Java Development

[nikita18]

My code below:

try{
    	Application.getApplication().invokeLater(new Thread(){    	
    		public void run(){     			
    			if(!checkForAppStop()){
    	    		FetchImg thrd=new FetchImg();				
    				thrd.start();				    										    	
    		    	new UploadThread().start();	//start thread		       
    	    	}
    	    	else 
    	    		System.out.println("Application stopped");    
    		}
    	});
    	} catch(Exception e){
    		 System.out.println("====Exception: "+e.getMessage());
    	}

The line highlighted above is giving me the exception " No application instance". Can anyone guide me a solution for this? Thanks a lot.

[simon_hain]

where do you use this code? maybe in the static main method?
in any case, the application object is not there at this time, you have to move the code some place else.

as a sidenote: don't use invokelater with a thread, it needs only a runnable.

[nikita18]

 Yes I've placed this code in main method. I edited my code to:

Application.getApplication().invokeLater(new Runnable(){

But its still giving me the same exception. What should I do now? 

[simon_hain · Accepted solution]

the main method is executed before there is an application instance, as you usually create one at its end and call enterEventDispatcher (which does not return).
place your code in the constructor, for example.

[nikita18]

I placed my code in the costructor and it solved my problem. Thanks so much Simon_hain. But I couldn't understand the reason for this. Could you please explain me a bit? Thanks again.

[simon_hain]

the constructor for the application creates the application instance. before that there is none.
without an application instance you cannot use invokelater.

[peter_strange]

Simon's explanation is exactly correct.  I don't think you can add much to it.  I will try to repeat it using different words and perhaps that will help.

When main is executed, there is NO application, there is just a Thread.  All main methods create an Application and then use enterEventDisplatcher to get the events running. 

When you code Application.getApplication(), you are trying to find the running application, this code goes to the OS and looks for the Application.  But in the middle of the Application constructor, you don't have one that the OS knows about.  Hence your problem.

Instead of using "Application.getApplication()", in your Application constructor you could actually code "this".   

HTH. 

[nikita18]

Thank you simon_hain and peter_strange. That was a wonderful explaination from both of you. I'm glad I'm a part of this forum. Thanks again.