Android中维度资源的绑定适配器

Question

I have an ImageView for which I wanted to write a custom binding adapter

    <ImageView
        android:id="@+id/item_list_picture"
        android:layout_height="@dimen/normal_475"
        android:layout_alignParentEnd="true"
        android:layout_alignParentTop="true"
        android:layout_above="@id/item_list_secondary_text"
        android:contentDescription="@{listItemViewModel.primaryText}"
        android:padding="@dimen/normal_100"
        android:displayImageUrl="@{listItemViewModel.pictureUrl}"
        android:placeHolderDrawable="@{@drawable/ic_baseline_image_24}"
        android:layout_width="@dimen/normal_475"
        android:specificWidth="@dimen/normal_475"
        android:goneUnless="@{listItemViewModel.pictureUrl != null}" />

The dimension for specificWidth is defined in dimens.xml as

<dimen name="normal_475">77dp</dimen>

And finally the BindingAdapter.kt file has the following code:

@BindingAdapter("android:displayImageUrl", "android:placeHolderDrawable", "android:specificWidth")
fun loadImage(view: ImageView, displayImageUrl: String?, placeHolderDrawable: Drawable, @DimenRes width: Int) {
    if (!displayImageUrl.isNullOrEmpty()) {
        Picasso.get().load(displayImageUrl).placeholder(placeHolderDrawable)
            .resize(view.context.resources.getDimensionPixelSize(width), view.context.resources.getDimensionPixelSize(width)).centerCrop().into(view)
    } else {
        view.setImageDrawable(placeHolderDrawable)
    }
}

If I use the binding adapter's loadImage without the specificWidth everything works. Otherwise, I get the following error

ERROR:C:\dev\projects\myapp\app\src\main\res\layout\item_list.xml:69: AAPT: error: attribute android:specificWidth not found.

What is the problem here? How can I get the specific width from the dimension defined? I also tried to add android:layout_width to the binding adapter instead of my custom android:specificWidth , but it doesn't work either. The possibility to use android:layout_width value in dp would be even better as I need to get the size given for the ImageView to resize the downloaded image from pictureUrl .

Answer 1

Because android:specificWidth 's type is resource you need to set it like below:

android:specificWidth="@{R.dimen.normal_475}"

also you need to import R in your data tag:

<import type="your.package.name.R" />

Or if you want to pass the dimen value you need to change your bindingAdapter specificWidth input to this:

fun loadImage(
view: ImageView,
displayImageUrl: String?,
placeHolderDrawable: Drawable,
width: Float // change the type to float and clear the `@dimenRes` annotation

also change your xml to:

 android:specificWidth="@{@dimen/normal_475}" // you need to pass the value in data-binding format

By the way you can also ignore this android:specificWidth attribute as you said and instead read the value from the view's width and height. you just need to do it on view.post{} to make sure the view is rendered and its size is valid. so your bindingAdapter fun would be something like this:

@BindingAdapter("android:displayImageUrl", "android:placeHolderDrawable")
fun loadImage(view: ImageView, displayImageUrl: String?, placeHolderDrawable: Drawable) {
    view.post {
        if (!displayImageUrl.isNullOrEmpty()) {
            Picasso.get().load(displayImageUrl).placeholder(placeHolderDrawable)
                .resize(
                    view.width,
                    view.height
                ).centerCrop().into(view)
        } else {
            view.setImageDrawable(placeHolderDrawable)
        }
    }
}

If you had any questions or I didn't get your problem well please don't hesitate to ask.

Answer 2

The solution that worked for me was to define the specific width as android:specificWidth="@{@dimen/normal_475}" .