在ExpandableListActivity中使用子项

Question

我正在使用可扩展列表,如下所示:

Expandable列表活动有一个名为"OnGroupExpand"的方法,它允许您在父项展开之前执行一些工作,并且它的子项被公开.

在我的情况下,我想将checkChangeHandler附加到每个孩子的复选框,这样当它被点击时,我可以将孩子标记为完整.我有列表显示,子窗口显示父级扩展,但我的复选框什么也没做.

然后,我尝试在"onGroupExpand"方法中动态添加复选框处理程序.但是,当触发onGroupExpand时,我在尝试获取对每个子视图的引用时会收到非法的强制转换异常.

public void  onGroupExpand (int groupPosition) {

      int numOfChildren = expListAdapter.getChildrenCount(groupPosition);


            for(int i = 0; i < numOfChildren; i++)
            {
                 //Get exception here because getChild() returns Object - but how else can
                 //can I attach a check box to each child?
                 View v = (View) expListAdapter.getChild(groupPosition, i);


                 CheckBox cb = (CheckBox)v.findViewById( R.id.checkComplete ); 
                 cb.setOnCheckedChangeListener(new OnCheckedChangeListener(){
                    public void onCheckedChanged(CompoundButton arg0, boolean arg1) {
                        Toast.makeText(getBaseContext(), "Check Changed for " + groupPosition, 2000);
                    }
                  });
             }

我的主要问题是获取对Child视图的引用,以便我可以动态附加处理程序.请参阅我正在尝试执行此操作的代码注释.谢谢你的时间...

Answer 1

我相信问题在于

View v = (View) expListAdapter.getChild(groupPosition, i);

不返回a View但返回该位置的数据.您可能正在使用字符串或prefs对象或其他内容.您将获得它的底层对象,您可以对该对象进行更改.当在下面的方法中创建视图(并且由ListView自动调用)时,您可以设置任何onCheckChanged侦听器:

abstract View    getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent)

添加示例代码

以下是执行您想要执行的操作的示例适配器.视图是在适配器上创建的,而不是活动.我假设您在Activity中创建了一个SimpleExpandableListAdapter.而不是那样,添加以下类并创建该视图.

import java.util.List;

import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.SimpleExpandableListAdapter;
import android.widget.Toast;
import android.widget.CompoundButton.OnCheckedChangeListener;

public class ExampleAdapter extends SimpleExpandableListAdapter {

    protected Context mContext;

    public ExampleAdapter(ExampleActivity exampleActivity, List createGroupList, int groupRow, String[] strings, int[] is, List createChildList, int childRow, String[] strings2, int[] is2) {
        super(exampleActivity, createGroupList, groupRow, strings, is, createChildList, childRow, strings2, is2);
        mContext = exampleActivity;
    }

    @Override
    public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
        View v = super.getChildView(groupPosition, childPosition, isLastChild, convertView, parent);

        if (v != null) {
            final String value = "Check Changed for " + groupPosition + " " + childPosition;
            CheckBox cb = (CheckBox)v.findViewById( R.id.checkComplete ); 
            cb.setOnCheckedChangeListener(new OnCheckedChangeListener(){
               public void onCheckedChanged(CompoundButton arg0, boolean arg1) {
                   Toast toast = Toast.makeText(mContext, value, 2000);
                   toast.show();
               }
             });
        }

        return v;
    }    
}