Android two-way databinding Float to EditText

Question

I am trying to use two-way databinding on a EditText. String values are working fine but I can't get it working for Float values.

I have tried to use a binding adapter that I found in this answer with no luck: Android DataBinding float to TextView

Then I found this Converter class on the android developers website. https://developer.android.com/topic/libraries/data-binding/two-way#kotlin

public class Converter {
    @InverseMethod("stringToFloat")
    public static String floatToString(float value) {
        try {
            return String.valueOf(value);
        } catch (Exception e) {
            return "";
        }
    }

    public static float stringToFloat(String value) {
        try {
            return Float.parseFloat(value);
        } catch (Exception e) {
            return 0.0f;
        }
    }
}

<com.google.android.material.textfield.TextInputLayout
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:layout_marginBottom="16dp">

                            <com.google.android.material.textfield.TextInputEditText
                                android:id="@+id/width"
                                android:layout_width="match_parent"
                                android:layout_height="wrap_content"
                                android:hint="Width"
                                android:inputType="number"
                                android:text="@={Converter.floatToString(product.width)}"/>

data class Product(
        val height: Float?,
        val length: Float?,
        val width: Float?,
        val weight: Float?,       
): BaseObservable() {

After using the converter class I get the following error when compiling:

error: cannot generate view binders java.lang.NullPointerException at android.databinding.tool.expr.Expr.lambda$join$0(Expr.java:771)

have you imported the Converter class in your xml? under data ``?? — Raghunandan, Aug 19 '19 at 11:04
Yes I have imported the class. When I remove the = from the text property compiling is working and the edittext have the data from the model. ```android:text"@{Converter.floatToString(product.width)}"``` — Danny Spijker, Aug 19 '19 at 11:11
Check null and then convert. When working with databinding for the initial time it will be null. — Rajnish suryavanshi, Aug 19 '19 at 11:20

score 7 · Accepted Answer · answered Aug 19 '19 at 12:12

Thanks for the suggestions. The problem was in my model. I had to change the width property from val to var. (val properties cannot be reassigned. These are like final properties in Java)

And instead of using a Converter class I have added a BindingAdapter. Looks more clean for me.

public class TextViewBindingAdapter {
    @BindingAdapter("android:text")
    public static void setText(TextView view, Float value) {
        if (value == null)
            return;

        view.setText(String.valueOf(value));
    }

    @InverseBindingAdapter(attribute = "android:text", event = "android:textAttrChanged")
    public static Float getTextString(TextView view) {
        return Float.valueOf(view.getText().toString());
    }
}

Android two-way databinding Float to EditText

1 Answers1