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I am having trouble with the Dagger 2 dependency injection framework. I would like to create an EagerSingleton. I assume that dagger 2 creates lazy loaded singletons when I use the @Singleton annotation. How do I create EagerSingleton using the Dagger 2 framework ?
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In order to use dependency injection with the help of dagger 2 libraries, we need to add it's dependency. Go to Gradle Scripts > build. gradle(Module: app) and add the following dependencies. After adding these dependencies you need to click on Sync Now.
Dagger automatically generates code that mimics the code you would otherwise have hand-written. Because the code is generated at compile time, it's traceable and more performant than other reflection-based solutions such as Guice. Note: Use Hilt for dependency injection on Android.
The return type annotated with a @Provides annotation is used to associate this instantiation with any other modules of the same type. The @Singleton annotation is used to declare to Dagger that the provided object is to be only initialized only once during the entire lifecycle of the Component which uses that Module.
In this tutorial, we'll take a look at Dagger 2 – a fast and lightweight dependency injection framework. The framework is available for both Java and Android, but the high-performance derived from compile-time injection makes it a leading solution for the latter.
You can use the @Singleton annotation to indicate that there should be only one instance of the object. This is the most basic example of using Dagger 2 without component dependencies, subcomponents, complex modules, or custom scopes. The main Dagger 2 features used are:
For example, if you need to create a new object every time, the provider will look like this: A provider can contain any arbitrary code, including network (please don’t) and factory method calls. However, if the constructor is public and all parameters can be provided by Dagger, you can annotate the constructor with @Inject like this:
Calling code like an application’s main method or an Android Application accesses that graph via a well-defined set of roots. In Dagger 2, that set is defined by an interface with methods that have no arguments and return the desired type.
It can be solved by using dagger multibindings. First, you need to create the interface:
public interface EagerInit {
void eagerInit();
}
In the EagerModule you bind EagerInit implementations to set, so you can access it in the EagerComponent:
@Module
public abstract class EagerModule {
@Binds
@IntoSet
abstract EagerInit eagerInitImpl1(EagerInitImpl1 eagerInitImpl1);
@Binds
@IntoSet
abstract EagerInit eagerInitImpl2(EagerInitImpl2 eagerInitImpl2);
}
@Component(modules = {EagerModule.class})
public interface EagerComponent {
Set<EagerInit> getEagerInits();
}
After creating the EagerComponent you simply call:
component.getEagerInits().forEach(EagerInit::eagerInit);
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