seyfullahpolat / DataBinding-ktx

DataBinding-ktx make easy declaring DataBinding.

DataBinding-ktx

DataBinding-ktx make easy declaring DataBinding.

ViewBinding-ktx is here.

Problems in DataBinding

• Forgetting to call setLifecycleOwner in DataBinding.
• 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

• DataBinding-ktx is automatically calling setLifecycleOwner.
• DataBinding-ktx provide the unified way of declaring the binding variable in Activity and Fragment.
• DataBinding-ktx is saving memory because of cleaning up the binding variable having the view tree after onDestroyView.
• DataBinding-ktx 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

private val binding: DataBindingActivityBinding by dataBinding()

Activity

• Use setContentView before using the binding variable.

class DataBindingActivity : FragmentActivity() {
    // Declare the `binding` variable using `by dataBinding()`.
    private val binding: DataBindingActivityBinding by dataBinding()
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.data_binding_activity)
        // You can use binding
    }
}

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

class DataBindingActivity : AppCompatActivity(R.layout.data_binding_activity) {
    // Declare the `binding` variable using `by dataBinding()`.
    private val binding: DataBindingActivityBinding by dataBinding()
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        // You can use binding
    }
}

Fragment

• Use inflater.inflate in onCreateView.

class DataBindingFragment : Fragment() {
    // Declare the `binding` variable using `by dataBinding()`.
    private val binding: DataBindingFragmentBinding by dataBinding()
    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        return inflater.inflate(R.layout.data_binding_fragment, container, false)
    }
    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        // You can use binding
    }
}

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

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

Note

Activity

• If you forget to use Activity's secondary constructor passing layout res id, your app crash.

// You can define and use DataBindingAppCompatActivity for not forgetting.
open class DataBindingAppCompatActivity<T : ViewDataBinding>(@LayoutRes contentLayoutId : Int) : AppCompatActivity(contentLayoutId) {
    protected val binding: T by dataBinding()
} 
class YourActivity : DataBindingAppCompatActivity<YourActivityBinding>(R.layout.your_activity) {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        // You can use binding
    }
}

Fragment

• If you forget to use Fragment's secondary constructor passing layout res id, Fragment is not shown.

// You can define and use DataBindingFragment for not forgetting.
open class DataBindingFragment<T : ViewDataBinding>(@LayoutRes contentLayoutId : Int) : Fragment(contentLayoutId) {
    protected val binding: T by dataBinding()
} 
class YourFragment : DataBindingFragment<YourFragmentBinding>(R.layout.your_fragment) {
    // DO NOT override onCreateView
    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        // You can use binding
    }
}

Gradle

android {
    buildFeatures {
        dataBinding = true
    }
}

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

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

License

Copyright (C) 2020 wada811

Licensed under the Apache License, Version 2.0