Author: Petrus Nguyễn Thái Học
- Simplify usage of Android View Binding with Kotlin Property Delegates and solve behavior of Fragment’s ViewLifecycleOwner.
- Simple one-liner ViewBinding in Fragments and Activities with Kotlin.
- Lightweight and simple library.
Month Week Android Tests Android build CI Jitpack GitHub ktlint Kotlin API Hits
Read ViewBinding Delegate — one line to get details about implementation.
Add it in your root build.gradle at the end of repositories:
- Kotlin
allprojects {
repositories {
...
maven(url = "https://jitpack.io")
}
}- Groovy
allprojects { repositories { ... maven { url 'https://jitpack.io' } } }
dependencies {
implementation("com.github.hoc081098:ViewBindingDelegate:1.3.1")
}https://developer.android.com/topic/libraries/view-binding#setup
import com.hoc081098.viewbindingdelegate.*
1. Activity (with reflection). See example
Click to expand
class MainActivity : AppCompatActivity(R.layout.activity_main) { private val viewBinding by viewBinding<ActivityMainBinding>() override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) viewBinding.button.setOnClickListener { startActivity(Intent(this@MainActivity, SecondActivity::class.java)) } } }
2. Activity (without reflection): Pass ::bind method reference. See example
Click to expand
class SecondActivity : AppCompatActivity(R.layout.activity_second) { private val binding by viewBinding(ActivitySecondBinding::bind) override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) binding.root } }
3. Fragment (with reflection). See example
Click to expand
class FirstFragment : Fragment(R.layout.fragment_first) { private val binding by viewBinding<FragmentFirstBinding> { button.setOnClickListener(null) } override fun onViewCreated(view: View, savedInstanceState: Bundle?) { super.onViewCreated(view, savedInstanceState) binding.button.setOnClickListener { findNavController().navigate(R.id.actionFirstFragmentToSecondFragment) } } }
4. Fragment (without reflection): Pass ::bind method reference. See example
Click to expand
class SecondFragment : Fragment(R.layout.fragment_second) { private val binding by viewBinding(FragmentSecondBinding::bind) override fun onViewCreated(view: View, savedInstanceState: Bundle?) { super.onViewCreated(view, savedInstanceState) binding.root } }
5. Includes <merge/> tag layout: Create 2 ViewBinding property. See example
Click to expand
class ThirdFragment : Fragment(R.layout.fragment_third) { private val includeBinding by viewBinding<FragmentThirdIncludeBinding>() private val binding by viewBinding<FragmentThirdBinding> { buttonThird.setOnClickListener(null) } override fun onViewCreated(view: View, savedInstanceState: Bundle?) { super.onViewCreated(view, savedInstanceState) includeBinding.textViewThirdInclude.text = "Working..." binding.buttonThird.setOnClickListener { Toast.makeText(requireContext(), "Clicked", Toast.LENGTH_SHORT).show() } } }
6. The Dialog of DialogFragmentSee example
Extends DefaultViewBindingDialogFragment or implements ViewBindingDialogFragment.
Click to expand
class DemoDialogFragment : DefaultViewBindingDialogFragment() { private val viewBinding by dialogFragmentViewBinding(R.id.root, DialogFragmentDemoBinding::bind) private val viewBinding2 by dialogFragmentViewBinding<DialogFragmentDemoBinding>(R.id.root) override fun onCreateDialog(savedInstanceState: Bundle?): Dialog { return AlertDialog.Builder(requireContext()) .setTitle("Demo dialog") .setNegativeButton("Cancel") { _, _ -> } .setPositiveButton("OK") { _, _ -> } .setView(R.layout.dialog_fragment_demo) .create() } override fun onResume() { super.onResume() viewBinding.textInputLayout viewBinding2.textInputLayout } }
7. inflateViewBinding extension methods on ViewGroup/LayoutInflater/Context. See example
Can be used in RecyclerView.Adapter # onCreateViewHolder to easily create a RecyclerView.ViewHolder with a ViewBinding.
Click to expand
import com.hoc081098.viewbindingdelegate.inflateViewBinding class DemoAdapter : ListAdapter<String, DemoAdapter.VH>(...) { override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) = VH(parent inflateViewBinding false) override fun onBindViewHolder(holder: VH, position: Int) = holder.bind(getItem(position)) class VH(private val binding: ItemRecyclerBinding) : RecyclerView.ViewHolder(binding.root) { fun bind(item: String) { ... } } }
Must setContentView before access ViewBinding property. This can be done easily with constructor:
public AppCompatActivity(@LayoutRes int contentLayoutId) { ... }
class MainActivity : AppCompatActivity(R.layout.activity_main) { ... }
Fragment's View must be not null before access ViewBinding property. This can be done easily with constructor:
public Fragment(@LayoutRes int contentLayoutId) { ... }
class FirstFragment : Fragment(R.layout.fragment_first) { ... }
If there is any problem with Proguard, add below to your app/proguard-rules.pro:
# ViewBindingDelegate uses Reflection.
-keepclassmembers class ** implements androidx.viewbinding.ViewBinding {
public static ** bind(android.view.View);
public static ** inflate(android.view.LayoutInflater, android.view.ViewGroup, boolean);
public static ** inflate(android.view.LayoutInflater, android.view.ViewGroup);
}
4. Throws IllegalStateException: "Attempt to get view binding when fragment view is destroyed" when accessing delegate property in onDestroyView
Since version 1.0.0-alpha03 - Feb 16, 2021, we cannot access ViewBinding delegate property in onDestroyView (this causes many problems). Recommended way is passing a lambda to onDestroyView: (T.() -> Unit)? = null parameter of extension functions, eg.
- private val binding by viewBinding<FragmentFirstBinding>() + private val binding by viewBinding<FragmentFirstBinding> { /*this: FragmentFirstBinding*/ + button.setOnClickListener(null) + recyclerView.adapter = null + } override fun onDestroyView() { super.onDestroyView() - binding.button.setOnClickListener(null) - binding.recyclerView.adapter = null }
Since version 1.2.0, minSdkVersion has been changed to 14.
MIT License
Copyright (c) 2020-2021 Petrus Nguyễn Thái Học