Tutorials : Java by Example : Section 6 :

Input Devices

Using Mousemove and Mousedrag

The last mouse method we haven't used yet, is mouseDrag. It is called whenever the mouse is clicked and then moved, holding the mousebutton pressed. We use it here to realize a very simple drawing applet. You can paint by clicking and dragging the mouse. Whenever the mouse changes position, a tiny line is drawn between the last position and the new one. If you want to implement an "eraze" function somewhere, you have to redraw the background once, like here inside the init() method.

//Sourcecode import java.awt.*; import java.applet.*; public class Project29 extends Applet { Image Buffer; Graphics gBuffer; int old_x, new_x, old_y, new_y; public void init() { Buffer=createImage(size().width,size().height); gBuffer=Buffer.getGraphics(); gBuffer.setColor(Color.white); gBuffer.fillRect(0,0,size().width,size().height); } public boolean mouseDown(Event evt,int x,int y) { old_x=new_x=x; old_y=new_y=y; repaint(); return true; } public boolean mouseDrag(Event evt,int x,int y) { old_x=new_x; old_y=new_y; new_x=x; new_y=y; repaint(); return true; } public void update(Graphics g) { paint(g); } public void paint(Graphics g) { gBuffer.setColor(Color.black); gBuffer.drawString("You can draw inside the applet!", 50,20); gBuffer.setColor(Color.blue); gBuffer.drawLine(old_x,old_y,new_x,new_y); g.drawImage (Buffer,0,0, this); } }

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