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Windows, Networking and Windows, Networking and other Tidbitsother Tidbits

Chapter Fourteen

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Topics:Topics:

Windows, menus and dialog boxes– allow real pop up windows now from

Java applets Networking - load HTML from

browser, retrieve files from web sites work with generic sockets

Extra stuff

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Windows, menus and Windows, menus and dialog boxesdialog boxes Frames AWT Window class

provides for windows that are independent (own titles, resize handels, menu bars)

Subclasses: Frame - fully functioning window

with menubar Dialog - more limited

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To create a frameTo create a frame

new Frame( ) // = no title new Frame(String) has given title Frames are containers “like panels” default layout is BorderLayout

– win = new Frame(“My Way Cool Window”);– win.setLayout(new Borderlayout(10,20));– win.add(“North”, new Button(“Start”));– win.add(“Center”, new Button(“Move”));

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Sizes moves location Sizes moves location show hideshow hide resize( ) to set size move( ) to set location location( ) can tell the applet

window is on screen win.resize(100, 200); Dimension d = location( ); win.move(d.width + 50, d.height +

50);

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When you create a window it is invisable

show( ); // to make it appear hide( ); // to make it disappear

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A popup window 14-1A popup window 14-1 public class GUI extends

java.applet.Applet { Frame window; public void init( ) {

– add(new Button(“Open Window”));– add(new Button(“Close Window”));– window = new MyFrame(“A Popup

Window”);– window.resize(150, 150);

window.show( );

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public boolean action(Event evt, Object arg) { if (evt.target instanceof Button) {

String label = (String)arg; if (label.equals(“Open Window”)) { if (!window.isShowing( ) )

– window.show( ); } else if (label = = “Close Window”) { if (window.isShowing( ) )

– window.hide( ); } return true; }

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List 14.1 contd.List 14.1 contd.

else return false; } } class MyFrame extends Frame { Label l // lowercase L is variable MyFarame(String title) { Super(title); setLayout(new GridLayout(1 ,1)); //ones l = new Label(“This is a Window”,

Label.center); add(l); } // l is lower L

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Programming hint: Do Not Programming hint: Do Not use lowercase letter L’s use lowercase letter L’s they look too much like they look too much like the digit One....the digit One....I keep telling publishers I keep telling publishers that and have done it that and have done it myself - choose something myself - choose something else. Old time keypunch else. Old time keypunch operators got sheets in operators got sheets in the writers hand Z vs. 2, l the writers hand Z vs. 2, l vs. 1 vs. 1This is not a new This is not a new concept...concept...

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Menus and MenubarsMenus and Menubars

To create:– MenuBar mb = new MenuBar( );

Set as default:– window.setMenuBar(mb);

Add individual menus (File, Edit etc.) menu m = new menu(“file”); mb.add(m); // Some systems NOT All // would allow mb.setHelpMenu(m);

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Menu ItemsMenu Items

Instances of the class MenuItem– Menu m = new Menu(“Tools”);

m.add(new MenuItem(“Info”)); Instances of the class

CheckBoxMenuItem Other menus with their own items Seperators = lines that divide

groups

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SubmenusSubmenus

To create: Menu sb = new Menu (“sizes”); m.add(sb) // sub to m in previous

slide sb.add(new MenuItem(“Small”)); medium and large etc. can also be

added

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CheckboxMenuItemCheckboxMenuItem

A menu item with a checkbox CheckboxMenuItem coords = new

CheckBoxMenuItem(“Show Coordinates”);

m.add(coords); Again m from previous menu

Any menu can be enable( ) disable( )

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Menu ActionsMenu Actions

public boolean action(Event evt, Object arg) { if (evt.target instanceof MenuItem) {

String label = (String)arg; if(label.equals(“Show Coordinates”))

toggleCoords( ); else if (label.equals(“Fill”))

fillcurrentArea( ); return true; } else return false; }

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Add a menu: Window from class MyFrame

MyFrame(String title) {– Super(title);– MenuBar mb = new MenuBar( );– Menu m = new Menu(“Colors”);– m.add(new MenuItem(“Red”));– m.add(new MenuItem(“Blue”));– m.add(new MenuItem(“Green”));– m.add(new MenuItem(“-”));– m.add(new CheckboxMenuItem(“Reverse

Text”)); mb.add(m); mb.setHelpMenu(m);– setMenuBar(mb); // ... }

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To run the last slide you need an action( ) method:

public boolean action(Event evt, Object arg) { String label = (String)arg;

if (evt.target instanceof MenuItem) { if (label.equals (“Red”))

setBackground(Color.red); else if (label.equals(“Blue”))

setBackgroundColor.blue); else if (label.equals(“Green”))

setBackgroundColor.green); return true; }

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if (evt.target instanceof CheckboxMenuItem) {

if (getForeground( ) = = Color.balck)

setForeground(Color.white); else setForeground(Color.black); return true; } return false; }

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Dialog BoxesDialog Boxes

transient windows - popup with warnings ask for info. etc.

Two types in AWT:– Dialog class = generic– FileDialog = platform specific

(save/open)files To create: Dialog(Frame, boolean) initial invisable

– true = modal false not modal

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Dialog(Frame, String, boolean) same as last slide BUT has titlebar and title

can be show( ) hide( ) just like Frames To add: m.add(new MenuItem(“Set Text...”)); dl = new Dialog(this, “Enter Text”, true); dl.setLAyout(new GridLayout(2, 1, 30,

30)); tf = new TextField(l.getText( ), 20); dl.add(tf); dl.add(new Button(“OK”)); dl/resize(150, 75); // Choose OK =

dismiss

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File Dialogs - Can’t File Dialogs - Can’t access or Severe access or Severe restrictions on local restrictions on local system Really just for system Really just for stand alonestand alone To create: FileDialog (Frame, String) FileDialog(Frame, String, int) //

(load/save)– FileDialog.SAVE. OR FileDialog.LOAD

FIleDialog fd = new FileDialog(this, “FileDialog”);

fd.show( );

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Window EventsWindow Events

WINDOW-DESTROY WINDOW-EXPOSE // brought forward WINDOW-ICONIFY WINDOW-DEICONIFY WINDOW-MOVED

Can test for all of these in the Event class

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AWT in Stand Alone AWT in Stand Alone ApplicationsApplications Can use all the applet stuff: Can use Graphics etc.

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Networking in JavaNetworking in Java

ShowDocument( ) // Load - link to other web page

openStream( ) open connect to URL

Socket classes: Socket and ServerSocket open standard socket connections (read/write to them)

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Create Links inside Create Links inside AppletsApplets URL class To create a new URL URL(String, String, int, String)

– http ftp gopher file– host name (www.lne.com,

ftp.netcom.com)– a port number (80 for http)

URL(String, String, String) Same as above minus port number

URL(String) String should include “All”

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Srting url = Srting url = “http//www.yahoo.com)/”);“http//www.yahoo.com)/”); try ( theURL = new URL(url); { catch (MAlformedURLException e) {

– System.out.println(“Bad URL: “ + theURL);

– } After you have the URL Link it: getAppletContext( ).showDocument

(theURL):

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Bookmark buttonsBookmark buttons

import java.awt.*; import java.net.URL; import

java.net.MalformedURLExceptions; public class ButtonLink extends

java.applet.Applet { Bookmark bmlist[] = new

Bookmark[3];

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public void init( ) { bmlist[0] = new Bookmark(“Laura’s

Home Page”, “http://www.lne.com/lemay/”);

bmlist[1] = new Bookmark(“Yahoo”, “http://www.yahoo.com”);

bmlist[2] = new Bookmark(“Java Home Page”, “http://www.java.sun.com”);

setLayout(new Bookmark(“GridLayout(bmlist.length,1,10,10)); for(int i=0; i< bmlist.length; i++);

add(new Button(bmlist[i].name)); } }

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public boolean action(Event evt, Object arg) {

if(evt.target instanceof Button) { linkto((String) arg); return true } else return false; } Void LinkTo(String name) { URL theURL = null; for (int i=0; i <

bmlist.length; i++) { if (name.equals(bmlist[i].name))

theURL = bmlist[i].url; }

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if (theURL != null) getAppletContext( ).showDocument(theURL); } }

class Bookmark { String name; URL url; Bookmark(String name, String theURL) { this.name = name; try { this URL = new URL(theURL); } catch (MalformedURLException e) { System.out.println(“Bad URL: “ +

theURL); } } }

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Opening Web ConnectionsOpening Web ConnectionsopenStream( )openStream( ) To open a net connection - given URL try { inputStream in =

theURL.openStream( ); DataInputStream data new

DataInputStream((new BufferedInputStream(in); String line;

while (( line = data.readLine( )) != null) {

System.out.println(line); } }

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catch (IOException e) { System.out.Pintln(“IO Error: “ +

e.getMessage( )); }

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The Get (Poe’s) Raven The Get (Poe’s) Raven classclass Page 293 - 294 complete text Note the following: All the imports - more than ever

before (7) public class GetRaven extends

java.applet.Applet implements Runnable { URL theURL; Thread runner; TextArea ta = new Text(“Getting text

...”,30,70);

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public void init( ) { String url =

“http:/www.lne.com/Web/Java/raven.txt”;

try { this.theURL = new URL(url); } catch (MalformedURLException e) {

– System.out.println(“Bad URL: “ + theURL);

– } add(ta); } NOT going to review insets( )

– start( ) stop( )

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public void run( ) { InputStream conn;

data = new DataInputStream(new BufferedInputStream(conn));

while((line = data.readLine( )) != null) {– buf.append(line + “\n”); }– ta.setText(buf.toString( )); }– catch (IOException e)

{ System.out.println(“IO Error:” + e.getMessage( )); } } }

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URLconnection ClassURLconnection Class

openStream( ) simple for URLconnection

class.URLconnection– A way to retrieve files

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SocketsSockets

Java provides socket and ServerSocket

They provide for networking applications beyond what URL and URLconnection classes offer

Socket connection = new Socket(hostname, portnum);

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DataInputStream in = new DataINputStream( new BufferedINputStream(connection.getInputStream( )));

DataoutputStream out = new DataOutputStream( new BufferedOutputStream(connection.getOutputStream( )));

connection.close( ) // when done & hide it ServerSocket sconnection = new

ServerSocket(8888); sconnection.accept( );

See java.net for more info java sockets

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Other Applet HintsOther Applet Hints

showStatus( ) // use print error etc. msgs:

getAppletContext( ).showStatus(“Change the color); // access browser features

Applet Information:– public String getAppletInfo( ) {– return “GetRaven copyright 1995 Laura

Lemay;’ }

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Communication Between Communication Between AppletsApplets for (Enumeration e =

getAppletContext( ).getApplets( ); e.hasMoreElements( );) { Applet current = (Applet)

(e.nextElement( )); current.sendMessage }

– //getApplets( ) returns Enumeration Object– A list of Applets on the page

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to call specific applet: <P> This applet sends information: <APPLET CODE=“MyApplet.class”

WIDTH=100 HEIGHT=150 NAME = “sender””> </APPLET> <P>This applet receives

information from the sender: <APPLET CODE=“MyApplet.class”

WIDTH=100 HEIGHT=150 NMAE=“receiver”><?APPLET>

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Finally:Finally:

//get ahold of the receiver applet Applet receiver =

getAppletContext( ).getApplet(“receiver”);

//tell it to update itself.– RECEIVER.UPDATE(TEXT, VALUE);