Dependency Injection in Android With Dagger2 (10)

Providers

Guowei Lv

1 minute read

Let’s take a look at the ViewMvcFactory:

class ViewMvcFactory @Inject constructor(
    private val layoutInflaterProvider: LayoutInflater,
    private val imageLoaderProvider: ImageLoader
)

One thing worth paying attention is that this is a factory. Factory is used to create objects. So this means that its dependencies: LayoutInflater and ImageLoader will be reused to create objects everytime.

We know that ImageLoader has no state so that it can be reused, but what if it can’t? What we know is that ImageLoader is on Dagger’s graph, it may be scoped or it may not be, but we want just to follow how it is defiined in the graph. In other words, if ImageLoader is scoped, then the ViewMvcFactory will get the same instance everytime it is used, otherwise, we will create new instance of ImageLoader everytime.

It is very simple to achieve this, just wrap it with Provider<>.

class ViewMvcFactory @Inject constructor(
    private val layoutInflaterProvider: Provider<LayoutInflater>,
    private val imageLoaderProvider: Provider<ImageLoader>
)
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