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ViewBinding(视图绑定)基础详解

作者：Monodyee | 2024-03-26 21:51:24

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viewbinding

一.简介

ViewBinding是Android Studio 3.6推出的新特性，旨在替代findViewById(内部实现还是使用findViewById)。通过ViewBinding，可以更轻松地编写可与视图交互的代码。在模块中启用ViewBinding之后，系统会为该模块中的每个 XML 布局文件生成一个绑定类。绑定类的实例包含对在相应布局中具有 ID 的所有视图的直接引用。

注：ViewBinding&DataBinding区别

1.两者都生成可用于直接引用视图的绑定类。

2.View binding旨在处理更简单的用例，有以下特点

<1> 更快的编译： 视图绑定不需要注释处理，因此编译时间更快。

<2> 易用性： 视图绑定不需要特别标记的 XML 布局文件，因此在您的应用程序中采用它的速度更快。在模块中启用视图绑定后，它会自动应用于该模块的所有布局。

<3> 视图绑定不支持布局变量或布局表达式，因此它不能用于直接从 XML 布局文件声明动态 UI 内容。

3.DataBinding可以支持变量刷新，布局表达式，可以直接从 XML 布局文件声明动态 UI 内容。

二.依赖及文件路径

1.添加依赖 

模块build.gradle文件android节点下添加如下代码

  1. android {
  2.       
  3.     viewBinding{
  4.         enabled = true
  5.     }
  6.  
  7. }

在 Android Studio 4.0 中，viewBinding 变成属性被整合到了 buildFeatures 选项中，所以配置要改成

  1. android {
  2.  
  3.  buildFeatures {
  4.  
  5.   viewBinding = true
  6.  
  7.  }
  8.  
  9. }

2.文件路径

配置好上述Gradle，成功编译后，在相应Module中对应的文件夹下回看到生成的内容

三.Activity使用

1.Activity代码

  1. public class BaseModuleMainActivity extends AppCompatActivity {
  2.  
  3.     ActivityBaseModuleMainBinding binding;
  4.  
  5.     @Override
  6.     protected void onCreate(Bundle savedInstanceState) {
  7.         super.onCreate(savedInstanceState);
  8.         binding = ActivityBaseModuleMainBinding.inflate(getLayoutInflater());
  9.         setContentView(binding.getRoot());
  10.  
  11.         binding.tvBaseModule.setText("我是TextView");
  12.         binding.tvBaseModule.setOnClickListener(v -> LoggerUtils.logD("BaseModuleMainActivity", "TextView点击..."));
  13.     }
  14.  
  15. }

2.Activity布局

  1. <?xml version="1.0" encoding="utf-8"?>
  2. <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
  3.     xmlns:tools="http://schemas.android.com/tools"
  4.     android:layout_width="match_parent"
  5.     android:layout_height="match_parent">
  6.  
  7.     <TextView
  8.         android:id="@+id/tv_base_module"
  9.         android:layout_width="match_parent"
  10.         android:layout_height="@dimen/dp_100"
  11.         android:background="@color/purple_200"
  12.         android:gravity="center"
  13.         android:textColor="@color/white"
  14.         tools:ignore="MissingConstraints" />
  15.  
  16. </androidx.constraintlayout.widget.ConstraintLayout>

3.结果

BaseModuleMainActivity  TextView点击...

4.说明

原本默认情况下Activity的onCreate方法是这样的

  1. @Override
  2. protected void onCreate(Bundle savedInstanceState) {
  3.     super.onCreate(savedInstanceState);
  4.  
  5.     setContentView(R.layout.activity_main);
  6.  
  7.     ...
  8. }

即，使用setContentView()方法设置布局。而使用ViewBinding则需要在setContentView()方法前获取XXXBinding对象。

binding = ActivityBaseModuleMainBinding.inflate(getLayoutInflater());

然后调用XXXBinding对象的getRoot方法获取XXXView设置到setContentView()方法。

setContentView(binding.getRoot());

5.源码

生成的XXXBinding文件是按照Activity布局的名称驼峰生成的。

比如上述我们的Activity布局名称是activity_base_module_main，

那么生成的Binding文件名称则是ActivityBaseModuleMainBinding。

  1. public final class ActivityBaseModuleMainBinding implements ViewBinding {
  2.   @NonNull
  3.   private final ConstraintLayout rootView;
  4.  
  5.   @NonNull
  6.   public final TextView tvBaseModule;
  7.  
  8.   private ActivityBaseModuleMainBinding(@NonNull ConstraintLayout rootView,
  9.       @NonNull TextView tvBaseModule) {
  10.     this.rootView = rootView;
  11.     this.tvBaseModule = tvBaseModule;
  12.   }
  13.  
  14.   @Override
  15.   @NonNull
  16.   public ConstraintLayout getRoot() {
  17.     return rootView;
  18.   }
  19.  
  20.   @NonNull
  21.   public static ActivityBaseModuleMainBinding inflate(@NonNull LayoutInflater inflater) {
  22.     return inflate(inflater, null, false);
  23.   }
  24.  
  25.   @NonNull
  26.   public static ActivityBaseModuleMainBinding inflate(@NonNull LayoutInflater inflater,
  27.       @Nullable ViewGroup parent, boolean attachToParent) {
  28.     View root = inflater.inflate(R.layout.activity_base_module_main, parent, false);
  29.     if (attachToParent) {
  30.       parent.addView(root);
  31.     }
  32.     return bind(root);
  33.   }
  34.  
  35.   @NonNull
  36.   public static ActivityBaseModuleMainBinding bind(@NonNull View rootView) {
  37.     // The body of this method is generated in a way you would not otherwise write.
  38.     // This is done to optimize the compiled bytecode for size and performance.
  39.     int id;
  40.     missingId: {
  41.       id = R.id.tv_base_module;
  42.       TextView tvBaseModule = rootView.findViewById(id);
  43.       if (tvBaseModule == null) {
  44.         break missingId;
  45.       }
  46.  
  47.       return new ActivityBaseModuleMainBinding((ConstraintLayout) rootView, tvBaseModule);
  48.     }
  49.     String missingId = rootView.getResources().getResourceName(id);
  50.     throw new NullPointerException("Missing required view with ID: ".concat(missingId));
  51.   }
  52. }

四.Fragment使用

1.Fragment代码

  1. public class BaseModuleMainFragment extends Fragment {
  2.  
  3.     FragmentBaseModuleMainBinding binding;
  4.  
  5.     @Override
  6.     public void onCreate(@Nullable Bundle savedInstanceState) {
  7.         super.onCreate(savedInstanceState);
  8.         LoggerUtils.logD("BaseModuleMainFragment", "onCreate方法执行...");
  9.     }
  10.  
  11.     @Nullable
  12.     @Override
  13.     public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
  14.         binding = FragmentBaseModuleMainBinding.inflate(inflater, container, false);
  15.         LoggerUtils.logD("BaseModuleMainFragment", "onCreateView方法执行...");
  16.         return binding.getRoot();
  17.     }
  18.  
  19.     @Override
  20.     public void onViewCreated(@NonNull View view, @Nullable @org.jetbrains.annotations.Nullable Bundle savedInstanceState) {
  21.         super.onViewCreated(view, savedInstanceState);
  22.  
  23.         binding.tv01.setText("我是textView");
  24.         binding.tv01.setOnClickListener(v -> LoggerUtils.logD("BaseModuleMainFragment", "TextView点击..."));
  25.  
  26.         binding.btn01.setText("我是Button");
  27.         binding.btn01.setOnClickListener(v -> LoggerUtils.logD("BaseModuleMainFragment", "Button点击..."));
  28.  
  29.         LoggerUtils.logD("BaseModuleMainFragment", "onViewCreated方法执行...");
  30.     }
  31. }

2.Fragment布局

  1. <?xml version="1.0" encoding="utf-8"?>
  2. <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
  3.     xmlns:tools="http://schemas.android.com/tools"
  4.     android:layout_width="match_parent"
  5.     android:layout_height="match_parent"
  6.     xmlns:app="http://schemas.android.com/apk/res-auto">
  7.  
  8.     <TextView
  9.         android:id="@+id/tv_01"
  10.         android:layout_width="match_parent"
  11.         android:layout_height="@dimen/dp_100"
  12.         android:background="@color/purple_200"
  13.         android:gravity="center"
  14.         android:textColor="@color/white"
  15.         tools:ignore="MissingConstraints" />
  16.  
  17.     <Button
  18.         android:id="@+id/btn_01"
  19.         android:layout_width="match_parent"
  20.         android:layout_height="@dimen/dp_100"
  21.         android:background="@color/purple_500"
  22.         app:layout_constraintTop_toBottomOf="@+id/tv_01"
  23.         android:layout_marginTop="10dp"
  24.         android:gravity="center"
  25.         android:textColor="@color/white"
  26.         tools:ignore="MissingConstraints" />
  27.  
  28. </androidx.constraintlayout.widget.ConstraintLayout>

3.结果

  1. ### 初始化打印内容 ###
  2. onCreate方法执行...
  3.                                                                                                     	onCreateView方法执行...
  4.  
  5. onViewCreated方法执行...
  6.  
  7.  
  8.  
  9. ### 点击TextView打印内容 ###
  10. TextView点击...
  11.  
  12.  
  13. ### 点击Button打印内容 ###
  14. Button点击...

4.说明

原本默认情况下Fragment的onCreateView方法是这样的

  1. @Nullable
  2. @Override
  3. public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
  4.     View view = inflater.inflate(R.layout.fragment_base_module_main, container, false);
  5.     
  6.     initView(view);
  7.     
  8.     return view;
  9. }

使用ViewBinding后变成

  1. binding = FragmentBaseModuleMainBinding.inflate(inflater, container, false);
  2.  
  3.  
  4. return binding.getRoot();

5.源码

  1. public final class FragmentBaseModuleMainBinding implements ViewBinding {
  2.   @NonNull
  3.   private final ConstraintLayout rootView;
  4.  
  5.   @NonNull
  6.   public final Button btn01;
  7.  
  8.   @NonNull
  9.   public final TextView tv01;
  10.  
  11.   private FragmentBaseModuleMainBinding(@NonNull ConstraintLayout rootView, @NonNull Button btn01,
  12.       @NonNull TextView tv01) {
  13.     this.rootView = rootView;
  14.     this.btn01 = btn01;
  15.     this.tv01 = tv01;
  16.   }
  17.  
  18.   @Override
  19.   @NonNull
  20.   public ConstraintLayout getRoot() {
  21.     return rootView;
  22.   }
  23.  
  24.   @NonNull
  25.   public static FragmentBaseModuleMainBinding inflate(@NonNull LayoutInflater inflater) {
  26.     return inflate(inflater, null, false);
  27.   }
  28.  
  29.   @NonNull
  30.   public static FragmentBaseModuleMainBinding inflate(@NonNull LayoutInflater inflater,
  31.       @Nullable ViewGroup parent, boolean attachToParent) {
  32.     View root = inflater.inflate(R.layout.fragment_base_module_main, parent, false);
  33.     if (attachToParent) {
  34.       parent.addView(root);
  35.     }
  36.     return bind(root);
  37.   }
  38.  
  39.   @NonNull
  40.   public static FragmentBaseModuleMainBinding bind(@NonNull View rootView) {
  41.     // The body of this method is generated in a way you would not otherwise write.
  42.     // This is done to optimize the compiled bytecode for size and performance.
  43.     int id;
  44.     missingId: {
  45.       id = R.id.btn_01;
  46.       Button btn01 = rootView.findViewById(id);
  47.       if (btn01 == null) {
  48.         break missingId;
  49.       }
  50.  
  51.       id = R.id.tv_01;
  52.       TextView tv01 = rootView.findViewById(id);
  53.       if (tv01 == null) {
  54.         break missingId;
  55.       }
  56.  
  57.       return new FragmentBaseModuleMainBinding((ConstraintLayout) rootView, btn01, tv01);
  58.     }
  59.     String missingId = rootView.getResources().getResourceName(id);
  60.     throw new NullPointerException("Missing required view with ID: ".concat(missingId));
  61.   }
  62. }

五.Dialog使用

1.Dialog代码

  1. public class PrivacyAgreementDialog extends Dialog implements View.OnClickListener {
  2.  
  3.     private IDialogCallback mIDialogCallback;
  4.     private DialogPrivacyagreementBinding binding;
  5.  
  6.     public PrivacyAgreementDialog(Activity activity) {
  7.         super(activity, R.style.dialog_style);
  8.         binding = DialogPrivacyagreementBinding.inflate(getLayoutInflater());
  9.     }
  10.  
  11.     @Override
  12.     protected void onCreate(Bundle savedInstanceState) {
  13.         super.onCreate(savedInstanceState);
  14.         setContentView(binding.getRoot());
  15.  
  16.         binding.tvContent1.setText("内容1111");
  17.         binding.tvContent2.setText("内容222");
  18.  
  19.         binding.tvCancel.setOnClickListener(this);
  20.         binding.tvSure.setOnClickListener(this);
  21.  
  22.         setCancelable(false);//点击外部 对话框不消失
  23.     }
  24.  
  25.     /**
  26.      * 点击事件
  27.      */
  28.  
  29.     @Override
  30.     public void onClick(View v) {
  31.         if (AntiShakeUtils.isInvalidClick(v)) return;
  32.         if (v.getId() == R.id.tvCancel && null != mIDialogCallback) {
  33.             mIDialogCallback.onCancelClick();
  34.         } else if (v.getId() == R.id.tvSure && null != mIDialogCallback) {
  35.             mIDialogCallback.onSureClick();
  36.         }
  37.     }
  38.  
  39.     /**
  40.      * 设置回调监听
  41.      */
  42.  
  43.     public void setDialogListener(IDialogCallback dialogListener) {
  44.         mIDialogCallback = dialogListener;
  45.     }
  46.  
  47. }

2.布局代码

  1. <?xml version="1.0" encoding="utf-8"?>
  2. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  3.     xmlns:tools="http://schemas.android.com/tools"
  4.     android:layout_width="match_parent"
  5.     android:layout_height="match_parent"
  6.     android:background="@color/transparent"
  7.     android:gravity="center">
  8.  
  9.     <LinearLayout
  10.         android:layout_width="match_parent"
  11.         android:layout_height="wrap_content"
  12.         android:layout_marginLeft="@dimen/dp_20"
  13.         android:layout_marginRight="@dimen/dp_20"
  14.         android:background="@drawable/drawable_while_bg_while_line_r3"
  15.         android:orientation="vertical">
  16.  
  17.         <TextView
  18.             android:id="@+id/tvTitle"
  19.             android:layout_width="match_parent"
  20.             android:layout_height="@dimen/dp_45"
  21.             android:gravity="center"
  22.             android:text="@string/privacy_agreement_textView01"
  23.             android:textColor="#000000"
  24.             android:textSize="@dimen/text_dp_14"
  25.             tools:ignore="SpUsage" />
  26.  
  27.         <LinearLayout
  28.             android:layout_width="match_parent"
  29.             android:layout_height="wrap_content"
  30.             android:layout_marginLeft="@dimen/dp_15"
  31.             android:layout_marginTop="@dimen/dp_10"
  32.             android:layout_marginRight="@dimen/dp_15"
  33.             android:layout_marginBottom="@dimen/dp_10"
  34.             android:orientation="vertical">
  35.  
  36.             <TextView
  37.                 android:id="@+id/tvContent1"
  38.                 android:layout_width="match_parent"
  39.                 android:layout_height="wrap_content"
  40.                 android:lineSpacingExtra="@dimen/dp_5"
  41.                 android:textColor="#FF37414E"
  42.                 android:textSize="@dimen/text_dp_14"
  43.                 tools:ignore="SpUsage" />
  44.  
  45.             <TextView
  46.                 android:id="@+id/tvContent2"
  47.                 android:layout_width="match_parent"
  48.                 android:layout_height="wrap_content"
  49.                 android:lineSpacingExtra="@dimen/dp_5"
  50.                 android:textColor="#FF37414E"
  51.                 android:textSize="@dimen/text_dp_14"
  52.                 tools:ignore="SpUsage" />
  53.  
  54.         </LinearLayout>
  55.  
  56.         <LinearLayout
  57.             android:layout_width="match_parent"
  58.             android:layout_height="@dimen/dp_45"
  59.             android:orientation="horizontal"
  60.             android:weightSum="2">
  61.  
  62.             <TextView
  63.                 android:id="@+id/tvCancel"
  64.                 android:layout_width="0dp"
  65.                 android:layout_height="match_parent"
  66.                 android:layout_weight="1"
  67.                 android:ellipsize="end"
  68.                 android:gravity="center"
  69.                 android:singleLine="true"
  70.                 android:text="@string/privacy_agreement_textView02"
  71.                 android:textColor="#FF37414E"
  72.                 android:textSize="@dimen/text_dp_14"
  73.                 tools:ignore="SpUsage" />
  74.  
  75.             <TextView
  76.                 android:id="@+id/tvSure"
  77.                 android:layout_width="0dp"
  78.                 android:layout_height="match_parent"
  79.                 android:layout_weight="1"
  80.                 android:ellipsize="end"
  81.                 android:gravity="center"
  82.                 android:singleLine="true"
  83.                 android:text="@string/privacy_agreement_textView03"
  84.                 android:textColor="#FF37414E"
  85.                 android:textSize="@dimen/text_dp_14"
  86.                 tools:ignore="SpUsage" />
  87.  
  88.         </LinearLayout>
  89.  
  90.     </LinearLayout>
  91.  
  92. </LinearLayout>

3.源码

  1. public final class DialogPrivacyagreementBinding implements ViewBinding {
  2.   @NonNull
  3.   private final LinearLayout rootView;
  4.  
  5.   @NonNull
  6.   public final TextView tvCancel;
  7.  
  8.   @NonNull
  9.   public final TextView tvContent1;
  10.  
  11.   @NonNull
  12.   public final TextView tvContent2;
  13.  
  14.   @NonNull
  15.   public final TextView tvSure;
  16.  
  17.   @NonNull
  18.   public final TextView tvTitle;
  19.  
  20.   private DialogPrivacyagreementBinding(@NonNull LinearLayout rootView, @NonNull TextView tvCancel,
  21.       @NonNull TextView tvContent1, @NonNull TextView tvContent2, @NonNull TextView tvSure,
  22.       @NonNull TextView tvTitle) {
  23.     this.rootView = rootView;
  24.     this.tvCancel = tvCancel;
  25.     this.tvContent1 = tvContent1;
  26.     this.tvContent2 = tvContent2;
  27.     this.tvSure = tvSure;
  28.     this.tvTitle = tvTitle;
  29.   }
  30.  
  31.   @Override
  32.   @NonNull
  33.   public LinearLayout getRoot() {
  34.     return rootView;
  35.   }
  36.  
  37.   @NonNull
  38.   public static DialogPrivacyagreementBinding inflate(@NonNull LayoutInflater inflater) {
  39.     return inflate(inflater, null, false);
  40.   }
  41.  
  42.   @NonNull
  43.   public static DialogPrivacyagreementBinding inflate(@NonNull LayoutInflater inflater,
  44.       @Nullable ViewGroup parent, boolean attachToParent) {
  45.     View root = inflater.inflate(R.layout.dialog_privacyagreement, parent, false);
  46.     if (attachToParent) {
  47.       parent.addView(root);
  48.     }
  49.     return bind(root);
  50.   }
  51.  
  52.   @NonNull
  53.   public static DialogPrivacyagreementBinding bind(@NonNull View rootView) {
  54.     // The body of this method is generated in a way you would not otherwise write.
  55.     // This is done to optimize the compiled bytecode for size and performance.
  56.     int id;
  57.     missingId: {
  58.       id = R.id.tvCancel;
  59.       TextView tvCancel = rootView.findViewById(id);
  60.       if (tvCancel == null) {
  61.         break missingId;
  62.       }
  63.  
  64.       id = R.id.tvContent1;
  65.       TextView tvContent1 = rootView.findViewById(id);
  66.       if (tvContent1 == null) {
  67.         break missingId;
  68.       }
  69.  
  70.       id = R.id.tvContent2;
  71.       TextView tvContent2 = rootView.findViewById(id);
  72.       if (tvContent2 == null) {
  73.         break missingId;
  74.       }
  75.  
  76.       id = R.id.tvSure;
  77.       TextView tvSure = rootView.findViewById(id);
  78.       if (tvSure == null) {
  79.         break missingId;
  80.       }
  81.  
  82.       id = R.id.tvTitle;
  83.       TextView tvTitle = rootView.findViewById(id);
  84.       if (tvTitle == null) {
  85.         break missingId;
  86.       }
  87.  
  88.       return new DialogPrivacyagreementBinding((LinearLayout) rootView, tvCancel, tvContent1,
  89.           tvContent2, tvSure, tvTitle);
  90.     }
  91.     String missingId = rootView.getResources().getResourceName(id);
  92.     throw new NullPointerException("Missing required view with ID: ".concat(missingId));
  93.   }
  94. }

六.Adapter使用

1.Adapter代码

  1. public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {
  2.  
  3.     private final List<String> mList;
  4.     private final LayoutInflater mInflater;
  5.  
  6.     public MyAdapter(Activity activity, List<String> list) {
  7.         mList = list;
  8.         mInflater = LayoutInflater.from(activity);
  9.     }
  10.  
  11.     @NonNull
  12.     @Override
  13.     public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
  14.         ItemMyRecyclerviewBinding binding = ItemMyRecyclerviewBinding.inflate(mInflater, parent, false);
  15.         return new ViewHolder(binding);
  16.     }
  17.  
  18.     @Override
  19.     public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
  20.         holder.textView.setText(mList.get(position));
  21.  
  22.         holder.itemView.setOnClickListener(v -> LoggerUtils.logD("MyAdapter", "Item点击..."));
  23.     }
  24.  
  25.     @Override
  26.     public int getItemCount() {
  27.         return mList.size();
  28.     }
  29.  
  30.     /**
  31.      * ViewHolder类
  32.      */
  33.  
  34.     static class ViewHolder extends RecyclerView.ViewHolder {
  35.  
  36.         private ItemMyRecyclerviewBinding binding;
  37.         private final TextView textView;
  38.  
  39.         public ViewHolder(ItemMyRecyclerviewBinding binding) {
  40.             super(binding.getRoot());
  41.             textView = binding.tvItem;
  42.         }
  43.     }
  44.  
  45. }

2.Item布局

  1. <?xml version="1.0" encoding="utf-8"?>
  2. <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
  3.     xmlns:tools="http://schemas.android.com/tools"
  4.     android:layout_width="match_parent"
  5.     android:layout_height="110dp">
  6.  
  7.     <TextView
  8.         android:id="@+id/tv_item"
  9.         android:layout_width="match_parent"
  10.         android:layout_height="100dp"
  11.         android:layout_marginBottom="10dp"
  12.         android:background="@color/purple_200"
  13.         android:gravity="center"
  14.         android:textColor="@color/white"
  15.         tools:ignore="MissingConstraints"
  16.         tools:text="我是Item内容" />
  17.  
  18. </androidx.constraintlayout.widget.ConstraintLayout>

3.源码

  1. public final class ItemMyRecyclerviewBinding implements ViewBinding {
  2.   @NonNull
  3.   private final ConstraintLayout rootView;
  4.  
  5.   @NonNull
  6.   public final TextView tvItem;
  7.  
  8.   private ItemMyRecyclerviewBinding(@NonNull ConstraintLayout rootView, @NonNull TextView tvItem) {
  9.     this.rootView = rootView;
  10.     this.tvItem = tvItem;
  11.   }
  12.  
  13.   @Override
  14.   @NonNull
  15.   public ConstraintLayout getRoot() {
  16.     return rootView;
  17.   }
  18.  
  19.   @NonNull
  20.   public static ItemMyRecyclerviewBinding inflate(@NonNull LayoutInflater inflater) {
  21.     return inflate(inflater, null, false);
  22.   }
  23.  
  24.   @NonNull
  25.   public static ItemMyRecyclerviewBinding inflate(@NonNull LayoutInflater inflater,
  26.       @Nullable ViewGroup parent, boolean attachToParent) {
  27.     View root = inflater.inflate(R.layout.item_my_recyclerview, parent, false);
  28.     if (attachToParent) {
  29.       parent.addView(root);
  30.     }
  31.     return bind(root);
  32.   }
  33.  
  34.   @NonNull
  35.   public static ItemMyRecyclerviewBinding bind(@NonNull View rootView) {
  36.     // The body of this method is generated in a way you would not otherwise write.
  37.     // This is done to optimize the compiled bytecode for size and performance.
  38.     int id;
  39.     missingId: {
  40.       id = R.id.tv_item;
  41.       TextView tvItem = rootView.findViewById(id);
  42.       if (tvItem == null) {
  43.         break missingId;
  44.       }
  45.  
  46.       return new ItemMyRecyclerviewBinding((ConstraintLayout) rootView, tvItem);
  47.     }
  48.     String missingId = rootView.getResources().getResourceName(id);
  49.     throw new NullPointerException("Missing required view with ID: ".concat(missingId));
  50.   }
  51. }

七.include标签使用

1.include标签所在的布局

  1. <?xml version="1.0" encoding="utf-8"?>
  2. <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
  3.     xmlns:tools="http://schemas.android.com/tools"
  4.     android:layout_width="match_parent"
  5.     android:layout_height="match_parent">
  6.  
  7.     <TextView
  8.         android:id="@+id/tv_include_flags"
  9.         android:layout_width="match_parent"
  10.         android:layout_height="@dimen/dp_100"
  11.         android:background="@color/purple_500"
  12.         android:gravity="center"
  13.         android:textColor="@color/white"
  14.         tools:ignore="MissingConstraints" />
  15.  
  16. </androidx.constraintlayout.widget.ConstraintLayout>

2.Activity布局

  1. <?xml version="1.0" encoding="utf-8"?>
  2. <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
  3.     xmlns:tools="http://schemas.android.com/tools"
  4.     android:layout_width="match_parent"
  5.     android:layout_height="match_parent"
  6.     xmlns:app="http://schemas.android.com/apk/res-auto">
  7.  
  8.     <include
  9.         android:id="@+id/include_layout"
  10.         layout="@layout/include_flags"/>
  11.  
  12. </androidx.constraintlayout.widget.ConstraintLayout>

3.Activity代码

  1. public class BaseModuleMainActivity extends AppCompatActivity {
  2.  
  3.     ActivityBaseModuleMainBinding binding;
  4.  
  5.     @Override
  6.     protected void onCreate(Bundle savedInstanceState) {
  7.         super.onCreate(savedInstanceState);
  8.         binding = ActivityBaseModuleMainBinding.inflate(getLayoutInflater());
  9.         setContentView(binding.getRoot());
  10.  
  11.         binding.includeLayout.tvIncludeFlags.setText("我是Include标签引入的布局");
  12.     }
  13.  
  14. }

4.说明

include 标签必须设置id，使用时直接使用该id就可以找到include标签引入的布局了

八.include标签内有merge标签使用

1.include标签所在的布局

  1. <?xml version="1.0" encoding="utf-8"?>
  2. <merge xmlns:android="http://schemas.android.com/apk/res/android">
  3.  
  4.     <Button
  5.         android:id="@+id/include_merge_button1"
  6.         android:layout_width="match_parent"
  7.         android:layout_height="100dp"
  8.         android:layout_marginTop="10dp"
  9.         android:background="@color/purple_200"
  10.         android:textColor="#FFFFFF" />
  11.  
  12.     <Button
  13.         android:id="@+id/include_merge_button2"
  14.         android:layout_width="match_parent"
  15.         android:layout_height="100dp"
  16.         android:layout_marginTop="10dp"
  17.         android:background="@color/purple_500"
  18.         android:textColor="#FFFFFF" />
  19.  
  20. </merge>

2.Activity布局

  1. <?xml version="1.0" encoding="utf-8"?>
  2. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  3.     android:layout_width="match_parent"
  4.     android:layout_height="match_parent"
  5.     android:orientation="vertical">
  6.  
  7.     <include layout="@layout/include_flags" />
  8.  
  9. </LinearLayout>

3.Activity代码

  1. public class BaseModuleMainActivity extends AppCompatActivity {
  2.  
  3.     ActivityBaseModuleMainBinding binding;
  4.  
  5.     @Override
  6.     protected void onCreate(Bundle savedInstanceState) {
  7.         super.onCreate(savedInstanceState);
  8.         binding = ActivityBaseModuleMainBinding.inflate(getLayoutInflater());
  9.         setContentView(binding.getRoot());
  10.  
  11.         IncludeFlagsBinding mergeBinding = IncludeFlagsBinding.bind(binding.getRoot());
  12.         mergeBinding.includeMergeButton1.setText("TextView001");
  13.         mergeBinding.includeMergeButton2.setText("TextView002");
  14.     }
  15. }

4.说明

<1> include 标签带 merge 标签，需要通过bind()将merge布局绑定到主布局上。

九.某些文件不想使用ViewBinding

如果为Module启用了视图绑定，则会为Module包含的每个XML布局文件生成一个绑定类。绑定类的名称是通过将XML文件的名称转换为 Pascal 大小写并在末尾添加Binding一词来生成的。

如果那个布局文件不需要生成绑定类(不想用这个功能)。可以将该布局的根视图中加入以下代码

tools:viewBindingIgnore="true"

添加改属性前

添加改属性后

  1. <?xml version="1.0" encoding="utf-8"?>
  2. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  3.     android:layout_width="match_parent"
  4.     android:layout_height="match_parent"
  5.     xmlns:tools="http://schemas.android.com/tools"
  6.     tools:viewBindingIgnore="true"
  7.     android:orientation="vertical">
  8.  
  9.     <include layout="@layout/include_flags" />
  10.  
  11. </LinearLayout>

十.原理

ViewBinding的原理就是 通过gradle插件在编译的中增加了新功能，当某个module开启ViewBinding功能后，编译的时候就去扫描此模块下的layout文件，生成对应的binding类。

文件路径

源码

  1. public final class ActivityBaseModuleMainBinding implements ViewBinding {
  2.   @NonNull
  3.   private final ConstraintLayout rootView;
  4.  
  5.   @NonNull
  6.   public final TextView tvBaseModule;
  7.  
  8.   private ActivityBaseModuleMainBinding(@NonNull ConstraintLayout rootView,
  9.       @NonNull TextView tvBaseModule) {
  10.     this.rootView = rootView;
  11.     this.tvBaseModule = tvBaseModule;
  12.   }
  13.  
  14.   @Override
  15.   @NonNull
  16.   public ConstraintLayout getRoot() {
  17.     return rootView;
  18.   }
  19.  
  20.   @NonNull
  21.   public static ActivityBaseModuleMainBinding inflate(@NonNull LayoutInflater inflater) {
  22.     return inflate(inflater, null, false);
  23.   }
  24.  
  25.   @NonNull
  26.   public static ActivityBaseModuleMainBinding inflate(@NonNull LayoutInflater inflater,
  27.       @Nullable ViewGroup parent, boolean attachToParent) {
  28.     View root = inflater.inflate(R.layout.activity_base_module_main, parent, false);
  29.     if (attachToParent) {
  30.       parent.addView(root);
  31.     }
  32.     return bind(root);
  33.   }
  34.  
  35.   @NonNull
  36.   public static ActivityBaseModuleMainBinding bind(@NonNull View rootView) {
  37.     // The body of this method is generated in a way you would not otherwise write.
  38.     // This is done to optimize the compiled bytecode for size and performance.
  39.     int id;
  40.     missingId: {
  41.       id = R.id.tv_base_module;
  42.       TextView tvBaseModule = rootView.findViewById(id);
  43.       if (tvBaseModule == null) {
  44.         break missingId;
  45.       }
  46.  
  47.       return new ActivityBaseModuleMainBinding((ConstraintLayout) rootView, tvBaseModule);
  48.     }
  49.     String missingId = rootView.getResources().getResourceName(id);
  50.     throw new NullPointerException("Missing required view with ID: ".concat(missingId));
  51.   }
  52. }

源码中可以看出，最终使用的仍然是findViewById，ViewBinding通过编译时扫描layout文件生成ViewBinding绑定类。

与findViewById相比优点

<1> 空安全：由于视图绑定会创建对视图的直接引用，因此不存在因视图 ID 无效而引发 Null 指针异常的风险。此外，如果视图仅出现在布局的某些配置中（比如横竖屏布局内容差异），则绑定类中包含其引用的字段会使用 @Nullable 标记。

<2> 类型安全：每个绑定类中的字段均具有与它们在 XML 文件中引用的视图相匹配的类型。这意味着不存在发生类转换异常的风险。

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