Identifiers must have user defined types from the XML file. View is missing it

一次粗心大意的记录，大家引以为戒。

Error:Execution failed for task ':compileDebugJavaWithJavac'.
> android.databinding.tool.util.LoggedErrorException: Found data binding errors.
  ****/ data binding error ****msg:Identifiers must have user defined types from the XML file. View is missing it
  file:D:\AKE\workspace\NB_BToI\src\main\res\layout\activity_device_new.xml
  loc:112:65 - 112:68
  loc:112:77 - 112:80
  ****\ data binding error ****

xml中代码如下

其实明明知道是visibility这行代码出问题了，可就是不知道是啥问题。找了很多资料才发现 

其实这个bug很简单就是忘记在xml 中导入android.view.View包了，导入就好了，但是我又绕了一圈，

在scanbean中写了个方法isHidExpend()

 获取这个值，我运算符运行不成功，就换个方式

public class ScanBindBean extends BaseObservable {
    /** 左上角搜索状态 */
    @Bindable
    public String scanStatus="正在搜索";
    /** 是否显示ll_expend layout*/
    @Bindable
    public boolean isHidExpend = true;
    @Bindable
    public String appName="物联网表蓝牙调试工具";
    @Bindable
    public String version="v2.0";
    /** 搜索开关 */
    @Bindable
    public String scanSwitch="停止";

    @Bindable
    public String isHidExpend() {
        return isHidExpend ? "gone" : "visible";
    }

结果又报了这个错，说我javabean中Bindable的方法isHidExpend未遵守约定，给我弄的一脸懵逼，

我去掉了bianable，就好了

@Bindable associated with method must follow JavaBeans convention isHidExpend()
错误: @Bindable associated with method must follow JavaBeans convention isHidExpend()
注: wrote intermediate bindable file com.gprs.blue -br.bin
注: ************* Generating BR file com.gprs.blue. use final: APPLICATION
注: writing file com.gprs.blue.BR
注: writing file com.android.databinding.library.baseAdapters.BR
注: writing file android.databinding.DataBinderMapper


其实官方文档上写的很清楚，只是自己太粗心大意，我未太在意，所以自己跳坑是正常的，不仅仅因为英语水平太一般，更是自己没有
耐心把文档好好读上几遍。对读几遍。读几遍。几遍。遍