视图绑定--如何获得包含的布局的绑定？

Question

在使用视图绑定时，我遇到了一些没有文档的案例。

第一:如何为包含的视图布局部件绑定？主绑定只看到主布局中定义的项。

第二:如何为合并的布局部件绑定。同样，主绑定只看到主布局中的项目？

Answer 1

在下列情况下：

1. 包含有通用布局(而不是合并节点)，我们需要为包含的部件分配ID，这样在绑定中我们就可以访问包含的子部件

<include
    android:id="@+id/your_id"
    layout="@layout/some_layout" />

这样在您的活动代码中：

private lateinit var exampleBinding: ActivityExampleBinding  //activity_example.xml layout

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    exampleBinding = ActivityExampleBinding.inflate(layoutInflater)
    setContentView(exampleBinding.root)
    //we will be able to access included layouts view like this
    val includedView: View = exampleBinding.yourId.idOfIncludedView
//[...]
}

1. 包含在外部布局中的合并块。我们不能向它添加ID，因为合并块不是视图。假设我们有这样一个永恒的合并布局(merge_layout.xm):

<?xml version="1.0" encoding="utf-8"?>
<merge xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    tools:showIn="@layout/activity_example">

    <TextView
        android:id="@+id/some_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World" />
</merge>

要正确绑定这样的合并布局，我们需要：

在您的活动代码中：

private lateinit var exampleBinding: ActivityExampleBinding  //activity_example.xml layout
private lateinit var mergeBinding: MergeLayoutBinding  //merge_layout.xml layout

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    exampleBinding = ActivityExampleBinding.inflate(layoutInflater)
    //we need to bind the root layout with our binder for external layout
    mergeBinding = MergeLayoutBinding.bind(exampleBinding.root)
    setContentView(exampleBinding.root)
    //we will be able to access included in merge layout views like this
    val mergedView: View = mergeBinding.someView
//[...]
}

Answer 2

关于第一个问题，您可以获得包含的布局的视图绑定。

下面是一个示例main_fragment.xml文件：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recycler_view_main"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1" />

    <include
        android:id="@+id/toolbar"
        layout="@layout/toolbar" />

</LinearLayout>

MainFragment.java可以是这样的：

public class MainFragment extends Fragment {

    private MainFragmentBinding binding;
    private ToolbarBinding toolbarBinding;

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

        binding = MainFragmentBinding.inflate(inflater, container, false);
        toolbarBinding = binding.toolbar;

        return binding.getRoot();
    }

    @Override
    public void onDestroy() {
        super.onDestroy();

        toolbarBinding = null;
        binding = null;
    }
}

现在有两个绑定:一个对应于主布局，另一个对应于包含的布局。

Answer 3

如果您想绑定包含的布局，

For Activity

YourMainLayoutBinding mainLayoutBinding = MainLayoutBinding.inflate(getLayoutInflater);

View view = mainLayoutBinding.getRoot();

YourIncludedLayoutBinding includedLayoutBinding = YourIncludedLayoutBinding.bind(View);

片段

YourMainLayoutBinding mainLayoutBinding = MainLayoutBinding.inflate(inflater,container,false);

View view = mainLayoutBinding.getRoot();

YourIncludedLayoutBinding includedLayoutBinding = YourIncludedLayoutBinding.bind(View);

确保如果主布局绑定父根是LinearLayout，那么includedLayoutBinding父布局也是线性布局

。