Input Devices
Using Mousemove and Mousedrag
We have not explored the funcion mouseMove yet, which is a useful and important one. It is called whenever you move the mouse inside the applet and can also detect, at which coordinates the cursor is. We use this function in the following applet, in order to display the actual mouse coordinates and to detect whether the mouse cursor is inside one of three colored rectangles. We use the Rectangle class here, which provides us with a convenient method inside(int x, int y), to tell whether a given point is inside the rectangle or not. Clicking just paints the background in a different color here.
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//Sourcecode
import java.awt.*;
import java.applet.*;
public class Project27 extends Applet
{
Image Buffer;
Graphics gBuffer;
int x, y;
boolean click, mouseInside, insideR1, insideR2, insideR3;
//for reference see package java.awt class Rectangle
Rectangle r1, r2, r3;
public void init()
{
Buffer=createImage(size().width,size().height);
gBuffer=Buffer.getGraphics();
//create 3 rectangle objects
r1=new Rectangle(20,70,80,100);
r2=new Rectangle(110,70,80,100);
r3=new Rectangle(200,70,80,100);
}
public void drawStuff()
{
//if mouse was clicked, paint background magenta, otherwise black
if(click)
gBuffer.setColor(Color.magenta);
else
gBuffer.setColor(Color.black);
gBuffer.fillRect(0,0,size().width,size().height);
//paint the 3 rectangles
gBuffer.setColor(Color.blue);
gBuffer.fillRect(r1.x, r1.y, r1.width, r1.height);
gBuffer.setColor(Color.green);
gBuffer.fillRect(r2.x, r2.y, r2.width, r2.height);
gBuffer.setColor(Color.red);
gBuffer.fillRect(r3.x, r3.y, r3.width, r3.height);
//draw the mouse coordinates
if (mouseInside)
{
gBuffer.setFont(new Font("Helvetica",Font.BOLD,12));
gBuffer.setColor(Color.white);
gBuffer.drawString ("X: "+x,30,30);
gBuffer.drawString ("Y: "+y,30,50);
}
else
{
gBuffer.setFont(new Font("Helvetica",Font.PLAIN,14));
gBuffer.setColor(Color.orange);
gBuffer.drawString ("Move the mouse inside the applet!",40,30);
}
//since we need this font several times, we create it here
Font bigFont=new Font("Helvetica",Font.BOLD,45);
if (insideR1)
{
gBuffer.setFont(bigFont);
gBuffer.setColor(Color.blue);
gBuffer.drawString ("BLUE",120,50);
gBuffer.setColor(Color.white);
gBuffer.drawRect(r1.x, r1.y, r1.width-1, r1.height-1);
}
if (insideR2)
{
gBuffer.setFont(bigFont);
gBuffer.setColor(Color.yellow);
gBuffer.drawString ("GREEN",120,50);
gBuffer.setColor(Color.white);
gBuffer.drawRect(r2.x, r2.y, r2.width-1, r2.height-1);
}
if (insideR3)
{
gBuffer.setFont(bigFont);
gBuffer.setColor(Color.red);
gBuffer.drawString ("RED",120,50);
gBuffer.setColor(Color.white);
gBuffer.drawRect(r3.x, r3.y, r3.width-1, r3.height-1);
}
}
//detects any mouse move within our applet
public boolean mouseMove(Event evt,int x,int y)
{
//submit the mouse coordinates to our instance variables
this.x=x;
this.y=y;
//"inside" is a method of the Rectangle class
if(r1.inside(x,y))
insideR1=true;
else
insideR1=false;
if(r2.inside(x,y))
insideR2=true;
else
insideR2=false;
if(r3.inside(x,y))
insideR3=true;
else
insideR3=false;
drawStuff();
repaint();
return true;
}
public boolean mouseEnter(Event evt,int x,int y)
{
mouseInside=true;
return true;
}
public boolean mouseExit(Event evt,int x,int y)
{
mouseInside=false;
repaint(500);
return true;
}
public boolean mouseDown(Event evt,int x,int y)
{
click=true;
repaint();
return true;
}
public boolean mouseUp(Event evt,int x,int y)
{
click=false;
repaint();
return true;
}
public void update(Graphics g)
{
paint(g);
}
public void paint(Graphics g)
{
drawStuff();
g.drawImage (Buffer,0,0, this);
}
}
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