rekire rekire - 5 months ago 45
Android Question

Two-way binding cannot resolve a setter for java.lang.String property

I am playing with the two-way binding of the data binding API which was introduced in Android Studio 2.1 AFIK.

I get this interesting error:


Error:Execution failed for task ':app:compileDebugJavaWithJavac'.

> java.lang.RuntimeException: Found data binding errors.

****/ data binding error ****msg:The expression address.street cannot cannot be inverted: Two-way binding cannot resolve a setter for java.lang.String property 'street'

file:/path/to/layout.xml

loc:34:37 - 34:50
****\ data binding error ****


When I try to google that error I just find a 4 day old Japanese Twitter posting from a guy who is crying about it...

<EditText
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="@string/edit_hint_zip"
android:text="@={address.zip}"
tools:text="12345"/>


That
address.zip
is a
String
. I am guessing that the problem here is
CharSequence
vs.
String
as the return value of
EditText.getText()
.

My idea was to defining it however this does not work for me:

@NonNull
@InverseBindingAdapter(attribute = "text")
public static String getText(EditText edit) {
return edit.getText().toString();
}


What did I miss?

Answer

This bug is ugly as hell and properly a bug in the data binding API. The solution is to generate a setter and a getter. I came up fast with the idea to create a setter, but not to create a getter.

Here is now my simplified model:

public class Address {
    public String street;

    public void setStreet(String street) {
        this.street = street;
    }

    public String getStreet() {
        return street;
    }
}

As you may note the getter and setter are useless, but required for two way binding.

If you think that this is a bug of the API please star my bug report: Two-way binding required setters AND ALSO getters