Passing a String[] to EntryPoint class sends a null object!

[Nipuna Perera]

I am using GWT 2.0.3 and smartGWT 2.2. I don't think this is a smartGWT specific problem its a GWT question. I am working on a building a GWT front end to a simple database. I have successfully made a datagrid and imported data from an MySQL database to a DataGrid item. I am using an extra class to do the AsyncCallBack and get the data. It works perfectly for one class. I need to populate a combo box and I created another class. Heres the code..

package org.gwt.venus.client;

import java.util.Vector;

import com.google.gwt.user.client.rpc.AsyncCallback;

public class DesignsAndCriteria {
	
	public RpcCallServiceAsync rpc;
	String[] designs;
	
	
	public DesignsAndCriteria() {
		rpc = RpcInit.initRpc();
		initializeDesignsArray();
	}
	
	
	
	
	
	public void initializeDesignsArray(){
		rpc.getDesign(new AsyncCallback<Design[]>() {

			@Override
			public void onFailure(Throwable caught) {
				// TODO Auto-generated method stub
				
			}

			@Override
			public void onSuccess(Design[] result) {
				//System.out.println(result.length);
				
				loadDesigns(result);
				
			}
		});
	}
	
	public void loadDesigns(Design[] result) {
		designs = new String[result.length];
		for(int i=0; i<result.length; i++){
			
			designs[i]=result[i].design; //result is a class which has a String design which is transported from the server
			 
                         System.out.println(design[i]); //this successfully prints out the data which means the callback was successful and the data was imported
			 
		}
	
		
	}
	
	public String[] getDesigns() { 
		
		return designs;
	}
	

}

In the class which has the onModuleLoad() method (entry point class) I am initializing the above class and using the getDesigns() method to get the data but the getDesigns ALWAYS returns a null object. I am utterly confused as to why.. I am doing the same thing on another class from which im getting all the other data from my database to populate the DataGrid and it works. There I am creating a DataSource and adding records to it and then using a getDataSource() method exactly like the above class, im importing the data to the entrypoint class. I can't understand why i cant pass a string array. Any help would be great!! Thanks!!
>

[Francois Nadeau]

Hello Nipuna,

I assume that you already solved this, but I figure I can always respond anyway.

You did not provide the code where you use the DesignsAndCriteria class, but I am assuming that you it looks like this:

DesignsAndCriteria theCriteria = new DesignsAndCriteria();
theCriteria.getDesigns() // Code which uses the String array....

The problem with that is that initializeDesignsArray calls a synchronous function. Therefore, there are no guaranties that the designs variable is set when you call the getDesigns function.

There are many ways to solve this problem, one that comes to mind by looking at your code is the following:

...
public class DesignsAndCriteria {  
...
       
     public DesignsAndCriteria(Runnable aFinishAction) {  
         rpc = RpcInit.initRpc();  
         initializeDesignsArray(aFinishAction);  
     }  
       

     public void initializeDesignsArray(final Runnable aFinishAction){  
         rpc.getDesign(new AsyncCallback<Design[]>() {  
   
             @Override  
             public void onFailure(Throwable caught) {  
                 // TODO Auto-generated method stub  
                   
             }  
   
             @Override  
             public void onSuccess(Design[] result) {  
                 //System.out.println(result.length);  
                   
                 loadDesigns(result);  
                 aFinishAction.run();
             }  
         });  
     }   

and then change your code calling DesignsAndCriteria:

DesignsAndCriteria theCriteria = new DesignsAndCriteria(new Runnable() {
	public void run() {
		theCriteria.getDesigns() // Code which uses the String array....
	}
});

This will basically delay your initilization code until you have recieved the data from the synchronous call.

Hopes this helps,

Cheers.