如何在可展开的列表视图中添加列表项

Question

我已经创建了一个带有子项目的可扩展列表视图，它工作得很好。我想向列表中添加另一个没有子项的项。我希望这个项目通过打开新的活动响应点击。我曾尝试将其添加为第4项，但当我单击此项目时应用程序崩溃。请建议我该做些什么改变。下面是我的MainActivity

的代码

    package com.example.dashboard;
    import java.util.ArrayList;
    import java.util.HashMap;
    import java.util.List;
    import android.app.Activity;
    import android.content.Intent;
    import android.os.Bundle;
    import android.view.View;
    import android.widget.ExpandableListView;
    import android.widget.ExpandableListView.OnChildClickListener;
    public class MainActivity extends Activity {
ExpandableListAdapter listAdapter;
ExpandableListView expListView;
List<String> listDataHeader;
HashMap<String, List<String>> listDataChild;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    // get the listview
    expListView = (ExpandableListView) findViewById(R.id.lvExp);
    // preparing list data
    prepareListData();
    listAdapter = new ExpandableListAdapter(this, listDataHeader, listDataChild);
    // setting list adapter
    expListView.setAdapter(listAdapter);
    // Listview on child click listener
    expListView.setOnChildClickListener(new OnChildClickListener() {
        @Override
        public boolean onChildClick(ExpandableListView parent, View v,
                int groupPosition, int childPosition, long id) {
            //selected item
                 if(listDataHeader.get(groupPosition).equalsIgnoreCase("Catalog")){
                 Intent i = new Intent(MainActivity.this, Departments.class);
                 // sending data to new activity
                  startActivity(i);
            }
            if(listDataChild.get(listDataHeader.get(groupPosition)).get(childPosition).equalsIgnoreCase("Check Holds")){
                    Intent i1 = new Intent(MainActivity.this,CheckHolds.class);
                    startActivity(i1);
            }
            if(listDataChild.get(listDataHeader.get(groupPosition)).get(childPosition).equalsIgnoreCase("Unreserve Books")){
                Intent i2 = new Intent(MainActivity.this,UnreserveBooks.class);
                startActivity(i2);
        }
            if(listDataChild.get(listDataHeader.get(groupPosition)).get(childPosition).equalsIgnoreCase("Library Hours")){
                Intent i3 = new Intent(MainActivity.this,LibraryHours.class);
                startActivity(i3);
        }
            if(listDataChild.get(listDataHeader.get(groupPosition)).get(childPosition).equalsIgnoreCase("Contact Library")){
                Intent i4 = new Intent(MainActivity.this,ContactLibrary.class);
                startActivity(i4);
        }
            if(listDataHeader.get(groupPosition).equalsIgnoreCase("Logout")){
                 Intent i5 = new Intent(MainActivity.this, Departments.class);
                  startActivity(i5);
            }
            return false;
        }
    });
}
/*
 * Preparing the list data
 */
private void prepareListData() {
    listDataHeader = new ArrayList<String>();
    listDataChild = new HashMap<String, List<String>>();
    // Adding child data
    listDataHeader.add("Catalog");
    listDataHeader.add("My Account");
    listDataHeader.add("Library Info");
    listDataHeader.add("Logout");
    // Adding child data
    List<String> catalog= new ArrayList<String>();
    catalog.add("Automobile");
    catalog.add("Computer Science");
    catalog.add("Civil");
    catalog.add("Electronics and Communication");
    catalog.add("Electrical and Electronics");
    catalog.add("Information science");
    catalog.add("Industrial Production");
    catalog.add("Mechanical");
    catalog.add("Basic Sciences");
    List<String> myaccount = new ArrayList<String>();
    myaccount.add("Check Holds");
    myaccount.add("Unreserve Books");
    List<String> libraryinfo = new ArrayList<String>();
    libraryinfo.add("Library Hours");
    libraryinfo.add("Contact library");
    listDataChild.put(listDataHeader.get(0), catalog); // Header, Child data
    listDataChild.put(listDataHeader.get(1), myaccount);
    listDataChild.put(listDataHeader.get(2), libraryinfo);
}
   }

这是logcat的样子

     03-22 02:13:38.814: I/Choreographer(2321): Skipped 251 frames!  The application may be doing too much work on its main thread.
     03-22 02:13:38.844: D/gralloc_goldfish(2321): Emulator without GPU emulation detected.
     03-22 02:13:39.004: I/Choreographer(2321): Skipped 84 frames!  The application may be doing too much work on its main thread.
     03-22 02:13:39.874: I/Choreographer(2321): Skipped 47 frames!  The application may be doing too much work on its main thread.
     03-22 02:13:40.894: D/AndroidRuntime(2321): Shutting down VM
     03-22 02:13:40.904: W/dalvikvm(2321): threadid=1: thread exiting with uncaught exception (group=0x41465700)
     03-22 02:13:40.934: E/AndroidRuntime(2321): FATAL EXCEPTION: main
     03-22 02:13:40.934: E/AndroidRuntime(2321): java.lang.NullPointerException
     03-22 02:13:40.934: E/AndroidRuntime(2321):    at com.example.dashboard.ExpandableListAdapter.getChildrenCount(ExpandableListAdapter.java:61)
     03-22 02:13:40.934: E/AndroidRuntime(2321):    at android.widget.ExpandableListConnector.refreshExpGroupMetadataList(ExpandableListConnector.java:563)
    03-22 02:13:40.934: E/AndroidRuntime(2321):     at android.widget.ExpandableListConnector.expandGroup(ExpandableListConnector.java:688)
    03-22 02:13:40.934: E/AndroidRuntime(2321):     at android.widget.ExpandableListView.handleItemClick(ExpandableListView.java:691)
    03-22 02:13:40.934: E/AndroidRuntime(2321):     at android.widget.ExpandableListView.performItemClick(ExpandableListView.java:651)
    03-22 02:13:40.934: E/AndroidRuntime(2321):     at android.widget.AbsListView$PerformClick.run(AbsListView.java:2788)
    03-22 02:13:40.934: E/AndroidRuntime(2321):     at android.widget.AbsListView$1.run(AbsListView.java:3463)
    03-22 02:13:40.934: E/AndroidRuntime(2321):     at  android.os.Handler.handleCallback(Handler.java:730)
    03-22 02:13:40.934: E/AndroidRuntime(2321):     at android.os.Handler.dispatchMessage(Handler.java:92)
    03-22 02:13:40.934: E/AndroidRuntime(2321):     at android.os.Looper.loop(Looper.java:137)
    03-22 02:13:40.934: E/AndroidRuntime(2321):     at android.app.ActivityThread.main(ActivityThread.java:5103)
    03-22 02:13:40.934: E/AndroidRuntime(2321):     at java.lang.reflect.Method.invokeNative(Native Method)
    03-22 02:13:40.934: E/AndroidRuntime(2321):     at java.lang.reflect.Method.invoke(Method.java:525)
    03-22 02:13:40.934: E/AndroidRuntime(2321):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
    03-22 02:13:40.934: E/AndroidRuntime(2321):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
    03-22 02:13:40.934: E/AndroidRuntime(2321):     at dalvik.system.NativeStart.main(Native Method)
    03-22 02:13:43.955: I/Process(2321): Sending signal. PID: 2321 SIG: 9

这是ExpandableListAdapter.java文件

   package com.example.dashboard;
   import java.util.HashMap;
   import java.util.List;
   import android.content.Context;
   import android.graphics.Typeface;
   import android.view.LayoutInflater;
   import android.view.View;
   import android.view.ViewGroup;
   import android.widget.BaseExpandableListAdapter;
   import android.widget.TextView;
   public class ExpandableListAdapter extends BaseExpandableListAdapter {
private Context _context;
private List<String> _listDataHeader; // header titles
// child data in format of header title, child title
private HashMap<String, List<String>> _listDataChild;
public ExpandableListAdapter(Context context, List<String> listDataHeader,
        HashMap<String, List<String>> listChildData) {
    this._context = context;
    this._listDataHeader = listDataHeader;
    this._listDataChild = listChildData;
}
@Override
public Object getChild(int groupPosition, int childPosititon) {
    return this._listDataChild.get(this._listDataHeader.get(groupPosition))
            .get(childPosititon);
}
@Override
public long getChildId(int groupPosition, int childPosition) {
    return childPosition;
}
@Override
public View getChildView(int groupPosition, final int childPosition,
        boolean isLastChild, View convertView, ViewGroup parent) {
    final String childText = (String) getChild(groupPosition, childPosition);
    if (convertView == null) {
        LayoutInflater infalInflater = (LayoutInflater) this._context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = infalInflater.inflate(R.layout.listitem, null);
    }
    TextView txtListChild = (TextView) convertView
            .findViewById(R.id.lblListItem);
    txtListChild.setText(childText);
    return convertView;
}
@Override
public int getChildrenCount(int groupPosition) {
    return this._listDataChild.get(this._listDataHeader.get(groupPosition))
            .size();
}
@Override
public Object getGroup(int groupPosition) {
    return this._listDataHeader.get(groupPosition);
}
@Override
public int getGroupCount() {
    return this._listDataHeader.size();
}
@Override
public long getGroupId(int groupPosition) {
    return groupPosition;
}
@Override
public View getGroupView(int groupPosition, boolean isExpanded,
        View convertView, ViewGroup parent) {
    String headerTitle = (String) getGroup(groupPosition);
    if (convertView == null) {
        LayoutInflater infalInflater = (LayoutInflater) this._context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = infalInflater.inflate(R.layout.listgroup, null);
    }
    TextView lblListHeader = (TextView) convertView
            .findViewById(R.id.lblListHeader);
    lblListHeader.setTypeface(null, Typeface.BOLD);
    lblListHeader.setText(headerTitle);
    return convertView;
}
@Override
public boolean hasStableIds() {
    return false;
}
@Override
public boolean isChildSelectable(int groupPosition, int childPosition) {
    return true;
}
   }

Answer 1

在您的可扩展列表适配器:

@Override
public int getChildrenCount(int groupPosition) {
    if(groupPosition == 3){
     return 0;
    }else{
    return this._listDataChild.get(this._listDataHeader.get(groupPosition))
            .size();
    }
}

由于您想要收听组中的点击，请使用这个而不是childclick侦听器:

expListView.setOnGroupClickListener(new OnGroupClickListener() {            
        @Override
        public boolean onGroupClick(ExpandableListView parent, View v,
                int groupPosition, long id) {
            //Catch the click that you want here.
            return false;
        }
    });

---

之前答:
在你的prepareListData():

listDataChild.put(listDataHeader.get(3), logout);