question - a animated canvas during HTTP connection

[melas21]

I ve designed a midlet which connects to server and creates an image on the screen from received data. My question is:
is it possible to write a code which shows user Canvas which displays received data count and animated image (3 frames) on the screen during the connection is made.
Correct me if i am wrong bu i think thath i will need:
1. Class extending FullCanvas and implementing Runnable - it will show the animation on the screen
2. A HttpConnectionWorker 0 class (thread) which connects to server and waits for response

??
am i right has anybody got an exacmple of such code??


Mchmiel

[jvohome]

Yes, indeed, to show an animation like that, you could use a Runnable Canvas. Basic code:

public void run() {
  onScreen  = true;
  for (;onScreen;) {
    // Draw image with index index
    index++;
    if (index >= MAX_INDEX) index = 0;
    try {
      Thread.sleep(40);
    } catch (Exception e) {
      // Never thrown
    }
  }
}

Just make a decent check to see whether the canvas is still visible and active.

[melas21]

The thing isn't so simple as far as i am concerned becouse we have to create a thread for working in background and an canvas class with Timer thread to repaint it. In my software i solved this case combinining those 3 into 1 class (my project required such design). I list my code below

public class ConnectionWorker extends FullCanvas implements Runnable {

    
    private midApp parent;
    private String URL_to_call;
    private Object obj_to_notify;
    
    private String response_content;
    private boolean containsErrors = false;
    private boolean hasReceivedResponse = false;
    
    private String theText = "AAAA";
    private Font sF = Font.getFont (Font.FACE_SYSTEM,Font.STYLE_BOLD,Font.SIZE_MEDIUM);
    private Font mF = Font.getFont (Font.FACE_SYSTEM,Font.STYLE_BOLD,Font.SIZE_LARGE);
    
    int quant = 0;
    private Timer scheduler;
    private ConnectionWorker.TimerRepainter repainter;
    
    public ConnectionWorker (midApp parent_, String url, Object monitor){
        parent = parent_;
        URL_to_call = url;
        obj_to_notify = monitor;
        this.repaint ();
        this.serviceRepaints ();
        scheduler = new Timer();
        repainter = new ConnectionWorker.TimerRepainter(this);
        scheduler.schedule(repainter,0,500);
        parent.displaj.setCurrent(this);
    }
    
    public boolean getHasReceivedResponse(){
        return hasReceivedResponse;
    }
    
    public void paint (Graphics g){
        g.setClip (0,0,getWidth (),getHeight ());
        g.drawImage (parent.chatBkg,0,0,20);
        g.setColor (0xFFFFFF);
        
        g.setFont (mF);
        g.drawString ("LOADING",getWidth ()/2 - mF.stringWidth ("LOADING")/2,10,20);
        g.drawString (" Connction to server",getWidth ()/2 - mF.stringWidth (" Connction to server")/2,25,20);
        
        g.setColor (0x000000);
        
        g.drawString ("LOADING",getWidth ()/2 - mF.stringWidth ("LOADING")/2 +1,11,20);
        g.drawString (" Connection to server",getWidth ()/2 - mF.stringWidth (" Connection to server")/2 +1,26,20);
        
        
        g.setColor (0x000000);
        g.setFont (sF);
        g.drawString (theText,getWidth ()/2 - sF.stringWidth (theText)/2,getHeight ()- 10 - sF.getHeight (),20);
        
        g.setClip (getWidth ()/2-38/2,getHeight ()/2-50/2,38,50);
        
        g.drawImage (parent.progressImg,getWidth ()/2-38/2,getHeight ()/2- 50/2 - 50*quant,20);
        
    }
    
    public void run (){
        
        try{
            //connection
/// here is my method for connecting to server 
            response_content = RawConnector.callServlet (URL_to_call);
            hasReceivedResponse = true;
        }catch (Exception e){
            e.printStackTrace ();
        }
        
        
        //notify
        
        
        try{
            
            Thread.sleep (10000);
        }catch(Exception e){
            
        }
        
        
    }
    

    public String get_response_content (){
        if (hasReceivedResponse)
            return response_content;
        else
            return null;
    }
    
    
    private class TimerRepainter extends TimerTask {
        
        private ConnectionWorker connWorker;
        
        
        public TimerRepainter(ConnectionWorker conWrk){
            connWorker = conWrk;
        }
        
        public void run(){
            connWorker.quant = (connWorker.quant+1) % 3;
            connWorker.repaint();
            connWorker.serviceRepaints ();
        }
        
    }
    
}

hope this would help in the future

[jvohome]

I prefer using basic Threads instead of Timers, but that is just my thing. When using repaint() statements, it is wise to use a boolean to make the paint methods only accesible once at a time. This prevents flooding and poor running. So you basically skip the next paint if the paint method it already running.

public void paint(Graphics g) {
  if (paintRunning) return;
  paintRunning = true;
  // Do your painting
  paintRunning = false;
}

You can ofcourse use multiple Threads running through the same class. So your run would look like this:

public void run() {
  if (Thread.currentThread() == firstThread) {
    // First Thread tasks
  } else if (Thread.currentThread() == secondThread) {
    // Second Thread tasks
  }
}