Android The layout "activity_main" in layout has no declaration in the base layout folder

报错：

The layout "activity_main" in layout has no declaration in the base layout folder; this can lead to crashes when the resource is queried in a configuration that does not match this qualifier.

详情：
If a resource is only defined in folders with qualifiers like -land or -en, and there is no default declaration in the base folder (layout or values etc), then the app will crash if that resource is accessed on a device where the device is in a configuration missing the given qualifier.  As a special case, drawables do not have to be specified in the base folder; if there is a match in a density folder (such as drawable-mdpi) that image will be used and scaled. Note however that if you only specify a drawable in a folder like drawable-en-hdpi, the app will crash in non-English locales.  There may be scenarios where you have a resource, such as a -fr drawable, which is only referenced from some other resource with the same qualifiers (such as a -fr style), which itself has safe fallbacks. However, this still makes it possible for somebody to accidentally reference the drawable and crash, so it is safer to create a default dummy fallback in the base folder. Alternatively, you can suppress the issue by adding tools:ignore="MissingDefaultResource" on the element.  (This scenario frequently happens with string translations, where you might delete code and the corresponding resources, but forget to delete a translation. There is a dedicated issue id for that scenario, with the id ExtraTranslation.)  Issue id: MissingDefaultResource

翻译：
如果资源仅在具有-land或-en等限定符的文件夹中定义，并且基本文件夹（布局或值等）中没有默认声明，则如果在设备所在的设备上访问该资源，则应用程序将崩溃在配置中缺少给定的限定符。

作为特殊情况，不必在基础文件夹中指定drawable;如果密度文件夹（例如drawable-mdpi）中存在匹配，则将使用和缩放图像。但请注意，如果您只在drawable-en-hdpi等文件夹中指定drawable，则应用程序将在非英语语言环境中崩溃。

在某些情况下，您可能会拥有一个资源，例如-fr drawable，它仅从具有相同限定符的某些其他资源（例如-fr样式）引用，该资源本身具有安全回退。但是，这仍然可以让某人意外地引用drawable和crash，因此在基础文件夹中创建默认的虚拟回退更安全。或者，您可以通过在元素上添加工具：ignore =“MissingDefaultResource”来解决此问题。

（这种情况经常发生在字符串翻译中，您可能会删除代码和相应的资源，但忘记删除翻译。该方案有一个专用的问题ID，ID为ExtraTranslation。）

解决方法：
添加

tools:ignore="MissingDefaultResource"

不知道会不会有后遗症，后续若有解决方法来此编辑~望有大佬指示。