Android: changing private static final field using java reflection

Question

Change private static final field using Java reflection

I followed the instructions in the link above to change a private static final field using java reflection. I have an object named "data." Inside "data," there is a private static final variable named "type." I want to set "type" to be null. Here is my code.

Field field = data.getClass().getDeclaredField("type");
field.setAccessible(true);
Field modifiersField = Field.class.getDeclaredField("modifiers");
modifiersField.setAccessible(true);
modifiersField.setInt(field, field.getModifiers() & ~Modifier.FINAL);
field.set(data, null);

I tried doing this on Java 1.7 with similar code and it worked. But running this code on Android produces the following error: java.lang.NoSuchFieldException: modifiers

I guess "modifiers" is not a field in the Field class on Android.

How do I fix this?

You...can't change the modifiers on a class field at runtime. — Louis Wasserman
– Louis Wasserman, Commented Jun 25, 2012 at 8:26
Do remember that the Java compiler can inline values of primitive static final fields. Doing this sort of reflection magic could lead to bizarre behaviour. — millimoose
– millimoose, Commented Jun 27, 2012 at 20:28

Andi · Accepted Answer · 2018-06-11 21:24:52Z

11

This works for non-static fields.

Field field = data.getClass().getDeclaredField("type");
field.setAccessible(true);
field.set(data, null);

edited Jun 11, 2018 at 21:24

Andi

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answered Jun 27, 2012 at 20:10

jas7

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3 Comments

Yoraco Gonzales Over a year ago

This worked. But why? Does ART remove the final modifier or does it simple allow to access it anyway?

prom85 Over a year ago

This works, because the first object in the field.set(...) function is the object to modify NOT the field

David Williams Over a year ago

data is not static in this case?

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