How to change font size programmatically in Android?

I need to change the font size of my application at runtime. I referred the following SO post where they speak about applying font size via styles.xml and applying it. I think it's applicable only for a particular element (like TextView or layout) but is it possible to apply the font size at application level and is it possible to set it programmatically?

Yes, setting text size is :

textView.setTextSize(20)// text size

added few more things here :)

1.If you want to set as DP

textView.setTextSize(coverPixelToDP(20));
    
private int coverPixelToDP (int dps) {
    final float scale = this.getResources().getDisplayMetrics().density;
    return (int) (dps * scale);
}

2.If you want to adjust font size automatically to fit boundaries use,

setAutoSizeTextTypeUniformWithConfiguration(int autoSizeMinTextSize, int autoSizeMaxTextSize, int autoSizeStepGranularity, int unit)

JAVA Version

TextView textView = new TextView(this);
textView.setText("Adjust font size for dynamic text");
//only works when width = 'match_parent', and give height
LinearLayout.LayoutParams p1 = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, 500); 
           
textView.setLayoutParams(p1);
textView.setAutoSizeTextTypeUniformWithConfiguration(8, 15, 1, TypedValue.COMPLEX_UNIT_DIP); 

XML Version (Programatically)

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

  <TextView
      android:layout_width="match_parent" // make sure it is match_parent
      android:layout_height="500dp" //make sure you give height 
      app:autoSizeTextType="uniform"
      app:autoSizeMinTextSize="12sp"
      app:autoSizeMaxTextSize="100sp"
      app:autoSizeStepGranularity="2sp" />

</LinearLayout>