我有一个对象的数组列表。每个对象都有一个数量。当用户加载StartersActivity时，我有ListView显示他们可以添加到订单中的商品列表。在每个列表中都有一个NumberPicker。
当用户第一次打开活动时，NumberPicker的值设置为0.但是当他们将订单添加到他们的订单时我会增加列表中项目的数量。返回StartersActivity后，我现在希望将NumberPicker的值设置为每个项目的数量。
目前这就是我试图实施他的方式。我打开StartersActivity：
FATAL EXCEPTION：main java.lang.IndexOutOfBoundsException：索引1无效，大小为1
这是在以下位置发生的行错误：
np.setValue(Order.getInstance().getOrderItems().get(position).getQty());
MenuItemArrayAdapter课程：
public class MenuItemArrayAdapter extends ArrayAdapter<MenuItem> {
//This list holds the items pulled from the web server.
private List<MenuItem> menuItems;
//This list holds the current items the user wants to add to their order.
//Number picker - lets user set quantity of item they wish to order. Adjusts the sub total of the order (price text view).
private static NumberPicker np;
//This text view is updated as user adds/removes items.
private TextView price;
//used to calculate the price.
private double amount = Order.getInstance().getAmount();
private double total = 0.0;
private OrderApplication app;
// Constructor - Takes reference to the Text View price - which will be updated when the value of number picker is adjusted.
public MenuItemArrayAdapter(Context context, List<MenuItem> menuItems,
TextView price) {
super(context, R.layout.menuitem_row, menuItems);
this.menuItems = menuItems;
this.price = price;
}
public MenuItemArrayAdapter(Context context) {
super(context, R.layout.menuitem_row);
}
public View getView(final int position, View convertView, ViewGroup parent) {
View v = convertView;
if (v == null) {
LayoutInflater vi = (LayoutInflater) getContext().getSystemService(
Context.LAYOUT_INFLATER_SERVICE);
v = vi.inflate(R.layout.menuitem_row, null);
v.setFocusable(true);
}
// assign values to view
final MenuItem item = this.menuItems.get(position);
TextView nameView = (TextView) v.findViewById(R.id.item_name);
final TextView priceView = (TextView) v.findViewById(R.id.item_price);
nameView.setText(item.getName() + " ");
priceView.setText("€" + String.valueOf(item.getPrice()));
// number picker
np = (NumberPicker) v.findViewById(R.id.numpick);
np.setMaxValue(20);
np.setMinValue(0);
if(Order.getInstance().getOrderItems().size()>0){
np.setValue(Order.getInstance().getOrderItems().get(position).getQty());
}else{
np.setValue(0);
}
np.setFocusable(false);
// calculation occurs when values are changed...
np.setOnValueChangedListener(new OnValueChangeListener() {
public void onValueChange(NumberPicker picker, int oldVal,
int newVal) {
//Add to order - increment price
if (newVal > oldVal) {
total = (item.getPrice() * newVal) - item.getPrice()
* oldVal;
Order.getInstance().addToOrder(item);
item.incQty();
amount += total;
Order.getInstance().setAmount(amount);
Toast.makeText(picker.getContext(), "Item Added: " + item.getName() + " Size: " + Order.getInstance().getOrderItems().size(), Toast.LENGTH_SHORT).show();
}
//remove from order - decrement price
if (newVal < oldVal) {
total = (item.getPrice() * oldVal) - item.getPrice()
* newVal;
Order.getInstance().removeFromOrder(position);
item.decQty();
amount -= total;
Order.getInstance().setAmount(amount);
Toast.makeText(picker.getContext(), "Item removed: " + item.getName() + " Size: " + Order.getInstance().getOrderItems().size(), Toast.LENGTH_SHORT).show();
}
//update the text view price.
price.setText("€" + String.valueOf(Order.getInstance().getAmount()));
}
});
return v;
}
}
任何人都可以解释我的代码出了什么问题。我无法弄清楚。非常感谢。
修改代码以将NumberPicker的值设置为：仍然获得NPE
if(Order.getInstance().getOrderItems().size() > 0){
//Loop to adjust the number picker to the quantity of dishes ordered.
for(int i = 0; i != Order.getInstance().getOrderItems().size(); i ++){
np.setValue(Order.getInstance().getOrderItems().get(position - 1).getQty());
}
}else{
np.setValue(0);
}
STACK TRACE：
02-21 06:00:51.979: E/AndroidRuntime(6876): FATAL EXCEPTION: main 02-21 06:00:51.979: E/AndroidRuntime(6876): java.lang.IndexOutOfBoundsException: Invalid index 1, size is 1 02-21 06:00:51.979: E/AndroidRuntime(6876): at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:251) 02-21 06:00:51.979: E/AndroidRuntime(6876): at java.util.ArrayList.get(ArrayList.java:304) 02-21 06:00:51.979: E/AndroidRuntime(6876): at com.example.waitronproto9.MenuItemArrayAdapter.getView(MenuItemArrayAdapter.java:84) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.widget.AbsListView.obtainView(AbsListView.java:2159) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.widget.ListView.makeAndAddView(ListView.java:1831) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.widget.ListView.fillDown(ListView.java:674) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.widget.ListView.fillFromTop(ListView.java:735) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.widget.ListView.layoutChildren(ListView.java:1652) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.widget.AbsListView.onLayout(AbsListView.java:1994) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.view.View.layout(View.java:14008) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.view.ViewGroup.layout(ViewGroup.java:4373) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1663) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1521) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.widget.LinearLayout.onLayout(LinearLayout.java:1434) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.view.View.layout(View.java:14008) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.view.ViewGroup.layout(ViewGroup.java:4373) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.widget.FrameLayout.onLayout(FrameLayout.java:448) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.view.View.layout(View.java:14008) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.view.ViewGroup.layout(ViewGroup.java:4373) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1663) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1521) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.widget.LinearLayout.onLayout(LinearLayout.java:1434) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.view.View.layout(View.java:14008) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.view.ViewGroup.layout(ViewGroup.java:4373) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.widget.FrameLayout.onLayout(FrameLayout.java:448) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.view.View.layout(View.java:14008) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.view.ViewGroup.layout(ViewGroup.java:4373) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:1892) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1711) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:989) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4351) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.view.Choreographer.doCallbacks(Choreographer.java:562) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.view.Choreographer.doFrame(Choreographer.java:532) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.os.Handler.handleCallback(Handler.java:725) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.os.Handler.dispatchMessage(Handler.java:92) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.os.Looper.loop(Looper.java:137) 02-21 06:00:51.979: E/AndroidRuntime(6876): at android.app.ActivityThread.main(ActivityThread.java:5041) 02-21 06:00:51.979: E/AndroidRuntime(6876): at java.lang.reflect.Method.invokeNative(Native Method) 02-21 06:00:51.979: E/AndroidRuntime(6876): at java.lang.reflect.Method.invoke(Method.java:511) 02-21 06:00:51.979: E/AndroidRuntime(6876): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 02-21 06:00:51.979: E/AndroidRuntime(6876): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 02-21 06:00:51.979: E/AndroidRuntime(6876): at dalvik.system.NativeStart.main(Native Method)