Roboguice 2.0 (android):POJO 注入错误(始终为空)

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问题描述

我的基础 POJO 类:

public class BaseDao {
   public BaseDao() {
   }
   // ... 
}

我的扩展POJO类:

public class KelvinDao extends BaseDao {
   public KelvinDao () {
      super();
   }
   // ... 
}

我想在这样的服务中使用 KelvinDao:

public class HanKelvinHandler extends HttpRequestHandler {

   @Inject
   private KelvinDao mKelvinDao;

   public void treatGet() {
      mKelvinDao.blabla(); !!! mKelvinDao is always NULL
   }

这真的很简单，但它不起作用:(

谢谢大家的帮助！

推荐答案

你是如何创建 HanKelvinHandler 的?如果您在 RoboGuice 类的子类中执行此操作，例如 RoboActivity，那么它应该可以正常工作.示例:

public class MyActivity extends RoboActivity
{
    @Inject
    private HanKelvinHandler m_handler;
    [...]
}

否则(即，您在另一个 POJO 中创建它)，您在常规 Guice 领域，我相信您将需要使用注入器来获取它的实例.示例:

public class MyClass
{
    public void doSomething()
    {
        Injector injector = Guice.createInjector( new YourGuiceBindings() );
        HanKelvinHandler handler = injector.getInstance( HanKelvinHandler.class );
        handler.treatGet(); // mKelvinDao should be good now
    }
}

如果你之前没有见过注入器的使用，或者你不知道给 YourGuiceBindings() 放什么，那么你可能需要阅读以下内容:

https://github.com/roboguice/roboguice/wiki/Simple-自定义绑定

https://code.google.com/p/google-guice/维基/入门

似乎应该有一种方法可以在不使用注射器的情况下做到这一点，但我不知道.

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问题描述

My base POJO class:

public class BaseDao {
   public BaseDao() {
   }
   // ... 
}

My extends POJO class:

public class KelvinDao extends BaseDao {
   public KelvinDao () {
      super();
   }
   // ... 
}

I want to use KelvinDao in a service like that:

public class HanKelvinHandler extends HttpRequestHandler {

   @Inject
   private KelvinDao mKelvinDao;

   public void treatGet() {
      mKelvinDao.blabla(); !!! mKelvinDao is always NULL
   }

It's really simple but it doesn't work :(

Thank you guys for your help!

推荐答案

How are you creating HanKelvinHandler? If you're doing it within a subclass of a RoboGuice class, such as RoboActivity, then it should just work. Example:

public class MyActivity extends RoboActivity
{
    @Inject
    private HanKelvinHandler m_handler;
    [...]
}

Otherwise (i.e., you're creating it within another POJO), you're in regular Guice land, and I believe you will need to use the injector to get an instance of it. Example:

public class MyClass
{
    public void doSomething()
    {
        Injector injector = Guice.createInjector( new YourGuiceBindings() );
        HanKelvinHandler handler = injector.getInstance( HanKelvinHandler.class );
        handler.treatGet(); // mKelvinDao should be good now
    }
}

If you haven't seen the use of the injector before, or you don't know what to put for YourGuiceBindings(), then you may need to read the following:

https://github.com/roboguice/roboguice/wiki/Simple-Custom-Binding

https://code.google.com/p/google-guice/wiki/GettingStarted

It seems like there should be a way to do this without using the injector, but I don't know.