Dagger2现在由google接管维护，它最主要的好处是通过apt插件在编译阶段时，用来生成注入的代码。
主要作用是为了解决耦合问题，具体讲解可以额看其他文章说的比较多了
我这里就是讲MVP于Dagger结合使用的一个实例，主要是看apt自动生成的文件，方便读者理解的一篇文章，在文章最后会放入代码
使用
在Project中build.gradle中添加apt支持。
dependencies {
...
classpath 'com.neenbedankt.gradle.plugins:android-apt:1.8'
...
}
在Module中build.gradle中添加
apply plugin: 'com.neenbedankt.android-apt'
dependencies {
compile 'com.google.dagger:dagger:2.0.2'
compile 'com.google.dagger:dagger-compiler:2.0.2'
compile 'org.glassfish:javax.annotation:10.0-b28'
}
基本注释讲解
Module
@Module用于类前注释，紧接着会用到@Provides用于当前类中的方法。
@Module
public class LoginModule {
private LoginControl.LoginView view;
public LoginModule(LoginControl.LoginView view) {
this.view = view;
}
@Provides
LoginControl.LoginView provideView() {
return view;
}
@Provides
LoginFunc provideFunc() {
return new LoginFunc();
}
}
来看一下apt生成两个Provides的代码：
LoginFunc方法apt实现：
public final class LoginModule_ProvideFuncFactory implements Factory {
private final LoginModule module;
public LoginModule_ProvideFuncFactory(LoginModule module) {
assert module != null;
this.module = module;
}
@Override
public LoginFunc get() {
LoginFunc provided = module.provideFunc();
if (provided == null) {
throw new NullPointerException("Cannot return null from a non-@Nullable @Provides method");
}
return provided;
}
public static Factory create(LoginModule module) {
return new LoginModule_ProvideFuncFactory(module);
}
}
LoginView方法apt实现：
public final class LoginModule_ProvideViewFactory implements Factory {
private final LoginModule module;
public LoginModule_ProvideViewFactory(LoginModule module) {
assert module != null;
this.module = module;
}
@Override
public LoginView get() {
LoginView provided = module.provideView();
if (provided == null) {
throw new NullPointerException("Cannot return null from a non-@Nullable @Provides method");
}
return provided;
}
public static Factory create(LoginModule module) {
return new LoginModule_ProvideViewFactory(module);
}
}
Inject
@Inject依赖支持，用于构造器、方法、作用域
public class LoginPresenter implements LoginControl.LoginPresenter {
private LoginControl.LoginView view;
@Inject
LoginFunc loginFunc;
@Inject
public LoginPresenter(LoginControl.LoginView view) {
this.view = view;
}
@Override
public void login() {
view.showProgress();
loginFunc.onLogin(new Subscriber() {
@Override
public void onCompleted() {
}
@Override
public void onError(Throwable e) {
view.dismissProgress();
view.onError(e.getMessage());
}
@Override
public void onNext(Login login) {
view.dismissProgress();
view.onResult(login);
}
});
}
}
在上面中有两处@Inject，需要注意的是在属性中apt生成的类会添加MembersInjector接口，而构造器中则不同，需要添加Factory接口，接着看apt生成文件
1.构造器上加@Inject
首先会在Module中找构造器中的参数，进行关联，如果没有则会报错，看一下apt生成代码，先说明一下，在生成Inject代码时候，create的时候都会传递一个引用的地方，即@Inject在哪使用的类，在此处（构造器中）当然就是自己的类
public final class LoginPresenter_Factory implements Factory {
private final MembersInjector membersInjector;
private final Provider viewProvider;
public LoginPresenter_Factory(MembersInjector membersInjector, Provider viewProvider) {
assert membersInjector != null;
this.membersInjector = membersInjector;
assert viewProvider != null;
this.viewProvider = viewProvider;
}
@Override
public LoginPresenter get() {
LoginPresenter instance = new LoginPresenter(viewProvider.get());
membersInjector.injectMembers(instance);
return instance;
}
public static Factory create(MembersInjector membersInjector, Provider viewProvider) {
return new LoginPresenter_Factory(membersInjector, viewProvider);
}
}
2.属性中加@Inject
2.1 LoginPresenter中的@Inject
public final class LoginPresenter_MembersInjector implements MembersInjector {
private final Provider loginFuncProvider;
public LoginPresenter_MembersInjector(Provider loginFuncProvider) {
assert loginFuncProvider != null;
this.loginFuncProvider = loginFuncProvider;
}
@Override
public void injectMembers(LoginPresenter instance) {
if (instance == null) {
throw new NullPointerException("Cannot inject members into a null reference");
}
instance.loginFunc = loginFuncProvider.get();
}
public static MembersInjector create(Provider loginFuncProvider) {
return new LoginPresenter_MembersInjector(loginFuncProvider);
}
}
2.2 LoginActivity中的@Inject
public final class LoginActivity_MembersInjector implements MembersInjector {
private final MembersInjector supertypeInjector;
private final Provider loginPresenterProvider;
public LoginActivity_MembersInjector(MembersInjector supertypeInjector, Provider loginPresenterProvider) {
assert supertypeInjector != null;
this.supertypeInjector = supertypeInjector;
assert loginPresenterProvider != null;
this.loginPresenterProvider = loginPresenterProvider;
}
@Override
public void injectMembers(LoginActivity instance) {
if (instance == null) {
throw new NullPointerException("Cannot inject members into a null reference");
}
supertypeInjector.injectMembers(instance);
instance.loginPresenter = loginPresenterProvider.get();
}
public static MembersInjector create(MembersInjector supertypeInjector, Provider loginPresenterProvider) {
return new LoginActivity_MembersInjector(supertypeInjector, loginPresenterProvider);
}
}
Component
@Component桥梁工具，将Module中的Provides于Inject连接起来
@Component(modules = LoginModule.class)
public interface LoginComponent {
void inject(LoginActivity activity);
}
Component的apt实现方式如下：
public final class DaggerLoginComponent implements LoginComponent {
private Provider provideFuncProvider;
private MembersInjector loginPresenterMembersInjector;
private Provider provideViewProvider;
private Provider loginPresenterProvider;
private MembersInjector loginActivityMembersInjector;
private DaggerLoginComponent(Builder builder) {
assert builder != null;
initialize(builder);
}
public static Builder builder() {
return new Builder();
}
private void initialize(final Builder builder) {
this.provideFuncProvider = LoginModule_ProvideFuncFactory.create(builder.loginModule);
this.loginPresenterMembersInjector = LoginPresenter_MembersInjector.create(provideFuncProvider);
this.provideViewProvider = LoginModule_ProvideViewFactory.create(builder.loginModule);
this.loginPresenterProvider = LoginPresenter_Factory.create(loginPresenterMembersInjector, provideViewProvider);
this.loginActivityMembersInjector = LoginActivity_MembersInjector.create((MembersInjector) MembersInjectors.noOp(), loginPresenterProvider);
}
@Override
public void inject(LoginActivity activity) {
loginActivityMembersInjector.injectMembers(activity);
}
public static final class Builder {
private LoginModule loginModule;
private Builder() {
}
public LoginComponent build() {
if (loginModule == null) {
throw new IllegalStateException("loginModule must be set");
}
return new DaggerLoginComponent(this);
}
public Builder loginModule(LoginModule loginModule) {
if (loginModule == null) {
throw new NullPointerException("loginModule");
}
this.loginModule = loginModule;
return this;
}
}
}
Demo
Github
文章中的代码都可以在项目中查看。
此文都是本人看apt总结写的，有不对的请大家指正。