showdocument.java

来自「有关java的源程序,为讲授java程序设计课程使用」· Java 代码 · 共 112 行

import java.applet.*;
import java.awt.*;
import java.net.*;
public class ShowDocument extends Applet
{
  URLWindow urlWindow;
  public void init()
  {
      Button  button=new Button("Bring up URL window");
      add(button);
      validate();
      urlWindow=new URLWindow(getAppletContext());
      urlWindow.pack();	
  }
  public void destroy()
  {
      urlWindow.hide();
      urlWindow=null;
  }
  public boolean action(Event event, Object obj)
  {
      urlWindow.show();
      return true;
  }

}
class URLWindow extends Frame
{
  TextField urlField;
  Choice choice;
  AppletContext appletContext;
  public URLWindow(AppletContext appletContext)
   {
     super("Show a Document !");
     this.appletContext=appletContext;
     GridBagLayout gridBag=new GridBagLayout();
     GridBagConstraints c=new GridBagConstraints();
     setLayout(gridBag);
     Label label1=new Label("URL of document to show:",Label.RIGHT);
     gridBag.setConstraints(label1,c);
     add(label1);
     urlField=new TextField("http://java.sun.com/",40);
     c.gridwidth=GridBagConstraints.REMAINDER;
     c.fill=GridBagConstraints.HORIZONTAL;
     c.weightx=1.0;
     gridBag.setConstraints(urlField,c);
     add(urlField);
     Label label2=new Label("Window/Frame to show it in:",Label.RIGHT);
     c.gridwidth=1;
     c.weightx=0.0;
     gridBag.setConstraints(label2,c);
     add(label2);
     choice=new Choice();
     choice.addItem("(browser's Choice)");
     choice.addItem("My Personal Window");
     choice.addItem("_blank");
     choice.addItem("_self");
     choice.addItem("_parent");
     choice.addItem("_top");
     c.fill=GridBagConstraints.NONE;
     c.gridwidth=GridBagConstraints.REMAINDER;
     c.anchor=GridBagConstraints.WEST;
     gridBag.setConstraints(choice,c);
     add(choice);
     Button button=new Button("Show document");
     c.weighty=1.0;
     c.ipadx=10;
     c.ipady=10;
     c.insets=new Insets(5,0,0,0);
     c.anchor=GridBagConstraints.SOUTH;
     gridBag.setConstraints(button,c);
     add(button);
   }
   public boolean handleEvent(Event event)
   { 
      if(event.id == Event.WINDOW_DESTROY)
        {
             hide();  
  	     return true;
        }
 	return super.handleEvent(event);
   }
   public boolean action(Event event, Object obj)
   {
      if((event.target instanceof Button) |(event.target instanceof TextField))
      {
         String urlString=urlField.getText();
         URL url=null;
         try{
		url=new URL(urlString);
            }
	  catch(MalformedURLException e)
	   {
		System.out.println("Malformed URL:"+urlString);
		return true;
	   }
         if(url != null)
	  {
	     if(choice.getSelectedIndex() ==0)
		{
                  appletContext.showDocument(url);
		}	
	     else
                {
		   appletContext.showDocument(url,choice.getSelectedItem());
  		}
	  }
      }
   	return true;
   }
}