@Init"
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'''Purpose:''' Marker annotation to identify a initial method. | '''Purpose:''' Marker annotation to identify a initial method. | ||
| − | Binder calls the method with this annotation when initializing a ViewModel. In a ViewModel class, '''only one initial method is allowed at the most'''. If you set annotation element '''superclass''' to '''true''', the ViewModel's parent class's | + | Binder calls the method with this annotation when initializing a ViewModel. In a ViewModel class, '''only one initial method is allowed at the most'''. If you set annotation element '''superclass''' to '''true''', the ViewModel's parent class's initial method will be invoked first then child's, and this logic repeats on super class. If a class has no method with @Init, no method will be called (including the super class's)<ref>If you override parent class's initial method e.g. Parent.m1() <- Child.m1(). Because of Java's limitation, binder still call Child.m1(), and Child.m1() will be called twice. To avoid this, you should set superclass to false of Child.m1() and call super.m1() inside it. |
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Latest revision as of 07:35, 8 July 2022
This article is out of date, please refer to zk-mvvm-book/8.0/syntax/viewmodel/init for more up to date information.
Syntax
@Init
@Init(superclass=true)
Description
Target: method, class (since 6.0.1)
Purpose: Marker annotation to identify a initial method.
Binder calls the method with this annotation when initializing a ViewModel. In a ViewModel class, only one initial method is allowed at the most. If you set annotation element superclass to true, the ViewModel's parent class's initial method will be invoked first then child's, and this logic repeats on super class. If a class has no method with @Init, no method will be called (including the super class's)[1].
For example, in a class hierarchy: A(has @init) <- B(has @init) <- C(no @init) <- D (has @init, superclass=true). D is the last child class.
- When binder initializes D as a view model, it will call D's initial method.
- When binder initializes C, no method will be called.
- When binder initializes B , it will call As' then B's.
- When binder initializes A, it will call A's.
We also can use parameter related annotation on initial method's parameters, please refer to subsections of ZK Developer's Reference/MVVM/Syntax/ViewModel/Parameters.
- ↑ If you override parent class's initial method e.g. Parent.m1() <- Child.m1(). Because of Java's limitation, binder still call Child.m1(), and Child.m1() will be called twice. To avoid this, you should set superclass to false of Child.m1() and call super.m1() inside it.
Example
public class FooViewModel{
@Init
public void initFoo(){
//initializing
}
}
public class BarViewModel extends FooViewModel{
@Init(superclass=true)
public void initBar(){
//initial method of super class FooViewModel will be called first.
}
}
//since 6.0.1
@Init(superclass=true)
public class ChildViewModel extends BarViewModel{
}
Version History
| Version | Date | Content |
|---|---|---|
| 6.0.0 | February 2012 | The MVVM was introduced. |