我创建了一个包含子项的可扩展列表视图，它工作正常。我想在列表中添加另一个没有任何子项目的项目。我希望此项目通过打开新活动来响应点击。我尝试将其添加为第4项，但是当我点击此项目时应用程序崩溃。请发布建议我应该做些什么改变。 这是我的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);
}
}
这就是logcat的外观
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;
}
}
答案 0 :(得分：2)
在您的可扩展列表适配器中：
@Override
public int getChildrenCount(int groupPosition) {
if(groupPosition == 3){
return 0;
}else{
return this._listDataChild.get(this._listDataHeader.get(groupPosition))
.size();
}
}
由于您希望收听群组的点击次数，请使用此代码而不是子级列表：
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;
}
});
上一个答案：
在prepareListData()：
listDataChild.put(listDataHeader.get(3), logout);