Android : Getting text size by obtainStyledAttributes in Android

// styles.xml
<style name="lab_attributeset_textview">
    <item name="android:textColor">@color/holo_text</item>
    <item name="android:padding">10dp</item>
    <item name="android:textSize">18sp</item>
</style>

// processing attributes
int[] attrs = {android.R.attr.textColor, android.R.attr.textSize, android.R.attr.padding};
TypedArray typedArray = obtainStyledAttributes(R.styles.lab_attributeset_textview, attrs);

int color = typedArray.getColor(0, Color.WHITE);
int color3 = typedArray.getResourceId(0, NO_ID);
int size = typedArray.getDimensionPixelSize(1, NO_ID);
float padding = typedArray.getDimension(2, NO_ID);

StringBuilder stringBuilder = new StringBuilder();
stringBuilder.append("Style Attributes").append("\n\n");
stringBuilder.append("color: ").append(Integer.toHexString(color)).append("\n");
stringBuilder.append("resource color: ").append(color3).append("\n");
stringBuilder.append("size: ").append(size).append("\n");
stringBuilder.append("padding: ").append(padding).append("\n");

It produces:

Style Attributes

color: ff474747 resource color: 2131165187 size: -1 padding: 10.0dip

Why textSize is not provided?