关于ListView中CheckBox 用程序全选的有关问题

关于ListView中CheckBox 用程序全选的问题
LisetView中view布局
XML code
<?xml version="1.0" encoding="UTF-8"?>
<RelativeLayout android:gravity="center_vertical" android:orientation="horizontal" android:paddingLeft="5.0px" android:paddingTop="5.0px" android:paddingBottom="5.0px" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_weight="1.0"
  xmlns:android="http://schemas.android.com/apk/res/android">
  <CheckBox android:id="@id/contact_checkbox" android:layout_width="wrap_content" android:layout_height="fill_parent" android:layout_alignParentLeft="true" android:focusable="false"/>  
    <LinearLayout android:orientation="vertical" android:id="@id/contact_item_layout" android:paddingLeft="8.0px" android:layout_width="fill_parent" android:layout_height="fill_parent" android:layout_toRightOf="@id/contact_checkbox"
      xmlns:android="http://schemas.android.com/apk/res/android">
        <TextView android:textSize="20.0sp" android:textStyle="bold" android:id="@id/contact_item_name1" android:layout_width="fill_parent" android:layout_height="fill_parent" android:layout_toRightOf="@id/contact_checkbox" />
        <TextView android:textSize="14.0sp" android:id="@id/contact_item_name2" android:layout_width="fill_parent" android:layout_height="fill_parent" />
    </LinearLayout>
</RelativeLayout>
自定义类继承BaseAdapter使用上面的控件布局

页面继承ListAcitivity 
setListAdapter(baseadapter);

acitivity中有个selectAll点击它 怎样用程序代码实现checkBox的全部选中

------解决方案--------------------
Java code
        ListView listView = this.getListView();
        int count = listView.getChildCount();
        for(int i = 0; i < count; i++){
            RelativeLayout layout = (RelativeLayout)listView.getChildAt(i);
            int c = layout.getChildCount();
            for(int j = 0; j < c; j++){
                View view = layout.getChildAt(j);
                if(view instanceof CheckBox){
                    ((CheckBox)view).setChecked(true);
                    break;
                }
            }
        }