如何在首页加载时按页面中列表/表的第一项？

我对ADF来说还很陌生，并且仍然获得了动手实践的经验。

我只想在用户最初打开JSFF页面时调用一次受管bean方法。该方法绑定到页面上表的SelectionListener上。我需要迭代器可用，因为处理程序会执行一些CRUD操作（下面是方法“ insertNewReturnReason”的代码）。

我已经从Shay Shmeltzer阅读了此链接，并且很好奇我如何可以通过编程方式进行相同的操作。

请告诉我。

谢谢，非常感谢您的帮助。

问候

package com.asrandisheh.mis.asset.viewcontroller;


import javax.faces.event.ActionEvent;

import oracle.adf.model.BindingContext;

import oracle.adf.model.binding.DCIteratorBinding;

import oracle.jbo.Row;

import com.asrandisheh.mis.asset.model.viewobject.AstAssetReturnsVORowImpl;
import com.asrandisheh.mis.asset.viewcontroller.JSFUtils;

import javax.faces.context.FacesContext;

import oracle.adf.model.binding.DCBindingContainer;

import oracle.jbo.server.Entity;

import org.apache.myfaces.trinidad.event.SelectionEvent;
import oracle.binding.BindingContainer;
import oracle.jbo.ViewObject;




import oracle.binding.OperationBinding;

import oracle.jbo.Key;

public class AssetReturn {
    public AssetReturn() {
        super();
    }


    public void insertNewReturnReason(SelectionEvent selectionEvent) {

        // Maintain the makecurrent behavior
        JSFUtils.resolveMethodExpression("#{bindings.AstAssetsVO.collectionModel.makeCurrent}", null, 
                                           new Class[]{SelectionEvent.class}, new Object[]{selectionEvent});        


        // Get the binding context
        BindingContext bctx = BindingContext.getCurrent(); 
        BindingContainer bindings = bctx.getCurrentBindingsEntry();


        // get the current row for AST_ASSET table
        DCIteratorBinding astAssetsVOIterator = (DCIteratorBinding) bindings.get("astAssetsVOIterator");        
        Key parentKey = astAssetsVOIterator.getCurrentRow().getKey();


        //Rollback any previously created row
        OperationBinding ob= bindings.getOperationBinding("Rollback");
        ob.execute();


        //Set again row key as current row
        astAssetsVOIterator.setCurrentRowWithKey(parentKey.toStringFormat(true));


        // get the AstAssetReturnsVOIterator and create a new row with default values        
        DCIteratorBinding astAssetReturnsVOIterator = (DCIteratorBinding) bindings.get("AstAssetReturnsVOIterator");
        ViewObject assetReturnVO = astAssetReturnsVOIterator.getViewObject();
        assetReturnVO.executeEmptyRowSet();

        // pre-set values for ast_asset_return 
        Row assetReturnRow = assetReturnVO.createRow();
        Row assetRow = astAssetsVOIterator.getCurrentRow();                        
        assetReturnRow.setAttribute("AsetId", assetRow.getAttribute("Id"));
        assetReturnRow.setAttribute("AsrtDate", "1395/12/31");
        assetReturnRow.setAttribute("Stat", 0);

        // insert the new row         
        assetReturnVO.insertRow( assetReturnRow );
    }

    public void saveAssetReturn(ActionEvent actionEvent) {
        // Get the bindings
        BindingContext bctx = BindingContext.getCurrent(); 
        BindingContainer bindings = bctx.getCurrentBindingsEntry();


        // get the current row for AST_ASSET table
        DCIteratorBinding astAssetsVOIterator = (DCIteratorBinding) bindings.get("AstAssetsVOIterator");        
        astAssetsVOIterator.getCurrentRow().setAttribute("Status", "Returned");

        OperationBinding ob = bindings.getOperationBinding("Commit");
        ob.execute();
    }

}

编辑：如果我使用方法调用活动作为初始活动，则在尝试访问迭代器的ViewObject时会得到空指针。为了防止万一，我已经标记了该行，提示了空指针异常。

    public void assetReturnInitialization() {    

        // Get the binding context
        BindingContext bctx = BindingContext.getCurrent(); 
        BindingContainer bindings = bctx.getCurrentBindingsEntry();

        // get the current row for AST_ASSET table
        DCIteratorBinding astAssetsVOIterator = (DCIteratorBinding) bindings.get("astAssetsVOIterator");        

        // get the AstAssetReturnsVOIterator and create a new row with default values        
        DCIteratorBinding astAssetReturnsVOIterator = (DCIteratorBinding) bindings.get("AstAssetReturnsVOIterator");
        ViewObject assetReturnVO = astAssetReturnsVOIterator.getViewObject();  // NULL POINTER EXCEPTION OCCURS HERE
        assetReturnVO.executeEmptyRowSet();

        System.out.println("assetReturnInitialization 40");

        // pre-set values for ast_asset_return 
        Row assetReturnRow = assetReturnVO.createRow();
        Row assetRow = astAssetsVOIterator.getCurrentRow();                        

        System.out.println("assetReturnInitialization 50");

        assetReturnRow.setAttribute("AsetId", assetRow.getAttribute("Id"));
        assetReturnRow.setAttribute("AsrtDate", "1395/12/31");
        assetReturnRow.setAttribute("Stat", 0);

        System.out.println("assetReturnInitialization 60");

        // insert the new row         
        assetReturnVO.insertRow( assetReturnRow );

        System.out.println("assetReturnInitialization 20");
    }