如何使用Fragment进行数据绑定

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最佳答案

数据绑定实现必须在片段的onCreateView方法中，删除存在于OnCreate方法中的任何数据绑定，你的onCreateView应该像这样:

public View onCreateView(LayoutInflater inflater,
@Nullable ViewGroup container,
@Nullable Bundle savedInstanceState) {
MartianDataBinding binding = DataBindingUtil.inflate(
inflater, R.layout.martian_data, container, false);
View view = binding.getRoot();
//here data must be an instance of the class MarsDataProvider
binding.setMarsdata(data);
return view;
}

小开

可以像下面提到的那样简单地检索视图对象

public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {


View view = DataBindingUtil.inflate(inflater, R.layout.layout_file, container, false).getRoot();


return view;


}

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在Android DataBinding中试试这个

FragmentMainBinding binding;


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
binding = DataBindingUtil.inflate(inflater, R.layout.fragment_main, container, false);
View rootView = binding.getRoot();
initInstances(savedInstanceState);
return rootView;
}

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在我的代码中工作。

private FragmentSampleBinding dataBiding;
private SampleListAdapter mAdapter;


@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
super.onCreateView(inflater, container, savedInstanceState);
dataBiding = DataBindingUtil.inflate(inflater, R.layout.fragment_sample, null, false);
return mView = dataBiding.getRoot();
}

小开

你实际上被鼓励使用你生成的Binding的inflate方法，而不是DataBindingUtil方法:

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
MainFragmentBinding binding = MainFragmentBinding.inflate(inflater, container, false);
//set variables in Binding
return binding.getRoot();
}

(MainFragmentBinding为r.b ayout.main_fragment自动生成)

databindingutil . inflation()文档:

仅在layoutId预先未知的情况下使用此版本。否则，使用生成的Binding的膨胀方法来确保类型安全的膨胀。

小开

芬兰湾的科特林语法:

lateinit var binding: MartianDataBinding
override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?, savedInstanceState: Bundle?): View? {
binding = DataBindingUtil.inflate(inflater, R.layout.martian_data, container, false)
return binding.root
}

小开

Kotlin中的另一个例子:

override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?, savedInstanceState: Bundle?): View? {
val binding = DataBindingUtil
.inflate< MartianDataBinding >(
inflater,
R.layout.bla,
container,
false
)


binding.modelName = // ..


return binding.root
}

注意，“MartianDataBinding”的名称取决于布局文件的名称。如果文件命名为“marti_data”，那么正确的名称应该是MartianDataBinding。

小开

一个完整的数据绑定片段的例子

FragmentMyProgramsBinding是为res/layout/fragment_my_programs生成的绑定类

public class MyPrograms extends Fragment {
FragmentMyProgramsBinding fragmentMyProgramsBinding;


public MyPrograms() {
// Required empty public constructor
}




@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
FragmentMyProgramsBinding    fragmentMyProgramsBinding = DataBindingUtil.inflate(inflater, R
.layout.fragment_my_programs, container, false);
return fragmentMyProgramsBinding.getRoot();
}


@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);


}
}

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如果你正在使用视图模型和LiveData，这是足够的语法

芬兰湾的科特林语法:

override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
return MartianDataBinding.inflate(
inflater,
container,
false
).apply {
lifecycleOwner = viewLifecycleOwner
vm = viewModel    // Attach your view model here
}.root
}

小开

每个人都在谈论inflate()，但是如果我们想在onViewCreated()中使用它呢?

你可以使用具体绑定类的bind(view)方法来获取view. xml对象的ViewDataBinding实例。

< br >

通常我们这样写BaseFragment(简化):

// BaseFragment.kt
abstract fun layoutId(): Int


override fun onCreateView(inflater, container, savedInstanceState) =
inflater.inflate(layoutId(), container, false)

并在子片段中使用它。

// ConcreteFragment.kt
override fun layoutId() = R.layout.fragment_concrete


override fun onViewCreated(view, savedInstanceState) {
val binding = FragmentConcreteBinding.bind(view)
// or
val binding = DataBindingUtil.bind<FragmentConcreteBinding>(view)
}

< br >

如果所有fragment都使用数据绑定，您甚至可以使用类型参数使其更简单。

abstract class BaseFragment<B: ViewDataBinding> : Fragment() {
abstract fun onViewCreated(binding: B, savedInstanceState: Bundle?)


override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
onViewCreated(DataBindingUtil.bind<B>(view)!!, savedInstanceState)
}
}

我不知道是否可以在这里断言非空，但是。你懂的。如果你想让它为空，你可以这样做。

小开

就像大多数人说的，但是不要忘记设置LifeCycleOwner
Java示例 即< / p >

public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {
super.onCreateView(inflater, container, savedInstanceState);
BindingClass binding = DataBindingUtil.inflate(inflater, R.layout.fragment_layout, container, false);
ModelClass model = ViewModelProviders.of(getActivity()).get(ViewModelClass.class);
binding.setLifecycleOwner(getActivity());
binding.setViewmodelclass(model);


//Your codes here


return binding.getRoot();
}

小开

非常有用的博客关于数据绑定: https://link.medium.com/HQY2VizKO1 < / p >

class FragmentBinding<out T : ViewDataBinding>(
@LayoutRes private val resId: Int
) : ReadOnlyProperty<Fragment, T> {


private var binding: T? = null


override operator fun getValue(
thisRef: Fragment,
property: KProperty<*>
): T = binding ?: createBinding(thisRef).also { binding = it }


private fun createBinding(
activity: Fragment
): T = DataBindingUtil.inflate(LayoutInflater.from(activity.context),resId,null,true)
}

在Fragment中像这样声明binding val:

private val binding by FragmentBinding<FragmentLoginBinding>(R.layout.fragment_login)

别忘了把这段话分段写下来

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

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我一直在为我的应用程序寻找答案，这里是Kotlin语言的答案。


private lateinit var binding: FragmentForgetPasswordBinding


override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?): View? {
binding=DataBindingUtil.inflate(inflater,R.layout.fragment_forget_password,container,false)
    

val viewModel=ViewModelProvider(this).get(ForgetPasswordViewModel::class.java)
binding.recoveryViewModel=viewModel
viewModel.forgetPasswordInterface=this
return binding.root
}

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这是你在kotlin中可以做到的:

//Pass the layout as parameter to the fragment constructor
class SecondFragment : Fragment(R.layout.fragment_second) {


private var _binding: FragmentSecondBinding? = null
private val binding  get() = _binding!!


override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
_binding = FragmentSecondBinding.bind(view)  //if the view is already inflated then we can just bind it to view binding.


}


//Note: Fragments outlive their views. Make sure you clean up any references to the binding class
// instance in the fragment's onDestroyView() method.
override fun onDestroyView() {
Toast.makeText(activity, "On destroy", Toast.LENGTH_SHORT).show()
super.onDestroyView()
_binding = null
}
}

你可以像这样从你的布局中访问视图元素:

binding.tvName.text = "Messi"

其中tvName是视图元素的id。

小开

芬兰湾的科特林

         override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View?
{
val binding = FragmentFirstBinding.inflate(inflater,container,false)
return  binding.root;
            



}

其中FragmentFirstBinding是android studio使用视图绑定自动生成的。在我的代码片段名称是FirstFragment。

首先，您需要将这一行添加到构建中。Gradle(app模块)文件。

buildFeatures{
viewBinding true
}

小开

Kotlin中的最短路径;

class HomeFragment : Fragment(R.layout.fragment_home) {




override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
val binding = FragmentHomeBinding.bind(view)
// todo
}