Not sure why you would need to dive into Java Reflection API for this. Its a simple styling matter. The attribute that you need to override is: textColorPrimary.
<style name="AppTheme" parent="@android:style/Theme.Holo.Light">
....
<item name="android:textColorPrimary">#ff0000</item>
</style>
If you're using the TimePicker inside a Dialog, override android:textColorPrimary in the dialog's theme.
That's about it.
Additional info:
Here's an insightful comment by Yoann Hercouet:
This solution does not change only the color on the NumberPicker, it
is a global change that will impact A LOT of components
This is correct, but it overlooks the possibilities I am hinting at. Moreover, global implies app-wide impact. That can be limited to activity-scope by applying this theme only to activities containing the NumberPicker. But, I agree, this may still be too corrosive.
The idea here is to somehow inject textColorPrimary=INTENDED_COLOR into the theme that will be seen by NumberPicker. There are multiple ways to achieve this. Here's one way:
Define a bare-bone style in res/values/styles.xml:
<style name="NumberPickerTextColorStyle">
<item name="android:textColorPrimary">@color/intended_color</item>
</style>
Now, create a custom NumberPicker:
public class ThemedNumberPicker extends NumberPicker {
public ThemedNumberPicker(Context context) {
this(context, null);
}
public ThemedNumberPicker(Context context, AttributeSet attrs) {
// wrap the current context in the style we defined before
super(new ContextThemeWrapper(context, R.style.NumberPickerTextColorStyle), attrs);
}
}
Finally, use ThemedNumberPicker in your layout(s):
<package.name.ThemedNumberPicker
android:id="@+id/numberPicker"
....
....
.... />
We have successfully contained the impact that textColorPrimary=INTENDED_COLOR has on our app.
This is of course just one option. For example, if you were inflating a layout containing a NumberPicker, you could use:
// In this case, the layout contains <NumberPicker... />, not <ThemedNumberPicker... />
LayoutInflater.from(new ContextThemeWrapper(context, R.style.NumberPickerTextColorStyle))
.inflate(R.layout.number_picker_layout, ...);
