import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import java.net.URL;
import java.net.MalformedURLException;
/**類AppletBrowser是Applet的子類，并實(shí)現(xiàn)了ActionListener接口*/
public class AppletBrowser extends Applet implements ActionListener{
	TextField tfObj;
	Choice choiceObj;
	/**方法init()用于布置組件的大小和位置*/
	public void init(){
		 GridBagLayout gridBag = new GridBagLayout();
		 GridBagConstraints c = new GridBagConstraints();
		 setLayout(gridBag);
		 
		 Label labelObj1 = new Label("需要顯示對象的URL:",Label.RIGHT);
		 gridBag.setConstraints(labelObj1,c);
		 add(labelObj1);
		 //tfObj用于用戶輸入需要顯示的URL對象
		 tfObj = new TextField("http://www.tsinghua.edu.cn/",35);
		 tfObj.addActionListener(this);
		 c.gridwidth = GridBagConstraints.REMAINDER;
		 c.fill = GridBagConstraints.HORIZONTAL;
		 c.weightx = 1.0;
		 gridBag.setConstraints(tfObj,c);
		 add(tfObj);
		 
		 Label labelObj2 = new Label("Window/frame to show it in:",Label.RIGHT);
		 
		 c.gridwidth = 1;
		 c.weightx   = 0.0;
		 gridBag.setConstraints(labelObj2,c);
		 add(labelObj2);
		 /*choiceObj對象用于選擇顯示URL對象的窗口類型*/
		 choiceObj = new Choice();
		 choiceObj.addItem("(選擇瀏覽器窗口類型)");
		 choiceObj.addItem("_blank");
		 choiceObj.addItem("_self");
		 choiceObj.addItem("_parent");
		 choiceObj.addItem("_top");
		 c.fill = GridBagConstraints.NONE;
		 c.gridwidth = GridBagConstraints.REMAINDER;
		 c.anchor = GridBagConstraints.WEST;
		 gridBag.setConstraints(choiceObj,c);
		 add(choiceObj);
		 /*按鈕button用于執(zhí)行頁面的顯示操作*/
		 Button button = new Button("顯示頁面");
		 button.addActionListener(this);
		 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);
	}
	/**方法actionPerformed用于處理界面事件*/
	public void actionPerformed(ActionEvent event){
		String urlString = tfObj.getText();
		URL url = null;
		
		try{
			url = new URL(urlString);
		}catch(MalformedURLException e){
			System.err.println("Malformed URL:"+urlString);
		}
		/*下面的語句中通過showDocument方法顯示url對象對應(yīng)的頁面*/
		if(url != null){
			if(choiceObj.getSelectedIndex()==0){
				getAppletContext().showDocument(url);
			}else{
				getAppletContext().showDocument(url,choiceObj.getSelectedItem());
			}
		}
	}
}