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属性的setLabel导致NPE

codenameone

Gauvain Klug · 技术社区 · 6 年前

我在试这个 BoundTableModel NullPointerException

[EDT] 0:0:8,239 - Exception: java.lang.NullPointerException - null
java.lang.NullPointerException
    at com.codename1.properties.PropertyBase.putClientProperty(PropertyBase.java:131)
    at com.codename1.properties.PropertyBase.setLabel(PropertyBase.java:192)
    at our.app.forms.UnitsForm.<init>(UnitsForm.java:54)

NPE被扔在这个代码块中,但我不明白为什么。这个 properties 是 public final UserHistory ,但没有设置标签。最好以后再设置,因为它们需要我们的翻译 TranslationManager .

UiBinding ui = new UiBinding();
List<UserHistory> histories = RestManager.getHistory();
UserHistory prototype = new UserHistory();
prototype.dateCreate.setLabel("Date"); 
prototype.balanceUpdate.setLabel("Variation"); 
prototype.action.setLabel("Action");

UiBinding.BoundTableModel tb = ui.createTableModel(histories, prototype);
tb.setColumnOrder(prototype.dateCreate, prototype.balanceUpdate, prototype.action);
Table table = new Table(tb);

我不明白这是怎么回事 setLabel(String) 属于 Property 空指针异常 你知道吗?

AbstractEntity

public abstract class AbstractEntity implements Serializable, PropertyBusinessObject 
{
    public final LongProperty<AbstractEntity> id = new LongProperty<>("id");

    public final IntProperty<AbstractEntity> version = new IntProperty<>("version");

    public final Property<Date, AbstractEntity> dateCreate = new Property<>("dateCreate", Date.class);

    public final Property<Date, AbstractEntity> dateUpdate = new Property<>("dateUpdate", Date.class);

    protected List<PropertyBase> getPropertyList() 
    {
        List<PropertyBase> list = new ArrayList<>();
        list.add(id);
        list.add(version);
        list.add(dateCreate);
        list.add(dateUpdate);
        return list;
    }

    protected List<PropertyBase> getExcludePropertyList()
    {
        List<PropertyBase> list = new ArrayList<>();
        return list;
    }

    @Override
    public PropertyIndex getPropertyIndex()
    {
        PropertyBase[] properties = getPropertyList().toArray(new PropertyBase[getPropertyList().size()]);
        PropertyIndex index =  new PropertyIndex(this, getName(), properties);

        for(PropertyBase excluded : getExcludePropertyList())
        {
            index.setExcludeFromJSON(excluded, true);
            index.setExcludeFromMap(excluded, true);
        }

        return index;
    }
}

下面是我试图在表格中显示的子类:

public class UserHistory extends AbstractEntity 
{

    public final Property<User, UserHistory> user = new Property<>("user", User.class);

    public final DoubleProperty<UserHistory> balanceUpdate = new DoubleProperty<>("balanceUpdate");

    public final Property<String, UserHistory> action = new Property<>("action");

    public UserHistory() {}

    @SuppressWarnings("rawtypes")
    protected List<PropertyBase> getPropertyList() 
    {
        List<PropertyBase> list = super.getPropertyList();
        list.add(user);
        list.add(balanceUpdate);
        list.add(action);
        return list;
    }
}

1 回复 | 直到 6 年前

Shai Almog 6 年前

这行不通。

您的方法很有趣,但它的行为与普通实现有一个显著的不同:索引是惰性创建的。因此,索引所做的初始化工作并不是在所有情况下都会发生。

更糟糕的是,每次调用get方法时都会创建多个索引,这也是有问题的。

public abstract class AbstractEntity implements Serializable, PropertyBusinessObject 
{
    public final LongProperty<AbstractEntity> id = new LongProperty<>("id");

    public final IntProperty<AbstractEntity> version = new IntProperty<>("version");

    public final Property<Date, AbstractEntity> dateCreate = new Property<>("dateCreate", Date.class);

    public final Property<Date, AbstractEntity> dateUpdate = new Property<>("dateUpdate", Date.class);

    private PropertyIndex index;


    protected AbstractEntity() {
        getPropertyIndex();
    }

    protected List<PropertyBase> getPropertyList() 
    {
        List<PropertyBase> list = new ArrayList<>();
        list.add(id);
        list.add(version);
        list.add(dateCreate);
        list.add(dateUpdate);
        return list;
    }

    protected List<PropertyBase> getExcludePropertyList()
    {
        List<PropertyBase> list = new ArrayList<>();
        return list;
    }

    @Override
    public PropertyIndex getPropertyIndex()
    {
        if(idx == null) {
            PropertyBase[] properties = getPropertyList().toArray(new PropertyBase[getPropertyList().size()]);
            index =  new PropertyIndex(this, getName(), properties);

            for(PropertyBase excluded : getExcludePropertyList())
            {
                index.setExcludeFromJSON(excluded, true);
                index.setExcludeFromMap(excluded, true);
            }
        }
        return index;
     }
}

原始答复如下: