如何使用Fragment进行数据绑定

Question

我正在尝试从官方谷歌文档https://developer.android.com/tools/data-binding/guide.html关注数据绑定示例

除了我试图将数据绑定应用于片段,而不是活动.

编译时我目前得到的错误是

Error:(37, 27) No resource type specified (at 'text' with value '@{marsdata.martianSols}.

onCreate 对于片段看起来像这样:

@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    MartianDataBinding binding = MartianDataBinding.inflate(getActivity().getLayoutInflater());
    binding.setMarsdata(this);
}

onCreateView 对于片段看起来像这样:

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    return inflater.inflate(R.layout.martian_data, container, false);
}

我的片段布局文件的部分内容如下所示:

<?xml version="1.0" encoding="utf-8"?>

<layout xmlns:android="http://schemas.android.com/apk/res/android">
    <data>
        <variable
            name="marsdata"
            type="uk.co.darkruby.app.myapp.MarsDataProvider" />
    </data>
...

        <TextView
            android:layout_height="wrap_content"
            android:layout_width="wrap_content"
            android:text="@{marsdata.martianSols}"
        />

    </RelativeLayout>
</layout>

我怀疑是MartianDataBinding不知道它应该绑定哪个布局文件 - 因此错误.有什么建议？

Answer 1

数据绑定实现必须在片段的onCreateView方法中,删除OnCreate方法中存在的任何数据Binding,onCreateView应如下所示:

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;
}

Answer 2

实际上,我们鼓励您使用inflate生成的Binding方法,而不是DataBindingUtil:

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

DataBindingUtil.inflate()的文档:

仅当layoutId事先未知时才使用此版本.否则,使用生成的Binding的膨胀方法来确保类型安全的膨胀.

Answer 3

即使其他答案也可能运作良好,但我想告诉最佳方法.

Binding class's inflate按照Android文档中的建议使用.

一种选择是通过膨胀,DataBindingUtil 但只有你不知道生成了绑定类.

- 你有自动生成binding class,使用该类而不是使用DataBindingUtil.

在Java中

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

在科特林

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

在DataBindingUtil类文档中,您可以看到.

膨胀

T inflate (LayoutInflater inflater, 
                int layoutId, 
                ViewGroup parent, 
                boolean attachToParent)

仅当layoutId事先未知时才使用此版本.否则,使用生成的Binding的膨胀方法来确保类型安全的膨胀.

如果未生成布局biniding类,请参阅此答案.

Answer 4

正如大多数人所说，但不要忘记在 Java 中设置LifeCycleOwner
Sample， 即

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();
}

Answer 5

如果您使用的是ViewModel和LiveData，这是足够的语法

Kotlin语法：

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

Answer 6

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;
}

Answer 7

可以简单地检索视图对象,如下所述

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;

}

Answer 8

数据绑定片段中的完整示例

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);

    }
}

Answer 9

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();
}

Answer 10

Kotlin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
}