numeroanddev / viewbinding-ktx

ViewBinding-ktx make easy declaring ViewBinding.

ViewBinding-ktx

ViewBinding-ktx make easy declaring ViewBinding.

DataBinding-ktx is here.

Problems in ViewBinding

• Differences in the way of declaring a binding variable in Activity and Fragment.
  • In Activity, you can declare the binding variable using by lazy.
  • In Fragment, you can't declare the binding variable using by lazy because of recreating Fragment's view.
• Wasted memory unless you set the binding variable to null after onDestroyView
  • If you use Navigation component, BackStack or detach in Fragment, Fragment is still alive but Fragment's view is dead after onDestroyView. Because the binding variable has view tree, your app wasted memory. For saving memory, you should set the binding variable to null after onDestroyView.

Overview

ViewBinding-ktx

• provides the unified way of declaring the binding variable
  • between Activity and Fragment.
  • between DataBinding-ktx and ViewBinding-ktx.
• is saving memory
  • The binding variable is stored as the Fragment's view's tag.
  • The binding variable is cleaning up along with the Fragment's view after onDestroyView.
• needs one of the following
  • calling setContentView in Activity and calling inflater.inflate in onCreateView of Fragment.
  • calling Activity/Fragment's secondary constructor passing layout res id.

Usage

Reflection

private val binding: ViewBindingActivityBinding by viewBinding()

No reflection

private val binding by viewBinding { ViewBindingActivityBinding.bind(it) }

Activity

• Use Activity's secondary constructor passing layout res id.

class ViewBindingActivity : AppCompatActivity(R.layout.view_binding_activity) {
    // Declare the `binding` variable using `by viewBinding()`.
    private val binding: ViewBindingActivityBinding by viewBinding()
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        // You can use binding
    }
}

Fragment

• Use Fragment's secondary constructor passing layout res id.

class ViewBindingFragment : Fragment(R.layout.view_binding_fragment) {
    // Declare the `binding` variable using `by viewBinding()`.
    private val binding: ViewBindingFragmentBinding by viewBinding()
    // DO NOT override onCreateView
    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        // You can use binding
    }
}

Gradle

android {
    buildFeatures {
        viewBinding = true
    }
}

repositories {
    maven { url "https://www.jitpack.io" }
}

dependencies {
    implementation 'com.github.wada811:ViewBinding-ktx:x.y.z'
}

License

Copyright (C) 2020 wada811

Licensed under the Apache License, Version 2.0