【RN-ReactFindViewUtil】根据nativeID

想要在原生代码里获取RN的View，就像原生代码里的findViewById，然后就可以在原生代码里调用view的一些函数，比如一些get方法，然后数据回调给RN或者做一些其他操作。
找到如下属性：

image.png

但是不会用。。。

通过原生UI组件封装的源码查看：SimpleViewManager -> BaseViewManager，
在BaseViewManager里找到了PROP_NATIVE_ID（nativeID）的属性设置方法，然后找到了ReactFindViewUtil类。

  @ReactProp(name = PROP_NATIVE_ID)
  public void setNativeId(T view, String nativeId) {
      view.setTag(R.id.view_tag_native_id, nativeId);
      ReactFindViewUtil.notifyViewRendered(view);
  }

最后通过ReactFindViewUtil中的方法可以找到View实例。

/**
   * Finds a view that is tagged with {@param nativeId} as its nativeID prop
   * under the {@param root} view hierarchy. Returns the view if found, null otherwise.
   * @param root root of the view hierarchy from which to find the view
   */
  public static @Nullable View findView(View root, String nativeId) {
    String tag = getNativeId(root);
    if (tag != null && tag.equals(nativeId)) {
      return root;
    }
    if (root instanceof ViewGroup) {
      ViewGroup viewGroup = (ViewGroup) root;
      for (int i = 0; i < viewGroup.getChildCount(); i++) {
        View view = findView(viewGroup.getChildAt(i), nativeId);
        if (view != null) {
          return view;
        }
      }
    }
    return null;
  }

  /**
   * Finds a view tagged with {@param onViewFoundListener}'s nativeID in the given {@param root}
   * view hierarchy. If the view does not exist yet due to React Native's async layout, a listener
   * will be added. When the view is found, the {@param onViewFoundListener} will be invoked.
   * @param root root of the view hierarchy from which to find the view
   */
  public static void findView(View root, OnViewFoundListener onViewFoundListener) {
    View view = findView(root, onViewFoundListener.getNativeId());
    if (view != null) {
      onViewFoundListener.onViewFound(view);
    }
    addViewListener(onViewFoundListener);
  }

root直接用getCurrentActivity().getWindow().getDecorView()就行。RN代码中nativeID注意大小写（nativeid、nativeId）。