Databinding搭配kotlin使用時與java有些區(qū)別，除了需要使用kapt依賴之外，由于kotlin沒有static的特性和null-safe檢查，還是踩了不少坑的，寫個博客記錄下。

業(yè)務(wù)場景：給ImageView添加一個自定義屬性imageUrl，處理網(wǎng)絡(luò)圖片加載,xml代碼如下：

    <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的時候是這么處理的：

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);
    }
}

直接把這個文件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)
    }
}

編譯沒問題，啟動應(yīng)用報錯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.

這是由于自動轉(zhuǎn)換成kotlin時丟失了static，給方法添加@JvmStatic注解后再次編譯運行，
這次報另一個錯誤，Caused by: java.lang.IllegalArgumentException: Parameter specified as non-null is null: method kotlin.jvm.internal.Intrinsics.checkParameterIsNotNull, parameter url

這是由于url參數(shù)沒有做可空處理，最終修改后如下：

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)
    }
}

編譯后正常運行