pictureviewer.java

来自「由浅入深的介绍JAVAse的基本编程思想」· Java 代码 · 共 100 行

import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import java.io.*;
import javax.imageio.*;

public class PictureViewer implements ActionListener{
    private Frame frame;
    private MyCanvas mc ;
    private String fpath;
    private String fname;
    private File[] files;
    private int findex ;
	private FileDialog fd_load;	
	private MyFilter filter;
	private Button previous ;
	private Button next ;
	public static void main( String args[]) throws Exception {
		new PictureViewer().init();
	}
	public void init(){
	    frame = new Frame("PictureViewer");
	    Panel pb = new Panel();
	    Button select = new Button("选择图片");
	    previous = new Button("上一张");
	    next = new Button("下一张");
	    select.addActionListener(this);
	    previous.addActionListener(this);
	    next.addActionListener(this);
	    pb.add(select);
	    pb.add(previous);
	    pb.add(next); 
	    mc = new MyCanvas();
	    mc.setBackground(new Color(200,210,230));
	    mc.addComponentListener(mc);
	    frame.add(pb,"North");
 	    frame.add(mc,"Center");
	    frame.setSize(360,360);
	    frame.setLocation(400,200);
	    frame.addWindowListener(new WindowAdapter(){
			public void windowClosing(WindowEvent e){
				System.exit(0);	
			}	
		});  
	    frame.setVisible(true); 
	    this.validateButton();
	    filter = new MyFilter();
	    fd_load = new FileDialog(frame,"打开文件",FileDialog.LOAD);
	    fd_load.setFilenameFilter(filter);
	}
	@Override
	public void actionPerformed(ActionEvent e){
		String command = e.getActionCommand();
		if(command.equals("选择图片")){
			fd_load.setVisible(true);
			fpath = fd_load.getDirectory();
			fname = fd_load.getFile();
			if((fpath != null) && (fname != null)){
				this.display(new File(fpath + fname));	
				files = new File(fpath).listFiles(filter);
				this.setIndex();
			}			
		}else if(command.equals("上一张")){
			findex--;
			if(findex<0)
				findex = 0;
			this.display(files[findex]);
		}else if(command.equals("下一张")){
			findex++;
			if(findex >= files.length)
				findex = files.length-1;
			this.display(files[findex]);
		}
		this.validateButton();
	}	
	public void display(File f){
		try{
		    BufferedImage bi = ImageIO.read(f);
		    mc.setImage(bi);
		    frame.setTitle("PictureViewer - [" +  f.getName() + "]");
	    }catch(Exception e){
	    	e.printStackTrace();	
	    }
	    mc.repaint();
	}
	public void setIndex(){
		File current = new File(fpath + fname);	
		if(files != null){
			for(int i=0;i<files.length;i++){
				if(current.equals(files[i])){
					findex = i;	
				}	
			}			
		}
	}
	public void validateButton(){
		previous.setEnabled((files!=null) && (findex > 0));
		next.setEnabled((files!=null) && (findex<(files.length-1)));	
	}
}