Where to place android BindingAdapter method?

Question

This has to be the most basic of question but after a full day of reading tutorials and the documentation here I can't seem to understand where to put these methods. None of the guides mention where this thing is placed it just mentions to use the annotation on a static method. What static method? Any static method at all regardless of class? What is a good practice? do I create a CustomBinding class to host all these static methods?

So long as I have the method has a BindingAdapter annotation and the first parameter is a View, it will work?

I assume if the first parameter is of type View I can place the binding attribute on any type of views and it will trigger the method? So if I have specific view say EditText, does this mean the method is only called when the attribute is found in an EditText view in the layout file?

Answer 1

After navigating through the internet I've finally found some info from one of the developers themselves. I wish they would have been more clear on the basics in the documentation.

Quote:

Binding adapters are annotated methods in any class that are used to do just this. Typically, you’d organize your adapters into [-a] classes based on the target View type.

This obviously means that at compile time all methods in any class with the annotation BindingAdapter will generate the BindingAdapter.

Answer 2

You place it in your model class.

Example:

XML:

 <data>

    <variable
        name="item"
        type="com.yourpackage.Model"/>
      </data>
         ......

           <ImageView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:src="@{item.resId}"/>

Model:

public class Model {

    @DrawableRes
    private final int resId;

    public Model(int resId) {
        this.resId = resId;
    }

    public int getResId() {
        return resId;
    }

    @BindingAdapter ("android:src")
    public static void setImageResource(ImageView imageView, int resource){
        imageView.setImageResource(resource);
    }
}