Databinding搭配kotlin使用时与java有些区别，除了需要使用kapt依赖之外，由于kotlin没有static的特性和null-safe检查，还是踩了不少坑的，写个博客记录下。

业务场景：给ImageView添加一个自定义属性imageUrl，处理网络图片加载,xml代码如下：

    <ImageView
        android:id="@+id/title_img"
        android:layout_width="200mm"
        android:layout_height="100mm"
        android:background="#66ccff"
        android:scaleType="fitCenter"
        app:imageUrl="@{vm.logoUrl}"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

之前用java的时候是这么处理的：

public class ImageBinds {
    @BindingAdapter("imageUrl")
    public static void bindImgUrl(ImageView imageView, String url) {

        GlideApp.with(imageView.getContext())
                .load(url)
                .placeholder(R.drawable.ic_launcher_background)
                .fitCenter()
                .into(imageView);
    }
}

直接把这个文件Convert Java File to Kotlin File如下：

object ImageBinds {
    @BindingAdapter("imageUrl")
    fun bindImgUrl(imageView: ImageView, url: String) {

        GlideApp.with(imageView.context)
                .load(url)
                .placeholder(R.drawable.ic_launcher_background)
                .fitCenter()
                .into(imageView)
    }
}

编译没问题，启动应用报错Caused by: java.lang.IllegalStateException: Required DataBindingComponent is null in class ActivityMainBinding. A BindingAdapter in com.shouzhan.quickpush.binding.ImageBinds is not static and requires an object to use, retrieved from the DataBindingComponent. If you don't use an inflation method taking a DataBindingComponent, use DataBindingUtil.setDefaultComponent or make all BindingAdapter methods static.

这是由于自动转换成kotlin时丢失了static，给方法添加@JvmStatic注解后再次编译运行，
这次报另一个错误，Caused by: java.lang.IllegalArgumentException: Parameter specified as non-null is null: method kotlin.jvm.internal.Intrinsics.checkParameterIsNotNull, parameter url

这是由于url参数没有做可空处理，最终修改后如下：

object ImageBinds {
    @BindingAdapter("imageUrl")
    @JvmStatic
    fun bindImgUrl(imageView: ImageView, url: String?) {

        GlideApp.with(imageView.context)
                .load(url)
                .placeholder(R.drawable.ic_launcher_background)
                .fitCenter()
                .into(imageView)
    }
}

编译后正常运行