cannot modify xxx because it is mapped and there is no active NodeElement

Hi, i´m doing a simple application.

I write in a input field, and retorn the rows of the table of r3 that same equals to the inputfield...

My problem is, when i write in the input field, appear an error:

com.sap.tc.webdynpro.progmodel.context.ContextException: DataNodeInfo(SearchView): cannot modify Material because it is mapped and there is no active NodeElement to take the value

The problem is in this method:

public void wdDoInit()

{

//@@begin wdDoInit()

Bapi_Material_Getbatches_Input input = new Bapi_Material_Getbatches_Input();

wdContext.nodeBapi_Material_Input().bind(input);

//@@end

}

If i write the previous, when i write in the inputfield and press search appear the error, but if i substitute the bold line by this:

input.setMaterial("201311630A08000011");

when i press search appear the rows with the material 201311630A08000011.

What am i doing wrong?

Thanks,