Java Swing小结

读取本地图片文件并显示在JLabel上

import java.awt.image.BufferedImage;
import java.awt.Image;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JLabel;

BufferedImage bufferedImage=null;
try {
    bufferedImage=ImageIO.read(new File("pics/test.jpg"));
}
catch(IOException e) {}
Image image=bufferedImage.getScaledInstance(
        bufferedImage.getWidth()/2,
        bufferedImage.getHeight()/2,
        Image.SCALE_SMOOTH); //将图片缩小为原来的1/2
JLabel label=new JLabel(new ImageIcon(image));
label.setHorizontalAlignment(JLabel.CENTER); //图片居中
label.setVerticalAlignment(JLabel.CENTER);

为控件设置边框setBorder

import java.awt.BorderLayout;
import javax.swing.border.Border;
import javax.swing.BorderFactory;
import javax.swing.JPanel;
import javax.swing.JButton;


//所有Border对象由BorderFactory创建
//createEmptyBorder(int top,int left,int bottom,int right)
//参数表示边距,不设置border,按钮会充满panel,设置后按钮与panel间
//将出现2像素的空隙。设置边距仅在BorderLayout内生效。
Border border=BorderFactory.createEmptyBorder(2,2,2,2);
JPanel panel1=new JPanel();
panel1.setLayout(new BorderLayout());
panel1.setBorder(border);
JButton button1=new JButton("EmptyBorder");
panel1.add(button1,BorderLayout.CENTER);

//LineBorder(Color c,int l)
//参数表示颜色和线条粗细，效果panel周围出现线框。
Border border=BorderFactory.createLineBorder(Color.BLUE,1);
JPanel panel=new JPanel();
panel.setBorder(border);

//蚀刻边框效果
Border border=BorderFactory.createEtchedBorder();

//标题效果
Border border=BorderFactory.createTitledBorder("标题");

//指定颜色的标题效果
Border lineBorder=BorderFactory.createLineBorder(Color.BLUE,1);
Border border=BorderFactory.createTitledBorder(lineBorder,"标题");

//组合边框效果，外边为蚀刻边框，里边为标题边框。
Border titledBorder=BorderFactory.createTitledBorder("标题");
Border etchedBorder=BorderFactory.createEtchedBorder();
Border border=BorderFactory.createCompoundBorder(
        etchedBorder, //外边框
        titledBorder);//内边框

BoxLayout使用简例

import javax.swing.JPanel;
import javax.swing.Box;
import javax.swing.BoxLayout;

JPanel panel=new JPanel();
//设置竖直排列，X_AXIS水平排列
panel.setLayout(new BoxLayout(panel,BoxLayout.Y_AXIS));
panel.add(...);
//在竖直排列的两个控件之间空出10像素空隙
panel.add(Box.createRigidArea(new Dimension(0,10)));
panel.add(...);

16进制或RGB颜色

import java.awt.Color;

Color c=Color.BLUE; //常见颜色
Color c=new Color(255,0,0); //RGB颜色，0-255
Color c=new Color(0.5f,0.4f,0.3f,0.6f); //rgb+透明度，0-1之间
Color c=Color.decode("0xFFFFFF"); //获取16进制颜色

16进制或RGB颜色对照表

JPanel键盘事件监听

import javax.swing.JPanel;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;

JPanel panel=new JPanel();
//当有按钮等事件监听优先级较高的控件存在时，panel的键盘监听可能没有
//作用，可以在按钮监听事件中使用panel.requestFocus()让panel获得
//焦点，使键盘监听生效。
panel.addKeyListener(new KeyAdapter() {

    @Override
    public void keyPressed(KeyEvent e) {
        switch(e.getKeyCode()) {
        case KeyEvent.VK_UP:
            ...
            break; //去掉，则会继续执行语句2
        case KeyEvent.VK_DOWN:
            ... //语句2
            break;
        }
    }
});

FlowLayout设置对齐方式

import java.awt.FlowLayout;

FlowLayout flayout=new FlowLayout(FlowLayout.RIGTH);
flayout.setAlignment(FlowLayout.CENTER); //也可采用此方式
setLayout(flayout);

匿名类内获取当前类对象

public class Myframe extends JFrame {

    public Myframe() {
        JButton b=new JButton("Hello,World!");
        b.addActionListener(new ActionListener(){

            @Override
            public void actionPerformed(ActionEvent e) {
                ...
                //获取Myframe对象
                Myframe.this.requestFocus(); //请求焦点
            }

        });
    }

}