Preferences are shown using view holders.
The previous code did not clear the listeners or hide the icons if
necessary.
The practical upshot of this was that if you had two or more slider
preferences, *and* they were situated more than a screen's height apart,
the viewholder from the first one would get reused.
And if the first one enabled icons then the second one would show them.
And clicking on the second one would also call the listeners for the
first one.
Font scaling is applied in addition to any scaling set in Android system preferences. So if the user set the Android font size to largest (a 1.3x increase) and then sets the preference to 120%, the total change is 1.56x.
Create SliderPreference to adjust the preference.
- Use Slider, which supports float values and step sizes > 1
- Display the selected value in the preference's summary
- Provide buttons to increment / decrement the value
Restart the activity if the preference changes so that the user sees the impact of the change immediately. Fix a bug in PreferencesActivity where the "EXTRA_RESTART_ON_BACK" intent was never processed. Fix this to ensure that other activities are restarted so the new font scale takes effect.
Implement the scaling in BaseActivity by overriding onAttachBaseContext, and providing a wrapped context with the font scaling applied.
Fixes https://github.com/tuskyapp/Tusky/issues/2982, https://github.com/tuskyapp/Tusky/issues/2461
