How do I access the default android style from code? - android-styles

Question

I'm trying to write my own version of android.widget.SeekBar by modifying the android source code: I can't use a derived class because I want to override some behaviour using private member variables which aren't visible to a derived class.
SeekBar, like most widgets, is styled. I want to change the behaviour, but not the style, so I need to get the default style that android.widget.SeekBar uses. The version in the android sources gets its style with something like this:-
final TypedArray a = context.obtainStyledAttributes(
attrs, R.styleable.SeekBar, defStyleAttr, defStyleRes);
final drawable thumb = a.getDrawable(R.styleable.SeekBar_thumb);
...
a.recycle();
Well R.styleable isn't accessible in user code. The answer to How do I access an Android internal style attributes via derived classes? suggests replacing R.styleable.SeekBar with
new int[] { android.R.attr.seekBarStyle }, but omits the a.recycle(), which I suspect may be wrong. It also says that only one style attribute at a time can be accessed in this way. Presumably you need to recycle the TypedArray each time
However SeekBar has a whole lot of style attributes, and the only thing exported from r.attr is android.R.attr.seekBarStyle, which is a single integer How do I get at the individual style attributes?

Answer 1

You can get the values of default resources with some code like this:-
Resources res = getResources();
int defStyleAttr = res.getIdentifier(
"android:attr/seekBarStyle", "", "android");
int resId = res.getIdentifier(
"android:attr/thumb", "", "android");
TypedArray a = obtainStyledAttributes(
null, new int[] {resId}, defStyleAttr, 0);
final Drawable thumb = a.getDrawable(0);
a.recycle();
resId = res.getIdentifier(
"android:attr/thumbTint", "", "android");
a = obtainStyledAttributes(
null, new int[] {resId}, defStyleAttr, 0);
ColorStateList ThumbTintList = null;
ThumbTintList = a.getColorStateList(0);
a.recycle();
resId = res.getIdentifier(
"android:attr/progressDrawable", "", "android");
a = obtainStyledAttributes(
null, new int[] {resId}, defStyleAttr, 0);
final Drawable track = a.getDrawable(0);
a.recycle();
resId = res.getIdentifier(
"android:attr/progressTint", "", "android");
a = obtainStyledAttributes(
null, new int[] {resId}, defStyleAttr, 0);
ColorStateList progressTintList = null;
progressTintList = a.getColorStateList(0);
a.recycle();
resId = res.getIdentifier(
"android:attr/paddingLeft", "", "android");
a = obtainStyledAttributes(
null, new int[] {resId}, defStyleAttr, 0);
int paddingLeft = a.getInt(0, 0);
a.recycle();
resId = res.getIdentifier(
"android:attr/paddingTop", "", "android");
a = obtainStyledAttributes(
null, new int[] {resId}, defStyleAttr, 0);
int paddingTop = a.getInt(0, 0);
a.recycle();
resId = res.getIdentifier(
"android:attr/paddingRight", "", "android");
a = obtainStyledAttributes(
null, new int[] {resId}, defStyleAttr, 0);
int paddingRight = a.getInt(0, 0);
a.recycle();
resId = res.getIdentifier(
"android:attr/paddingBottom", "", "android");
a = obtainStyledAttributes(
null, new int[] {resId}, defStyleAttr, 0);
int paddingBottom = a.getInt(0, 0);
a.recycle();
getIdentifier is deprecated, but currently (4 January 2022) still works. Of course you need to know the names of the resources. These you can get from R.styleable by chopping off the initial class name and the underscore.
getResources and obtainStyledAttributes are member functions of Context, so if you aren't calling them from a class which inherits Context (Activities do, but widgets don't), you need a context. in front.
You can get the name for defStyleAttr by looking in the source code of the widget that you're replacing: it seems to be the name of the widget class with initial letter lower-cased and "Style" appended. If you're creating a completely new widget, 0 should do, but I haven't properly tested that.