Android 基本适配器上的空点异常
我正在使用带有基本适配器的自定义listview。当我在listview上设置适配器时,它给出了空点异常。我正在检查空值,但它仍然给出异常 这是我的检查点Android 基本适配器上的空点异常,android,listview,android-listview,nullpointerexception,baseadapter,Android,Listview,Android Listview,Nullpointerexception,Baseadapter,我正在使用带有基本适配器的自定义listview。当我在listview上设置适配器时,它给出了空点异常。我正在检查空值,但它仍然给出异常 这是我的检查点 if(product_title.size() > 0 && product_quantity.size() > 0){ materialList.setAdapter(new MaterialListAdapter(MaterialList.this, product_title,pro
if(product_title.size() > 0 && product_quantity.size() > 0){
materialList.setAdapter(new MaterialListAdapter(MaterialList.this, product_title,product_quantity));
}
这是我的全班
public class MaterialList extends Activity{
ListView materialList;
List<Book> list;
private List<String> product_title = new ArrayList<String>();
private List<String> product_quantity = new ArrayList<String>();
JCGSQLiteHelper db;
Book selectedProduct;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.material_list);
ActionBar actionBar = getActionBar();
actionBar.hide();
db = new JCGSQLiteHelper(getApplicationContext());
list = db.getAllBooks();
for (int i = 0; i < list.size(); i++) {
product_title.add(i, list.get(i).getTitle());
product_quantity.add(i, list.get(i).getAuthor());
}
if(product_title.size() > 0 && product_quantity.size() > 0){
materialList.setAdapter(new MaterialListAdapter(MaterialList.this, product_title,product_quantity));
}
}
public class MaterialListAdapter extends BaseAdapter{
List<String> title = new ArrayList<String>();
List<String> quantity = new ArrayList<String>();
Context context;
private LayoutInflater inflater=null;
public MaterialListAdapter(MaterialList mainActivity, List<String> catalog_title, List<String> catalog_quantity ) {
// TODO Auto-generated constructor stub
context=mainActivity;
title =catalog_title;
quantity = catalog_quantity;
inflater = ( LayoutInflater )context.
getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
@Override
public int getCount() {
// TODO Auto-generated method stub
return title.size();
}
@Override
public Object getItem(int position) {
// TODO Auto-generated method stub
return position;
}
@Override
public long getItemId(int position) {
// TODO Auto-generated method stub
return position;
}
public class ViewHolder
{
TextView Title, Quanity, remove ;
}
@Override
public View getView(final int position, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
ViewHolder holder;
holder =new ViewHolder();
View rowView;
rowView = inflater.inflate(R.layout.cust_material_lis_item, null);
holder.Title=(TextView) rowView.findViewById(R.id.product);
holder.Quanity=(TextView) rowView.findViewById(R.id.quantity);
holder.remove=(TextView) rowView.findViewById(R.id.remove);
holder.Title.setText(title.get(position));
holder.Quanity.setText(quantity.get(position));
holder.remove.setText("Remove");
holder.remove.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
int id = list.get(position).getId();
selectedProduct =db.readBook(id);
db.deleteBook(selectedProduct);
}
});
return rowView;
}
}
}
public class MaterialList扩展活动{
ListView材料专家;
名单;
私有列表产品_title=new ArrayList();
私有列表产品_数量=新ArrayList();
jcgsqlitedb;
图书精选产品;
@凌驾
创建时受保护的void(Bundle savedInstanceState){
//TODO自动生成的方法存根
super.onCreate(savedInstanceState);
setContentView(R.layout.material_列表);
ActionBar ActionBar=getActionBar();
actionBar.hide();
db=新的JCGSQLiteHelper(getApplicationContext());
list=db.getAllBooks();
对于(int i=0;i0&&product_quantity.size()>0){
materialList.setAdapter(新materialList.this,产品名称,产品数量);
}
}
公共类MaterialListAdapter扩展了BaseAdapter{
列表标题=新建ArrayList();
列表数量=新的ArrayList();
语境;
专用充气机=空;
公共物料适配器(物料列表主活动、列表目录标题、列表目录数量){
//TODO自动生成的构造函数存根
上下文=主要活动;
标题=目录标题;
数量=目录数量;
充气器=(充气器)上下文。
getSystemService(上下文布局\充气机\服务);
}
@凌驾
public int getCount(){
//TODO自动生成的方法存根
返回title.size();
}
@凌驾
公共对象getItem(int位置){
//TODO自动生成的方法存根
返回位置;
}
@凌驾
公共长getItemId(int位置){
//TODO自动生成的方法存根
返回位置;
}
公共类视图持有者
{
文本视图标题、数量、删除;
}
@凌驾
公共视图getView(最终整数位置、视图转换视图、视图组父视图){
//TODO自动生成的方法存根
视窗座;
holder=新的ViewHolder();
视图行视图;
行视图=充气机。充气(R.layout.cust\u material\u lis\u item,空);
holder.Title=(TextView)rowView.findViewById(R.id.product);
holder.quantity=(TextView)rowView.findViewById(R.id.quantity);
holder.remove=(TextView)rowView.findViewById(R.id.remove);
holder.Title.setText(Title.get(position));
holder.quantity.setText(quantity.get(position));
holder.remove.setText(“移除”);
holder.remove.setOnClickListener(新的OnClickListener(){
@凌驾
公共void onClick(视图v){
//TODO自动生成的方法存根
int id=list.get(position.getId();
selectedProduct=db.readBook(id);
db.deleteBook(所选产品);
}
});
返回行视图;
}
}
}
这是我的适配器
public class MaterialListAdapter extends BaseAdapter{
List<String> title = new ArrayList<String>();
List<String> quantity = new ArrayList<String>();
Context context;
private LayoutInflater inflater=null;
public MaterialListAdapter(MaterialList mainActivity, List<String> catalog_title, List<String> catalog_quantity ) {
// TODO Auto-generated constructor stub
context=mainActivity;
title =catalog_title;
quantity = catalog_quantity;
inflater = ( LayoutInflater )context.
getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
@Override
public int getCount() {
// TODO Auto-generated method stub
return title.size();
}
@Override
public Object getItem(int position) {
// TODO Auto-generated method stub
return position;
}
@Override
public long getItemId(int position) {
// TODO Auto-generated method stub
return position;
}
public class ViewHolder
{
TextView Title, Quanity, remove ;
}
@Override
public View getView(final int position, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
ViewHolder holder;
holder =new ViewHolder();
View rowView;
rowView = inflater.inflate(R.layout.cust_material_lis_item, null);
holder.Title=(TextView) rowView.findViewById(R.id.product);
holder.Quanity=(TextView) rowView.findViewById(R.id.quantity);
holder.remove=(TextView) rowView.findViewById(R.id.remove);
holder.Title.setText(title.get(position));
holder.Quanity.setText(quantity.get(position));
holder.remove.setText("Remove");
holder.remove.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
int id = list.get(position).getId();
selectedProduct =db.readBook(id);
db.deleteBook(selectedProduct);
}
});
return rowView;
}
}
公共类MaterialListAdapter扩展了BaseAdapter{
列表标题=新建ArrayList();
列表数量=新的ArrayList();
语境;
专用充气机=空;
公共物料适配器(物料列表主活动、列表目录标题、列表目录数量){
//TODO自动生成的构造函数存根
上下文=主要活动;
标题=目录标题;
数量=目录数量;
充气器=(充气器)上下文。
getSystemService(上下文布局\充气机\服务);
}
@凌驾
public int getCount(){
//TODO自动生成的方法存根
返回title.size();
}
@凌驾
公共对象getItem(int位置){
//TODO自动生成的方法存根
返回位置;
}
@凌驾
公共长getItemId(int位置){
//TODO自动生成的方法存根
返回位置;
}
公共类视图持有者
{
文本视图标题、数量、删除;
}
@凌驾
公共视图getView(最终整数位置、视图转换视图、视图组父视图){
//TODO自动生成的方法存根
视窗座;
holder=新的ViewHolder();
视图行视图;
行视图=充气机。充气(R.layout.cust\u material\u lis\u item,空);
holder.Title=(TextView)rowView.findViewById(R.id.product);
holder.quantity=(TextView)rowView.findViewById(R.id.quantity);
holder.remove=(TextView)rowView.findViewById(R.id.remove);
holder.Title.setText(Title.get(position));
holder.quantity.setText(quantity.get(position));
holder.remove.setText(“移除”);
holder.remove.setOnClickListener(新的OnClickListener(){
@凌驾
公共void onClick(视图v){
//TODO自动生成的方法存根
int id=list.get(position.getId();
selectedProduct=db.readBook(id);
db.deleteBook(所选产品);
}
});
返回行视图;
}
}
此行给出了空点异常
materialList.setAdapter(新materialList.this,产品名称,产品数量);
materialList = findViewById(R.id.listViewID);
materialList = findViewById(R.id...)