Java 获取按钮时ListView中的NullPointException
我有个奇怪的问题,似乎找不到是什么引起的。my ArrayAdapter中的每个视图组件都位于getView方法中,但my button除外,它会导致NullPointerException 适配器:Java 获取按钮时ListView中的NullPointException,java,android,Java,Android,我有个奇怪的问题,似乎找不到是什么引起的。my ArrayAdapter中的每个视图组件都位于getView方法中,但my button除外,它会导致NullPointerException 适配器: public class ItemAdapter extends ArrayAdapter<Item>{ private Context context; private int resource; private List<Item> list; public Ite
public class ItemAdapter extends ArrayAdapter<Item>{
private Context context;
private int resource;
private List<Item> list;
public ItemAdapter(Context context, int resource, List<Item> list)
{
super(context, resource, list);
this.context = context;
this.resource = resource;
this.list = list;
}
@Override
public View getView(int position, View convertView, ViewGroup parent)
{
if (convertView == null)
convertView = LayoutInflater.from(context).inflate(resource, parent,false);
TextView name = (TextView) convertView.findViewById(R.id.itemName);
ImageView itemImg = (ImageView) convertView.findViewById(R.id.itemImg);
Button addToCart = (Button) convertView.findViewById(R.id.button1);
final Item item = list.get(position);
name.setText(item.getName());
UrlImageViewHelper.setUrlDrawable(itemImg, item.getPicture());
addToCart.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View view)
{
Toast.makeText(context, "Clicked", Toast.LENGTH_LONG).show();
}
});
return convertView;
}
}
公共类ItemAdapter扩展了ArrayAdapter{
私人语境;
私有int资源;
私人名单;
公共项适配器(上下文、int资源、列表)
{
超级(上下文、资源、列表);
this.context=上下文;
这个资源=资源;
this.list=列表;
}
@凌驾
公共视图getView(int位置、视图转换视图、视图组父视图)
{
if(convertView==null)
convertView=LayoutInflater.from(上下文).inflate(资源,父项,false);
TextView名称=(TextView)convertView.findViewById(R.id.itemName);
ImageView itemImg=(ImageView)convertView.findViewById(R.id.itemImg);
按钮addToCart=(按钮)convertView.findViewById(R.id.button1);
最终项目=列表。获取(位置);
name.setText(item.getName());
UrlImageViewHelper.setUrlDrawable(itemImg,item.getPicture());
addToCart.setOnClickListener(新的OnClickListener(){
@凌驾
公共void onClick(视图)
{
Toast.makeText(上下文“单击”,Toast.LENGTH_LONG.show();
}
});
返回视图;
}
}
带有listview的片段
@InjectView(R.id.itemList) private ListView listView;
@Inject private ItemDao dao;
private ArrayAdapter<Item> adapter;
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
return inflater.inflate(R.layout.fragment_shop, container, false);
}
@Override
public void onViewCreated(View view, Bundle savedInstanceState)
{
super.onViewCreated(view, savedInstanceState);
dao.open();
List<Item> items = dao.findAll();
dao.close();
adapter = new ItemAdapter(getActivity(),R.layout.list_product_item, items);
listView.setAdapter(adapter);
}
@InjectView(R.id.itemList)私有ListView ListView;
@注入私有项dao-dao;
专用阵列适配器;
CreateView上的公共视图(布局、充气机、视图组容器、捆绑包保存状态)
{
返回充气机。充气(R.layout.fragment_shop,容器,假);
}
@凌驾
已创建视图上的公共void(视图,捆绑保存状态)
{
super.onViewCreated(视图,savedInstanceState);
dao.open();
List items=dao.findAll();
dao.close();
adapter=newitemAdapter(getActivity(),R.layout.list\u product\u item,items);
setAdapter(适配器);
}
列出产品项目
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal"
android:paddingBottom="5dp"
android:paddingLeft="10dp"
android:paddingRight="10dp"
android:paddingTop="5dp" >
<ImageView
android:id="@+id/itemImg"
android:layout_width="100dp"
android:layout_height="100dp"
android:layout_marginRight="5dp"
android:scaleType="centerCrop" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<TextView
android:id="@+id/itemName"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Medium Text"
android:textAppearance="?android:attr/textAppearanceMedium" />
<TextView
android:id="@+id/itemStoreName"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView" />
<Button
android:id="@+id/button1"
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button" />
</LinearLayout>
现在,对convertView.findViewById(R.id.button1)的调用返回一个空实例。造成这种情况的原因是什么?我如何修复它。您对布局的名称了解吗 adapter=new GroceryItemAdapter(getActivity(),R.layout.list\u textview,items) vs 列出产品项目
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal"
android:paddingBottom="5dp"
android:paddingLeft="10dp"
android:paddingRight="10dp"
android:paddingTop="5dp" >
<ImageView
android:id="@+id/itemImg"
android:layout_width="100dp"
android:layout_height="100dp"
android:layout_marginRight="5dp"
android:scaleType="centerCrop" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<TextView
android:id="@+id/itemName"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Medium Text"
android:textAppearance="?android:attr/textAppearanceMedium" />
<TextView
android:id="@+id/itemStoreName"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView" />
<Button
android:id="@+id/button1"
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button" />
</LinearLayout>
(我假设这是R.layout.list\u product\u item的文件名)请尝试在构造函数中初始化充气器,而不是使用from方法获取布局充气器
mInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
在获取视图中
convertView = mInflater.inflate(your layout, null);
作物粘贴错误的碎片。很抱歉要更新我的假设,请检查。请粘贴logcat输出?请发布logcat结果,