Dagger Android Support framework dependency injection principle analysis
Dagger Android Support framework dependencies in injection principle analysis
In modern Android applications, a common requirement is management and resolving dependencies in applications.The Dagger Android Support framework is a solution to the officially recommended by Google to achieve dependent injection.This article will analyze the principle of the Dagger Android Support framework and introduce related programming code and configuration.
Dependency Injection is a software design mode. Its purpose is to achieve decoulation between objects by giving the object's creation and the analysis of the dependencies to the dedicated container.In Android applications, dependency injection can help us better manage and organize the dependency relationship between each component, and improve the maintenance and testability of code.
Dagger Android SUPPPORT framework is an extension of Dagger's dependency of injection framework, which aims to simplify the dependent injection process in Android applications.It provides some functions specific to Android, such as the injection of Activity, Fragment, and ViewModel, as well as dependency management of life cycle perception.
When using Dagger Android Support framework for dependencies, we usually need to perform the following steps:
First of all, we need to introduce the dependencies of the Dagger Android Support framework in the project Gradle file:
gradle
implementation 'com.google.dagger:dagger-android-support:<version>'
annotationProcessor 'com.google.dagger:dagger-android-processor:<version>'
We then need to define an injector interface to manage the components that depend on injection.The interface should inherit from `AndroidInjector` and use the@Component` annotation to mark.For example, for the Activity injector interface, we can define this:
@Component(modules = {ActivityModule.class})
public interface MyActivityInjector extends AndroidInjector<MyActivity> {
@Component.Builder
interface Builder {
@BindsInstance
Builder activity(MyActivity activity);
MyActivityInjector build();
}
}
In this interface, we can specify a module to be injected through the `Modules` property, such as` ActivityModule`.At the same time, we also need to define a nested `Builder` interface to build an injection instance.
Next, we need to create a PROVIDER class to provide an instance of dependent objects.This class should be marked with the `@module` annotation, and use the method of`@provides' to provide a method of dependent instance.For example, we can create an ActivityModule class to provide dependent examples:
@Module
public class ActivityModule {
@Provides
static SomeDependency provideSomeDependency() {
return new SomeDependency();
}
}
In this class, the `providesomedependency` method uses the`@provides' annotation mark, and returns an object of the type of `SOMEDEPENDENCY.
Finally, in the component of dependence injection, we need to use the dependent object that needs to be injected with the `@inject` annotation mark.For example, for dependency injection in Activity, we can handle this:
public class MyActivity extends AppCompatActivity {
@Inject SomeDependency someDependency;
@Override
protected void onCreate(Bundle savedInstanceState) {
// ...
MyActivityInjector injector = DaggerMyActivityInjector
.builder()
.activity(this)
.build();
injector.inject(this);
// ...
}
}
In this example, we use the@inject` annotation to mark the dependent object of the type of `SOMEDEPENDENCY 在, and then create an injection instance with the` DaggerMactivityInjector` class generated by the dagger, and call the `Inject` method for dependent injection.
Through the above steps, we can use the Dagger Android Support framework in Android applications for dependence.The framework will be responsible for automatic analysis and management dependencies, and provide correct dependent object instances when needed.
To sum up, the Dagger Android Support framework is based on the Dagger dependencies of injection framework, which aims to simplify the dependent injection process in Android applications.By using this framework, we can better manage the dependence of applications and improve the maintenance and testability of code.
