没有@Provides批注就无法提供SharedPreferences

Question

我有一个在其中使用Dagger的项目。我添加了以下课程：

private const val CATEGORY = "category"

@Singleton
class Storage @Inject constructor(
    private var prefs: SharedPreferences,
    private var editor: SharedPreferences.Editor,
    private var adapter: JsonAdapter<List<Category>>,
    context: Context
) {

    init {
        prefs = PreferenceManager.getDefaultSharedPreferences(context)
        editor = prefs.edit()

        val moshi = Moshi.Builder().build()
        val listType = Types.newParameterizedType(List::class.java, Category::class.java)
        adapter = moshi.adapter(listType)
    }

    fun setCategories(categories: List<Category>) {
        editor.putString(CATEGORY, adapter.toJson(categories))
    }

    fun getCategories() = adapter.fromJson(prefs.getString(CATEGORY, null))
}

构建时，收到以下匕首编译时错误：

error: [Dagger/MissingBinding] android.content.SharedPreferences cannot be provided without an @Provides-annotated method.
public abstract interface AppComponent extends dagger.android.AndroidInjector<com.sample.android.cafebazaar.FoursquareApplication> {
                ^
      android.content.SharedPreferences is injected at
          com.sample.android.cafebazaar.util.Storage(prefs, …)
      com.sample.android.cafebazaar.util.Storage is injected at
          com.sample.android.cafebazaar.ui.MainFragment.storage
      com.sample.android.cafebazaar.ui.MainFragment is injected at
          dagger.android.AndroidInjector.inject(T) [com.sample.android.cafebazaar.di.AppComponent → com.sample.android.cafebazaar.di.ActivityBindingModule_MainActivity$app_debug.MainActivitySubcomponent → com.sample.android.cafebazaar.di.MainModule_MainFragment$app_debug.MainFragmentSubcomponent]   

我该如何解决？

Answer 1

如果您在@Inject带注释的构造函数中具有任何属性，则意味着Dagger试图为您创建那些属性。换句话说，这些是类Storage中的依赖项。我认为您至少需要将其从构造函数中移开，因为我看到您是在代码中自行创建的。

尝试一下是否有帮助：

@Singleton
class Storage @Inject constructor(context: Context) {
    private val prefs: SharedPreferences
    private val editor: SharedPreferences.Editor
    private val adapter: JsonAdapter<List<Category>>

    init {
        prefs = PreferenceManager.getDefaultSharedPreferences(context)
        editor = prefs.edit()

        val moshi = Moshi.Builder().build()
        val listType = Types.newParameterizedType(List::class.java, Category::class.java)
        adapter = moshi.adapter(listType)
    }