Lap trinh huong doi tuong 9

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B MN CNG NGH PHN MM

ViN CNG NGH THNG TIN V TRUYN THNG

TRNG I HC BCH KHOA H NI

LP TRNH HNG I TNG

Bi 9. Applet

Nguyn Th Thu Trang

Ni dung

1. Tng quan v Applet

2. Vng i ca Applet

3. Lp Graphics

4. Cac phng thc ca Applet

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Applet l chng trnh Java c nhng trong m ngun HTML.

C th chy trn trnh duyt Web c ci JVM (JRE) sau khi ti v.

Nh cc applet, trang Web c thm c sc sng v applet c th th hin multimedia, to c s tng tc vi user nh hi-tr li

C th nguy him, khng m bo tnh an ton

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c th chy applet, trnh duyt ca ngi dung phi bt chc nng Java Plug-in

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to 1 applet, xy dng 1 lp con ca lp Applet hoc lp JApplet. import java.applet.Applet; class MyApplet extends Applet

{...}

hoc

import javax.swing.JApplet; class MyApplet extends JApplet

{...}

Thng t tn lp applet ny trng tn vi tn file.html.

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java.lang.Object

java.awt.Component

java.awt.Container

java.awt.Panel

java.applet.Applet

AppletTemplate

import java.applet.Applet;

import java.awt.*;

public class AppletTemplate extends Applet

{

// Khai bao bien

public void init() {

// Khoi tao cac bien, tai cac hinh anh...

}

public void paint(Graphics g) {

// Cac thao tac ve (draw)

}

}

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To 1 ti liu HTML cha applet

thc thi mt applet, to mt tp tin HTML c s dng th applet hoc th object Th applet/object c hai thuc tnh:

Width Height

V d:

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Applet HTML Template

A Template for Loading Applets

A Template for Loading Applets

Error! You must use a Java-enabled browser.

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Chng trnh Applet u tin


import java.awt.Graphics;

public class FirstApplet extends Applet {

public void paint(Graphics g) { g.drawString("This is my first applet!",20,100);

}

}

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appletviewer FirstApplet.java

hoc Ctrl + 3 (Textpad)

Chng trnh Applet u tin (2)

K tha t lp Applet

ha t Abstract Window Toolkit (AWT)

Chy sau khi bin dch: Trn cmd: appletviewer FirstApplet.html hoc

appletviewer FirstApplet.java

Textpad: Ctrl + 3

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S dung .html

First Applet

First Applet

Sorry, this example

requires Java.

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Mozilla Firefox

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Ni dung


2. Vng i ca Applet

3. Lp Graphics


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2. Vng i ca Applet

init(): Ch c gi khi applet bt u thc thi

start(): c gi sau init() hoc khi applet c tr li

paint(): c gi sau khi trinh duyt init va start, va c gi li khi trinh duyt c ve li

stop(): c gi khi applet c thu nh

destroy(): c gi khi applet kt thc (tt trinh duyt)

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Vi du



public class AppletLifeCycle extends Applet {

String str = "";


str += "init; ";

}

public void start() {

str += "start; ";

}

public void stop() {

str += "stop; ";

}

public void destroy() {

System.out.println("destroy");

}

public void paint(Graphics g){

g.drawString(str, 10, 25);

}

}

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Ni dung


2. Vng i ca Applet

3. Lp Graphics


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Cac phng thc trong Graphics

drawString(string, left, bottom) Ve mt xu vi font ch va mau hin ti vi goc trai (left)

va ay (bottom) ca xu c ch ra

drawRect(left, top, width, height) Ve ng vin hinh ch nht (1-pixel border) vi mau

hin ti

fillRect(left, top, width, height) Ve hinh ch nht c vi mau hin ti

drawLine(x1, y1, x2, y2) Ve mt ng vi day 1 pixel t ta (x1, y1) n ta

(x2, y2)

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Cac phng thc trong Graphics

drawOval, fillOval Ve hinh elip (vin/c) vi cac tham s ch ra la hinh ch nht bao

quanh elip (oval)

drawPolygon, fillPolygon Ve hinh a giac (vin/c) vi cac im c xac nh bi cac mng

hoc mt i tng Polygon (mt lp lu mt lot cac im) c ch ra trong tham s

Mc nh hinh a giac c ve khep kin, ve hinh a giac m s dng phng thc drawPolyline

drawImage Ve mt hinh nh Hinh nh co th co nh dng JPEG hoc GIF (gm GIF89A)

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public class DrawTest extends Applet{

public void paint(Graphics g){

//Ve hcn xq vung hien thi applet

g.drawRect(0, 0,

getWidth()-1,getHeight()-1);

//Ve xau trong hcn

g.drawString("Ve Applet", 5, 15);

g.fillOval(30, 30, 120, 160);

g.drawLine(30, 30, 150, 30);

}

}

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Cc phng thc trong Graphics drawArc(int x, int y, int w, int h, int degreesO, int degrees1)

fillArc(int x, int y, int w, int h, int degree0, int degree1)

drawPolygon(int x[], int u[], int n)

fillPolygon(int x[], int y[], int n)

drawPolyline(int x[], int y[], int n)

Color getColor()

Font getFont()

setFont(Font f)

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Vi du



public class DrawArc extends Applet {


g.drawArc(20, 20, 160, 160, 0, 135);

}

}

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Graphics Font

setFont, getFont Ch ra font c s dng ve vn bn Xac nh kich thc ca ky t thng qua FontMetrics (trong Java 2 s dng LineMetrics)

Thit lp font cho i tng Graphics khng tn ti qua cac li gi k tip ca paint

Thit lp font ca window (vi d gi phng thc setFont) cho vic thay i lu dai cho i tng Graphics.

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Graphics Color

setColor, getColor Ch ra mau mt trc (foreground color) cho cac thao tac

ve Mc nh, i tng Graphics nhn mau mt trc t mau

ca window. AWT nh nghia 16 mau (Color.red, Color.blue...)

hoc bn co th to ra mau ca ring minh bng new Color(r, g, b)

Thay i mau ca i tng Graphics ch nh hng n i tng Graphics tng ng thay i mau lu dai, gi phng thc setForeground ca

applet

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Vi du


import java.awt.Color;


import java.awt.Font;

public class BlueString extends Applet {


g.setFont(new Font("SansSerif", Font.BOLD, 30));

g.setColor(Color.blue);

g.drawString("Blue String", 100, 50);

}

}

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Tai mt hinh anh

ng ky Image (trong phng thc init)

Image image = getImage(getCodeBase(), "file");

Image image = getImage(url);

Nu URL la tuyt i, cn s dng try/catch

Ve mt hinh nh (trong phng thc paint) g.drawImage(image, x, y, window);

g.drawImage(image, x, y, w, h, window);

Co th ve mt phn ca hinh nh S dng applet (this) cho tham s window

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Tai mt hinh anh t URL tng i


import java.awt.*;

/** An applet that loads an image

from a relative URL. */

public class JavaMan1 extends Applet {

private Image javaMan;


javaMan = getImage(getCodeBase(),

"images/Java-Man.gif");

}


g.drawImage(javaMan, 0, 0, this);

}

}

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Tai mt hinh anh t URL tuyt i import java.applet.Applet;

import java.awt.*;

import java.net.*;

...

private Image javaMan;


try {

URL imageFile =

new URL("http://www.corewebprogramming.com" +

"/images/Java-Man.gif");

javaMan = getImage(imageFile);

} catch(MalformedURLException mue) {

showStatus("Bogus image URL.");

System.out.println("Bogus URL");

}

}

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Ni dung


2. Vng i ca Applet

3. Lp Graphics


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Cac phng thc khac cua Applet

getCodeBase, getDocumentBase Ly v URL ca:

Applet file - getCodeBase HTML file - getDocumentBase

getParameter(String name) Ly v gia tr t phn t PARAM trong HTML file

getSize() Tr v Dimension (width, height) ca applet

getGraphics() Ly v i tng Graphics hin ti ca applet i tng Graphics khng tn ti gia cac ln gi paint()

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import java.applet.*;

import java.awt.*;

public class Circle extends Applet{


Dimension d = getSize();

int xc = d.width / 2;

int yc = d.height / 2;

int radius = (int)((d.width < d.height) ?

0.4 * d.width : 0.4 * d.height);

g.drawOval(xc - radius, yc - radius,

2 * radius, 2 * radius);

}

}

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Cac phng thc khac (2)

showDocument () getAppletContext().showDocument(java.net.URL url)

getAppletContext().showDocument(java.net.URL url, String

targetWindow)

Hin th mt tai liu trn trinh duyt

showStatus(String str) Hin th mt xu trong dong trng thai cui trinh duyt

Cursor getCursor(), setCursor(Cursor cur) Ly v hoc thit lp Cursor cho chut, vi d nh CROSSHAIR_CURSOR, HAND_CURSOR, WAIT_CURSOR

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V d import java.applet.Applet;


public class TestApplet extends Applet {


g.drawString("This is my first

applet!",

20, 100);

showStatus("Applet is running!");

g.drawString("Context: " +

getAppletContext(), 20, 120);

}

}

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Cac phng thc khac (3)

getAudioClip, play Ly v tp m thanh t mt v tri t xa va chi no JDK 1.1 ch h tr .au. Java 2 con h tr thm MIDI, .aiff

va .wav getBackground, setBackground

Ly v/thit lp mau nn cho applet Lp SystemColor cung cp truy cp n cac mau ca

man hinh nn getForeground, setForeground

Ly v/thit lp mau ve ca applet (mau mc nh cho cac thao tac ve - draw)

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Vi du

import java.applet.*;

import java.awt.*;

public class BackgroundForeground extends Applet {


setBackground(Color.yellow);

setForeground(Color.blue);

g.drawLine(0, 0, 200, 200);

g.fillRect(100, 40, 50, 50);

}

}

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Phn t APPLET trong HTML file

...

Cac thuc tinh bt buc CODE

Ch ra tn ca lp Java cn ti Tn tp c thng dch vi th mc ca trang HTML hin ti (mc

nh) tr khi CODEBASE c cung cp

WIDTH va HEIGHT Ch ra vung ma applet se hin th Cac gia tr c a ra theo pixel hoc theo phn trm ca ca s

trinh duyt

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Phn t APPLET trong HTML file (2)

Cac thuc tinh khac ALIGN, HSPACE, va VSPACE

Kim soat v tri va khong cach vi vin theo pixel

ARCHIVE Ch ra cac tp JAR (tp zip vi phn mi rng .jar) cha tt c cac

lp va hinh nh c s dng bi applet

Tit kim ang k thi gian ti v nhiu tp class

NAME Tn ca applet dung cho vic lin kt vi cac applet khac hoc vi

JavaScript

MAYSCRIPT (khng chun) Cho phep JavaScript iu khin applet

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Vi du: Thit lp thuc tinh Param

Customizable HelloWWW Applet




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Applet HelloWWW2 oc cac tham s S dng getParameter(name) ly v gia tr ca

phn t PARAM, tn ca tham s co phn bit ch hoa ch thng

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import java.awt.*;

public class HelloWWW2 extends Applet {


setFont(new Font("SansSerif", Font.BOLD, 30));

Color background = Color.GRAY;

Color foreground = Color.DARK_GRAY;

String backgroundType = getParameter("BACKGROUND");

Applet HelloWWW2 oc cac tham s 39

if (backgroundType != null) {

if (backgroundType.equalsIgnoreCase("LIGHT")){

background = Color.WHITE;

foreground = Color.BLACK;

} else if (backgroundType.equalsIgnoreCase("DARK")){

background = Color.BLACK;

foreground = Color.WHITE;

}

}

setBackground(background);

setForeground(foreground);

}


g.drawString("Hello, World Wide Web.", 5, 35);

}

}

Ly tham s t HTML Kt qua

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S dung JavaJump.html

Jumping Java

Jumping Java


import java.awt.*;

/** An applet that draws an image. */

public class JavaJump extends Applet{

private Image jumpingJava;


setBackground(Color.white);

setFont(new Font("SansSerif", Font.BOLD, 18));

jumpingJava = getImage(getDocumentBase(), getParameter(image));

add(new Label("Great Jumping Java!"));

System.out.println("Yow! I'm jiving with Java.");

}


g.drawImage(jumpingJava, 0, 50, this);

}

}

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JavaJump.java

Documents

Lap trinh huong doi tuong 9