Android BaseExpandableListAdapter运行时错误NullPointerException
我尝试在ExpandableListView中查看数据库中的数据(我首先尝试使用硬编码字符串) 我使用了以下示例: 但是,当我点击一个组来获取childView时,会出现运行时错误 Categories1.javaAndroid BaseExpandableListAdapter运行时错误NullPointerException,android,arraylist,expandablelistview,Android,Arraylist,Expandablelistview,我尝试在ExpandableListView中查看数据库中的数据(我首先尝试使用硬编码字符串) 我使用了以下示例: 但是,当我点击一个组来获取childView时,会出现运行时错误 Categories1.java public class CategoriesActivity1 extends Activity { { 私有数组列表组; 私人ArrayList儿童; 私人语境; 公共MyExpandableListAdapter(上下文上下文、ArrayList组、ArrayList子级)
public class CategoriesActivity1 extends Activity
{
{
私有数组列表组;
私人ArrayList儿童;
私人语境;
公共MyExpandableListAdapter(上下文上下文、ArrayList组、ArrayList子级)
{
this.context=上下文;
这个组=组;
这个。孩子=孩子;
}
@凌驾
公共布尔值areAllItemsEnabled()
{
返回true;
}
@凌驾
公共ArrayList getChild(int-groupPosition,int-childPosition)
{
返回children.get(groupPosition).get(childPosition);
}
@凌驾
公共长getChildId(int-groupPosition,int-childPosition)
{
返回子位置;
}
@凌驾
公共视图getChildView(int-groupPosition、int-childPosition、,
布尔值isLastChild、视图转换视图、视图组父级)
{
String child=(String)((ArrayList)getChild(groupPosition,childPosition)).get(0);
if(convertView==null)
{
LayoutInflater LayoutInflater=(LayoutInflater)context.getSystemService(context.LAYOUT\u INFLATER\u SERVICE);
convertView=LayoutFlater.充气(R.layout.categories\u组,空);
}
TextView childTxt=(TextView)convertView.findViewById(R.id.TextViewChild01);
childTxt.setText(child);
返回视图;
}
@凌驾
公共整数getChildrenCount(整数组位置)
{
返回children.get(groupPosition.size();
}
@凌驾
公共对象getGroup(int-groupPosition)
{
返回groups.get(groupPosition);
}
@凌驾
public int getGroupCount()
{
返回组。size();
}
@凌驾
公共长getGroupId(int-groupPosition)
{
返回组位置;
}
@凌驾
公共视图getGroupView(int-groupPosition,布尔值isExpanded,
视图(视图、视图组父级)
{
字符串组=(字符串)getGroup(groupPosition);
if(convertView==null)
{
LayoutInflater LayoutInflater=(LayoutInflater)context.getSystemService(context.LAYOUT\u INFLATER\u SERVICE);
convertView=LayoutFlater.充气(R.layout.categories\u组,空);
}
TextView组txt=(TextView)convertView.findViewById(R.id.TextViewGroup);
groupTxt.setText(组);
返回视图;
}
@凌驾
公共布尔表ID()
{
返回true;
}
@凌驾
公共布尔值isChildSelectable(int-groupPosition,int-childPosition)
{
返回true;
}
}
categories\u group.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/categoriesLLayout2"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<TextView
android:id="@+id/TextViewGroup"
android:layout_width="wrap_content"
android:layout_height="50dp"
android:layout_marginLeft="50dp"
android:gravity="center_vertical"
>
</TextView>
<TextView
android:id="@+id/TextViewChild01"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="30dp"
>
</TextView>
</LinearLayout>
日志:
03-17 15:16:13.468:E/AndroidRuntime(370):致命异常:主
03-17 15:16:13.468:E/AndroidRuntime(370):java.lang.NullPointerException
03-17 15:16:13.468:E/AndroidRuntime(370):位于nl.test.listing.activity.MyExpandableListAdapter.getChildView(MyExpandableListAdapter.java:64)
03-17 15:16:13.468:E/AndroidRuntime(370):位于android.widget.ExpandableListConnector.getView(ExpandableListConnector.java:450)
03-17 15:16:13.468:E/AndroidRuntime(370):在android.widget.AbsListView.obtainView(AbsListView.java:1430)
03-17 15:16:13.468:E/AndroidRuntime(370):在android.widget.ListView.MeasureHeightOChildren(ListView.java:1216)
03-17 15:16:13.468:E/AndroidRuntime(370):在android.widget.ListView.onMeasure(ListView.java:1127)上
03-17 15:16:13.468:E/AndroidRuntime(370):在android.view.view.measure(view.java:8313)
03-17 15:16:13.468:E/AndroidRuntime(370):在android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
03-17 15:16:13.468:E/AndroidRuntime(370):在android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1017)
03-17 15:16:13.468:E/AndroidRuntime(370):在android.widget.LinearLayout.measureVertical(LinearLayout.java:386)
03-17 15:16:13.468:E/AndroidRuntime(370):在android.widget.LinearLayout.onMeasure(LinearLayout.java:309)
03-17 15:16:13.468:E/AndroidRuntime(370):在android.view.view.measure(view.java:8313)
03-17 15:16:13.468:E/AndroidRuntime(370):在android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
03-17 15:16:13.468:E/AndroidRuntime(370):位于android.widget.FrameLayout.onMeasure(FrameLayout.java:250)
03-17 15:16:13.468:E/AndroidRuntime(370):在android.view.view.measure(view.java:8313)
03-17 15:16:13.468:E/AndroidRuntime(370):在android.widget.LinearLayout.measureVertical(LinearLayout.java:531)
03-17 15:16:13.468:E/AndroidRuntime(370):在android.widget.LinearLayout.onMeasure(LinearLayout.java:309)
03-17 15:16:13.468:E/AndroidRuntime(370):在android.view.view.measure(view.java:8313)
03-17 15:16:13.468:E/AndroidRuntime(370):在android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
03-17 15:16:13.468:E/AndroidRuntime(370):位于android.widget.FrameLayout.onMeasure(FrameLayout.java:250)
03-17 15:16:13.468:E/AndroidRuntime(370):在android.view.view.measure(view.java:8313)
03-17 15:16:13.468:E/AndroidRuntime(370):在android.view.ViewRoot.performTraversals(ViewRoot.java:839)
03-17 15:16:13.468:E/AndroidRuntime(370):在android.view.ViewRoot.handleMessage(ViewRoot.java:1859)
03-17 15:16:13.468:E/AndroidRuntime(370):在android.os.Handler.dispatchMessage(Handler.java:99)上
03-17 15:16:13.468:E/AndroidRuntime(370):在android.os.Looper.loop(Looper.java:123)
03-17 15:16:13.468:E/AndroidRuntime(370):位于android.app.ActivityThread.main(ActivityThread.java:3683)
03-17 15:16:13.468:E/AndroidRuntime(370):位于java.lang.reflect.Method.Invokenactive(本机方法)
03-17 15:16:13.468:E/AndroidRuntime(370):在java.lang.reflect.Method.invoke(Method.java:507)
03-17 15:16:13.468:E/AndroidRuntime(370):在com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
03-17 15:16:13.468:E/AndroidRuntime(370):位于com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
03-17 15:16:1
public class MyExpandableListAdapter extends BaseExpandableListAdapter
private ArrayList<String> groups;
private ArrayList<ArrayList<ArrayList<String>>> children;
private Context context;
public MyExpandableListAdapter(Context context, ArrayList<String> groups, ArrayList<ArrayList<ArrayList<String>>> children)
{
this.context = context;
this.groups = groups;
this.children = children;
}
@Override
public boolean areAllItemsEnabled()
{
return true;
}
@Override
public ArrayList<String> getChild(int groupPosition, int childPosition)
{
return children.get(groupPosition).get(childPosition);
}
@Override
public long getChildId(int groupPosition, int childPosition)
{
return childPosition;
}
@Override
public View getChildView(int groupPosition, int childPosition,
boolean isLastChild, View convertView, ViewGroup parent)
{
String child = (String) ((ArrayList<String>)getChild(groupPosition, childPosition)).get(0);
if(convertView == null)
{
LayoutInflater layoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = layoutInflater.inflate(R.layout.categories_group, null);
}
TextView childTxt = (TextView)convertView.findViewById(R.id.TextViewChild01);
childTxt.setText(child);
return convertView;
}
@Override
public int getChildrenCount(int groupPosition)
{
return children.get(groupPosition).size();
}
@Override
public Object getGroup(int groupPosition)
{
return groups.get(groupPosition);
}
@Override
public int getGroupCount()
{
return groups.size();
}
@Override
public long getGroupId(int groupPosition)
{
return groupPosition;
}
@Override
public View getGroupView(int groupPosition, boolean isExpanded,
View convertView, ViewGroup parent)
{
String group = (String) getGroup(groupPosition);
if(convertView == null)
{
LayoutInflater layoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = layoutInflater.inflate(R.layout.categories_group, null);
}
TextView groupTxt = (TextView) convertView.findViewById(R.id.TextViewGroup);
groupTxt.setText(group);
return convertView;
}
@Override
public boolean hasStableIds()
{
return true;
}
@Override
public boolean isChildSelectable(int groupPosition, int childPosition)
{
return true;
}
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/categoriesLLayout2"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<TextView
android:id="@+id/TextViewGroup"
android:layout_width="wrap_content"
android:layout_height="50dp"
android:layout_marginLeft="50dp"
android:gravity="center_vertical"
>
</TextView>
<TextView
android:id="@+id/TextViewChild01"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="30dp"
>
</TextView>
</LinearLayout>