private TypeSpec createType(int sdk) {
    // 生成类名为 bindingClassName 的公共类，比如 MainActivity_ViewBinding
    TypeSpec.Builder result = TypeSpec.classBuilder(bindingClassName.simpleName())
            .addModifiers(PUBLIC);
    // 是否修饰为 final ，默认是 false
    if (isFinal) {
        result.addModifiers(FINAL);
    if (parentBinding != null) {
        // 如果有父类的话，那么要继承父类
        result.superclass(parentBinding.bindingClassName);
    } else {
        // 如果没有父类，那么实现 Unbinder 接口
        result.addSuperinterface(UNBINDER);
    // 增加一个变量名为target，类型为targetTypeName的成员变量
    if (hasTargetField()) {
        result.addField(targetTypeName, "target", PRIVATE);
    // 如果没有 View 绑定
    if (!constructorNeedsView()) {
        // Add a delegating constructor with a target type + view signature for reflective use.
        // 该生成的构造方法被 @deprecated ，一般作为反射使用
        result.addMethod(createBindingViewDelegateConstructor(targetTypeName));
    // 生成构造方法，另外 findViewById 类似的代码都在这里生成
    // Xxxx_ViewBinding 一般都是执行这个方法生成构造器
    result.addMethod(createBindingConstructor(targetTypeName, sdk));
    if (hasViewBindings() || parentBinding == null) {
        //生成unBind方法
        result.addMethod(createBindingUnbindMethod(result, targetTypeName));
    return result.build();
}复制代码

private MethodSpec createBindingConstructor(TypeName targetType, int sdk) {
    // 创建构造方法，方法修饰符为 public ，并且添加注解为UiThread
    MethodSpec.Builder constructor = MethodSpec.constructorBuilder()
            .addAnnotation(UI_THREAD)
            .addModifiers(PUBLIC);
    // 如果有方法绑定，比如 @OnClick
    if (hasMethodBindings()) {
        // 如果有，那么添加 targetType 类型，final 修饰，参数名为 target 的构造方法参数
        constructor.addParameter(targetType, "target", FINAL);
    } else {
        // 如果没有，和上面比起来就少了一个 final 修饰符
        constructor.addParameter(targetType, "target");
    // 如果有注解的 View
    if (constructorNeedsView()) {
        // 那么添加 View source 参数
        constructor.addParameter(VIEW, "source");
    } else {
        // 否则添加 Context context 参数
        constructor.addParameter(CONTEXT, "context");
    if (hasUnqualifiedResourceBindings()) {
        // Aapt can change IDs out from underneath us, just suppress since all will work at runtime.
        constructor.addAnnotation(AnnotationSpec.builder(SuppressWarnings.class)
                .addMember("value", "$S", "ResourceType")
                .build());
    // 如果有父类，那么会根据不同情况调用不同的 super 语句
    if (parentBinding != null) {
        if (parentBinding.constructorNeedsView()) {
            constructor.addStatement("super(target, source)");
        } else if (constructorNeedsView()) {
            constructor.addStatement("super(target, source.getContext())");
        } else {
            constructor.addStatement("super(target, context)");
        constructor.addCode("\n");
    // 如果有绑定 Field 或者方法，那么添加 this.target = target 语句
    if (hasTargetField()) {
        constructor.addStatement("this.target = target");
        constructor.addCode("\n");
    // 如果有 View 绑定
    if (hasViewBindings()) {
        if (hasViewLocal()) {
            // Local variable in which all views will be temporarily stored.
            constructor.addStatement("$T view", VIEW);
        for (ViewBinding binding : viewBindings) {
            // 为 View 绑定生成类似于 findViewById 之类的代码
            addViewBinding(constructor, binding);
        // 为 View 的集合或者数组绑定
        for (FieldCollectionViewBinding binding : collectionBindings) {
            constructor.addStatement("$L", binding.render());
        if (!resourceBindings.isEmpty()) {
            constructor.addCode("\n");
    // 绑定 resource 资源的代码
    if (!resourceBindings.isEmpty()) {
        if (constructorNeedsView()) {
            constructor.addStatement("$T context = source.getContext()", CONTEXT);
        if (hasResourceBindingsNeedingResource(sdk)) {
            constructor.addStatement("$T res = context.getResources()", RESOURCES);
        for (ResourceBinding binding : resourceBindings) {
            constructor.addStatement("$L", binding.render(sdk));
    return constructor.build();
private void addViewBinding(MethodSpec.Builder result, ViewBinding binding) {
    if (binding.isSingleFieldBinding()) {
        // Optimize the common case where there's a single binding directly to a field.
        FieldViewBinding fieldBinding = binding.getFieldBinding();
        // 注意这里直接使用了 target. 的形式，所以属性肯定是不能 private 的
        CodeBlock.Builder builder = CodeBlock.builder()
                .add("target.$L = ", fieldBinding.getName());
        // 下面都是 View 绑定的代码
        boolean requiresCast = requiresCast(fieldBinding.getType());
        if (!requiresCast && !fieldBinding.isRequired()) {
            builder.add("source.findViewById($L)", binding.getId().code);
        } else {
            builder.add("$T.find", UTILS);
            builder.add(fieldBinding.isRequired() ? "RequiredView" : "OptionalView");
            if (requiresCast) {
                builder.add("AsType");
            builder.add("(source, $L", binding.getId().code);
            if (fieldBinding.isRequired() || requiresCast) {
                builder.add(", $S", asHumanDescription(singletonList(fieldBinding)));
            if (requiresCast) {
                builder.add(", $T.class", fieldBinding.getRawType());
            builder.add(")");
        result.addStatement("$L", builder.build());
        return;
    List requiredBindings = binding.getRequiredBindings();
    if (requiredBindings.isEmpty()) {
        result.addStatement("view = source.findViewById($L)", binding.getId().code);
    } else if (!binding.isBoundToRoot()) {
        result.addStatement("view = $T.findRequiredView(source, $L, $S)", UTILS,
                binding.getId().code, asHumanDescription(requiredBindings));
    addFieldBinding(result, binding);
    // OnClick 等监听事件绑定
    addMethodBindings(result, binding);
}复制代码
  @UiThread
  public MainActivity_ViewBinding(final T target, View source) {
    this.target = target;
    View view;
    view = Utils.findRequiredView(source, R.id.button, "field 'button' and method 'onClick'");
    target.button = Utils.castView(view, R.id.button, "field 'button'", Button.class);
    view2131427413 = view;
    view.setOnClickListener(new DebouncingOnClickListener() {
      @Override
      public void doClick(View p0) {
        target.onClick(p0);
    target.tv = Utils.findRequiredViewAsType(source, R.id.tv, "field 'textView'", TextView.class);
  @Override
  @CallSuper
  public void unbind() {
    T target = this.target;
    if (target == null) throw new IllegalStateException("Bindings already cleared.");
    target.button = null;
    target.tv = null;
    view2131427413.setOnClickListener(null);
    view2131427413 = null;
    this.target = null;
}复制代码

@NonNull @UiThread
public static Unbinder bind(@NonNull Activity target) {
  View sourceView = target.getWindow().getDecorView();
  return createBinding(target, sourceView);
@NonNull @UiThread
public static Unbinder bind(@NonNull View target) {
  return createBinding(target, target);
...复制代码