具有视图绑定的BaseFragment

Question

要在android应用程序中使用viewbinding，我基本上是在为Activity&Fragment删除了每次编写充气代码的样板。

活动：

BaseActivity与viewbinding:

abstract class BaseActivity<VB : ViewBinding> : AppCompatActivity() {

override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = getViewBinding()
}
abstract fun getViewBinding(): VB
}

MainActivity:

class MainActivity : BaseActivity<ActivityMainBinding>() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(binding.root)
//we can directly use binding now and it works fine inside activity
//binding.view.doSomething() 
}
override fun getViewBinding(): ActivityMainBinding = ActivityMainBinding.inflate(layoutInflater)
}

碎片：

BaseFragment:

abstract class BaseFragment<VB : ViewBinding> : Fragment() {
var binding: VB? = null
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
binding = getViewBinding(view)
}
abstract fun getViewBinding(view: View): VB
}

DemoFragment:

class DemoFragment : BaseFragment<DemoFragmentBinding>() {
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
//problem is here
binding.txtData.text="Something"
}
override fun getViewBinding(view: View): DemoFragmentBinding = DemoFragmentBinding.bind(view)
}

demo_fragment.xml：

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".ui.fragments.DemoFragment">
<TextView
android:id="@+id/txt_data"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text="Hello" />
</FrameLayout>

问题：无法使用Demofrage内部的绑定访问视图。我不知道为什么它适用于活动而不适用于片段。

我不想做的第二种方式：

实现'androidx.fragment:fragment ktx:1.3.1'

class DemoFragment : Fragment(R.layout.demo_fragment) {
lateinit var binding: DemoFragmentBinding
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
binding = DemoFragmentBinding.bind(view).apply {
txtData.text = "Hello World"
}
}
}

Answer 1

您需要覆盖BaseFragment中的onCreateView并初始化视图绑定

override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
_binding = getViewBinding()
return binding.root
}

然后更改这条线路

override fun getViewBinding(view: View): DemoFragmentBinding = DemoFragmentBinding.bind(view)

带有

override fun getViewBinding() = DemoFragmentBinding.inflate(layoutInflater)

BaseFragment：

abstract class BaseFragment<VB : ViewBinding> : Fragment() {
private var _binding: VB? = null
val binding get() = _binding!!
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
_binding = getViewBinding()
return binding.root
}
abstract fun getViewBinding(): VB
}

DemoFragment：

class DemoFragment : BaseFragment<DemoFragmentBinding>() {
override fun getViewBinding() = DemoFragmentBinding.inflate(layoutInflater)
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
binding.apply {
txtData.text = "Something"
}
}
}

Answer 2

这里是用ViewBinding实现这个工厂抽象的另一种方法。我将在下面分享实现代码。我在这里使用genrics。如果有人需要进一步的解释，我在这里。确保已在build.gradle文件中启用viewbinding功能。然后使用以下BaseFragment.kt作为片段抽象。

基本片段：

typealias Inflate<T> = (LayoutInflater, ViewGroup?, Boolean) -> T
abstract class BaseFragment<V: ViewBinding>(
private val inflate: Inflate<V>
) : Fragment() {
private lateinit var _binding: V
val binding get() = _binding
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
_binding = inflate(inflater, container, false)
return binding.root
}
}

N： 了解更多关于typealias的信息。

主页片段：

// Implement the BaseFragment like below
class HomeFragment : BaseFragment<FragmentHomeBinding>(FragmentHomeBinding::inflate) {
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
// usages by calling public variable 'binding' from base class
binding.message.text = "update $value"
}
}

Answer 3

我查看了文档，我不确定这是否打破了BaseFragment中抽象模式的要求，但我用这个更改测试了您的代码，它成功了。唯一的变化是DemoFragment:

//Add this for the onCreateView implementation
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View {
binding = DemoFragmentBinding.inflate(LayoutInflater.from(context), null, false)
val view = binding!!.root
return view
}

然后我在onViewCreated:中进行了测试

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
//problem is here
binding?.txtData?.text="Something"
}

它奏效了。我看的文件是的这一部分

我认为这样做仍然可以避免一些样板，但onCreateView覆盖对于每个片段都是必要的，因为不同的视图绑定膨胀(例如DemoFragmentBinding.inflate etc etc(

Answer 4

使用https://github.com/hoc081098/ViewBindingDelegate

abstract class BaseFragment<VB : ViewBinding>(@LayoutRes layoutId: Int) : Fragment(layoutId) {
protected abstract val binding: VB
}

import com.hoc081098.viewbindingdelegate.*
class MainFragment: BaseFragment<FragmentMainBinding>(R.layout.fragment_main) {
override val binding by viewBinding()
}