安卓||在 Hilt 不支持的类中注入依赖项，例如 Helper 类

Posted 2023-04-19

【中文标题】安卓||在 Hilt 不支持的类中注入依赖项，例如 Helper 类

【英文标题】：Android || Inject dependencies in classes not supported by Hilt like Helper class

【发布时间】：2021-08-19 21:29:00

【问题描述】：

我在我的应用程序中使用了 Hilt，我成功地在 Activity 类中注入了依赖项并获得了所需的结果，但无法在其他类中注入依赖项，例如 helper 类。

请检查我在 MainActivity 类下面尝试过的以下代码

package com.inn.hiltdemo;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;

import com.inn.hiltdemo.hilt.MyFirstHelperClass;

import javax.inject.Inject;
import javax.inject.Named;

import dagger.hilt.android.AndroidEntryPoint;

@AndroidEntryPoint
public class MainActivity extends AppCompatActivity 


    @Inject
    @Named("MyHelperClass")
    MyFirstHelperClass myFirstHelperClass;

    @Override
    protected void onCreate(Bundle savedInstanceState) 
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        ////IT IS RUNNING SUCCESSFULLY
        System.out.println("HERE IS THE HELPER CLASS DATA==>>>> "+ myFirstHelperClass.getStringData());


        MySecondHelperClass mySecondHelperClass = new MySecondHelperClass();
        mySecondHelperClass.getSecondaryDataFromHelper(this);

    

我的MyModule类

package com.inn.hiltdemo.hilt

import dagger.Module
import dagger.Provides
import dagger.hilt.InstallIn
import dagger.hilt.components.SingletonComponent
import javax.inject.Named
import javax.inject.Singleton

@Module
@InstallIn(SingletonComponent::class)
class MyModule 

    @Singleton
    @Provides
    @Named("MyHelperClass")
    fun provideMyHelperClass(): MyFirstHelperClass 
        return MyFirstHelperClass()
    

请检查 MyFirstHelperClass 类

 package com.inn.hiltdemo.hilt;

public class MyFirstHelperClass 

    public String getStringData() 
        return "My Data";
    

这是我的 MySecondHelperClass.java，我试图在其中获取 Hilt 依赖注入，请检查以下代码。

 package com.inn.hiltdemo;
    
    import android.content.Context;
    
    import com.inn.hiltdemo.hilt.MyFirstHelperClass;
    
    import javax.inject.Singleton;
    
    import dagger.hilt.EntryPoint;
    import dagger.hilt.InstallIn;
    import dagger.hilt.android.EntryPointAccessors;
    import dagger.hilt.components.SingletonComponent;
    
    @Singleton
    public class MySecondHelperClass 
    
    
        @EntryPoint
        @InstallIn(SingletonComponent.class)
        interface DeviceDiagnosticHelperEntryPoint 
            public MyFirstHelperClass provideMyFirstHelperClass();
        
    
        public void getSecondaryDataFromHelper(Context mContext) 
    
            Context appContext = mContext.getApplicationContext();
            DeviceDiagnosticHelperEntryPoint hiltEntryPoint =
                    EntryPointAccessors.fromApplication(appContext,
                            DeviceDiagnosticHelperEntryPoint.class);
            MyFirstHelperClass myFirstHelperClass =
                    hiltEntryPoint.provideMyFirstHelperClass();
    
            System.out.println("HERE WE CAN USE==>>>> " + myFirstHelperClass.getStringData());
    
    
        
    
    
    

从 MySecondHelperClass.java ，我想在我的上面的类中进行依赖注入但是得到如下异常

[Dagger/MissingBinding] com.inn.hiltdemo.hilt.MyFirstHelperClass 不能在没有@Inject 构造函数或@Provides 注释的方法的情况下提供。 com.inn.hiltdemo.hilt.MyFirstHelperClass 请求在 com.inn.hiltdemo.MySecondHelperClass.DeviceDiagnosticHelperEntryPoint.provideMyFirstHelperClass()

【问题讨论】：

你返回的是MyFirstHelperClass而不是MySecondHelperClass

其实从我的 SecondClassHelper 我想要我的 FirtClassHelper 的依赖注入并且想要访问它的 dtaa

MyFirstHelperClass 不归你所有，所以你真的需要那个 Module-class 吗？

【参考方案1】：

您在第二个 Helper 中错过了 @Named 注释：

public class MySecondHelperClass 

   @EntryPoint
   @InstallIn(SingletonComponent.class)
   interface DeviceDiagnosticHelperEntryPoint 
       @Named("MyHelperClass")
       MyFirstHelperClass provideMyFirstHelperClass();
   

   public void getSecondaryDataFromHelper(Context mContext) 

       Context appContext = mContext.getApplicationContext();
       DeviceDiagnosticHelperEntryPoint hiltEntryPoint =
               EntryPointAccessors.fromApplication(appContext,
                       DeviceDiagnosticHelperEntryPoint.class);
       MyFirstHelperClass myFirstHelperClass =
               hiltEntryPoint.provideMyFirstHelperClass();

       System.out.println("HERE WE CAN USE==>>>> " + 
       myFirstHelperClass.getStringData());
   

第二个选项是用注入注解MyFirstHelperClass的构造函数并完全移除Module类（如果MyFirstHelperClass是你的）