Reference a string value in a styleable attribute

Question

I am trying to extend an android.widget.Button and added a styleable attribute to my custom widget, which should hold a reference to a value in res/values/strings.xml.

 <resources>
      <attr name="infoText" format="reference" />
      <declare-styleable name="FooButton">
           <attr name="infoText" />
      </declare-styleable>
 </resources

In my layout I have something like this:

 <LinearLayout
      android:layout_height="wrap_content"
      android:layout_width="fill_parent"
      android:orientation="horizontal">
      <com.example.FooButton
           android:layout_height="wrap_content"
           android:layout_width="wrap_content"
           android:id="@+id/fooButton"
           infoText="@string/fooButtonInfoText" />
 </LinearText>

My res/values/strings.xml looks like this:

 <?xml version="1.0" encoding="utf-8"?>
 <resources>
      <string name="fooButtonInfoText">BAR</string>
 </resources>

The extraction of the attribute value in my custom FooButton looks like this:

 TypedArray typedArray = context.obtainStyledAttributes(attributeSet, R.styleable.FooButton);
 Integer infoTextId = typedArray.getResourceId(R.styleable.FooButton_infoText, 0);
 if (infoTextId > 0) {
      infoText = context.getResources().getString(infoTextId);
 }
 typedArray.recycle();

I've got these three constructors implemented:

 public FooButton(Context context) {
      super(context);
 }

 public FooButton(Context context, AttributeSet attributeSet) {
      super(context, attributeSet);
      setInfoText(context, attributeSet);
 }

 public FooButton(Context context, AttributeSet attributeSet, int defStyle) {
      super(context, attributeSet, defStyle);
      setInfoText(context, attributeSet);
 }

The method FooButton.setInfoText(context, attributeSet) is called every time there is a FooButton declared.

I am fighting this problem for too long and read dozens of Stackoverflow questions... why does this not work?

Paul Burke · Accepted Answer · 2013-08-24 18:35:56Z

1

You must declare the namespace for custom attributes. It should look like this:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res/auto"
    android:layout_height="wrap_content"
    android:layout_width="fill_parent"
    android:orientation="horizontal">
    <com.example.FooButton
         android:layout_height="wrap_content"
         android:layout_width="wrap_content"
         android:id="@+id/fooButton"
         app:infoText="@string/fooButtonInfoText" />
 </LinearText>

answered Aug 24, 2013 at 18:35

Paul Burke

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2 Comments

s.froehlich Over a year ago

To clarify: Where xmlns:app="schemas.android.com/apk/res/auto" would be xmlns:app="schemas.android.com/apk/res/com.example" in case your apps namespace is declared as com.example in the AndroidManifest.xml. Thanks!

Paul Burke Over a year ago

Actually, res/auto does what it sounds like: automatically maps your application's namespace. :-)

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