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Java by Example - using methods and basic mouse functions
This example demonstrates the use of a simple method with more than one parameter. The smiley is drawn from inside the method void Smiley(int x, int y), so you can draw several smileys by just calling that method with different parameters for the coordinates.
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//Sourcecode
import java.awt.*;
import java.applet.*;
//Introduces methods with more than one parameter
//and getting the size of the applet
public class Project4 extends Applet
{
//global graphics object
public Graphics g;
//our method with 2 parameters for the x- and y coordinate of our smiley
public void Smiley(int x, int y)
{
//smileys face
g.setColor(Color.yellow);
g.fillOval(x,y,30,30);
//his eyes
g.setColor(Color.black);
g.fillOval(x+6,y+7,6,6);
g.fillOval(x+18,y+7,6,6);
//the mouth, a red oval and a yellow one shifted upwards
g.setColor(Color.red);
g.fillOval(x+5,y+15,20,8);
g.setColor(Color.yellow);
g.fillOval(x+6,y+13,18,8);
}
public void paint (Graphics gr)
{
g=gr;
//paint the background blue - this time we measure the size
//of the applet to get the size of the background rectangle
g.setColor(Color.blue);
g.fillRect(0,0,size().width,size().height);
//now we call our method with different parameters
Smiley(50,50);
Smiley(150,90);
Smiley(250,80);
Smiley(180,10);
Smiley(120,230);
}
}
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Here you can see how to use the Java methods for determining whether the mouse cursor is inside or outside the applet (mouseEnter and mouseExit), and how to process mouse clicks inside the applet.
The expression clicks=clicks+1;, which increments the variable clicks, is usually written in short form: clicks++, which we will also do from now on. The expression clicks+=2 would increment it with 2 instead of 1.
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//Sourcecode
import java.awt.*;
import java.applet.*;
public class Project5 extends Applet
{
int mouseX, mouseY, clicks;
boolean mouseIn;
public boolean mouseDown(Event evt,int x,int y)
{
clicks=clicks+1;
mouseX=x;
mouseY=y;
repaint();
return true;
}
public boolean mouseEnter(Event evt,int x,int y)
{
mouseIn=true;
repaint();
return true;
}
public boolean mouseExit(Event evt,int x,int y)
{
mouseIn=false;
repaint();
return true;
}
public void paint(Graphics g)
{
g.setFont(new Font("Helvetica",Font.PLAIN,13));
g.setColor(Color.black);
g.drawString("Mouse clicks: "+clicks, 100,80);
g.drawString("Mouseclick coordinates: x="+mouseX+", y="+mouseY, 40,110);
if(mouseIn==true)
{
g.setColor(Color.red);
g.drawString("Mouse is inside the applet",70,180);
}
else
{
g.setColor(Color.blue);
g.drawString("Mouse is outside the applet",70,180);
}
}
}
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