Creating Canvas Form Example
This example shows that how to use the Canvas Class in a Form. In this example we take two field in which integer number passed from the form and result will display on a Canvas circle. The Following methods are used in this example:
- getWidth()
- getHeight()
- setColor()
- fillRect()
- setGrayScale()
- drawString()
We calculate the both integer value ("A" and "B") in the calculator() function and store the result in a integer value ("result") variable which is integer value.
See The Application Below:
Source Code CanvasForm.java
import javax.microedition.lcdui.*;
import javax.microedition.midlet.*;
public class CanvasForm extends MIDlet implements CommandListener{
private Display display;
private Form form;
private Displayable current;
private TextField one, two;
private StringItem item;
private long result;
private Command quit, add ;
private CanvasClass canvas;
int first=0, second=0;
public CanvasForm(){
form = new Form("Calculator");
one = new TextField(null, "10000002", 8, TextField.NUMERIC );
two = new TextField(null, "10000003", 8, TextField.NUMERIC );
item = new StringItem("Result", "");
quit = new Command("Quit", Command.EXIT, 0);
add = new Command("Add", Command.SCREEN, 0);
form.append(one);
form.append(two);
form.append(item);
form.addCommand(add);
form.addCommand(quit);
form.setCommandListener(this);
}
public void startApp(){
display=Display.getDisplay(this);
if (current!=null)
display.setCurrent(current);
else{
display.setCurrent(form);
current=form;
}
}
public void pauseApp(){}
public void destroyApp(boolean b){}
private void calculate(){
try {
first = Integer.parseInt( one.getString() );
second = Integer.parseInt( two.getString() );
result = first + second ;
item.setText( result + "" );
} catch (NumberFormatException e){
item.setText("unknown");
e.printStackTrace();
}
}
public void commandAction(Command c, Displayable s){
if (c == quit){
notifyDestroyed();
return;
}
calculate();
if (canvas==null) canvas= new CanvasClass() ;
current=canvas;
display.setCurrent(canvas);
}
class CanvasClass extends Canvas implements CommandListener{
CanvasClass(){
this.addCommand( new Command("Back", Command.BACK, 0 ) );
this.setCommandListener(this);
}
protected void paint(Graphics g){
int w = getWidth();
int h = getHeight();
g.setColor(244,244,244);
g.fillRect( 0,0,w,h );
g.setGrayScale(12*14);
h = Math.min( w, h );
long mf = 100000000;
int angle = (int)(( (first*(36000*mf/result)) +50*mf)/(100*mf)) ;
int origin=180;
g.fillArc(0,0,h,h, origin, (int)angle);
g.setGrayScale(13*16);
g.fillArc(0,0,h,h, (int)(origin+angle), (int)(360-angle) );
g.setColor(123);
g.drawString("A = "+first+" ", h/2, h/2-10, Graphics.BASELINE|Graphics.RIGHT);
g.drawString(" B = "+second, h/2, h/2-10, Graphics.BASELINE|Graphics.LEFT);
g.drawString("Total = "+(first+second), h/2, h/2, Graphics.TOP|Graphics.HCENTER);
}
public void commandAction( Command c, Displayable d){
current=form;
display.setCurrent(form);
}
}
}