Attempt to set model object on null model of component
2014-05-10 01:44
435 查看
wicket开发web项目是遇到这个异常,分析总结如下:
1.在采用单个值的控件如input:textfield,label等,其默认值可以为单个String,定义这些控件同时默认指定一个Model给它,并且提供对应String的get方法。如下:
定义label:
Label updateInfo = new Label("updateInfo", new PropertyModel<String>(this, "updateInfo"));
get函数:
public String getUpdateInfo() { return updateInfo; }
2.在采用选项有多个,默认值为单个的控件如RadioChoice(只能选一个),不仅要提供选项Model,一般为List类型,而且还需提供默认值Model,一般为String类型。如下:
定义RadioChoice:
final RadioChoice<String> updatePastTimeChoice = new RadioChoice<String>("pastTimeChoice",new Model<String>(pastTime), new PropertyModel<List<String>>(this, "pastTimeList"));
上面代码中pastTime为默认值Model,pastTimeList为选项Model。
get函数:
public List<String> getPastTimeList() { pastTimeList = googleNews_Constants.pastTimeList; return pastTimeList; }
3.总结:
即对于控件所对应的每一项都不能为NULL,在定义时应为其设置Model,否则会出现异常。新手或者不熟悉总会碰到这样的问题。
相关文章推荐
- Attempt to set a non-property-list object null as an NSUserDefaults
- Unity: “NullReferenceException: Object reference not set to an instance of an object”的可能解決方法
- Attempt to invoke virtual method 'void android.graphics.drawable.Drawable.setAlpha(int)' on a null o
- NullReferenceException: Object reference not set to an instance of an object
- Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null objec
- java.lang.NullPointerException:Attempt to invoke virtual method xxx on a null object reference
- Attempt to invoke interface method 'boolean java.util.List.add(java.lang.Object)' on a null
- Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null obj
- 解决Attempt to invoke virtual method '...ListAdapter'on a null object reference
- Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null objec
- NullReferenceException: Object reference not set to an instance of an object
- 关于Unity3D的错误:NullReferenceException: Object reference not set to an instance of an object 的解答
- Attempt to invoke interface method 'java.lang.Object[] java.util.Collection.toArray()' on a null obj
- Android开发中出现Attempt to invoke virtual method...on a null object reference
- Attempt to read from field 'int android.view.View.mViewFlags' on a null object reference
- 解决Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null···
- Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null objec
- Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null objec
- Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null objec
- 安卓开发——报错:Attempt to invoke interface method 'boolean java.util.List.add(java.lang.Object)' on a null