j2me-绘制圆弧

一、原理

圆弧的2个角度，一个角度是圆弧的起始点，另一个角度是圆弧的终点。在一个钟表上，3点的位置是0度，当逆时针方向移动时，度数会增加，12点是90度，当顺时针方面移动时，度数会减少。

二、图

三、代码

Midlet.java

package test;

 

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;

public class Midlet extends MIDlet {
    privateDisplay display;
    privateMIDPCanvas midpcanvas;
    publicMidlet(){
        display=Display.getDisplay(this);
        midpcanvas=new MIDPCanvas(this);
    }
    public voidstartApp() {
       display.setCurrent(midpcanvas);
    }

    publicvoid pauseApp() {
    }
    public voidexitMIDlet() {
       destroyApp(true);
       notifyDestroyed();
    }
    public voiddestroyApp(boolean unconditional) {
    }
}
MIDPCanvas.java

 

package test;

import javax.microedition.lcdui.*;

public class MIDPCanvas extends Canvas implements CommandListener{
   
    privateCommand cmd_exit;
   private  Midlet midlet;
    publicMIDPCanvas(Midlet midlet) {
       try {
    // Set up this canvas to listen to command events
           this.midlet=midlet;
           cmd_exit=new Command("退出",Command.EXIT,1);
           addCommand(cmd_exit);
    setCommandListener(this);
       } catch(Exception e) {
           e.printStackTrace();
       }
    }
   
   
    public voidpaint(Graphics g) {
     g.setColor(255,255,255);
     g.fillRect(0,0, getWidth(), getHeight());
     g.setColor(0,255,0);
     g.drawArc(0, 0, getWidth(), getHeight(), 180, 180);
    }
   
   
   protected  void keyPressed(int keyCode) {
    }
   
   
   protected  void keyReleased(int keyCode) {
    }

   
   protected  void keyRepeated(int keyCode) {
    }
   
   
   protected  void pointerDragged(int x, int y){
    }

   
   protected  void pointerPressed(int x, int y){
    }

   
   protected  void pointerReleased(int x, int y){
    }
   
   
    public voidcommandAction(Command command, Displayable displayable) {
       if (command==cmd_exit){
           midlet.exitMIDlet();
       }
    }

}