException?e)?{
e.printStackTrace();
i++;
else
i=0;
repaint();
public?static?void?main(String[]?args)?{
F?f=new?F();
Thread?t=new?Thread(f);
t.start();
运行结果
本来是在drawcomponent这个里边使用setBackground,你想啊drawcomponent是继承JComponent的所以它是一个容器,所以它同样有setBackground这个方法来设置它的背景颜色
但是因为你在设置它本身为一个画布,因为你用了paintComponent(Graphics?g)
这个方法,所以setBackground这个方法即使你用了也看不到很大的效果.但是有一种取代的方法就是在paintComponent(Graphics?g)方法中首先就用Graphics?所含有的方法g.setColor(Color.black);来设置背景颜色再用g.fillRect(0,?0,?this.getWidth(),?this.getHeight());来填满整个容器,这就达到了设置背景目的.然后你再g.setColor(其他颜色);来绘制其它图形.
具体代码:(在你以上的代码上修改了点)
public?void?paintComponent(Graphics?g)
{
g.setColor(Color.black);//这里设置背景颜色
g.fillRect(0,?0,?this.getWidth(),?this.getHeight());//这里填充背景颜色
double?x=100;
double?y=100;
ellipse.setFrame(rect);
double?centerx=rect.getCenterX();
double?centery=rect.getCenterY();
测试结果图
JButton btnYellow = null;
JButton btnBlue = null;
JButton btnRed = null;
btnYellow.setActionCommand("yellow");
btnBlue.setActionCommand("blue");
btnRed.setActionCommand("red");
public void actionPerformed(ActionEvent e) {
String command = event.getActionCommand();
if( "yellow".equals(command) ){
setBackground(Color.yellow);
btnYellow.setBackground(Color.yellow);
}else if( "blue".equals(command) ){
setBackground(Color.blue);
btnBlue.setBackground(Color.blue);
}else if( "red".equals(command) ){
setBackground(Color.red);
btnRed.setBackground(Color.red);
写出了部分代码
**************************************************************
新建一个类ChangeColor.java,代码如下：
import?java.awt.event.MouseEvent;
import?java.awt.event.MouseMotionListener;
/**
*/
public?class?ChangeColor?extends?JFrame?implements?MouseMotionListener?{
public?ChangeColor()?{
this.setTitle("Change?Color");
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setVisible(true);
this.getContentPane().setBackground(Color.GREEN);
this.addMouseMotionListener(this);
public?void?mouseMoved(MouseEvent?e)?{
this.getContentPane().setBackground(Color.RED);
}?else?{
this.getContentPane().setBackground(Color.BLUE);
public?void?mouseDragged(MouseEvent?e)?{
new?ChangeColor();
运行结果如下：
import java.awt.BorderLayout;
import java.awt.Button;
import java.awt.Color;
import java.awt.FlowLayout;
import java.awt.Frame;
import java.awt.Insets;
import java.awt.TextArea;
import java.awt.TextField;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextPane;
import javax.swing.border.EmptyBorder;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.SimpleAttributeSet;
import javax.swing.text.StyleConstants;
import javax.swing.text.StyleContext;
import javax.swing.text.StyledDocument;
public class main {
static String tf_str=null;
public static void main(String[] args) {
Frame a = new Frame("打印");
a.setLayout(new FlowLayout());
Button c = new Button("确定");
Button e = new Button("红色");
Button f = new Button("蓝色");
JTextPane d=new JTextPane();
d.setMargin(new Insets(100,100, 100, 100));
a.add(b);
a.add(c);
a.add(d);
a.add(e);
a.add(f);
a.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
});
c.addActionListener(new ActionListener() {
d.setText("");
tf_str = b.getText().trim();
b.setText("");
appendToPane(d, tf_str, Color.black);
b.requestFocus();
e.addActionListener(new ActionListener() {
appendToPane(d, tf_str, Color.RED);
f.addActionListener(new ActionListener() {
appendToPane(d, tf_str, Color.BLUE);
a.setVisible(true);
private static void appendToPane(JTextPane tp, String msg, Color c) {
StyleContext sc = StyleContext.getDefaultStyleContext();
AttributeSet aset = sc.addAttribute(SimpleAttributeSet.EMPTY, StyleConstants.Foreground, c);
aset = sc.addAttribute(aset, StyleConstants.FontFamily, "宋体");
aset = sc.addAttribute(aset, StyleConstants.Alignment, StyleConstants.ALIGN_JUSTIFIED);
int len = tp.getDocument().getLength();
tp.setCaretPosition(len);
tp.setCharacterAttributes(aset, false);
tp.replaceSelection(msg);
分析题目:
一 分析布局: 题目明确的指出了按钮的位置和大小 ,那么说明需要使用的布局是空布局(绝对布局) , 而JFrame窗口的内容面板默认布局是边界布局(BorderLayout),所以需要设置一下
setLayout(null);//设置为绝对布局
二了解颜色. Color 可以通过红,绿,蓝 三原色, 不同的搭配, 形成不同的颜色.
三添加颜色 ,java给JFrame添加颜色,比较特殊. 必须添加到内容面板上,才能正常显示(因为JFrame分了好多层)
getContentPane().setBackground(new?Color(r,g,b));//设置窗口的面板背景色
五 具体参考代码
import?java.awt.*;
import?java.awt.event.*;
import?javax.swing.*;
//?本类继承JFrame,实现了ActionListener接口
public?class?MyFrame?extends?JFrame?implements?ActionListener{
public?MyFrame()?{
//组件的初始化
JButton?jbRed?=?new?JButton("red");
JButton?jbGreen?=?new?JButton("green");
jbGreen.addActionListener(this);
JButton?jbBlue?=?new?JButton("blue");
jbBlue.addActionListener(this);
//添加组件到窗口
add(jbRed);
add(jbGreen);
add(jbBlue);
//窗口的设置
setLayout(null);//因为每一个按钮都设置了位置和大小,?那么应该把窗口设置为空布局,?那么位置和大小才能有效
setTitle("窗口标题");
addWindowListener(new?WindowAdapter()?{
@Override
System.out.println("通过WindowListener实现关闭");
System.exit(0);//退出
public?void?actionPerformed(ActionEvent?e)?{
String?cmd=e.getActionCommand();
r+=10;
}else?if("green".equals(cmd))?{
g+=10;
}else?if("blue".equals(cmd)){
b+=10;
this.getContentPane().setBackground(new?Color(r,g,b));
//System.out.println(this.getContentPane().getBackground());
EventQueue.invokeLater(new?Runnable()?{
new?MyFrame().setVisible(true);//启动窗口并设置可见