BindingAdapter

Class Overview

BindingAdapter is applied to methods that are used to manipulate how values with expressions are set to views. The simplest example is to have a public static method that takes the view and the value to set:

@BindingAdapter("android:bufferType")
 public static void setBufferType(TextView view, TextView.BufferType bufferType) {
     view.setText(view.getText(), bufferType);
 }

In the above example, when android:bufferType is used on a TextView, the method setBufferType is called.

It is also possible to take previously set values, if the old values are listed first:

@BindingAdapter("android:onLayoutChange")
 public static void setOnLayoutChangeListener(View view, View.OnLayoutChangeListener oldValue,
                                              View.OnLayoutChangeListener newValue) {
     if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
         if (oldValue != null) {
             view.removeOnLayoutChangeListener(oldValue);
         }
         if (newValue != null) {
             view.addOnLayoutChangeListener(newValue);
         }
     }
 }

When a binding adapter may also take multiple attributes, it will only be called when all attributes associated with the binding adapter have binding expressions associated with them. This is useful when there are unusual interactions between attributes. For example:

@BindingAdapter({"android:onClick", "android:clickable"})
 public static void setOnClick(View view, View.OnClickListener clickListener,
                               boolean clickable) {
     view.setOnClickListener(clickListener);
     view.setClickable(clickable);
 }

The order of the parameters must match the order of the attributes in values in the BindingAdapter.

A binding adapter may optionally take a class extending DataBindingComponent as the first parameter as well. If it does, it will be passed the value passed in during binding, either directly in the inflate method or indirectly, using the value from getDefaultComponent().

If a binding adapter is an instance method, the generated DataBindingComponent will have a getter to retrieve an instance of the BindingAdapter's class to use to call the method.

Summary

[Expand] Inherited Methods

From interface java.lang.annotation.Annotation abstract Class<? extends Annotation> annotationType() Returns the type of this annotation. abstract boolean equals(Object obj) Determines whether or not this annotation is equivalent to the annotation passed. abstract int hashCode() Returns the hash code of this annotation. abstract String toString() Returns a String representation of this annotation.