Applet in Java
● Applet is a special type of program that is embedded in the webpage to generate the dynamic content. It runs inside the browser and works at client side.
● Advantage of Applet
There are many advantages of applet. They are as follows:– It works at client side so less response time.
– Secured
● It can be executed by browsers running under many platforms, including Linux, Windows, Mac Os etc.
● Drawback of Applet
● Plugin is required at client browser to execute applet.
Lifecycle of Java Applet :-
● Applet is initialized.
● Applet is started.
● Applet is painted.
● Applet is stopped.
● Applet is destroyed.
How to run an Applet? ??
● There are two ways to run an applet
– By html file.
– By appletViewer tool
setBackground and setForeground
● To set the color of the background of an applet window, setBackground ()
method is used.
● The general form of the setBackground () method is
void setBackground(mycolor)
● Similarly, to set the foreground color to a specific color, that is, the color of
text, setForeground () method is used.
● The general form of the setForeground () method is
void setForeground(mycolor)
● mycolor is one of the color constants or the new color created by the user
● The list of color constants is given below:
• Color.red • Color.orange • Color.gray • Color.darkGray • Color.lightGray •
Color.cyan •Color.pink • Color.white • Color.blue • Color.green • Color.black
• Color.yellow
Image in Applet
● Displaying Image in Applet
● Applet is mostly used in games and animation. For this purpose image is required to be displayed. The java.awt.Graphics class provide a method drawImage() to display the image. Syntax of drawImage() method: public abstract boolean drawImage(Image img, int x, int y, ImageObserver observer) is used draw the specified image.
● How to get the object of Image: The java.applet.Applet class provides getImage() method that returns the object of Image.
● Syntax: public Image getImage(URL u, String image){}
● Other required methods of Applet class to display image: public URL getDocumentBase(): is used to return the URL of the document in which applet is embedded.
● public URL getCodeBase(): is used to return the base URL.
repaint(), paint() and update()
● i) public void update(Graphics):
By default update(Graphics) fills the drawable area of a Component with its background color, and then sends paint(Graphics) to the object. Thus, flicker that comes from redrawing the background over and over, can sometimes be fixed by overriding update().
● ii) public void paint(Graphics) :
● Every Java Component implements paint(Graphics), which is responsible for painting that component in the Graphics context passed in the parameter. When you extend a Component (like when you write a Applet), if you want to display it differently than its superclass, you override public void paint(Graphics) .
● iii) repaint() :
● The repaint() method is sent to a Component when it needs to be repainted. This happens when a window is moved, or resized, or unhidden. It also happens when a webpage contains an image and the pixels of the image are arriving slowly down the wire. Calling the repaint method causes the whole component to be repainted. repaint() -> update() -> paint()
NeXt Artical Related APPLET With Demo Example in Java
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