Input Devices
Using Mousemove and Mousedrag
This applet enhances our last one, by making the colored boxes objects of a self-defined class SwitchRectangle. This class features the possibility to change the colors of the rectangles by clicking at them. The current color of the three SwitchRectangle objects is also reported back, to enable drawing the correct color name. The colors are represented by three constant integer variables, which are declared as static final in Java. Such variables must be initialized with a value at the same time they are declared and cannot accidentally be changed during program runtime. In this program I used expressions like if(inside) instead of if(inside==true) and if(!inside) instead of if(inside==false) (inside being a boolean variable). This is shorter and you should get accustomed to use it yourself. Study the sourcecode carefully, even though it might seem like child's play to you. Small examples like this quickly enable you to succeed in bigger projects.
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//Sourcecode
import java.awt.*;
import java.applet.*;
class SwitchRectangle
{
public Rectangle r=new Rectangle();
private int color;
//we declare 3 int variables to store color values here
//"static final" are constant variables that must not be changed
//they have to be initialized at the same time they are declared!
static final int RED=1;
static final int GREEN=2;
static final int BLUE=3;
private boolean inside;
Graphics g;
//our constructor, it initializes the rectangle coordinates and color
public SwitchRectangle(int x, int y, int w, int h, int color)
{
r.x=x;
r.y=y;
r.width=w;
r.height=h;
this.color=color;
}
//if mouse is moved inside our rectangle, the flag "inside" is set
public void SubmitMouseCoord(int x, int y)
{
if(r.inside(x, y))
inside=true;
else
inside=false;
}
public void switchColor(int x, int y)
{
if(r.inside(x, y))
{
if(color<BLUE)
color++;
else
color=RED;
}
}
//a method that is not of type void has to return a value.
//the key word "else" is not neccessary here, but can be used
public int getColor()
{
//if the mouse cursor is not inside our rectangle,
//we return 0, otherwise the active color variable value
if(!inside)
return 0;
else
return color;
}
public void paint(Graphics gr)
{
g=gr;
if(color==RED)
g.setColor(Color.red);
else if(color==GREEN)
g.setColor(Color.green);
else
g.setColor(Color.blue);
g.fillRect(r.x, r.y, r.width, r.height);
if(inside)
{
g.setColor(Color.white);
g.drawRect(r.x, r.y, r.width-1, r.height-1);
}
}
}
public class Project28 extends Applet
{
Image Buffer;
Graphics gBuffer;
int x, y;
boolean mouseInside, insideRed, insideGreen, insideBlue;
SwitchRectangle sr1, sr2, sr3;
//the constant color variables have to be declared here too!
static final int RED=1;
static final int GREEN=2;
static final int BLUE=3;
public void init()
{
Buffer=createImage(size().width,size().height);
gBuffer=Buffer.getGraphics();
//create 3 objects of our SwitchRectangle class
sr1=new SwitchRectangle(20,70,80,100,RED);
sr2=new SwitchRectangle(110,70,80,100,GREEN);
sr3=new SwitchRectangle(200,70,80,100,BLUE);
}
public void drawStuff()
{
gBuffer.setColor(Color.black);
gBuffer.fillRect(0,0,size().width,size().height);
//paint the 3 rectangles
sr1.paint(gBuffer);
sr2.paint(gBuffer);
sr3.paint(gBuffer);
//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 ("Click the three rectangles!",70,30);
}
//since we need this font several times, we create it here
Font bigFont=new Font("Helvetica",Font.BOLD,45);
if (insideRed)
{
gBuffer.setFont(bigFont);
gBuffer.setColor(Color.red);
gBuffer.drawString ("Red",120,50);
}
if (insideGreen)
{
gBuffer.setFont(bigFont);
gBuffer.setColor(Color.green);
gBuffer.drawString ("Green",120,50);
}
if (insideBlue)
{
gBuffer.setFont(bigFont);
gBuffer.setColor(Color.blue);
gBuffer.drawString ("Blue",120,50);
}
}
//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;
sr1.SubmitMouseCoord(x, y);
sr2.SubmitMouseCoord(x, y);
sr3.SubmitMouseCoord(x, y);
detectColor();
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)
{
sr1.switchColor(x, y);
sr2.switchColor(x, y);
sr3.switchColor(x, y);
detectColor();
repaint();
return true;
}
//this method detects the color that's under the mouse cursor,
//to tell if it's "Red", "Green" or "Blue"
void detectColor()
{
//if one of our 3 SwitchingRectangles reports RED, we set the flag
//"insideRed" to true, otherwise to false
if(sr1.getColor()==RED||sr2.getColor()==RED||sr3.getColor()==RED)
insideRed=true;
else
insideRed=false;
if(sr1.getColor()==GREEN||sr2.getColor()==GREEN||sr3.getColor()==GREEN)
insideGreen=true;
else
insideGreen=false;
if(sr1.getColor()==BLUE||sr2.getColor()==BLUE||sr3.getColor()==BLUE)
insideBlue=true;
else
insideBlue=false;
}
public void update(Graphics g)
{
paint(g);
}
public void paint(Graphics g)
{
drawStuff();
g.drawImage (Buffer,0,0, this);
}
}
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