Android 在可展开列表视图的子视图中设置图像时出现空指针异常
我在Android 在可展开列表视图的子视图中设置图像时出现空指针异常,android,adapter,expandablelistview,expandablelistadapter,Android,Adapter,Expandablelistview,Expandablelistadapter,我在child.bg[I]=bground[0]行中得到一个Null指针异常。我正在尝试在子项的ImageView中设置图像。我在子项布局中有一个ImageView和TextView。以下是在可扩展列表视图中填充数据的代码 List<GroupItem> items = new ArrayList<GroupItem>(); int[] bground ={R.drawable.hawamahal,R.drawable.tajmahal,R.drawable.m
child.bg[I]=bground[0]行中得到一个Null指针异常
代码>。我正在尝试在子项的ImageView
中设置图像。我在子项布局中有一个ImageView
和TextView
。以下是在可扩展列表视图中填充数据的代码
List<GroupItem> items = new ArrayList<GroupItem>();
int[] bground ={R.drawable.hawamahal,R.drawable.tajmahal,R.drawable.mysorepalace};
// Populate our list with groups and it's children
for(int i = 0; i < 3; i++) {
GroupItem item = new GroupItem();
switch(i){
case 0: item.title = "Western India";
{
ChildItem child = new ChildItem();
child.title = getString(R.string.WestDescription);
child.bg[i] = bground[0];
item.items.add(child);
}
break;
case 1: item.title = "Northern India";
{
ChildItem child = new ChildItem();
child.title = getString(R.string.NorthDescription);
child.bg[i] = bground[1];
item.items.add(child);
}
break;
case 2: item.title = "Southern India";
{
ChildItem child = new ChildItem();
child.title = getString(R.string.SouthDescription);
child.bg[i] = bground[2];
item.items.add(child);
}
break;
}
items.add(item);
}
List items=new ArrayList();
int[]bground={R.drawable.hawamahal,R.drawable.tajmahal,R.drawable.mysorepaluage};
//用组及其子项填充我们的列表
对于(int i=0;i<3;i++){
GroupItem=新的GroupItem();
开关(一){
案例0:item.title=“西印度”;
{
ChildItem child=新的ChildItem();
child.title=getString(R.string.WestDescription);
child.bg[i]=bground[0];
item.items.add(子项);
}
打破
案例1:item.title=“北印度”;
{
ChildItem child=新的ChildItem();
child.title=getString(R.string.NorthDescription);
child.bg[i]=bground[1];
item.items.add(子项);
}
打破
案例2:item.title=“南印度”;
{
ChildItem child=新的ChildItem();
child.title=getString(R.string.southsdescription);
child.bg[i]=bground[2];
item.items.add(子项);
}
打破
}
项目。添加(项目);
}
`
以及适配器和支架的代码
private static class GroupItem {
String title;
List<ChildItem> items = new ArrayList<ChildItem>();
}
private static class ChildItem {
String title;
int[] bg;
}
private static class ChildHolder {
TextView title;
ImageView childimage;
}
private static class GroupHolder {
TextView title;
}
/**
* Adapter for our list of {@link GroupItem}s.
*/
private class ExampleAdapter extends AnimatedExpandableListView.AnimatedExpandableListAdapter {
private LayoutInflater inflater;
private List<GroupItem> items;
public ExampleAdapter(Context context) {
inflater = LayoutInflater.from(context);
}
public void setData(List<GroupItem> items) {
this.items = items;
}
@Override
public ChildItem getChild(int groupPosition, int childPosition) {
return items.get(groupPosition).items.get(childPosition);
}
@Override
public long getChildId(int groupPosition, int childPosition) {
return childPosition;
}
@Override
public View getRealChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
ChildHolder holder;
int[] bg={R.drawable.taj};
ChildItem item = getChild(groupPosition, childPosition);
if (convertView == null) {
holder = new ChildHolder();
convertView = inflater.inflate(R.layout.list_item, parent, false);
holder.title = (TextView) convertView.findViewById(R.id.textTitle);
holder.childimage= (ImageView) convertView.findViewById(R.id.ChildImageView);
convertView.setTag(holder);
} else {
holder = (ChildHolder) convertView.getTag();
}
holder.title.setText(item.title);
holder.childimage.setImageResource(bg[groupPosition]);
return convertView;
}
@Override
public int getRealChildrenCount(int groupPosition) {
return items.get(groupPosition).items.size();
}
@Override
public GroupItem getGroup(int groupPosition) {
return items.get(groupPosition);
}
@Override
public int getGroupCount() {
return items.size();
}
@Override
public long getGroupId(int groupPosition) {
return groupPosition;
}
@Override
public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {
GroupHolder holder;
GroupItem item = getGroup(groupPosition);
if (convertView == null) {
holder = new GroupHolder();
convertView = inflater.inflate(R.layout.group_item, parent, false);
holder.title = (TextView) convertView.findViewById(R.id.textTitle);
convertView.setTag(holder);
} else {
holder = (GroupHolder) convertView.getTag();
}
holder.title.setText(item.title);
return convertView;
}
@Override
public boolean hasStableIds() {
return true;
}
@Override
public boolean isChildSelectable(int arg0, int arg1) {
return true;
}
}
private静态类GroupItem{
字符串标题;
列表项=新建ArrayList();
}
私有静态类ChildItem{
字符串标题;
int[]bg;
}
私有静态类儿童持有者{
文本视图标题;
图像查看儿童图像;
}
私有静态类GroupHolder{
文本视图标题;
}
/**
*用于我们的{@link GroupItem}列表的适配器。
*/
私有类ExampleAdapter扩展AnimatedExpandableListView.AnimatedExpandableListAdapter{
私人充气机;
私人清单项目;
公共示例适配器(上下文){
充气器=充气器。从(上下文);
}
公共无效设置数据(列表项){
这个项目=项目;
}
@凌驾
公共子项getChild(int-groupPosition,int-childPosition){
返回items.get(groupPosition).items.get(childPosition);
}
@凌驾
公共长getChildId(int-groupPosition,int-childPosition){
返回子位置;
}
@凌驾
公共视图getRealChildView(int-groupPosition、int-childPosition、boolean-isLastChild、视图转换视图、视图组父视图){
儿童持有人;
int[]bg={R.drawable.taj};
ChildItem item=getChild(groupPosition,childPosition);
if(convertView==null){
holder=新的儿童holder();
convertView=充气机。充气(R.layout.list_项,父项,false);
holder.title=(TextView)convertView.findViewById(R.id.textTitle);
holder.childimage=(ImageView)convertView.findViewById(R.id.ChildImageView);
convertView.setTag(支架);
}否则{
holder=(ChildHolder)convertView.getTag();
}
holder.title.setText(项目名称);
holder.childimage.setImageResource(bg[groupPosition]);
返回视图;
}
@凌驾
公共整数getRealChildrenCount(整数组位置){
return items.get(groupPosition.items.size();
}
@凌驾
public GroupItem getGroup(int groupPosition){
返回项目。获取(groupPosition);
}
@凌驾
public int getGroupCount(){
返回items.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isExpanded、视图convertView、视图组父级){
股东;
GroupItem item=getGroup(groupPosition);
if(convertView==null){
holder=新的GroupHolder();
convertView=充气机。充气(R.layout.group_项,父项,false);
holder.title=(TextView)convertView.findViewById(R.id.textTitle);
convertView.setTag(支架);
}否则{
holder=(GroupHolder)convertView.getTag();
}
holder.title.setText(项目名称);
返回视图;
}
@凌驾
公共布尔表ID(){
返回true;
}
@凌驾
公共布尔值isChildSelectable(int arg0,int arg1){
返回true;
}
}
我是android开发的新手,如果您需要任何进一步的细节,请告诉我。在这里,我试图从ChildItem的ImageView中的drawable文件夹设置一个图像。如果有其他方法,请告诉我。提前感谢。您未能在ChildItem类中初始化child.bg[]数组。
按如下方式更改代码:
ChildItem child = new ChildItem();
child.title = getString(R.string.WestDescription);
child.bg[] = new int[3]; // <----- initiliaze bg[] arrays
child.bg[i] = bground[0];
item.items.add(child);
ChildItem child=new ChildItem();
child.title=getString(R.string.WestDescription);
child.bg[]=新整数[3];//标记发生异常的行。