Decrypting Android dependence on the design ideas and source code analysis of the injection library
Decrypt the design ideas and source analysis of Android dependence on the library
Android dependency injection is a way to manage and solve the dependency relationship in Android applications.Dependent injection library is a tool that supports this design pattern, which provides the function of simplifying the injecting process.This article will explore the design ideas and source analysis of Android dependence on libraries.
Design ideas:
1. Note: The dependent injection library is usually used to mark the dependencies that need to be injected.Common annotations include@inject,@Component, and @module.During the compilation or running, the dependent injecting library will scan these annotations and generate the corresponding code.
2. Injecting: The dependency injection library is responsible for injecting the dependency item into the target class or object.This usually involves finding dependencies, creating instances, and assigning them to the corresponding attributes or constructing function parameters.
3. Life cycle management: The dependency injecting library can manage the creation and destruction of dependencies according to the life cycle strategy specified in the annotation.This ensures that the dependent item is available when required and resource releases in time.
4. Modularization: Relying on the concept of module -based injection libraries to organize dependencies.Developers can create different modules to manage different dependencies and assemble these modules as needed.
Source code analysis:
The following is a simple example. It demonstrates how to use Dagger 2, the popular Android dependencies in the injection library:
1. Add dependencies: Add Dagger 2 dependency items to the Build.gradle file.
dependencies {
implementation 'com.google.dagger:dagger:2.x'
annotationProcessor 'com.google.dagger:dagger-compiler:2.x'
}
2. Create dependencies: Create the dependency item that needs to be injected.
public class UserService {
public void login(String username, String password) {
// Implement login logic
}
}
public class UserRepository {
public void saveUser(String username, String password) {
// Implement user preservation logic
}
}
3. Define module: Create a module class and use the @Module annotation mark.
@Module
public class UserModule {
@Provides
public UserService provideUserService() {
return new UserService();
}
@Provides
public UserRepository provideUserRepository() {
return new UserRepository();
}
}
4. Create a component: Create a component interface and use the @Component annotation mark.Pass the module class as a parameter to the component interface.
@Component(modules = {UserModule.class})
public interface UserComponent {
void inject(MainActivity activity);
}
5. Injecting dependencies: Use the @Inject annotation mark to inject the dependencies that need to be injected and call the injection method in the onCreate method in the MAICTITY.
public class MainActivity extends AppCompatActivity {
@Inject
UserService userService;
@Inject
UserRepository userRepository;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
UserComponent userComponent = DaggerUserComponent.create();
userComponent.inject(this);
userService.login("username", "password");
userRepository.saveUser("username", "password");
}
}
In this example, we use Dagger 2 to achieve dependent injection.By defining modules and components, we can inject the dependent items required in MainActivity.
Summarize:
Android dependence in injection libraries simplify the process of management and resolution of dependencies by using annotations and code generation technologies.Developers can choose the appropriate dependency injection library according to their needs, and use and expand according to design ideas.
It is hoped that this article will help understand the design ideas and source code analysis of Android dependencies!
