How to use abstraction with ViewBinding with base activity?

Question

I was making a base class so that all bindings for child will be set in base

I have done till this

abstract class BaseActivity2<B : ViewBinding?, T : BaseViewModel?> : AppCompatActivity() {
    private var viewBinding: B? = null
    private var baseViewModel: T? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
    }
}

but am unable to get a way to bind view in oncreat() generally we bind layout in view binding as

binding = ActivityLoginBinding.inflate(layoutInflater)
        setContentView(binding.root)

but i am looking for generalized way in base activity

Does this answer your question? [How using ViewBinding with an abstract base class](https://stackoverflow.com/questions/62407823/how-using-viewbinding-with-an-abstract-base-class) — Chetan Gupta, Dec 06 '20 at 10:34

Sinner of the System · Answer 1 · 2021-07-08T02:48:29.353

You can declare a lambda property in the constructor to create the binding object

abstract class BaseActivity<B : ViewBinding>(val bindingFactory: (LayoutInflater) -> B) : AppCompatActivity() {
    private lateinit var binding: B

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = bindingFactory(layoutInflater)
        setContentView(binding.root)
    }
}

You can also define binding as lazy property

private val binding: B by lazy { bindingFactory(layoutInflater) }

Then you need to override nothing in your activities

class MainActivity : BaseActivity<ActivityMainBinding>(ActivityMainBinding::inflate)

You can also define `binding` by lazy delegate. – YaMiN Jul 01 '21 at 18:29 — YaMiN, Jul 01 '21 at 18:29

score 15 · Accepted Answer · answered Oct 21 '20 at 10:12

15

Other answer will also solve problem but I would like to do in a clean way.

My Base Class

abstract class BaseVMActivity<VM : ViewModel, B : ViewBinding> : BaseActivity() {

    lateinit var viewModel: VM
    lateinit var binding: B


    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        viewModel = ViewModelProvider(this, factory).get(getViewModelClass())
        binding = getViewBinding()
        setContentView(binding.root)
    }

    private fun getViewModelClass(): Class<VM> {
        val type = (javaClass.genericSuperclass as ParameterizedType).actualTypeArguments[0]
        return type as Class<VM>
    }

    abstract fun getViewBinding(): B

}

My activity:

class MainActivity : BaseVMActivity<AppViewModel, ActivityMainBinding>() {
    override fun getViewBinding() = ActivityMainBinding.inflate(layoutInflater)
   
}

Now I can directly access viewModel or binding:

fun dummy(){
        binding.bvReport.text = viewModel.getReportText()
    }

answered Oct 21 '20 at 10:12

Mirza Ahmed Baig

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Nice and easy way. Thanks – Bhavnik Dec 13 '20 at 10:13
3

can you please do this in JAVA, thanks in advance – Ali Tamoor Jun 23 '21 at 05:04
doesn't work with inheritance, e.g. if you have MySecondaryActivity : MainActivity() – Kibotu Jul 08 '21 at 09:31
you have to make MainActivity open/abstract and MainActivity : BaseVMActivity() – Mirza Ahmed Baig Jul 09 '21 at 05:36
you'r right @Kibotu. the issue come when we want using different layout and inheritance to other activity class. and why android force me to using the leak inheritance? or any other way to reach it using view binding? – Abah Adilah Feb 14 '22 at 08:05

score 6 · Answer 3 · answered Jan 27 '22 at 07:35

It's cleaner to override binding object getter inside the child activity I think. So:

abstract class VBActivity<VB : ViewBinding> : AppCompatActivity() {
  protected abstract val binding: VB

  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(binding.root)
  }
}

And lets say MainActivity will be something like:

class MainActivity : VBActivity<ActivityMainBinding>() {

  override val binding get() = ActivityMainBinding.inflate(layoutInflater)

}

if you want to extend MainActivity with different layout, how can i reach it? view binding can't do it. not prefer using view binding, i guess it — Abah Adilah, Feb 14 '22 at 07:15

How to use abstraction with ViewBinding with base activity?

3 Answers3

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